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INST 230 (Motor Controls), section 2 Lab Reversing three

1. Finally develop a rule you may use when assessing the value of each proposed test based on a comprehensive list of possible faults Suggestions for Socratic discussion e Identify which fundamental principles of electric circuits apply to each step of your analysis of this circuit In other words be prepared to explain the reason s why for every step of your analysis rather than merely describing those steps e Suppose the fault were intermittent sometimes the lamp lights up and other times it goes out Explain how you could use a digital multimeter DMM set to record voltage as a troubleshooting tool to determine where the fault is located in the circuit over a span of time too long for you to personally observe the circuit file 101746 58 Question 50 The grades_template spreadsheet provided for you on the Y network drive allows you to calculate your grade for any course by entering exam scores attendance data etc as well as project to the future for courses you have not yet taken Download the spreadsheet file if you have not done so yet and enter all the data you can for grade calculation at this point in the quarter Also locate the pages in your course worksheet entitled Sequence of Second Year Instrumentation Courses to identify which courses you will need to register for next quarter Suggestions for Socratic discussion e If you do not yet have enough
2. Demonstrate proper use of safety equipment and application of safe procedures while using power tools and working on live systems Communicate effectively with teammates to plan work arrange for absences and share responsibilities in completing all labwork Construct and commission a three phase reversing motor starter system Connect three power transformers together to form a three phase transformer bank with specified configuration e g Delta Delta Delta Wye Generate an accurate wiring diagram compliant with industry standards documenting your team s motor control system Construct and test a PLC trainer board utilizing a small PLC connected to input switches and indicator lamps e Independently perform the following tasks on a functioning motor starter system with 100 accuracy mastery Multiple re tries are allowed with different specifications conditions each time Properly wire a start stop motor control circuit given components randomly selected by the instructor Test for ground faults in a motor starter system using an insulation tester megger Demonstrate how to secure power to a motor starter using proper lock out and testing procedures Diagnose a random fault placed in another team s motor control system by the instructor within a limited time using no test equipment except a multimeter logically justifying your steps in the instructor s direct presence COURSE OUTLINE A c
3. Single phase AC power source Trace the directions of current through all four diodes and determine the polarity of DC voltage across the motor terminals A three phase bridge rectifier circuit is made of six diodes arranged like this Once again trace the directions of current through all six diodes and determine the polarity of DC voltage across the motor terminals file 101437 Three phase AC power source 43 Question 35 Connect an oscilloscope in parallel with the VFD s power line connections through a step down transformer to monitor the input voltage waveform while the drive is running and while it is stopped What effect do you notice on the sine wave s shape when the drive is active Try sketching each waveshape drive running vs not running here Line voltage waveform VFD stopped Line voltage waveform VFD running Another experiment to try is operating an AM radio near a VFD when it is stopped versus when it is running Explain why the radio responds as it does to the VFD s status Suggestions for Socratic discussion e How might the harmonics generated by a VFD interfere with nearby electronic equipment e How can a technician detect the presence of harmonics and more importantly locate the precise source of harmonic distortion in a power system e How is it possible to shield other equipment on the power system from harmonics generated by a particular VFD file 104065
4. A good rule to apply when evaluating proposed tests is to ask the question Will this test give me the exact same result no matter which one of the possible faults is true If so the test is useless If not i e the results would differ depending on which of the possible faults was true then the test has value because it will help narrow the field of possibilities Answer 50 You may locate the grades_template on the Y network drive at BTC provided you log in to the computer system using your individual student ID and password not a generic login such as btc It is also available for download at the Socratic Instrumentation website Answer 51 The rotating magnetic field from a three phase motor stator assembly will exert a torque on any conductive object The magnetic properties of the object within the field are largely irrelevant The only reason iron is placed in the rotor is to eliminate what would otherwise be a huge air gap between the stator poles thereby strengthening the stator s magnetic field for heightened effect This stronger magnetic field then acts upon the aluminum squirrel cage bars to produce more torque than would otherwise be possible 110 Answer 52 The concept to bear in mind here is that overload heaters function to protect the motor by serving as thermal models of the motor As such they must carry current at all times the motor is carrying current in order to heat up and cool d
5. Answer 21 The Start contactor must be energized first then at a later time is de energized as the Run contactor is simultaneously energized Either timing relays or a PLC handles this sequencing of contactors 104 Answer 22 Start Fuses _ B To three phase _ a 86 gt TT G OAT Run Answer 23 Answer 24 Answer 25 If you have access to an AC induction motor and some batteries feel free to experiment with DC injection braking in the class or lab All you need to do is connect a source of low voltage DC to the stator winding s of an AC induction motor and you will be able to feel the braking effect as you try to spin the motor s shaft with your fingers Answer 26 Answer 27 Answer 28 Answer 29 Answer 30 Answer 31 In the start up mode the motor s rotor winding is short circuited by the Start contact This makes the motor behave like a normal squirrel cage induction motor with its rotor bars and shorting rings As soon as the speed switch detects adequate rotor speed the Start coil de energizes and the Run coil energizes connecting the rotor winding directly to a DC power source to magnetize it and lock it into synchronous mode 105 Answer 32 Three phase AC power source 60 Hz 1720 RPM 60 Hz Speed 860 RPM Answer 33 The inductor would most likely overheat and burn up As frequency decreases so does indu
6. Normally open flow switch on Normally closed pressure switch Ss Normally closed level switch Normally closed temperature switch a Normally closed flow switch ca ae Define normal for each of these process switches In other words explain what condition s each process switch must be in to ensure it is in the normal state and conversely what condition s need to be applied to each switch to force it into its other state file 102966 29 Question 13 Limit switches are electrical switches designed to actuate based on the motion or position of an object rather than the touch of a human operator Simple limit switches rely on direct physical contact using a lever sometimes tipped with a roller for low friction Direct contact limit switch Bate Light bulb silt 6 Show how you would connect the limit switch in the above illustration so that it makes the light turn off when actuated i e the light will be on when no one touches the switch lever file 102242 Question 14 Below is an illustration of a diaphragm operated pressure switch designed to actuate when the process fluid pressure applied to the impulse line tube exceeds a certain set value A schematic diagram shows how the switch contacts relate to the screw terminals seen on the outside of the switch illustration Pressure switch Schematic diagram s NO Com i NC Process fluid impulse line Explain
7. and one run to sequence the motor from start up to full speed run The impedances ideally take the form of inductors reactors Run Start Explain how and why this method of starting is gentler than across the line starting Suggestions for Socratic discussion e Identify some means to time the closure of the two sets of power contacts Start and Run so that the motor is soft started for an appropriately before having full power applied e Would large high power resistors work instead of inductors e Would large capacitors work instead of inductors e Suppose one of the series reactors failed open What effect s would this have on the circuit s operation file 102310 34 Question 22 An interesting way to achieve reduced voltage starting for a three phase motor is to use a 6 lead motor where the three stator winding sets are individually wired so as to allow either wye start or delta configurations Wye connection 1 6 lead 3 phase motor Delta connection a KA e A Start contactor sends power to the stator windings in a wye configuration for a short start up time perhaps 10 seconds then that starter disengages and a Run starter energizes to send power to the stator windings in a delta configuration In the wye configuration each winding receives A of the line voltage In the delta configuration each winding receives the full line voltage S
8. 22 Question 6 Determine the functions of all pressure switches and relays in this steam boiler monitoring circuit and what each of their designations mean Low steam warning lamp High steam warning lamp Boiler shutdown solenoid 10 sec Also explain the significance of the switch symbols normally open versus normally closed The time delay relay TD1 is especially important here Finally add a Lamp Test pushbutton switch to this circuit which will force all lamps to energize when pressed in order to test the proper operation of the lamps without waiting for an abnormal process condition to occur Suggestions for Socratic discussion e Why do you suppose a time delay relay is used in this particular control application e Is the boiler shutdown solenoid energize to trip or de energize to trip Explain how we can tell from an examination of the schematic e Identify a circuit fault that would cause the boiler to needlessly shut down a safe fault e Identify a circuit fault that would cause the boiler to not be able to shut down when it needs to a dangerous fault file 100221 23 Question 7 Examine this ladder diagram for a solenoid valve control circuit where the status of a solenoid valve either on or off is controlled by hand switches and a pressure switch Then answer the questions that follow Identify the meaning of the square boxes each one
9. General tool and supply list Wrenches e Combination box and open end wrench set 1 4 to 3 4 the most important wrench sizes are 7 16 1 2 9 16 and 5 8 get these immediately Adjustable wrench 6 handle sometimes called Crescent wrench Hex wrench Allen wrench set fractional 1 16 to 3 8 Optional Hex wrench Allen wrench set metric 1 5 mm to 10 mm Optional Miniature combination wrench set 3 32 to 1 4 sometimes called an ignition wrench set Note when turning any threaded fastener one should choose a tool engaging the maximum amount of surface area on the fastener s head in order to reduce stress on that fastener e g Using box end wrenches instead of adjustable wrenches using the proper size and type of screwdriver never using any tool that mars the fastener such as pliers or vise grips unless absolutely necessary Pliers e Needle nose pliers e Tongue and groove pliers sometimes called Channel lock pliers e Diagonal wire cutters sometimes called dikes Screwdrivers e Slotted 1 8 and 1 4 shaft e Phillips 1 and 2 e Jeweler s screwdriver set e Optional Magnetic multi bit screwdriver e g Klein Tools model 70035 Electrical e Multimeter Fluke model 87 IV or better e Alligator clip jumper wires Soldering iron 10 to 40 watt and rosin core solder Resistor potentiometer diode assortments from first year lab kits Packag
10. Variable Speed Motor Controls chapter in your Lessons In Industrial Instrumentation textbook Note the page numbers where important illustrations photographs equations tables and other relevant details are found Prepare to thoughtfully discuss with your instructor and classmates the concepts and examples explored in this reading file 103841 36 Question 27 Connect a VFD to a three phase induction motor and to a power cord in preparation for a set of experiments Research the user s manual for the VFD as well as the nameplate on the induction motor to figure out the correct wire connections Power plug Motor Your instructor will inspect all connections before you apply power Be sure all connections are made through terminal blocks no taped or twisted wire joints and that there are no exposed sections of copper wire for someone to accidently contact Next configure the following parameters in the VFD e Base parameters voltage frequency maximum speed etc these values are found on the motor s nameplate and should always be set first in the VFD before setting any other parameters Failure to properly configure the VFD s base parameters with the motor s nameplate data may result in motor damage e Acceleration and deceleration times Note that you should not set these parameters for unreasonably short times 5 seconds is a good minimum value or else you may damage the motor
11. files comprising them without having to ask me the author and licensor for permission The one thing you must do is properly credit my original authorship Basically this protects my efforts against plagiarism without hindering the end user as would normally be the case under full copyright protection This gives educators a great deal of freedom in how they might adapt my learning materials to their unique needs removing all financial and legal barriers which would normally hinder if not prevent creative use Nothing in the License prohibits the sale of original or adapted materials by others You are free to copy what I have created modify them if you please or not and then sell them at any price Once again the only catch is that you must give proper credit to myself as the original author and licensor Given that these worksheets will be continually made available on the internet for free download though few people will pay for what you are selling unless you have somehow added value Nothing in the License prohibits the application of a more restrictive license or no license at all to derivative works This means you can add your own content to that which I have made and then exercise full copyright restriction over the new derivative work choosing not to release your additions under the same free and open terms An example of where you might wish to do this is if you are a teacher who desires to add a detailed answer key for y
12. independently perform the following tasks Multiple re tries are allowed on mastery 100 accuracy objectives each with a different set of problems Calculate voltages and currents in a DC series parallel resistor circuit given source and resistor values with 100 accuracy mastery Sketch proper wire connections for a relay control circuit given a pictorial or schematic diagram of the components with 100 accuracy mastery Determine status of a relay logic circuit given a schematic diagram and switch stimulus conditions with 100 accuracy mastery Calculate current and horsepower ratings of a single phase electrical motor for a given line voltage with 100 accuracy mastery Solve for specified variables in algebraic formulae with 100 accuracy mastery Determine the possibility of suggested faults in a simple circuit given measured values voltage current a schematic diagram and reported symptoms with 100 accuracy mastery Predict the response of electric motor control systems to component faults and changes in process conditions given pictorial and or schematic illustrations Sketch proper power and signal connections between individual motor control components to fulfill a specified control system function given pictorial and or schematic illustrations of those instruments e In a team environment and with full access to references notes and instructor assistance perform the following tasks
13. polarity for the transformers and then connect the necessary wires in order to build the desired circuit You may find the section titled Transformer Polarity in your Lessons In Industrial Instrumentation textbook helpful in explaining this concept The instructor must inspect your plan as well as the constructed circuit before you are allowed to apply power to the transformer bank 91 The following pictorial diagram might be useful for you and your team to use for sketching the necessary Delta Wye connections and transformer winding jumpers to achieve the necessary step down ratios From three phase I power source Schematic diagram for each transformer 240 x 480 primary X 120 x 240 secondary To three phase load 92 Lab Exercise troubleshooting The most challenging aspect of this lab exercise is troubleshooting where you demonstrate your ability to logically isolate a problem in the system All troubleshooting is done on an individual basis no team credit and must be done on a system you did not help build so that you must rely on schematic diagrams to find your way around the system instead of from your own memory of building it Each student is given a limited amount of time to identify both the general location and nature of the fault logically justifying all diagnostic steps taken All troubleshooting activities will take place under direct instructor supervision to ensure students are w
14. 44 Question 36 Experiment with different V Hz volts per hertz profile settings for a VFD controlling the speed of an induction AC motor Then operate the motor at different frequencies while measuring line voltage to the motor between terminals T1 T2 T2 T3 or T1 T3 using a true RMS AC voltmeter Calculate the actual V Hz ratio at each speed by taking the measured voltage and dividing by the frequency General Purpose setting Frequency Voltage V RMS V Hz calculated 10 Hz 20 Hz 30 Hz 40 Hz 50 Hz 60 Hz High Starting Torque setting Frequency Voltage V RMS V Hz calculated 10 Hz 20 Hz 30 Hz 40 Hz 50 Hz 60 Hz Explain in your own words how the VFD achieves a greater starting torque by modifying the V Hz ratio in the high starting torque setting file 104083 45 Question 37 An AC electric power system has a bank of capacitors connected to correct for low power factor One day a new VFD is installed to provide variable speed control for an existing AC motor The VFD has its own line reactors connected on the input side to help filter harmonics from the rest of the AC power system The problem is the line reactors and the power factor correction capacitors now form a resonant circuit that may produce high currents and or voltages at a certain frequency 3 phase 480 VAC _ _ 60 Hz Fuses l l l Fuses Pow
15. begin studying the next day s material Above all cultivate persistence Persistent effort is necessary to master anything non trivial The keys to persistence are 1 having the desire to achieve that mastery and 2 realizing challenges are normal and not an indication of something gone wrong A common error is to equate easy with effective students often believe learning should be easy if everything is done right The truth is that mastery never comes easy file question0O 19 Creative Commons License This worksheet is licensed under the Creative Commons Attribution License version 1 0 To view a copy of this license visit http creativecommons org licenses by 1 0 or send a letter to Creative Commons 559 Nathan Abbott Way Stanford California 94305 USA The terms and conditions of this license allow for free copying distribution and or modification of all licensed works by the general public Simple explanation of Attribution License The licensor Tony Kuphaldt permits others to copy distribute display and otherwise use this work In return licensees must give the original author s credit For the full license text please visit http creativecommons org licenses by 1 0 on the internet More detailed explanation of Attribution License Under the terms and conditions of the Creative Commons Attribution License you may make freely use make copies and even modify these worksheets and the individual source
16. found on the BTC campus Y network drive A printed copy is posted in the Instrumentation classroom Locate industry documents assigned for reading use the Instrumentation Reference provided by your instructor on CD ROM and on the BTC campus Y network drive There you will find a file named 00_index_OPEN_THIS FILE html1 readable with any internet browser Click on the Quick Start Links to access assigned reading documents organized per course in the order they are assigned Study for the exams Mastery exams assess specific skills critically important to your success listed near the top of the front page of each course worksheet for your review Familiarize yourself with this list and pay close attention when those topics appear in homework and practice problems Proportional exams feature problems you haven t seen before that are solvable using general principles learned throughout the current and previous courses for which the only adequate preparation is independent problem solving practice every day Answer the feedback questions practice exams in each course section to hone your problem solving skills as these are similar in scope and complexity to proportional exams Answer these feedback independently i e no help from classmates in order to most accurately assess your readiness Calculate course grades download the Course Grading Spreadsheet grades_template xlsx from the Socratic Instrumentation website or
17. Identify a means of doing so i e limiting the inrush current that will occur when fully discharged capacitors are connected to a voltage source that is easy and safe to implement e Identify a practical application for a remote speed control such as this file 104074 40 Question 31 Synchronous AC motors by their nature rotate at precisely the same speed as the rotating magnetic field produced by the stator windings The practical problem with this is how to get a synchronous motor started since it is physically impossible for the rotor to jump from a stand still to 100 speed in zero time Therefore synchronous motors are usually started as regular induction motors at first and then they are switched to synchronous mode when their speed is very near 100 The following control circuit shows one scheme for this dual mode start up The rotor on this synchronous motor has its own winding Three phase synchronous motor oL M EREE a m Line power Stator windings Run 125 VDC Rotor winding Control circuit wiring L L Stop Start OL 7 F Explain how this start up circuit functions and what goes on with the switching of the rotor winding to make the motor start up and then run in two different modes Suggestions for Socratic discussion e What practical applications might warrant the use of a synchronous AC motor instead of an induction AC motor file 103758 41 Question 32 D
18. Line 2 Line 3 F Schematic use diagram Shaft Contactor jira Overload block After years of faithful service one day this motor refuses to start It makes a humming sound when the contactor is energized relay contacts close but it does not turn A mechanic checks it out and determines that the shaft is not seized but is free to turn The problem must be electrical in nature 54 You are called to investigate Using a clamp on ammeter you measure the current through each of the lines immediately after each fuse as another start is once again attempted You then record the three current measurements Line Current 1 52 7 amps 2 51 9 amps 3 0 amps Determine at least two possible faults either one fully capable of causing the motor s refusal to start and the three current measurements taken Then decide what your next measurement s will be to isolate the exact location and nature of the fault Suggestions for Socratic discussion e Is there a way we could have determined a lack of current in line 3 without the use of a clamp on ammeter using a multimeter incapable of directly measuring current over 10 amps file 101445 Question 46 An instrument technician finds a great deal on a lathe for his home machine shop The only problem is this lathe has a three phase motor and his shop only has single phase electric power This technician knows however that
19. PLCs you must first install and run software called RSLinz which manages communications between your PC and PLC before you start up the programming software RSLogiz After that your next step is to use programming software installed in a personal computer to program your PLC with some simple function consisting of contact and coil instructions The purpose of a virtual contact in a PLC program is to read data bits from memory while the purpose of a virtual coil in a PLC program is to write data bits to memory Thus you will create programs for the PLC using virtual contacts to read the states of real world switches connected to inputs on the PLC and using virtual coils to control real world outputs on the PLC to energize loads such as lamps and solenoids The interconnections and arrangements of these virtual contacts and coils determine the logic implemented by the PLC specifying the conditions necessary to energize real world devices based on input conditions You will find step by step instructional tutorials for both Allen Bradley MicroLogix and Koyo CLICK PLCs in your Instrumentation Reference provided by the instructor Follow these tutorials to establish communication between your PC and your PLC and to write a simple contact and coil ladder diagram program before attempting the exercises that follow You will also find much pertinent information for programming Allen Bradley MicroLogix PLCs in the RSLogiz 500 Getting Resul
20. Watts per square meter Kelvin W m K Molar gas constant R 8 314 Joules per mole Kelvin J mol K Properties of Water Freezing point at sea level 32 F 0 C Boiling point at sea level 212 F 100 C Density of water at 4 C 1000 kg m 1 g cm 1 kg liter 62 428 lb ft 1 94 slugs ft Specific heat of water at 14 C 1 00002 calories g C 1 BTU Ib F 4 1869 Joules g C Specific heat of ice 0 5 calories g C Specific heat of steam 0 48 calories g C Absolute viscosity of water at 20 C 1 0019 centipoise cp 0 0010019 Pascal seconds Pa s Surface tension of water in contact with air at 18 C 73 05 dynes cm pH of pure water at 25 C 7 0 pH scale 0 to 14 Properties of Dry Air at sea level Density of dry air at 20 C and 760 torr 1 204 mg cm 1 204 kg m 0 075 lb ft 0 00235 slugs ft Absolute viscosity of dry air at 20 C and 760 torr 0 018 centipoise cp 1 8 x 1075 Pascal seconds Pa s file conversion_constants 18 Question 0 How to get the most out of academic reading Articulate your thoughts as you read i e have a conversation with the author This will develop metacognition active supervision of your own thoughts Write your thoughts as you read noting points of agreement disagreement confusion epiphanies and connections between different concepts or applications These notes should also document important math formulae explaining in y
21. a 4 20 mA control signal from one of the channels of an analog output card on a programmable logic controller PLC The PLC in turn receives operating instructions from a touch screen panel HMI where the operators can monitor and control the process Touch screen panel HMI data cable Power supply 4 20 mA signal cable power cable Circuit breaker From 480 VAC power source power cable This system is newly constructed and has not yet worked The operators try starting up the pump by pressing the Pump start icon on the touch screen but nothing happens A technician disconnects the signal cable from the PLC s analog output terminals and then connects the cable s end to a loop calibrator to send 12 mA DC to the VFD for a test At this the motor starts up and runs at half speed Identify the likelihood of each specified fault for this circuit Consider each fault one at a time i e no coincidental faults determining whether or not each fault could independently account for all measurements and symptoms in this circuit Fault Possible Impossible Circuit breaker off Touch screen panel malfunctioning Programming error in PLC Faulted power cable between VFD and motor Faulted power cable between breaker and VFD Analog output card malfunctioning Shorted signal cable Finally identify the next diagnostic test or measurement you would make o
22. and normally closed M contacts provide seal in and interlock functions respectively The time delay relays prevent the motor from being immediately reversed Answer 60 ie en i ollel lelle lele lelo 2 2 e l e e Pa eee a 2121212 Answer 61 This is a graded question no answers or hints given Answer 62 This is a graded question no answers or hints given Answer 63 This is a graded question no answers or hints given Answer 64 This is a graded question no answers or hints given Answer 65 This is a graded question no answers or hints given Answer 66 This is a graded question no answers or hints given 113 Answer 67 This is a graded question no answers or hints given Answer 68 This is a graded question no answers or hints given Answer 69 This is a graded question no answers or hints given Answer 70 This is a graded question no answers or hints given Answer 71 Answer 72 For the Allen Bradley MicroLogix example the lamp will energize only when switch 0 is turned off and switch 1 is turned on For the Siemens 7 200 example the lamp will energize when switch 0 is turned on or if switch 1 is turned off or both conditions occur simultaneously For the Koyo example the lamp will energize according to the Exclusive OR function with switch 1 and switch 2 The lamp energizes when switch
23. as well file 100799 64 Question 57 Determine what each of the lamps will do in the following circuit when pushbutton A is pressed for 10 seconds and then released Time delay relays are important circuit elements in many applications L wn xe Cc O O Yn lt Show your answer by completing this timing diagram For each of the relay contacts shown in this circuit identify whether it would be properly called an on delay or an off delay contact file 102500 65 Question 58 An electric motor is used to power a large conveyor belt Before the motor actually starts a warning siren activates to alert workers of the conveyor s forthcoming action The following relay circuit accomplishes both tasks motor control plus siren alert L L Stop Start ale 5 sec Study this ladder logic diagram then explain how the system works file 102501 66 Question 59 The following ladder logic diagram is for a reversing motor control circuit L Bi ee M2 M OL M1 Reverse ae M2 M1 OL To 3 phase power source al M2 L Study this diagram then explain how motor reversal is accomplished Also identify the function of each M contact in the control circuit especially those normally closed contacts in series with the motor starter coils Now consider the following modification made to the reversing motor control circuit motor and power contacts not shown her
24. diagram must be comprehensive and detailed showing every wire connection every cable every terminal block etc The principle to keep in mind here is to make the schematic diagram so complete and unambiguous that anyone can follow it to see what connects to what even someone unfamiliar with motor control circuits In industry systems are often constructed by contract personnel with limited understanding of how the system is supposed to function The schematic diagrams they follow must be so complete that they will be able to connect everything properly without necessarily understanding how it is supposed to work Note that each and every wire in your system needs to be labeled with a number Wires electrically common to each other at all times i e connected at terminal blocks not passing through any component must bear the same label number An easy way to label wires is to wrap a short piece of masking tape around each wire then writing on that masking tape with a permanent marker Furthermore each number or other label appearing on a device terminal e g the screw terminals on an octal base relay socket must be shown on your schematic diagram in parentheses to distinguish those labels from wire numbers used to identify wires With each wire and each device terminal clearly labeled one cannot go wrong in re connecting wires that were undone This is important when technicians remove components for repair and replacement as the schematic diagra
25. e What are some of the advantages that proximity switches have over traditional direct contact limit switches e What are some good applications where we could use proximity switches in industry e Suppose you needed to make a DC proximity switch with transistor output switch power to an AC load How could you accomplish this function since the proximity switch can only handle DC not AC file 104504 27 Question 11 An improvement over direct contact limit switches for many applications is the inductive proximity switch This type of switch actuates simply when an object gets near it no direct physical contact necessary Explain how these devices work and what kinds of material they are able to detect Inductive proximity switches are powered devices by necessity They usually require a DC voltage for power and their output is usually not a dry switch contact Instead it is usually a transistor with the output signal being standard TTL logic 0 to 5 volts Inductive proximity switches are often manufactured as three wire devices Switch actuates when object approaches this end fe Show how you would connect the limit switch in the above illustration so that it makes the LED turn on when actuated assuming the switch s internal transistor is configured to source current through the output lead Suggestions for Socratic discussion Identify an object a capacitive proximity switch would be able to
26. from the BTC campus Y network drive Enter your quiz scores test scores lab scores and attendance data into this Excel spreadsheet and it will calculate your course grade You may compare your calculated grades against your instructors records at any time Identify courses to register for read the Sequence page found in each worksheet Identify scholarship opportunities check your BTC email in box daily Identify job openings regularly monitor job search websites Set up informational interviews at workplaces you are interested in Participate in jobshadows and internships Apply to jobs long before graduation as some employers take months to respond Check your BTC email account daily because your instructor broadcast emails job postings to all students as employers submit them to BTC Impress employers sign the FERPA release form granting your instructors permission to share academic records then make sure your performance is worth sharing Document your project and problem solving experiences for reference during interviews Honor all your commitments Begin your career participate in jobshadows and internships while in school to gain experience and references Take the first Instrumentation job that pays the bills and give that employer at least two years of good work to pay them back for the investment they have made in you Employers look at delayed employment as well as short employment spans very negatively Failure to p
27. full lab session 3 hours if all components are readily available and the team is working efficiently 87 Lab Exercise insulation tester usage An insulation tester is a special kind of ohmmeter designed to detect high resistance paths for electric current in the hundreds of megaohms The purpose of using an insulation tester when checking the integrity of electric motors and motor control circuits is to reveal any breakdowns of electrical insulation that might not otherwise be detected using a regular low range ohmmeter What makes an insulation tester different from a regular ohmmeter is its use of relatively high voltage to perform the test Unlike a regular ohmmeter which only applies a few volts or even just a few tenths of a volt for many modern DMM ohmmeter functions to the circuit under test an insulation tester contains within it a high voltage generator capable of supplying hundreds or even thousands of volts to the test leads in order to stress the circuit under test and reveal any breakdown of insulation This makes an insulation tester capable of delivering an electrical shock to the user if incorrectly operated Legacy insulation testers especially the Megger brand whose name has become synonymous with insulation test instruments used hand crank electromechanical generators to create this high voltage Early Megger testers actually had a small crank handle protruding from the side which the user would turn a
28. how an insulation tester might cause damage to circuit components if improperly used Explain how to configure a multi voltage induction motor for different operating voltages given the information shown on a motor nameplate Explain what arc flash and arc blast are and what causes these effects e Explain how overload heaters in a motor control circuit perform a function fundamentally different from a fuse or a circuit breaker e Mental math no calculator allowed e Convert horsepower rating of a three phase AC electric motor into a current rating at a specified line voltage Convert current rating of a three phase AC electric motor into a horsepower rating at a specified line voltage e Diagnostics e Determine whether or not a given diagnostic test will provide useful information given a set of symptoms exhibited by a failed system Identify at least two plausible faults given the results of a diagnostic test and a set of symptoms exhibited by a failed system Propose a diagnostic test for troubleshooting a failed system and then explain the meanings of two different test results 94 Lab Exercise decommissioning and clean up The final step of this lab exercise is to decommission your team s entire system and re stock certain components back to their proper storage locations the purpose of which being to prepare the lab for the next lab exercise Remove your system documentation e g wiring diagram from the common holding
29. not having to be in sequence while others are offered three out of the four quarters and must be taken in sequence The following layout shows four typical course sequences for second year Instrumentation students depending on when they first enter the second year of the program Possible course schedules depending on date of entry into 2nd year Beginning in Summer Beginning in Fall Beginning in Winter Beginning in Spring Jan Winter quarter INST 200 1 wk Intro to Instrumentation INST 250 5 cr Final Control Elements INST 251 5 cr PID Control INST 252 4 cr Loop Tuning CHEM amp 161 5 cr Chemistry Jan Winter quarter INST 205 1 cr Job Prep INST 250 5 cr Final Control Elements Mar INST 251 5 cr PID Control INST 252 4 cr Loop Tuning CHEM amp 161 5 cr Jan Winter quarter Mar Chemistry INST 205 1 cr Job Prep Graduation Graduation Graduation Graduation INST 250 5 cr Final Control Elements INST 251 5 cr PID Control INST 252 4 cr Loop Tuning CHEM amp 161 5 cr Chemistry Mar Jan Winter quarter INST 206 1 cr Job Prep Il INST 250 5 cr Final Control Elements INST 251 5 cr PID Control INST 252 4 cr Loop Tuning CHEM amp 161 5 cr Mar Chemistry file sequence 11
30. recommended ADDITIONAL INSTRUCTIONAL RESOURCES The BTC Library hosts a substantial collection of textbooks and references on the subject of Instrumentation as well as links in its online catalog to free Instrumentation e book resources available on the Internet BTCInstrumentation channel on YouTube http www youtube com BTCInstrumentation hosts a variety of short video tutorials and demonstrations on instrumentation ISA Student Section at BTC meets regularly to set up industry tours raise funds for scholarships and serve as a general resource for Instrumentation students Membership in the ISA is 10 per year payable to the national ISA organization Membership includes a complementary subscription to InTech magazine ISA website http www isa org provides all of its standards in electronic format many of which are freely available to ISA members Cad Standard CadStd or similar AutoCAD like drafting software useful for sketching loop and wiring diagrams Cad Standard is a simplified clone of AutoCAD and is freely available at http www cadstd com CAMPUS EMERGENCIES If an emergency arises your instructor may inform you of actions to follow You are responsible for knowing emergency evacuation routes from your classroom If police or university officials order you to evacuate do so calmly and assist those needing help You may receive emergency information alerts via the building enunciation system text message ema
31. techniques to dynamic braking In each of these techniques where does the grinding wheel s kinetic energy go during the braking process file 103843 47 Question 39 This lift station pump control circuit has a problem The sump pump is supposed to come on when the high level is reached and turn off when the water pumps down to the low level point Instead however the motor cycles on and off at the high level point M1 OL To 3 phase AC power rotor 480 V 120 VAC LSH B LSL o M1 e G Using an AC voltmeter you measure a voltage from point D to point E that switches back and forth between 120 volts and 0 volts Identify the likelihood of each specified fault for this circuit Consider each fault one at a time i e no coincidental faults determining whether or not each fault could independently account for all measurements and symptoms in this circuit Fault Possible Impossible High level switch failed open Low level switch failed open Broken wire between D and M1 coil Contactor auxiliary contact failed open 480 volt fuse s blown Contactor main contact s failed open Broken wire between B and G Thermal overload unit tripped Low level switch failed shorted Transformer secondary winding failed open Finally identify the next diagnostic test or measurement you would make on this system Explain how the result s of this next te
32. to the wastewater treatment plant usually located miles away From homes From homes From homes To WWTP Tilt switches often use a small glass vial containing liquid mercury as the tilt sensor Explain how a glass tube partially filled with mercury works as an electrical tilt switch and also perform a thought experiment where you describe this system s function from start to finish through a complete start stop cycle of the pump motor L L LSL LSH MI OL M1 M1 OL To 3 phase AC power Suggestions for Socratic discussion What would happen if the OL switch failed open in this system What would happen if the LSL switch failed open in this system What would happen if the LSH switch failed open in this system What would happen if the LSL switch failed shorted in this system What would happen if the LSH switch failed shorted in this system What would happen if the LSH switch failed shorted in this system 25 e What would happen if the M1 seal in contact failed open in this system e What would happen if the M1 seal in contact failed shorted in this system file 100303 Question 9 Examine this ladder diagram for a solenoid valve control circuit where the status of a solenoid valve either on or off is controlled by hand switches and a pressure switch Suppose the solenoid valve refuses to energize when the Hand Off Auto switch has been placed in Auto the Reset pushb
33. what is meant by the normally closed NC and normally open NO labels next to two of the electrical screw terminals Identify the status of the switch when process pressure exceeds the switch s set value file 100222 30 Question 15 Two pressure switches are plumbed together so as to receive the exact same pressure at all times and they both sense the pressure of compressed air in a pneumatic system Based on the wiring diagram for these switches identify the function of the lamp L L 85 PSI 115PSI file 102964 Question 16 Identify which lamp in the following ladder logic diagram is the high flow alarm and which is the low flow alarm given the flow switch symbols shown L L file 100548 Question 17 Label the components in this ladder diagram for a pressure alarm circuit identifying the following L L e Which lamp is the low pressure warning lamp e Which lamp is the high pressure warning lamp e Which pressure switch should have the low pressure trip point of 10 PSI e Which pressure switch should have the high pressure trip point of 250 PSI file 103967 31 Question 18 Identify the state of the light bulb when the normally closed pressure switch contact opens To 480 volt AC source Pressure switch To process impulse tube connection Assuming the light bulb functions as a pressure alarm to alert operators to an unsafe condition determine whether this i
34. you can wire most VFDs to input single phase AC power and output three phase AC power so he buys a used VFD and wires it up in this manner to power his lathe Not only does this fix allow him to run his lathe on single phase power but it also gives him the ability to vary the lathe s motor speed and also to suddenly stop it if needed Now this particular VFD is an inexpensive model and it has no braking resistor connected to it Based on this information identify the likely technique this VFD uses to brake the lathe motor and identify where the lathe s kinetic energy will be dissipated Suggestions for Socratic discussion e What are some alternative braking techniques to dynamic braking In each of these techniques where does the grinding wheel s kinetic energy go during the braking process e Explain what would happen to a VFD with dynamic braking if the braking resistor failed open e Explain what would happen to a VFD with dynamic braking if the braking resistor failed shorted e Explain what would happen to a VFD s braking ability if the circuit breaker feeding AC line power to it were to trip open file 103871 55 Question 47 A technician has wired a proximity switch to a relay such that one LED lamp is supposed to come on when nothing is near the switch and the other lamp is supposed to come on when the switch detects the presence of a metal object 24 VDC supply Proximity switch How
35. 1 is on and switch 2 is off or when switch 1 is off and switch 2 is on 114
36. EAE ee eee SIMATIC IM 1L 00 o1 02 03 04 2M a 05 06 o7 10 14 e m wt ovo 7 200 CPU 224XP on0000000400 DC DC DC CI SF DIAG WA A G S B N CI RUN CI STOP ROG E E S Gaez Ao al 22 eh eh i W OOOOOO00 10o00000 0 0 0 1 02 03 0 05 06 07 2M 10 11 12 13 14 15 M L 22000000 208 Port 1 Port 0 Ladder Diagram program written to PLC TOTO Q0 0 END Note how Siemens I O is labeled in the program input bits designated by the letter I and output bits designated by the letter Q Based on the wiring and program you see for this PLC identify the switch state combinations resulting in an energized lamp Try duplicating this program in your own PLC even if it is a different brand or model and see how it functions Be sure to activate the color highlighting feature of your programming editor so you may see the live status of the program s virtual contacts and coil 99 This example shows a Koyo CLICK PLC model C0 02DD1 D wired to two toggle switches and one LED indicator lamp complete with a demonstration program CLICK C0 02DD1 D Koyo PWR J RUN J ERR J LED with dropping resistor RUN PORT 1 1 CO RX1 LI TX2 LI RX2 LI PORT 2 PORT3 RS 485 T 3 LI RX3 CI 2 LG SKKNI 24 VDC Ladder Diagram program written to PLC Wal KI 2 x2 7 END Note how Koyo I O is labe
37. INST 230 Motor Controls section 2 Lab Reversing three phase motor starter circuit and PLC trainer construction Question 71 completed objectives due by the end of day 4 PLC trainer details Question 72 Exam Day 4 only a simple calculator may be used Specific objectives for the mastery exam Electricity Review Calculate voltages and currents in a DC series parallel resistor circuit given source and resistor values e Sketch proper wire connections for a relay control circuit e Determine status of a relay logic circuit given a schematic diagram and switch stimulus conditions e Calculate either the full load current or the horsepower of an electric motor single phase given the line voltage and one of the other parameters e Solve for a specified variable in an algebraic formula e Determine the possibility of suggested faults in a simple circuit given measured values voltage current a schematic diagram and reported symptoms e INST241 Review Identify American wire colors for different thermocouple types e INST251 Review Determine the effect of a component fault or condition change in a single loop controlled process INST260 Review Convert between different numeration systems decimal binary hexadecimal octal Recommended daily schedule Day 1 Theory session topic Process switches and control circuits Questions 1 through 20 answer questions 1 9 in preparation for discussion remainder
38. ON off t2 t3 off ON off ON ON off t3 t4 off ON ON off ON off t4 ts off ON ON off off ON ts te ON off ON off off ON te t7 ON off off ON off ON If PWM is being used to modulate the output into a quasi sine wave then the ON states shown in the table do not necessarily represent full continuous on states within the specified timeframes but rather series of on off pulses The off states shown in the table however do indeed represent full continuous off states within each specified timeframe To be more precise in my answer the table should look like this Time period Q Q2 Q3 Qs Qs Q6 ty te pulse off off pulse pulse off to t3 off pulse off pulse pulse off t3 t4 off pulse pulse off pulse off t4 ts off pulse pulse off off pulse ts te pulse off pulse off off pulse te t7 pulse off off pulse off pulse Answer 41 Answer 42 Answer 43 Answer 44 Partial answer The line voltage at the generator bus is given to us by the alternator rating of 4160 volts Unless otherwise specified the voltage or current rating of a three phase device is always a line quantity 108 Answer 45 Here are some possibilities Fuse 3 blown open Third relay contact damaged failed open inside the contactor Overload heater 3 failed open One winding failed open inside the motor assuming a Y winding configurat
39. al or practical weakness Then both will work together to select an appropriate extra credit activity focusing on those identified weaknesses for the purpose of strengthening the student s competence A due date will be assigned typically two weeks following the request which must be honored in order for any credit to be earned from the activity Extra credit may be denied at the instructor s discretion if the student has not invested the necessary preparatory effort to perform well e g lack of preparation for daily class sessions poor attendance no feedback questions submitted etc REQUIRED STUDENT SUPPLIES AND MATERIALS Course worksheets available for download in PDF format Lessons in Industrial Instrumentation textbook available for download in PDF format Access worksheets and book at http www ibiblio org kuphaldt socratic sinst Ampacity ratings of wire from the National Electrical Code NFPA 70 reference available for free online viewing at http www nfpa org NFPA 70E Standard for Electrical Safety in the Workplace Spiral bound notebook for reading annotation homework documentation and note taking Instrumentation reference CD ROM free from instructor This disk contains many tutorials and datasheets in PDF format to supplement your textbook s Tool kit see detailed list Simple scientific calculator non programmable non graphing no unit conversions no numeration system conversions TI 30Xa or TI 30XIIS
40. and or the VFD After this you may try running the motor The VFD should provide pushbutton or knob control of the motor s speed as well as Start and Stop functions Suggestions for Socratic discussion e Describe by way of illustration what may happen if the base parameters within a VFD are set incorrectly being as specific as possible 37 e Some large VFDs need to be gently powered up if they have been left un powered for long periods of time to avoid shocking the capacitors used to filter their DC busses Identify a means of doing so i e limiting the inrush current that will occur when fully discharged capacitors are connected to a voltage source that is easy and safe to implement Describe a realistic example of how improper base parameters set in a VFD could cause trouble How should one set the accel and decel times if the goal is to absolutely minimize inrush current Explain why a deceleration time that is too short may result in a VFD DC bus overvoltage condition How do the accel and decel features of the VFD duplicate the function of a soft start unit file 104295 Question 28 Use a clamp on ammeter to measure line current to the VFD and or from the VFD to the motor Compare the measurement given by the ammeter when it is clamped around a single conductor versus when it is clamped around multiple conductors Does it register differently Why or why not Another interesting expe
41. and what kinds of material they are able to detect Inductive proximity switches are powered devices by necessity They usually require a DC voltage for power and their output is usually not a dry switch contact Instead it is usually a transistor with the output signal being standard TTL logic 0 to 5 volts Inductive proximity switches are often manufactured as three wire devices Switch actuates when object approaches this end fe Show how you would connect the limit switch in the above illustration so that it makes the LED turn on when actuated assuming the switch s internal transistor is configured to sink current through the output lead Suggestions for Socratic discussion Identify an object an inductive proximity switch would be able to detect Identify an object an optical proximity switch would be able to detect Identify an object a capacitive proximity switch would not be able to detect Identify an object an ultrasonic proximity switch would not be able to detect file 102244 Question 5 Read and outline the Pressure Switches section of the Discrete Process Measurement chapter in your Lessons In Industrial Instrumentation textbook Note the page numbers where important illustrations photographs equations tables and other relevant details are found Prepare to thoughtfully discuss with your instructor and classmates the concepts and examples explored in this reading file 103934
42. apply these hours to any missed time this is not done automatically Students may donate unused sick time to whomever they specifically choose You must contact your instructor and lab team members immediately if you know you will be late or absent or must leave early Absence on an exam day will result in a zero score for that exam unless due to a documented emergency Time Management You are expected to budget and prioritize your time just as you will be on the job You will need to reserve enough time outside of school to complete homework and strategically apply your time during school hours toward limited resources e g lab equipment Frivolous activities e g games social networking internet surfing are unacceptable when work is unfinished Trips to the cafeteria for food or coffee smoke breaks etc must not interfere with team participation Independent Study This career is marked by continuous technological development and ongoing change which is why self directed learning is ultimately more important to your future success than specific knowledge To acquire and hone this skill all second year Instrumentation courses follow an inverted model where lecture is replaced by independent study and class time is devoted to addressing your questions and demonstrating your learning Most students require a minimum of 3 hours daily study time outside of school Arriving unprepared e g homework incomplete is unprofessio
43. area either discarding it or keeping it for your own records Also remove all wire labels from wiring and cables Leave the following components in place mounted on the racks Large electric motors Large variable frequency drive VFD units Cables inside conduit interconnecting junction boxes together Pipe and tube fittings do not unscrew pipe threads Supply air pressure regulators Return the following components to their proper storage locations e Manual e g pushbutton switches e Jumper cables used to connect terminal blocks within a single junction box e Power cables and extension cords 95 Lab Exercise tool kit and email usage Two additional objectives that are not technically a part of making this lab project function but are nevertheless very important to your continued success in the Instrumentation program include assembling a personal tool kit and using your BTC email account which is automatically created for every student at the college You will be using your tool kit throughout the remainder of this program and so it is very important to have it complete and ready to use by the end of this lab exercise Note that there are several optional items listed in addition to mandatory items These optional tools are useful but not 100 necessary for the work you will be doing in the lab Also note that there are some consumable items in your tool list such as electrical compression terminals which you will n
44. ass a drug test is an immediate disqualifier as is falsifying any information Criminal records may also be a problem file howto General Values and Expectations Success in this career requires professional integrity resourcefulness persistence close attention to detail and intellectual curiosity Poor judgment spells disaster in this career which is why employer background checks including social media and criminal records and drug testing are common The good news is that character and clear thinking are malleable traits unlike intelligence these qualities can be acquired and improved with effort This is what you are in school to do increase your human capital which is the sum of all knowledge skills and traits valuable in the marketplace Mastery You must master the fundamentals of your chosen profession Mastery assessments challenge you to demonstrate 100 competence with multiple opportunities to re try Failure to complete any mastery objective s by the deadline date caps your grade at a C Failure to complete by the end of the next school day results in a failing F grade Punctuality and Attendance You are expected to arrive on time and be on task all day just as you would for a job Each student has 12 hours of sick time per quarter applicable to absences not verifiably employment related school related weather related or required by law Each student must confer with the instructor to
45. asy connection and disconnection of external devices to your PLC without wearing out the screws on the PLC s terminal block prematurely Separate terminal blocks are easily replaced whereas the terminal block on your PLC is likely much more expensive and inconvenient to replace Consult the user s manual for your PLC in order to determine how all devices should be wired to the input and output I O terminals Note that often there are different types of I O AC DC sourcing sinking available for the same or similar model of PLC Most PLC user s manuals give detailed diagrams showing how to connect devices to discrete I O points so be sure to follow the proper diagram for your specific PLC model Once you have your PLC wired the next step is to install and run the software used to program your programmable logic controller PLC and try to get the two devices communicating with each other This of course requires you have a special cable connecting your PC to your PLC with any necessary drivers installed on your PC to allow it to communicate Like all serial based communications the PC needs to be properly configured with regard to bit rate number of data bits number of stop bits and parity in order to communicate with the PLC The software you will be using should have an auto detect feature which will sequentially try various combinations of these parameters until it finds one combination that works Note on Allen Bradley
46. at it does or what it fails to do Another detail important to the planning of your system is identifying the necessary gauge size of the wires used Consult article 310 of the National Electrical Code the NEC also known as NFPA 70 book regarding ampacity ratings for different gauges of stranded copper wire Your motor s nameplate will provide the information you will need on line current Planning a functioning system should take no more than an hour if the team is working efficiently and will save you hours of frustration and possible component destruction 83 Lab Exercise circuit design challenge Connect an ice cube relay to a low voltage DC source as well as 120 volts AC so that a hand operated switch will control the energization of a 120 VAC load All electrical connections must be made using a terminal strip no twisted wires crimp splices wire nuts spring clips or alligator clips permitted and the 120 VAC portion of the circuit must be fused for overcurrent protection This exercise tests your ability to properly interpret the pinout of an electromechanical relay properly wire a switch to control a relay s coil properly wire a load to the contacts of a relay properly select NO NC contacts on both the switch and the relay and use a terminal strip to organize all electrical connections Relay socket Switch Batteries 2J Fuse holder AC power AC The following comp
47. blocking harmonic frequencies generated by the VFD from corrupting the AC power supply system 3 phase 480 VAC Line reactor Suppose each winding of a line reactor for a 10 horsepower VFD has 0 119 2 of resistance and 1 5 mH of inductance Calculate the amount of impedance offered by each winding to the following harmonics Frequency f Impedance Z 60 Hz 1st harmonic 180 Hz 3rd harmonic 300 Hz 5th harmonic VEO OD OD 420 Hz 7th harmonic 540 Hz 9th harmonic Hint you may consider each reactor coil to be a series connected inductor and resistor together producing a certain amount of impedance for each frequency file 103242 77 Question 69 This multi voltage motor has been configured to operate on a power supply voltage of 480 VAC Motor winding diagram 2 5 8 3 5 3 1 480 VAC 3 phase Calculate the amount of current through each individual winding of this motor assuming a mechanical power output of 18 3 horsepower at an efficiency of 91 Assume a power factor of 1 unity Also calculate the expected voltage drop between terminals 1 and 4 on the motor while it is running file 103249 78 Question 70 A brand new control system for a chemical reaction process uses a variable frequency drive VFD to control the speed of the charge pump introducing chemical fluids into a reaction vessel This VFD gets
48. bonded to the metal subpanel Plastic wire duct will be used to route all wires between components Here is a model layout note that yours may look different Li L2 L3 Gnd Som Stop Fwd Rvs O R g a Subpanel DIN rail la All wires need to enter and exit the wire duct perpendicularly for a neat and professional appearance All conductors must be stranded copper of sufficient gauge for the full load motor current according to the National Electrical Code NEC Each wire should bear its number label at each end where it terminates Before applying power to your motor control starter circuit it must be inspected under instructor supervision Testing will be performed using a high voltage insulation tester sometimes called a Megger in honor of a proper brand name for this type of instrument to check for proper connections proper fuse operation i e when a fuse is pulled out of its socket continuity to the protected device is interrupted etc Common mistakes e Failing to tug on each and every wire where it terminates to ensure a mechanically sound connection e Students working on portions of the system in isolation not sharing with their teammates what they did and how It is important that the whole team learns all aspects of their system Building a functioning system should take no more than one
49. ctive reactance Xz As reactance decreases there is less opposition in the inductor to AC current so current increases proportionately This increased current will overheat the inductor as well as saturate its magnetic core Thus we limit inductor current to its normal value through the inductor by reducing voltage as we reduce frequency 106 Answer 34 Single phase AC power source Arrows drawn in the direction of conventional flow notation Three phase AC power source Arrows drawn in the direction of conventional flow notation Answer 35 Answer 36 Answer 37 These components will indeed resonate at 180 Hz This is a problem because 180 Hz is the 3rd harmonic of a 60 Hz AC power system and we expect significant odd harmonic frequencies to come from an operating VFD Answer 38 The braking energy here will be dissipated in a braking resistor connected to the VFD 107 Answer 39 Fault Possible Impossible High level switch failed open Low level switch failed open Broken wire between D and M1 coil Contactor auxiliary contact failed open y 480 volt fuse s blown Contactor main contact s failed open Broken wire between B and G V Thermal overload unit tripped Low level switch failed shorted Transformer secondary winding failed open SIYIN SNIS ISS Answer 40 Time period Q Q2 Q3 Q4 Qs Q6 t t2 ON off off ON
50. ctor to determine if all components will be correctly connected for their safe function For example if you intend to connect field devices to a PLC Programmable Logic Controller your prototype sketch must show how those devices will connect to typical input output terminals on the PLC where electrical power will be supplied etc Prototype sketches need not show all intermediary connections between components such as terminal blocks in junction boxes between the field device and the controller You should practice good problem solving techniques when creating your prototype sketch such as consulting equipment manuals for information on component functions and marking directions of electric current voltage polarities and identifying electrical sources loads Use this task as an opportunity to strengthen your analytical skills Remember that you will be challenged in this program to do all of this on your own during capstone assessments so do not make the mistake of relying on your teammates to figure this out for you instead treat this as a problem you must solve and compare your results with those of your teammates Your team s prototype sketch is so important that the instructor will demand you provide this plan before any construction on your team s working system begins Any team found constructing their system without a verified plan will be ordered to cease construction and not resume until a prototype plan has been drafted a
51. data to calculate a final grade for a course using the spreadsheet experiment with plugging scores into the spreadsheet to obtain the grade you would like to earn How might this be a useful strategy for you in the future e Why do you suppose this spreadsheet is provided to you rather than the instructor simply posting your grades or notifying you of your progress in the program courses e Identify any courses that are elective rather than required for your 2 year AAS degree file 102659 Question 51 Examining a squirrel cage motor rotor you see the aluminum bars of the squirrel cage assembly embedded in what appears to be a mass of iron constituting the bulk of the rotor s mass An electrician explains to you that the iron is necessary in the rotor for the stator s magnetic field to act upon Without the iron there says the electrician the rotor wouldn t spin Explain what is incorrect about the electrician s reasoning Suggestions for Socratic discussion e This is a very common misconception among students and working technicians alike Explain why so many people tend to get this concept wrong e One way to disprove an assertion is by demonstrating that the assertion leads to one or more logical absurdities This technique is called reductio ad absurdum reducing to an absurdity Apply this technique to the disproof of the assertion that iron is necessary in the rotor of an induction moto
52. detect Identify an object an ultrasonic proximity switch would be able to detect Identify an object an inductive proximity switch would not be able to detect Identify an object an optical proximity switch would not be able to detect file 102243 28 Question 12 Switches whether they be hand actuated or actuated by a physical process come in two varieties normally open NO and normally closed NC You are probably accustomed to seeing both types of switch represented in pushbutton form on schematic diagrams Normally open pushbutton switch L e o Normally closed pushbutton switch aes Pe Normally open pushbutton switches close pass current when actuated pressed When un actuated they return to their normal open state Normally closed pushbutton switches are just the opposite they open stop current when actuated pressed and return to their normal closed passing current state when un actuated This is simple enough to comprehend the normal status of a momentary contact pushbutton switch is the state it is in when no one is touching it When pressed the pushbutton switch goes to the other opposite state Things get more confusing though when we examine process switches such as pressure switches level switches temperature switches and flow switches Normally open pressure switch Normally open level switch se Normally open temperature switch a
53. diagram for the components at hand Basing your diagram off of a team mate s diagram rather than closely inspecting the system for yourself Forgetting to label all wires see example diagram Forgetting to label all terminals see example diagram Forgetting to note all wire colors Forgetting to put your name on the schematic diagram Creating and inspecting accurate schematic diagrams should take no more than one full lab session 3 hours if the team is working efficiently 86 Lab Exercise building the system After getting your wiring diagram approved by the instructor you are cleared to begin building your system Mount all control components control power transformer contactors overload unit fuse holders on a metal subpanel plate designed to insert into an electrical enclosure Locate the pushbutton switched at some other location such as the main control panel for the lab This ensures a long enough cable run for the switches to make the system realistic for testing and troubleshooting Note you must marshall all switch wiring through terminal blocks on the subpanel so that the switches may be disconnected from the rest of the control circuit without disturbing any other wiring Power to your control circuit will come through four terminals located at one edge of the metal subpanel three fused terminals for the three phase power lines L1 L2 and L3 and one unfused terminal for earth safety ground which will be
54. e L L Sto Forward p Tp2 M2 M1 OL Se l Reverse TD1 LL What extra functionality do the time delay relays contribute to this motor control circuit file 102496 68 Question 60 Draw the necessary wire connections to build the circuit shown in this ladder diagram Ladder diagram Ll L2 Start M1 Ql M1 M1 Motor Illustration showing components Relay Motor Dashed lines represent connections between relay terminals and socket screw lugs hidden from sight file 102305 69 Question 61 On a job you are asked to disconnect a five conductor cable from a terminal strip in preparation for that cable s complete removal Another technician tells you that the other end of that cable has already been completely disconnected and therefore there can be no dangerous voltage present on the cable Your next step is to confirm the absence of dangerous voltage on the conductors before physically touching any of them This confirmation of course is done with a voltmeter and we all know that voltage is measured between two points The question now is how many different combinations of points must you measure between to ensure there is no hazardous voltage present O gt 8 List all possible pairs of points you should test for voltage between in order to ensure the conductors are safe for you to touch Don t forget to include earth ground as one of thos
55. e inches e Necessary arc flash protective clothing to wear e Approach distance for a qualified worker inches e Necessary gloves to wear e Whether or not electrically insulated tools are required e Citations showing where in NFPA 70E you obtained the information 90 Lab Exercise wiring the step down transformer bank In order to power your 240 VAC or 208 VAC motor from the 480 VAC receptacle in the lab you will need to wire three transformers together to create a three phase transformer bank Here are your configuration options based on the different possible primary secondary voltage ratings available for the transformers Delta Delta configuration 480 VAC 240 VAC from receptacle to motor 480 volt primaries 240 volt secondaries Delta Wye configuration 480 VAC 208 VAC from receptacle bd a to motor A 480 volt primaries 120 volt secondaries Wye Delta configuration 480 VAC 240 VAC from receptacle to motor 277 volt primaries 240 volt secondaries Wye Wye configuration 480 VAC z 208 VAC from receptacle f A to motor 480 volt primaries 120 volt secondaries D You may have multiple options available to you depending on the rating of your motor and the particular transformers used to for the three phase bank If this is the case your instructor will choose one of the configurations for you After this you must work as a team to determine the proper phasing
56. e been left un powered for long periods of time to avoid shocking the capacitors used to filter their DC busses Identify a means of doing so i e limiting the inrush current that will occur when fully discharged capacitors are connected to a voltage source that is easy and safe to implement e Identify a practical application for a remote start stop switch such as this file 104075 39 Question 30 Connect a potentiometer to the VFD in such a way that the pot s position controls the speed of the motor rather than a knob or buttons on the VFD s front panel You will need to research the VFD s User Manual both for determining where to connect the potentiometer as well as which parameter to change to make the VFD responsive to this external pot setting Potentiometer Power plug Motor As always your wire connections should be marshalled through terminal blocks no taped or twisted wire joints with no bare copper showing at the connection points Suggestions for Socratic discussion e Describe what the base parameters in a VFD refer to and explain why these parameters are among the most important settings in the VFD Describe by way of illustration what may happen if these base parameters are set incorrectly e Some large VFDs need to be gently powered up if they have been left un powered for long periods of time to avoid shocking the capacitors used to filter their DC busses
57. e of insulated compression style fork terminals 14 to 18 AWG wire size 10 stud size Wire strippers terminal crimpers for 10 AWG to 18 AWG wire and insulated terminals Optional ratcheting terminal crimp tool e g Paladin 1305 Ferrules Direct FDT10011 or equivalent Safety e Safety glasses or goggles available at BTC bookstore e Earplugs available at BTC bookstore Miscellaneous e Simple scientific calculator non programmable non graphing no conversions TI 30Xa or TI 30XIIS recommended Required for some exams Masking tape for making temporary labels Permanent marker pen Teflon pipe tape Utility knife Tape measure 12 feet minimum Flashlight An inexpensive source of tools is your local pawn shop Look for tools with unlimited lifetime guarantees e g Sears Craftsman brand Check for BTC student discounts as well file tools 12 Methods of instruction This course develops self instructional and diagnostic skills by placing students in situations where they are required to research and think independently In all portions of the curriculum the goal is to avoid a passive learning environment favoring instead active engagement of the learner through reading reflection problem solving and experimental activities The curriculum may be roughly divided into two portions theory and practical Theory In the theory portion of each course students independently research subjects prior to entering the classroom fo
58. e points Next write a mathematical formula to calculate the number of point pair combinations i e the number of different voltage measurements that must be taken given N number of connection points in the circuit file 104258 70 Question 62 Complete the table of values for this circuit 790 Q 2 2 KQ Ri 8 6 KQ R3 Rs 8 6 kQ file 101178 71 Question 63 Sketch connecting wires such that the relay will de energize and turn on the lamp when the normally closed NC pushbutton switch is pressed Use the following schematic diagram as a guide switch Relay BEK plugged into socket Schematic diagram ale Note how the relay coil and lamp are separate parallel branches in this circuit The pushbutton switch only carries coil current while the relay s switch contact only carries lamp current file 102233 72 Question 64 Examine this switch circuit and determine what process condition s must be met in order to turn the lamp on Pressure switch Temperature switch Level switch Sensor bulb 480 VAC 120 VAC file 102227 73 Question 65 An electrician brings a motor contactor to you for testing She wants to be sure everything is in perfect working condition before she installs it into a new system Explain in detail what you would do to thoroughly test this contactor on the bench Be sure to address the following e Making sure the armature assembly moves freely e En
59. e useful Find a wiring diagram for the SMC Flex unit and identify where Start and Stop pushbutton switches may be connected to control the motor Also identify the normal status for each of these switches and explain why they are like that Suggestions for Socratic discussion e Identify some of the other useful features of this solid state soft start unit and explain how these features would be difficult or impossible to emulate using mechanical style contactors file 102991 Question 24 Read and outline the AC Motor Speed Control section of the Variable Speed Motor Controls chapter in your Lessons In Industrial Instrumentation textbook Note the page numbers where important illustrations photographs equations tables and other relevant details are found Prepare to thoughtfully discuss with your instructor and classmates the concepts and examples explored in this reading file 104498 Question 25 Read and outline the AC Motor Braking section of the Variable Speed Motor Controls chapter in your Lessons In Industrial Instrumentation textbook Note the page numbers where important illustrations photographs equations tables and other relevant details are found Prepare to thoughtfully discuss with your instructor and classmates the concepts and examples explored in this reading file 104761 Question 26 Read and outline the Use of Line Reactors section of the
60. e with your email account with password management or any other network based technology necessary for your learning at BTC the library staff are well trained and helpful in this regard Your readiness for email use will be assessed by your reply to an email message sent to you by your instructor Replying to this email message with an email message of your own is a mastery level objective for every new student in this lab exercise When you graduate from this program and enter the workforce your BTC email account will remain active for some time but not in perpetuity Therefore you must inform your instructors of your preferred email account for post graduation correspondence before you leave BTC We use email to regularly communicate job announcements of interest to graduates so it is in your best interest to remain connected file 102132 96 Question 72 In order to learn PLC programming and perform the exercises necessary for exams in this course you must have your own PLC trainer consisting of a working PLC and input switches all wired and ready to use Input switches i es es E peels 2 2 Indicator lamps All components should be securely mounted to a wood board or some other structure making it easy to transport and use You must have a terminal block in between the switches indicators and PLC I O terminals to allow for e
61. eed to keep stocked as you use them in your labwork Likewise you will be relying on email to receive important messages from your instructor s throughout the remainder of the program These messages include but are not limited to job announcements guest speaker appearances schedule changes emergency notifications scholarship announcements and feedback on your personal performance in the program The reason we use email as opposed to using learning management software is because it is imperative you learn how to appropriately use email for your chosen career Email is simply the most common and most practical medium businesses use for day to day electronic communication Every BTC student is automatically given an email account upon registration and this account remains active for some time after graduation If you would rather not add one more email account to your electronic life there is the option of having all messages received in your BTC email inbox automatically forwarded to the email platform of your choice Yahoo Hotmail Gmail Live etc which may be selected as an option within your BTC email management webpage It is your responsibility to log in to your BTC email account set up any forwarding features you would like and to check your email account daily to receive these important messages The library staff at BTC provide technical support for all school related IT Information Technology needs If you are experiencing troubl
62. el Flow switch low or no flow Answer 7 Partial answer e Identify the meaning of the square boxes each one with a unique number inside these are terminals in a terminal block or terminal strip assembly e Identify the meaning of the numbers near each side of the relay contacts these are terminal numbers on the relay base the socket the relay plugs into e Identify whether the pressure switch enables the solenoid to energize under if the sensed pressure exceeds the trip point or falls below the trip point the solenoid energizes when the applied pressure rises above exceeds the trip point Answer 8 Be sure to review the operation of this simple motor start stop circuit in your answer Answer 9 Answer 10 101 Answer 11 Switch actuates when object approaches this end Answer 12 The normal condition for a process switch is the condition of least stimulus For example e A pressure switch will be in its normal state when there is minimum pressure applied e A level switch will be in its normal state when there is no level detected by the switch e A temperature switch will be in its normal state when it is cold e A flow switch will be in its normal state when there is no flow detected by the switch Answer 13 Light bulb turns off when limit switch actuates Battery Light bulb 102 Answer 14 As with all process switches the no
63. er factor correction capacitors Line reactor 1700 uF each 0 46 mH each Ti T2 T3 AC motor Calculate the resonant frequency of the circuit formed by the reactor coils and power factor correction capacitors then determine whether or not resonance will be a problem in this system Explain why or why not showing all your mathematical work Note for the sake of simplicity you may model each resonant circuit as simple pairs of one reactor coil and one capacitor in series with each other file 103133 46 Question 38 Suppose a large grinding machine used in a production machine shop is powered by an induction motor which in turn receives its electrical power from a VFD The time for this machine to coast to a stop after running at full speed is quite long owing to the mass of the spinning griding wheel This coast time has a negative effect on production because the operators must wait until the wheel finally stops before they can take the freshly ground parts off the machine and replace them with new parts to be ground Your supervisor would like to shorten this stopping time by using the dynamic braking feature of the VFD which up to this point in time had never been configured for use Explain where the stored kinetic energy of the spinning grinding wheel goes when the VFD dynamically brakes it to a quick stop Suggestions for Socratic discussion e What are some alternative braking
64. er to call the contact NO or NC if they don t know the normal operating conditions of your process and the purpose for which you will use their switch The standard convention of defining normal switch contact status as that state in a condition of minimum stimulus low pressure for a pressure switch low temperature for a temperature switch etc while potentially confusing is actually less confusing than the alternative most students immediately envision Answer 15 The lamp s illumination signifies a condition where the compressed air pressure is somewhere between 85 and 115 PSI The lamp will turn off if the pressure drops below 85 PSI or if the pressure rises above 115 PSI Answer 16 High flow alarm Low flow alarm 103 Answer 17 250 PSI need Answer 18 When the pressure switch contact opens the relay de energizes closing the normally closed relay contact and turning the light on This circuit functions as a high pressure alarm turning the light bulb on if the process pressure ever rises above switch s trip value Answer 19 There are two viable ways to connect the remote pushbutton switches to this electric actuator Connection A Connection B a Open 0 Open pen pen cI Close ci Close ose ose Stop Stop Stop Common Common Stop A good exercise in circuit analysis is to determine how the operation of these two connection schemes will differ Answer 20
65. etermine the directions of electric current where you see question marks in the following schematic diagram for a variable speed AC motor drive at the moment in time t1 specific on the oscillograph Three phase AC power source 60 Hz 1720 RPM 60 Hz Input current Output current O0 ww 7 lt 7 ti Use conventional flow notation to show current direction a positive current flowing from power source to motor and a negative current flowing from motor to power source If there is no current going through a labeled wire or component just write NO instead of drawing an arrow on the diagram Also estimate the speed of the electric motor based on the waveforms shown in the oscillographs file 101715 42 Question 33 Most AC motor drives modulate voltage to the motor in proportion to frequency This is called the volts per hertz ratio V Hz and it is often configured as a constant value for the full operating range of the motor In order to understand why motor voltage must be modulated in proportion to frequency as we vary its speed it is helpful to model the electric motor as a simple inductor powered by a variable voltage variable frequency AC power source Variable V Variable f What would happen to the inductor if we decreased the AC frequency while holding AC voltage constant file 101441 Question 34 A single phase bridge rectifier circuit is made of four diodes arranged like this
66. ever there is a problem in the wiring of this circuit First identify what this circuit will actually do Next identify the wiring problem and propose a correction so that the circuit will function as it was intended Suggestions for Socratic discussion e Is this a sinking or a sourcing proximity switch How can we tell e This is a very common wiring mistake seen in student work Explain why many people are tempted to make this mistake and how it may be avoided by thinking more carefully about the circuit s function file 103759 56 Question 48 This lift station pump control circuit has a problem The sump pump is supposed to come on when the high level is reached and turn off when the water pumps down to the low level point Instead however the motor cycles on and off at the low level point Using an AC voltmeter you measure a voltage from point B to point D that switches back and forth between 120 volts and 0 volts OL To 3 phase AC power 480 V 120 VAC Identify the likelihood of each specified fault for this circuit Consider each fault one at a time i e no coincidental faults determining whether or not each fault could independently account for all measurements and symptoms in this circuit Fault Possible Impossible High level switch failed open Low level switch failed open Broken wire between D and M1 coil Contactor auxiliary contact failed open Contactor auxiliary con
67. for practice Day 2 Theory session topic Soft start and variable frequency drives Questions 21 through 40 answer questions 21 30 in preparation for discussion remainder for practice Day 3 Theory session topic Review for exam Questions 41 through 60 answer questions 41 50 in preparation for discussion remainder for practice Feedback questions 61 through 70 are optional and may be submitted for review at the end of the day How To Access the worksheets and textbook go to the Socratic Instrumentation website located at http www ibiblio org kuphaldt socratic sinst to find worksheets for every 2nd year course section organized by quarter as well as both the latest stable and development versions of the Lessons In Industrial Instrumentation textbook Download and save these documents to your computer Maximize your learning come to school prepared each and every day this means completing all your homework before class starts Use every minute of class and lab time productively Follow all the tips outlined in Question 0 in every course worksheet as well as your instructor s advice Don t ask anyone to help you solve a problem until you have made every reasonable effort to solve it on your own Identify upcoming assignments and deadlines read the first page of each course worksheet Relate course days to calendar dates reference the calendar spreadsheet file calendar x1sx
68. fter having connected the test leads to the circuit If something went wrong and the user became shocked by the tester s output voltage they would naturally stop cranking the handle Modern insulation testers have battery powered high voltage generator circuits and use a pushbutton to trigger the application of high voltage to the circuit under test Again the notion being that anyone shocked by the output of the instrument will naturally stop pressing the button All insulation testers have rather high output impedance so that when connected across a short circuit the high voltage power source inside the tester will not be damaged by excessive current This makes insulation testers perfectly valid for testing continuity in addition to testing for the presence of non continuity i e that conductors are insulated from each other Most insulation testers provide a way to vary the amount of voltage output by the tester for different testing applications When using an insulation tester you want to use a test voltage greater than that normally experienced by the device or circuit under test in order to adequately stress that device or circuit to ensure its proper operation when energized by its normal supply voltage However you do not want to use so much voltage that you actually cause damage to the device or circuit under test This means the tester s output voltage should be configured to be just one step above the circuit s normal operat
69. he motor to spin from 0 RPM to 1800 RPM the wiper here is drawn in a position nearer 100 speed Motor 3 phase line power One day the operations manager approaches you to request you modify this speed command system so that the operators cannot call for a speed less than 100 RPM or greater than 1670 RPM You consult the manual for the motor drive and are surprised to find it lacks this sort of capability a resistance input of 0 to 10 kQ will only translate to a speed range of 0 to 1800 RPM This means you must figure out a way to set the adjustable speed range limits externally to the drive i e by limiting the range of the potentiometer s resistance adjustment You know you cannot mechanically limit the turning of the potentiometer knob but you can connect fixed value resistors to the potentiometer to electrically limit its range so that full clockwise will only command the drive to go as high as 1670 RPM and full counterclockwise will only command the drive to go as low as 100 RPM Modify this diagram to include any necessary fixed value resistors and also calculate their necessary values file 103289 76 Question 68 A common accessory device for a variable frequency drive VFD is a line reactor which is nothing more than a large inductor connected in series with each of the motor drive s power line conductors The purpose of a line reactor is to act as a low pass filter allowing 60 Hz power to the VFD but
70. i 107 Symbol m Micro 1078 Symbol p Nano 107 Symbol n Pico 10 Symbol p Femto 1071 Symbol f Atto 107 8 Symbol a Zepto 107 Symbol z Yocto 10774 Symbol y METRIC PREFIX SCALE T G M k m u n p tera giga mega kilo none milli micro nano pico POE CTO OP Ao TOP MO OTe TOT 0S roS IOIO 1 054 hecto deca deci centi h da d c Conversion formulae for temperature F C 9 5 32 C F 32 5 9 R F 459 67 K C 273 15 Conversion equivalencies for distance 1 inch in 2 540000 centimeter cm 1 foot ft 12 inches in 1 yard yd 3 feet ft 1 mile mi 5280 feet ft 16 Conversion equivalencies for volume 1 gallon gal 231 0 cubic inches in 4 quarts qt 8 pints pt 128 fluid ounces fl oz 3 7854 liters 1 1 milliliter ml 1 cubic centimeter cm Conversion equivalencies for velocity 1 mile per hour mi h 88 feet per minute ft m 1 46667 feet per second ft s 1 60934 kilometer per hour km h 0 44704 meter per second m s 0 868976 knot knot international Conversion equivalencies for mass 1 pound Ibm 0 45359 kilogram kg 0 031081 slugs Conversion equivalencies for force 1 pound force lbf 4 44822 newton N Conversion equivalencies for area 1 acre 43560 square feet ft 4840 square yards yd 4046 86 square meters m Conversion equivalencies for common pressure units either all gauge or a
71. ify the consequences of jumpering across the M contactor coil in this circuit using a piece of wire e Identify the consequences of jumpering between the Hand and Auto terminals on the manual selector switch using a piece of wire 51 file 104056 Question 43 Examine this motor control circuit designed to bring the motor to a quick halt whenever the Stop button is pressed The system uses two motor contactors F and R each one wired to power the motor in a different direction forward versus reverse L s L Speed switch F A100 RPM Explain how this automatic braking system works Suggestions for Socratic discussion Does this braking strategy remind you of one sometimes implemented in VFDs Can you think of any disadvantages to this braking scheme Modify the schematic diagram to contain a hand switch that disables the braking feature Identify any potentially dangerous failure modes in this circuit i e ways in which a component might fail that would make the motor run in a dangerous way Why doesn t the reverse contactor coil R have OL contacts connected in series like the forward contactor coil F e Identify the consequences of jumpering across the R contactor coil in this circuit using a piece of wire e Identify the consequences of jumpering across the F contactor coil in this circuit using a piece of wire e Identify the consequence
72. il or BTC s webpage http www btc ctc edu Facebook or Twitter Refer to the emergency flipchart in the lab room located on the main control panel for more information on specific types of emergencies ACCOMMODATIONS If you think you could benefit from classroom accommodations for a disability physical mental emotional or learning please contact our Accessibility Resources office Call 360 752 8345 email ar btc ctc edu or stop by the AR Office in the Admissions and Student Resource Center ASRC Room 106 College Services Building file INST230syllabus Sequence of second year Instrumentation courses Core Electronics 3 qtrs including MATH 141 Precalculus 1 Only if 4th quarter was Summer INST23x Offered 1 week of Fall Winter and Spring quarters Prerequisite for all INST24x INST25x and INST26x courses gt Prerequisite for INST206 Offered 1 week of Fall Winter and Spring quarters 10 The particular sequence of courses you take during the second year depends on when you complete all first year courses and enter the second year Since students enter the second year of Instrumentation at four different times beginnings of Summer Fall Winter and Spring quarters the particular course sequence for any student will likely be different from the course sequence of classmates Some second year courses are only offered in particular quarters with those quarters
73. ing voltage Devices most susceptible to damage from mis use of an insulation tester are semiconducting in nature Diodes transistors SRCs TRIACs and associated devices may all be damaged rather easily by the mis application of an insulation tester This means one should not use an insulation tester on a circuit containing complex and expensive semiconductor components such as variable speed motor drives VSDs or VFDs 88 Lab Exercise safety demonstrations This lab exercise more than any other harbors a significant level of personal danger due to the use of 480 VAC power Exercising safe work habits is not just an objective of this lab but it is essential for avoiding injury This lab requires you to demonstrate the following procedures e The one hand rule working only with your right hand keeping the left hand in a pocket or behind your back when working on any energized circuit e Lock out Tag out properly documenting work to be done on a tag then attaching both tag and lock to the disconnect device securing power e Attempt to start the motor as a crude check to see that power has been disconnected e Proper use of meter to check for dangerous voltage check for voltage between all possible pairs of points including earth ground and then verifying the meter s operation against a known voltage source 89 Lab Exercise hazard risk assessment Here you will work with your team to perform an asses
74. ing in your career e Classroom sessions a combination of Socratic discussion short lectures small group problem solving and hands on demonstrations experiments review and illuminate concepts covered in the preparatory questions The purpose of this is to develop problem solving skills strengthen conceptual understanding and practice both quantitative and qualitative analysis techniques e Lab activities an emphasis on constructing and documenting working projects real instrumentation and control systems to illuminate theoretical knowledge with practical contexts Special projects off campus or in different areas of campus e g BTC s Fish Hatchery are encouraged Hands on troubleshooting exercises build diagnostic skills e Feedback questions sets of practice problems at the end of each course section challenge your knowledge and problem solving ability in current as as well as first year Electronics subjects These are optional assignments counting neither for nor against your grade Their purpose is to provide you and your instructor with direct feedback on what you have learned STUDENT ASSIGNMENTS REQUIREMENTS All assignments for this course are thoroughly documented in the following course worksheets located at http www ibiblio org kuphaldt socratic sinst index html e INST230_sec1 pdf e INST230_sec2 pdf EVALUATION AND GRADING STANDARDS out of 100 for the course grade e Completion of all mastery objectives 50 Maste
75. ion There are several valid next steps you could take from this point Discuss alternatives with your classmates Answer 46 Answer 47 The way this circuit is presently wired the lower LED will always be on regardless of proximity switch status Answer 48 Partial answer Fault Possible Impossible High level switch failed open Low level switch failed open J Broken wire between D and M1 coil J Contactor auxiliary contact failed open Contactor auxiliary contact failed shorted Contactor main contact s failed open Broken wire between B and G Thermal overload unit tripped High level switch failed shorted Transformer secondary winding failed open lt n 109 Answer 49 Here is a comprehensive list of faults each one individually capable of accounting for the symptom no light and the measurement of 24 volts between C and D e Lamp burned out failed open e Wire failed open between A and C e Wire failed open between B and D Based on this short list of possible faults assuming only one of them is actually true the value of each proposed test is as follows Diagnostic test Yes No Measure Vor y Measure Vgp J Measure Vag Measure V4p Measure Vcg Measure Ver Measure current through wire connecting A and C Jumper A and C together y Jumper B and D together J Jumper A and B together J lt I v v
76. ion of the exam each re try There is no penalty levied on your course grade for re taking mastery exams but failure to successfully pass a mastery exam by the due date i e by the date of the nezt exam in the course sequence will result in a failing grade F for the course If any other mastery objectives are not completed by their specified deadlines your overall grade for the course will be capped at 70 C grade and you will have one more school day to complete the unfinished objectives Failure to complete those mastery objectives by the end of that extra day except in the case of documented unavoidable emergencies will result in a failing grade F for the course Lab questions are assessed by individual questioning at any date after the respective lab objective mastery has been completed by your team These questions serve to guide your completion of each lab exercise and confirm participation of each individual student Grading is as follows full credit for thorough correct answers half credit for partially correct answers and zero credit for major conceptual errors All lab questions must be answered by the due date of the lab exercise Extra credit opportunities exist for each course and may be assigned to students upon request The student and the instructor will first review the student s performance on feedback questions homework exams and any other relevant indicators in order to identify areas of conceptu
77. ipment outside of school e g at their place of employment if applicable Labwork completed outside of school must be validated by a supervisor and or documented via photograph or videorecording Conventional students may opt to switch to distance mode at any time This has proven to be a benefit to students whose lives are disrupted by catastrophic events Likewise distance students may switch back to conventional mode if and when their schedules permit Although the existence of alternative modes of student participation is a great benefit for students with challenging schedules it requires a greater investment of time and a greater level of self discipline than the traditional mode where the student attends school for 6 hours every day No student should consider the distance mode of learning a way to have more free time to themselves because they will actually spend more time engaged in the coursework than if they attend school on a regular schedule It exists merely for the sake of those who cannot attend during regular school hours as an alternative to course withdrawal file distance 15 Metric prefixes and conversion constants Metric prefixes Yotta 1074 Symbol Y Zeta 107 Symbol Z Exa 10 8 Symbol E Peta 10 Symbol P Tera 10 Symbol T Giga 10 Symbol G Mega 10 Symbol M Kilo 10 Symbol k Hecto 10 Symbol h Deca 10 Symbol da Deci 107 Symbol d Centi 107 Symbol c Mill
78. ketch the proper wire connections to create just such a wye delta motor starter Hint terminals 1 2 and 3 of the motor always connect to the three phase power lines Start 4H 4 Motor Fuses m To three phase m power source 4h 4b 4b Suggestions for Socratic discussion e Explain the purpose of using reduced voltage starting for a large electric motor file 103870 35 Question 23 Read portions of the Rockwell SMC Flex motor controller Application Guide publication 150 AT002B EN P June 2004 and answer the following questions Devices such as the SMC Flex motor controller are often referred to in the industry as solid state soft start units Explain what is meant by the term soft start and why this feature might be desirable for large AC induction motors Explain how SCRs Silicon Controlled Rectifiers are used to provide reduced voltage starting for any electric motor receiving its three phase power through an SMC Flex unit How does this technique compare with other methods of reduced voltage starting In addition to using SCRs to control motor voltage the SMC Flex unit also contains an SCR bypass contactor Explain what this is and under what conditions it pulls in operates One of the additional features provided by this motor controller is something called kickstart Explain what this feature is how it works and identify an application where it might b
79. led in the program input bits designated by the letter X and output bits designated by the letter Y Based on the wiring and program you see for this PLC identify the switch state combinations resulting in an energized lamp Try duplicating this program in your own PLC even if it is a different brand or model and see how it functions Be sure to activate the color highlighting feature of your programming editor so you may see the live status of the program s virtual contacts and coil file 104513 100 Answers Answer 1 Answer 2 Answer 3 Answer 4 Answer 5 Answer 6 e PSL Pressure Switch Low e PSH Pressure Switch High e PSHH Pressure Switch High High Both warning lamps should be off when the steam pressure is between 80 and 200 PSI The boiler will automatically shut down when the shutdown solenoid de energizes and this will happen if the steam pressure exceeds 220 PSI for at least 10 seconds The difference between a normally open process switch and a normally closed process switch is vitally important for technicians to understand The normal condition referred to in each label does not mean the condition that is typical for the process Rather it refers to a condition where the switch is subjected to minimum stimulus In other words the normal condition for each switch is Temperature switch cold Pressure switch low or no pressure Level switch empty vess
80. ll absolute 1 pound per square inch PSI 2 03602 inches of mercury in Hg 27 6799 inches of water in W C 6 894757 kilo pascals kPa 0 06894757 bar 1 bar 100 kilo pascals kPa 14 504 pounds per square inch PSI Conversion equivalencies for absolute pressure units only 1 atmosphere Atm 14 7 pounds per square inch absolute PSIA 101 325 kilo pascals absolute kPaA 1 01325 bar bar 760 millimeters of mercury absolute mmHgA 760 torr torr Conversion equivalencies for energy or work 1 british thermal unit Btu International Table 251 996 calories cal International Table 1055 06 joules J 1055 06 watt seconds W s 0 293071 watt hour W hr 1 05506 x 101 ergs erg 778 169 foot pound force ft lbf Conversion equivalencies for power 1 horsepower hp 550 ft lbf s 745 7 watts W 2544 43 british thermal units per hour Btu hr 0 0760181 boiler horsepower hp boiler Acceleration of gravity free fall Earth standard 9 806650 meters per second per second m s 32 1740 feet per second per second ft s 17 Physical constants Speed of light in a vacuum c 2 9979 x 108 meters per second m s 186 281 miles per second m s Avogadro s number N4 6 022 x 10 per mole mol Electronic charge e 1 602 x 107 Coulomb C Boltzmann s constant k 1 38 x 107 3 Joules per Kelvin J K Stefan Boltzmann constant o 5 67 x 1078
81. lyze its function before constructing it Identify what it is you need to solve identify all relevant data identify all units of measurement identify any general principles or formulae linking the given information to the solution and then identify any missing pieces to a solution Annotate all diagrams with this data Perform thought experiments to explore the effects of different conditions for theoretical problems When troubleshooting real systems perform diagnostic tests rather than visually inspecting for faults Simplify the problem and solve that simplified problem to identify strategies applicable to the original problem e g change quantitative to qualitative or visa versa substitute easier numerical values eliminate confusing details add details to eliminate unknowns consider simple limiting cases apply an analogy Often you can add or remove components in a malfunctioning system to simplify it as well and better identify the nature and location of the problem Work backward from a hypothetical solution to a new set of given conditions How to create more time for study Kill your television and video games Seriously these are incredible wastes of time Eliminate distractions e g cell phone internet socializing in your place and time of study Use your in between time productively Don t leave campus for lunch Arrive to school early If you finish your assigned work early
82. m is their only guide to proper re connection of the new or repaired components When your entire team is finished drafting your individual schematic diagrams call the instructor to do an inspection of the system Here the instructor will have students take turns going through the entire system with the other students checking their diagrams for errors and omissions along the way During this time the instructor will also inspect the quality of the installation identifying problems such as frayed wires improperly crimped terminals poor cable routing missing labels lack of wire duct covers etc The team must correct all identified errors in order to receive credit for their system After successfully passing the inspection each team member needs to place their schematic diagram in the diagram holder located in the middle of the lab behind the main control panel When it comes time to troubleshoot another team s system this is where you will go to find a schematic diagram for that system 85 Note that this sample diagram is shown only to illustrate the conventions you should use in documenting wire labels terminal labels etc Your team s diagram will differ substantially from this one most notably because it is a reversing motor control circuit whereas this example diagram shows a one directional motor control circuit 480x120 VAC control power transformer Terminal labels shown as red letters Wire labels shown as blue number
83. ments e Incorrect multimeter usage e g AC rather than DC wrong range wrong test lead placement This is especially true when a student comes to lab unprepared and must borrow someone else s meter that is different from theirs Remember that the purpose of the troubleshooting exercise is to foster and assess your ability to intelligently diagnose a complex system Finding the fault by luck or by trial and error inspection is not a successful demonstration of skill The only thing that counts as competence is your demonstrated ability to logically analyze and isolate the problem correctly explaining all your steps Troubleshooting takes a lot of lab time usually at least two 3 hour lab sessions for everyone in a full class to successfully pass Be sure your team budgets for this amount of time as you plan your work and also be sure to take advantage of your freedom to observe others as they troubleshoot to better learn this art 93 Lab questions e Wiring connections e Determine correct wire connections between components to create a working 3 phase motor control circuit based on diagrams of components with terminals labeled Commissioning and Documentation Explain the meanings of the various ratings specified on a motor nameplate Explain the meanings of the coil and contact ratings specified on a contactor nameplate Explain how an insulation tester may be used to test the integrity of an electric motor s windings Explain
84. n this system Explain how the result s of this next test or measurement help further identify the location and or nature of the fault file i00067 79 Question 71 Lab Exercise introduction Your team s task is to construct a three phase reversing motor starter circuit complete with a transformer bank to convert 480 VAC power to 240 VAC or 208 120 VAC power You will also demonstrate proper safety precautions appropriate for working with three phase power circuitry including lock out tag out and verification of safe conditions using a multimeter The following table of objectives show what you and your team must complete within the scheduled time for this lab exercise Note how some of these objectives are individual while others are for the team as a whole Objective completion table Performance objective Grading 1 2 3 4 Team Team meeting and prototype sketch do first mastery Circuit design challenge mastery SSeS Final schematic diagram and system inspection mastery Sas Proper use of insulation tester mastery SS Safety demonstrations mastery a Hazard risk assessment as per NFPA 70E mastery Transformer bank wiring inspection mastery Proper motor control function mastery Troubleshooting mastery yem Lab question Wiring connections proportional Lab question Commissioning proportional Lab question Mental math proportional Lab questi
85. nal and counter productive Question 0 of every worksheet lists practical study tips Independent Problem Solving The best instrument technicians are versatile problem solvers General problem solving is arguably the most valuable skill you can possess for this career and it can only be built through persistent effort This is why you must take every reasonable measure to solve problems on your own before seeking help It is okay to be perplexed by an assignment but you are expected to apply problem solving strategies given to you see Question 0 and to precisely identify where you are confused so your instructor will be able to offer targeted help Asking classmates to solve problems for you is folly this includes having others break the problem down into simple steps The point is to learn how to think on your own When troubleshooting systems in lab you are expected to run diagnostic tests e g using a multimeter instead of visually seeking circuit faults as well as consult the equipment manual s before seeking help Initiative No single habit predicts your success or failure in this career better than personal initiative which is why your instructor will demand you do for yourself rather than rely on others to do for you Examples include setting up and using your BTC email account to communicate with your instructor s consulting manuals for technical information before asking for help regularly checking the course calendar and a
86. nd approved Similarly you should not deviate from the prototype design without instructor approval to ensure nothing will be done to harm equipment by way of incorrect connections Each member on the team should have ready access to this plan ideally possessing their own copy of the plan throughout the construction process Prototype design sketching is a skill and a habit you should cultivate in school and take with you in your new career When selecting components for this lab exercise you will need to choose a step down control power transformer a pair of three phase contactors one for forward and one for reverse and an overload heater assembly A three pushbutton Forward Reverse Stop control station has already been constructed for you having four wires ready to connect to your motor starter assembly Pushbutton switch station wiring diagram Stop J Fwd i Rvs Com After locating suitable components you should qualitatively test them prior to construction of your system For an electric motor this means checking continuity through all the windings For switches ohmmeter continuity measurements will tell you if the switch contacts are actuating as they should For the contactor you may manually actuate the contacts and also check the contacts and coil for continuity 82 using your ohmmeter If any component fails to respond properly notify the instructor and then tag it with a label explaining wh
87. ng scenario might stress this particular mis wired motor more than others given the improper overload heater installation file 103499 60 Question 53 Safety is a paramount concern in electrical systems Generally we try to design electrical circuits so that if and when they fail they will do so in the manner safest to those people working around them and to the equipment and process es controlled by the circuit One of the more common failure modes of circuits having wires strung through metal conduit is the accidental ground or ground fault where the electrical insulation surrounding a wire fails resulting in contact between that wire and a grounded metal surface Suppose an accidental ground were to occur at the point shown in this ladder diagram L L Master power Indicator control lamp Heater on Heater High pressure switch Relief solenoid Ground fault What would be the result of this fault Hint you will need to know something about the L1 L2 power source in order to answer this question What would be the result if the L1 L2 power connections were reversed file 102313 61 Question 54 Examine this motor control circuit for a start stop jog control L1 Explain in your own words what distinguishes the Start function from the Jog function and think of a practical application where this might be useful file 102459 62 Question 55 Predict how the operation of this m
88. nnot start lamp never energizes e Relay contact CR1 1 fails open Motor starts and lamp energizes when Start button is pressed but both immediately de energize when it is released e Relay contact CR1 2 fails open Motor run lamp turns on and off as expected but the motor itself never runs e Relay coil CR1 fails open Motor cannot start but the lamp energizes when the Start pushbutton is pressed 111 Answer 56 L L Onor 80 PSI 105Ps1 M OL OL M i ag Answer 57 Time scale 1 second per mark Each contact with an arrowhead pointed toward the energized position is an on delay contact whereas each contact with an arrowhead pointed away from the energized position i e toward the normal state is an off delay contact Time delay relays are not the easiest for some students to understand The purpose of this question is to introduce students to the four basic types of time delay relay contacts and their respective behaviors Discuss with your students how the contact symbols make sense arrows on the switch actuators describing direction of delay Note to your students how it is possible to have different types of time delay contacts actuated by the same relay coil 112 Answer 58 The siren immediately activates when the Start pushbutton is pressed and then cuts out 5 seconds later when the motor actually starts Answer 59 The normally open
89. offenses are grounds for immediate termination in this career and as such will not be tolerated here file expectations Course Syllabus INSTRUCTOR CONTACT INFORMATION Tony Kuphaldt 360 752 8477 office phone 360 752 7277 fax tony kuphaldt btc ctc edu DEPT COURSE INST 230 CREDITS 3 Lecture Hours 10 Lab Hours 50 Work based Hours 0 COURSE TITLE Motor Controls COURSE DESCRIPTION In this course you will learn how to wire configure and use electromechanical contactors to control electric motors and other discrete on off control elements for real processes You will also learn how to wire configure and use variable frequency motor controls to use three phase AC motors as final control elements Prerequisite courses ELTR145 Digital 2 and MATH amp 141 Precalculus 1 with a minimum grade of C COURSE OUTCOMES Commission analyze and efficiently diagnose motor control systems incorporating electromechanical relays and variable frequency drive VFD units COURSE OUTCOME ASSESSMENT Motor control system commissioning analysis and diagnosis outcomes are ensured by measuring student performance against mastery standards as documented in the Student Performance Objectives Failure to meet all mastery standards by the next scheduled exam day will result in a failing grade for the course STUDENT PERFORMANCE OBJECTIVES e Without references or notes within a limited time 3 hours total for each exam session
90. on Diagnostics proportional ees Decommission and lab clean up mastery Personal tool kit complete show on last day mastery as Reply to email message on BTC account mastery The only proportional scoring in this activity are the lab questions which are answered by each student individually A listing of potential lab questions are shown at the end of this worksheet question The lab questions are intended to guide your labwork as much as they are intended to measure your comprehension and as such the instructor may ask these questions of your team day by day rather than all at once on a single day In addition to this motor control system you must individually construct a PLC trainer for learning PLC programming An example is documented in the next question of this worksheet PLC objective completion table Performance objective Grading 1 2 3 4 Team All components unwired before construction mastery All inputs switches function properly mastery All outputs lights function properly mastery It is essential that your team plans ahead what to accomplish each day A short 10 minute team meeting at the beginning of each lab session is a good way to do this reviewing what s already been done what s left to do and what assessments you should be ready for There is a lot of work involved with building documenting and troubleshooting these w
91. one as a team with instructor One or two days Each team member calibrates configures the instrument s Remaining days up to last Each team member troubleshoots the instrument loop 3 End of practical lab session debriefing where each team reports on their work to the whole class Troubleshooting assessments must meet the following guidelines e Troubleshooting must be performed on a system the student did not build themselves This forces students to rely on another team s documentation rather than their own memory of how the system was built e Each student must individually demonstrate proper troubleshooting technique e Simply finding the fault is not good enough Each student must consistently demonstrate sound reasoning while troubleshooting e Ifa student fails to properly diagnose the system fault they must attempt as many times as necessary with different scenarios until they do reviewing any mistakes with the instructor after each failed attempt file instructional 14 Distance delivery methods Sometimes the demands of life prevent students from attending college 6 hours per day In such cases there exist alternatives to the normal 8 00 AM to 3 00 PM class lab schedule allowing students to complete coursework in non traditional ways at a distance from the college campus proper For such distance students the same worksheets lab activities exams and academic standards still apply Instead of wo
92. onents and materials will be available to you assorted ice cube relays with DC rated coils and matching sockets assorted pushbutton switches terminal strips lengths of hook up wire battery clips holders 120 VAC power cord with fuse assembly 120 VAC lamp or other suitable load Terminal strip 2 2 Je je Je fe fe e e e e e jo You will be expected to supply your own screwdrivers and multimeter for assembling and testing the circuit at your desk The instructor will supply the battery ies to power your circuit when you are ready to see if it works Until that time your circuit will remain unpowered Load switch status instructor chooses On when pressed or Off when pressed Study reference the Control Relays section of Lessons In Industrial Instrumentation 84 Lab Exercise documenting the system Given the hazards associated with three phase AC power circutry it is essential that you carefully plan your circuit in its entirety prior to assembling it For this reason the instructor will require a complete detailed schematic diagram of your motor starter circuit These diagrams must be thoroughly checked for accuracy and electrical safety to ensure no unnecessary hazards are present when power is applied A sample schematic diagram for a one direction motor starter circuit is shown on the next page Your schematic
93. ontacts How does each contactor latch itself in and keep running after its respective start pushbutton switch has been released Identify how to wire remote Stop Open and Close pushbutton switches to this actuator so that it may be operated from a remote location instead of directly at the actuator Suggestions for Socratic discussion e What advantages do electrically actuated valves enjoy over pneumatically actuated valves besides not needing a compressed air supply e What advantages do pneumatically actuated valves enjoy over electrically actuated valves e Suppose a model L120 actuator were shipped to you from the factory configured for 380 volt operation What would you have to change in order to adapt it to work on 480 volts file 102339 Question 20 33 Question 21 The most common method of starting up a three phase induction motor is to simply apply full power all at once by closing the three contacts of a large contactor relay This is called across the line starting Across the line motor starter 3 0 power oo Across the line starting is simple but results in huge inrush currents at the moment of contactor closure and also places a lot of mechanical and thermal stress on the motor as it rushes to attain full speed A gentler method of starting an induction motor is to place impedances in series with the three phase power using two contactors one start
94. or an air compressor where a pair of pressure switches controls the starting and stopping of the electric motor turning the air compressor Control circuit schematic Cut out switch Control switch Pictorial diagram of system Cut out switch Control switch Intake filter Compressor Compressed air Condensate drain valve Explain what the Hand Off Auto switch does in this circuit and also describe the functions of each pressure switch Suggestions for Socratic discussion e Which of these two pressure switches should have the greater trip setting and why e Why do you think operations personnel might find it useful to have a Hand position as well as an Auto position on the switch in this air compressor system e Some Hand Off Auto switches place the Auto position in the middle between the Hand and the Off settings explain why this might be a better way to arrange the three position switch e Identify the consequences of jumpering across the OL switch contacts in this circuit using a piece of wire e Identify the consequences of jumpering across the Cut out pressure switch contacts in this circuit using a piece of wire e Identify the consequences of jumpering across the M contactor coil in this circuit using a piece of wire e Identify the consequences of jumpering across the Control pressure switch contacts in this circuit using a piece of wire e Ident
95. orking instrument systems 80 As you and your team work on this system you will invariably encounter problems You should always attempt to solve these problems as a team before requesting instructor assistance If you still require instructor assistance write your team s color on the lab whiteboard with a brief description of what you need help on The instructor will meet with each team in order they appear on the whiteboard to address these problems 81 Lab Exercise team meeting prototype sketch and instrument selection An important first step in completing this lab exercise is to meet with your instructor as a team to discuss safety concerns team performance and specific roles for team members If you would like to emphasize exposure to certain equipment e g use a particular type of control system certain power tools techniques e g fabrication or tasks to improve your skill set this is the time to make requests of your team so that your learning during this project will be maximized An absolutely essential step in completing this lab exercise is to work together as a team to sketch a prototype diagram showing what you intend to build This usually takes the form of a simple electrical schematic and or loop diagram showing all electrical connections between components as well as any tubing or piping for fluids This prototype sketch need not be exhaustive in detail but it does need to show enough detail for the instru
96. orking independently and efficiently Failure to correctly identify both the general location and nature of the fault within the allotted time and or failing to demonstrate rational diagnostic procedure to the supervising instructor will disqualify the effort in which case the student must re try with a different fault Multiple re tries are permitted with no reduction in grade A standard multimeter is the only test equipment allowed during the time limit No diagnostic circuit breaks are allowed except by instructor permission and then only after correctly explaining what trouble this could cause in a real system The instructor will review each troubleshooting effort after completion highlighting good and bad points for the purpose of learning Troubleshooting is a skill born of practice and failure so do not be disappointed in yourself if you must make multiple attempts to pass One of the important life lessons embedded in this activity is how to deal with failure because it will eventually happen to you on the job There is no dishonor in failing to properly diagnose a fault after doing your level best The only dishonor is in taking shortcuts or in giving up Common mistakes e Neglecting to take measurements with your multimeter e Neglecting to check other measurements in the system e g pressure gauge readings e Incorrectly interpreting the wiring diagram e g thinking you re at the wrong place in the system when taking measure
97. otor control circuit will be affected as a result of the following faults Consider each fault independently i e one at a time no coincidental faults L L Stop CR1 2 Stop pushbutton switch fails open e Relay contact CR1 1 fails open e Relay contact CR1 2 fails open Relay coil CR1 fails open For each of these conditions explain why the resulting effects will occur Suggestions for Socratic discussion e Is this a single phase motor or a three phase motor How can you tell e What would need to be changed in this circuit to reverse the rotation of the motor e Suppose another technician suggests to you that the Run indicator lamp should be connected in parallel with the motor rather than in parallel with relay coil CR1 Do you think this is a good idea Why or why not e Modify this circuit to include a Jog pushbutton switch that runs the motor when pressed but immediately stops the motor when released i e no latching function file 102321 63 Question 56 Draw a ladder logic control circuit for the electric motor of an air compressor controlled by two pressure switches one switch turns the motor on when the pressure falls to 80 PSI while the other switch turns the motor off when the pressure rises to 105 PSI L L M OL Be sure to include the overload OL contact in the 120 volt control circuit L1 amp L2 and include a manual on off switch
98. our own words what each formula means and the proper units of measurement used Outline don t highlight Writing your own summary or outline is a far more effective way to comprehend a text than simply underlining and highlighting key words A suggested ratio is one sentence of your own thoughts per paragraph of text read Note points of disagreement or confusion to explore later Work through all mathematical exercises shown within the text to ensure you understand all the steps Imagine explaining concepts you ve just learned to someone else Teaching forces you to distill concepts to their essence thereby clarifying those concepts revealing assumptions and exposing misconceptions Your goal is to create the simplest explanation that is still technically accurate Write your own questions based on what you read as though you are a teacher preparing to test students comprehension of the subject matter How to effectively problem solve and troubleshoot Study principles not procedures Don t be satisfied with merely knowing how to compute solutions learn why those solutions work In mathematical problem solving this means being able to identify the practical meaning and units of measurement of every intermediate calculation In other words every step of your solution should make logical sense Sketch a diagram to help visualize the problem When building a real system always prototype it on paper and ana
99. our own benefit but not to make this answer key available to anyone else e g students Note the text on this page is not a license It is simply a handy reference for understanding the Legal Code the full license it is a human readable expression of some of its key terms Think of it as the user friendly interface to the Legal Code beneath This simple explanation itself has no legal value and its contents do not appear in the actual license file license 20 Questions Question 1 Read and outline the Normal Status of a Switch section of the Discrete Process Measurement chapter in your Lessons In Industrial Instrumentation textbook Note the page numbers where important illustrations photographs equations tables and other relevant details are found Prepare to thoughtfully discuss with your instructor and classmates the concepts and examples explored in this reading Note this is a subject of much confusion for students especially with regard to process switches such as pressure level temperature and flow switches A special practice worksheet has been made for students on this very subject called Process Switches and Switch Circuits available on the Socratic Instrumentation website Given the importance of this topic as well as the confusing meaning of the word normal when describing switch contacts this reading exercise is an excellent opportunity for you to practice active reading strategie
100. ourse calendar in electronic format Excel spreadsheet resides on the Y network drive and also in printed paper format in classroom DMC130 for convenient student access This calendar is updated to reflect schedule changes resulting from employer recruiting visits interviews and other impromptu events Course worksheets provide comprehensive lists of all course assignments and activities with the first page outlining the schedule and sequencing of topics and assignment due dates These worksheets are available in PDF format at http www ibiblio org kuphaldt socratic sinst e INST230 Section 1 Motors and relay controls 5 days theory and labwork e INST230 Section 2 Solid state motor controls 4 days theory and labwork 1 day for mastery proportional Exams METHODS OF INSTRUCTION Course structure and methods are intentionally designed to develop critical thinking and life long learning abilities continually placing the student in an active rather than a passive role e Independent study daily worksheet questions specify reading assignments problems to solve and experiments to perform in preparation before classroom theory sessions Open note quizzes and work inspections ensure accountability for this essential preparatory work The purpose of this is to convey information and basic concepts so valuable class time isn t wasted transmitting bare facts and also to foster the independent research ability necessary for self directed learn
101. own along with the motor With two overload heater assemblies in this circuit one for each direction only one of these OL heater assemblies will heat at any given time the motor is running If the motor switches direction current will now pass through the cold heater while the warm heater cools off despite the fact the motor itself continues to remain warm from use If the motor is run hard in one direction then reversed the cold overload heater assembly will not accurately reflect the pre heated status of the motor This may lead to a condition of overload where the motor is allowed to heat up too much because the too cold OL heaters haven t been heating as long as the motor has Answer 53 In a properly designed system with L2 grounded at the power source this fault will result in a blown fuse when the pressure switch closes In a circuit with L1 and L2 reversed this same ground fault would energize the relief solenoid with or without the pressure switch s permission Follow up question explain how a test instrument called a megger could be used to detect the presence of a ground fault Answer 54 The Start function is latching whereas the Jog function is not A common application of this concept is in a kitchen blender where one button starts and latches the blender while another simply pulses the blender Answer 55 e Stop pushbutton switch fails open Motor ca
102. r discussion This means working through all the day s assigned questions as completely as possible This usually requires a fair amount of technical reading and may also require setting up and running simple experiments At the start of the classroom session the instructor will check each student s preparation with a quiz Students then spend the rest of the classroom time working in groups and directly with the instructor to thoroughly answer all questions assigned for that day articulate problem solving strategies and to approach the questions from multiple perspectives To put it simply fact gathering happens outside of class and is the individual responsibility of each student so that class time may be devoted to the more complex tasks of critical thinking and problem solving where the instructor s attention is best applied Classroom theory sessions usually begin with either a brief Q amp A discussion or with a Virtual Troubleshooting session where the instructor shows one of the day s diagnostic question diagrams while students propose diagnostic tests and the instructor tells those students what the test results would be given some imagined virtual fault scenario writing the test results on the board where all can see The students then attempt to identify the nature and location of the fault based on the test results Each student is free to leave the classroom when they have completely worked through all problems and ha
103. r in order for that rotor to generate a torque e Describe the direction s that induced current s take in the bars of a squirrel cage rotor as that rotor experiences a rotating magnetic field from the stator windings of an induction motor Refer to a photograph or picture of a squirrel cage rotor or point to the rotor bars of a real rotor as you trace the directions of current with your fingers file 103970 59 Question 52 An electrician wires a reversing motor control circuit as follows 480 VAC motor power 120 VAC control power A wiser electrician warns the one who wired it that it is wrong to have multiple overload heater assemblies in a reversing motor control circuit For one motor he says there should be only one overload heater block The first electrician ignores the second one s advice and puts this reversing motor control system in service Several months later the motor fails from overheating despite the overload heater elements being properly sized for this motor Explain how it is possible for the motor to overheat in this system Suggestions for Socratic discussion e How would you have chosen to communicate the flaw to the first electrician so that your advice would be better heeded e What is the proper way to wire a single thermal overload heater in a reversing motor control circuit so that the motor gets the protection it needs e What sort of operati
104. riment is to loop a single current carrying conductor around the ammeter s jaws so that it passes through the center of the clamp more than once What effect does this arrangement have on the ammeter s reading and why Suggestions for Socratic discussion e Identify a practical application for passing all power conductors feeding a VFD through the center of a single current transformer CT What exactly would that CT s output signal represent file 103860 38 Question 29 Connect a toggle switch to the VFD in such a way that the switch status controls the starting and stopping of the motor rather than starting and stopping the motor from the VFD s front panel controls You will need to research the VFD s User Manual both for determining where to connect the switch as well as which parameter to change to make the VFD responsive to this external switch input Switch a Power plug Motor As always your wire connections should be marshalled through terminal blocks no taped or twisted wire joints with no bare copper showing at the connection points Suggestions for Socratic discussion e Describe what the base parameters in a VFD refer to and explain why these parameters are among the most important settings in the VFD Describe by way of illustration what may happen if these base parameters are set incorrectly e Some large VFDs need to be gently powered up if they hav
105. rking in small groups and in teams to complete theory and lab sections though students participating in an alternative fashion must do all the work themselves Participation via teleconferencing video or audio recorded small group sessions and such is encouraged and supported There is no recording of hours attended or tardiness for students participating in this manner The pace of the course is likewise determined by the distance student Experience has shown that it is a benefit for distance students to maintain the same pace as their on campus classmates whenever possible In lieu of small group activities and class discussions comprehension of the theory portion of each course will be ensured by completing and submitting detailed answers for all worksheet questions not just passing daily quizzes as is the standard for conventional students The instructor will discuss any incomplete and or incorrect worksheet answers with the student and ask that those questions be re answered by the student to correct any misunderstandings before moving on Labwork is perhaps the most difficult portion of the curriculum for a distance student to complete since the equipment used in Instrumentation is typically too large and expensive to leave the school lab facility Distance students must find a way to complete the required lab activities either by arranging time in the school lab facility and or completing activities on equivalent equ
106. rmal status refers to the electrical status of the switch in a condition of minimum stimulus In this particular case when the process pressure is below the set value the switch will be in its normal status as drawn in the schematic with electrical continuity between Com and NC and no electrical continuity between Com and NO It is very important to distinguish the normal status of a process switch from its typical status while installed in a working process For instance if this switch s set value was 50 PSI we could use it as a low pressure alarm PAL switch whose duty it is to energize an alarm if the process pressure ever drops below 50 PSI In this case the alarm circuit would use the Com and NC contacts on the switch with regular process pressure above 50 PSI holding the normally closed contact in its open state letting that contact fall back to its normal closed state if the process pressure ever drops below 50 PSI Here the NC contact typically resides in the open state even though it is a normally closed contact simply because of how we are using it in the process Some students may balk at this convention Why not call the contact either normally open or normally closed depending on which state that contact normally resides while operating in the process they may ask The answer is simple the switch manufacturer has no idea how you intend to use it How would they know wheth
107. ry exam score first attempt 10 Proportional exam score 30 Lab questions 10 Quiz penalty 1 per failed quiz Tardiness penalty 1 per incident 1 free tardy per course Attendance penalty 1 per hour 12 hours sick time per quarter Extra credit 5 per project All grades are criterion referenced i e no grading on a curve 100 gt A gt 95 95 gt A gt 90 90 gt B gt 86 86 gt B gt 83 83 gt B gt 80 80 gt C gt 76 76 gt C gt 73 73 gt C gt 70 minimum passing course grade 70 gt D gt 66 66 gt D gt 63 63 gt D gt 60 60 gt F A graded preparatory quiz at the start of each classroom session gauges your independent learning prior to the session A graded summary quiz at the conclusion of each classroom session gauges your comprehension of important concepts covered during that session If absent during part or all of a classroom session you may receive credit by passing comparable quizzes afterward or by having your preparatory work reading outlines work done answering questions thoroughly reviewed prior to the absence Absence on a scheduled exam day will result in a 0 score for the proportional exam unless you provide documented evidence of an unavoidable emergency If you fail a mastery exam you must re take a different version of that mastery exam on a different day Multiple re tries are allowed on a different vers
108. s Reversing motor control circuits always contain normally closed interlocking relay contacts to prevent simultaneous energization of both Forward and Reverse contactors The one direction motor control circuit shown above lacks interlock contacts because there is only one direction it can turn Feel free to consult the Typical Wiring Diagrams booklet produced by Allen Bradley for manual and magnetic full voltage starter units contained on your Instrumentation Reference This booklet shows a wide variety of starter circuit configurations including diagrams for reversing starter circuits Note that wiring diagrams for motor control circuits often take two forms schematic and pictorial Schematic diagrams are laid out in such a way as to minimize the number of wire crossings in order to aid visual analysis of the circuit Pictorial diagrams on the other hand are laid out in a manner resembling the physical orientation of circuit components and therefore typically are more difficult to analyze because there are many more wires crossing over each other in order to reach their intended terminal points It is highly recommended that you make your diagrams schematic rather than pictorial especially for ease of interpretation when you do troubleshooting on motor control circuits and must use the diagram to determine your diagnostic tests Common mistakes e Copying verbatim a sample diagram from a book rather than customizing the
109. s In particular you should write your own outline of this textbook section expressing all the major thoughts in your own words so that you will have a firmer grasp of these important concepts This should be your goal for all Read and outline assignments in order to maximize your learning file 104501 Question 2 Read and outline the Hand Switches and Limit Switches sections of the Discrete Process Measurement chapter in your Lessons In Industrial Instrumentation textbook Note the page numbers where important illustrations photographs equations tables and other relevant details are found Prepare to thoughtfully discuss with your instructor and classmates the concepts and examples explored in this reading file 104502 Question 3 Read and outline the Proximity Switches section of the Discrete Process Measurement chapter in your Lessons In Industrial Instrumentation textbook Note the page numbers where important illustrations photographs equations tables and other relevant details are found Prepare to thoughtfully discuss with your instructor and classmates the concepts and examples explored in this reading file 104503 21 Question 4 An improvement over direct contact limit switches for many applications is the inductive proximity switch This type of switch actuates simply when an object gets near it no direct physical contact necessary Explain how these devices work
110. s a low pressure alarm or a high pressure alarm Hint remember that the normal status of a switch is defined as the status of minimum stimulus when the switch is exposed to the lowest possible degree of process stimulation in this particular case to the lowest possible pressure file 103204 32 Question 19 Large shut off valves used on oil and gas pipelines are often opened and closed by electric valve actuators Such valve actuators are often used in remote locations where other sources of power such as compressed air are not available Electric valve actuators are also frequently used in water treatment facilities both for actuating valves and also large gates weirs and other water directing machinery Examine the schematic diagram on page 21 of the Limitorque L120 series actuator L120 10 through L120 40 manual published by FlowServe document FCD LMENIM1201 01 07 06 and answer the following questions Identify how the direction of the motor s rotation is controlled Specifically explain what must happen to make the motor spin in the open direction versus the closed direction Explain what the lettered taps on the control power transformer CPT are used for Under what circumstances do you think a technician would need to change the tap connections here if ever Just to the left of each motor contactor coil is a normally closed contact linked to the other contactor Explain the purpose of these c
111. s of jumpering across the normally closed F relay contacts in this circuit using a piece of wire Identify the consequences of jumpering across the normally open F relay contacts in this circuit using a piece of wire Identify the consequences of jumpering across the speed switch contacts in this circuit using a piece of wire file 103983 52 Question 44 Assuming all three alternators are equally sharing the load in this power system that the primary secondary turns ratio in the three phase transformer is 30 1 that the power factor is 1 throughout the system and that all disconnect switches are closed calculate the following Alternator Alternator Alternator 4160 VAC 4160 VAC 4160 VAC Generator bus Motor bus 0 0 2 D 2 35 HP 93 eff 35 HP 93 eff Secondary 10Q g E Load bus e Line voltage of the generator bus volts e Line voltage of the load bus volts e Line current at each alternator amps e Total power transferred in this system with all loads running kilowatts file 101046 53 Question 45 Examine this three phase motor control circuit sometimes referred to as a bucket where fuses protect against overcurrent faults a three pole relay called a contactor turns power on and off to the motor and a set of overload heaters detect mild overcurrent conditions Control circuit wiring has been omitted for simplicity s sake Only the power wiring is shown Line 1
112. sment of hazards and risks posed by a particular job assignment selected by your instructor Your assessment needs to be based on the NFPA 70E Standard for Electrical Safety in the Workplace document Your assessment shall account for arc flash as well as for electric shock and will detail necessary PPE Personal Protective Equipment and procedures necessary for safe work Your instructor will randomly select a job task Examples include e Attaching 4 20 mA wires to the back of a panel mounted loop controller while the controller is powered by 120 VAC e U e U e U e U sing a multimeter to take voltage measurements on a 208 VAC motor starter circuit while it is powered through the step down transformer bank sing a multimeter to take voltage measurements on the 480 VAC lines feeding the step down transformer bank sing a multimeter to take voltage measurements on a live 480 VAC motor starter circuit fed directly from a three phase transformer with a specified MVA rating sing a multimeter to take voltage measurements on a VFD while it is powered through an isolation transformer of specified KVA rating just like some of the VFDs in our lab e Racking in a 4160 VAC circuit breaker into a live panel e Using a clamp on ammeter to measure current through a line feeding a 480 VAC motor Here are some details which must be included in your final assessment of hazards and risks e Arc flash boundary distanc
113. ssignment deadlines avoiding procrastination fixing small problems before they become larger problems etc If you find your performance compromised by poor understanding of prior course subjects re read those textbook sections and use the practice materials made available to you on the Socratic Instrumentation website don t wait for anyone else to diagnose your need and offer help General Values and Expectations continued Safety You are expected to work safely in the lab just as you will be on the job This includes wearing proper attire safety glasses and closed toed shoes in the lab at all times implementing lock out tag out procedures when working on circuits with exposed conductors over 30 volts using ladders to access elevated locations and correctly using all tools If you need to use an unfamiliar tool see the instructor for directions Orderliness You are expected to keep your work area clean and orderly just as you will be on the job This includes discarding trash and returning tools at the end of every lab session and participating in all scheduled lab clean up sessions If you identify failed equipment in the lab label that equipment with a detailed description of its symptoms Teamwork You will work in instructor assigned teams to complete lab assignments just as you will work in teams to complete complex assignments on the job As part of a team you must keep your teammates informed of your whereabouts in the even
114. st or measurement help further identify the location and or nature of the fault file 103844 48 Question 40 This variable frequency motor drive VFD circuit converts three phase AC power at 60 Hz into rectified and filtered DC then switches that DC into three phase AC of whatever frequency desired The control circuitry for triggering the MOSFETs is not shown in this diagram for the sake of simplicity Three phase AC power source 60 Hz Your task is to determine the states ON or OFF of those six transistors during each of the time periods shown in the oscillograph T1 T2 T3 K X_X Output current 0 t fp gt Time period Q Q2 Q3 Q4 Qs Q6 ti te t2 t3 t3 t4 t4 ts ts te te t7 Assume a positive current on the graph is one where the drive sources current to the motor and a negative current on the graph is one where the drive sinks current from the motor Suggestions for Socratic discussion e What would be different if anything about the switching of these six power transistors to make the motor spin faster e What would be different if anything about the switching of these six power transistors to make the motor spin in reverse rather than forward file 101723 Question 41 Identify any area s of your study in which you would like to become stronger Examples include technical reading elec
115. suring the coil is in good working order e Ensuring all power contacts open as they should and close with low resistance e Checking to see that the auxiliary contact is in good order file 102228 74 Question 66 The following relay circuit has a problem The LED lamp never comes on regardless of the amount of pressure or temperature sensed by the switches 1 amp G Trip 97 F Trip 15 PSI 24 VDC Using a digital multimeter you measure 23 5 volts DC between points D and B when the temperature is 102 degrees F and the pressure is 18 PSI Identify the likelihood of each specified fault for this circuit Consider each fault one at a time i e no coincidental faults determining whether or not each fault could independently account for all measurements and symptoms in this circuit Fault Possible Impossible Pressure switch failed open Temperature switch failed open 0 5 amp fuse blown 1 amp fuse blown Relay coil failed open Pressure switch failed shorted Temperature switch failed shorted Relay coil failed shorted Finally explain why no further diagnostic tests or measurements are necessary to identify the location and nature of the fault file 102231 75 Question 67 The following variable speed motor drive receives a variable DC voltage from a potentiometer as a speed command signal from a human operator In this case the potentiometer s full range commands t
116. t you must step away from the lab or will be absent for any reason Any student regularly compromising team performance through lack of participation absence tardiness disrespect or other disruptive behavior s will be removed from the team and required to complete all labwork individually for the remainder of the quarter The same is true for students found relying on teammates to do their work for them Cooperation The structure of these courses naturally lends itself to cooperation between students Working together students significantly impact each others learning You are expected to take this role seriously offering real help when needed and not absolving classmates of their responsibility to think for themselves or to do their own work Solving problems for classmates and or explaining to them what they can easily read on their own is unacceptable because these actions circumvent learning The best form of help you can give to your struggling classmates is to share with them your tips on independent learning and problem solving for example asking questions leading to solutions rather than simply providing solutions for them Grades Employers prize trustworthy hard working knowledgeable resourceful problem solvers The grade you receive in any course is but a partial measure of these traits What matters most are the traits themselves which is why your instructor maintains detailed student records including individual exam scores at
117. tact failed shorted Contactor main contact s failed open Broken wire between B and G Thermal overload unit tripped High level switch failed shorted Transformer secondary winding failed open Finally identify the next diagnostic test or measurement you would make on this system Explain how the result s of this next test or measurement help further identify the location and or nature of the fault file 104018 57 Question 49 Suppose the lamp refuses to light up A voltmeter registers 24 volts between test points C and D C E 24 volts 0 25 amps current limited D First list all the possible single faults that could account for all measurements and symptoms in this circuit including failed wires as well as failed components Now determine the diagnostic value of each of the following tests based on the faults you listed above If a proposed test could provide new information to help you identify the location and or nature of the one fault mark yes Otherwise if a proposed test would not reveal anything relevant to identifying the fault already discernible from the measurements and symptoms given so far mark no Diagnostic test Yes No Measure Vor Measure Vep Measure VAB Measure Vap Measure Vcg Measure Ver Measure current through wire connecting A and C Jumper A and C together Jumper B and D together Jumper A and B together
118. tendance tardiness and behavioral comments and will share these records with employers if you have signed the FERPA release form You are welcome to see your records at any time and to compare calculated grades with your own records i e the grade spreadsheet available to all students You should expect employers to scrutinize your records on attendance and character and also challenge you with technical questions when considering you for employment Representation You are an ambassador for this program Your actions whether on tours during a jobshadow or internship or while employed can open or shut doors of opportunity for other students Most of the job opportunities open to you as a BTC graduate were earned by the good work of previous graduates and as such you owe them a debt of gratitude Future graduates depend on you to do the same Responsibility For Actions If you lose or damage college property e g lab equipment you must find repair or help replace it If you represent BTC poorly to employers e g during a tour or an internship you must make amends The general rule here is this If you break it you fix it Non negotiable terms disciplinary action up to and including immediate failure of a course will result from academic dishonesty e g cheating plagiarism willful safety violations theft harassment intoxication destruction of property or willful disruption of the learning work environment Such
119. trical circuit analysis solving particular types of problems time management and or skills applied in the lab Cite specific examples if possible and bring these to your instructor s attention so that together you may target them for improvement As a starting point try consulting the list of topics on the first page of the worksheet for the upcoming mastery exam as well as the General Values and Expectations list near the beginning of the worksheet identifying the habits and qualities necessary for success in this career Next identify practical strategies you will use to strengthen these areas Examples include focusing on specific types of problem solving whenever those types appear in the homework working through practice problems for a particular subject and or coordinating with your lab team to give you more practice on specific skills Suggestions for Socratic discussion e One useful strategy is to maintain a journal of all you ve learned in a course of study Explore ways you could take the work yow re already doing to prepare for homework daily discussions with your instructor and turn this into a journal or even a weblog blog for your own reflection and eventual use as a portfolio to showcase your capabilities to employers e Where exactly are the practice problem worksheets located on the Socratic Instrumentation website file 100999 50 Question 42 Examine this control circuit diagram f
120. ts Guide since the SLC 500 97 line of Allen Bradley PLCs program so similarly to the MicroLogix line This example shows an Allen Bradley MicroLogix 1000 series PLC model 1761 L10BWA wired to two toggle switches and one LED indicator lamp complete with a demonstration program Note that line power 120 VAC wire connections to power the PLC have been omitted so the focus is solely on the I O wiring Q OAW ADP PAPOP 1 0 1 1 1 2 3 DC 1 4 1 5 COM L CHONG Oa Co Power Allen Bradley Ct Run c Fault MicroLogix C Force 1009 r r r VAC VAC VAC voc O1 ypc 22 vpo Of DDOD LED with dropping resistor Ladder Diagram program written to PLC T T0 i Note how Allen Bradley I O is labeled in the program input bits designated by the letter I and output bits designated by the letter 0 Based on the wiring and program you see for this PLC identify the switch state combinations resulting in an energized lamp Try duplicating this program in your own PLC even if it is a different brand or model and see how it functions Be sure to activate the color highlighting feature of your programming editor so you may see the live status of the program s virtual contacts and coil 98 This example shows a Siemens 7 200 series PLC model 224XP wired to two toggle switches and one LED indicator lamp complete with a demonstration program LED with dropping resistor CHTO SIEMENS
121. utton pressed and a high pressure condition exists The solenoid can however be made to energize by placing the switch in the Hand position Beginning your troubleshooting steps you first note that the red indicator light never comes on Identify at least three possible faults that could each one individually account for these symptoms Also identify at least three components you know to be fully functional in this circuit Three possible faults Three known good components file 104158 26 Question 10 Using a terminal strip to organize all wire connections construct a circuit to turn on a DC load e g lamp relay coil using a proximity switch as the sensor The instructor will provide all necessary components to you during class time Be sure to bring appropriate tools to class for this exercise e g phillips and slotted screwdrivers multimeter Suggestions for Socratic discussion e A problem solving technique useful for constructing circuits is to sketch a schematic diagram of the intended circuit before making a single connection This important step not only helps you to identify potential problems before they arise but is also useful when constructing circuits as a team because it prompts all team members to exchange ideas and ask questions before committing to a plan of action e Is your proximity switch NO or NC How can you tell e Is your proximity switch sourcing or sinking How can you tell
122. ve answered a summary quiz designed to gauge their learning during the theory session If a student finishes ahead of time they are free to leave or may help tutor classmates who need extra help The express goal of this inverted classroom teaching methodology is to help each student cultivate critical thinking and problem solving skills and to sharpen their abilities as independent learners While this approach may be very new to you it is more realistic and beneficial to the type of work done in instrumentation where critical thinking problem solving and independent learning are must have skills 13 Lab In the lab portion of each course students work in teams to install configure document calibrate and troubleshoot working instrument loop systems Each lab exercise focuses on a different type of instrument with a eight day period typically allotted for completion An ordinary lab session might look like this 1 Start of practical lab session announcements and planning a The instructor makes general announcements to all students b The instructor works with team to plan that day s goals making sure each team member has a clear idea of what they should accomplish 2 Teams work on lab unit completion according to recommended schedule First day Select and bench test instrument s One day Connect instrument s into a complete loop One day Each team member drafts their own loop documentation inspection d
123. with a unique number inside Identify the three positions of the Hand Off Auto switch and the meaning of each one Explain why diodes are found in parallel with the solenoid and relay coils but not in parallel with the lamp Identify the meaning of the numbers near each side of the relay contacts Identify whether the pressure switch enables the solenoid to energize if the sensed pressure exceeds the trip point or falls below the trip point Identify the meaning of the red indicator light Suggestions for Socratic discussion Explain what would happen if either of the two diodes in this circuit were reversed What would happen if the reset switch contacts failed open in this system What would happen if the remote stop switch contacts failed open in this system What would happen if the CR1 1 relay contacts failed open in this system What would happen if the CR1 2 relay contacts failed open in this system What would happen if the solenoid coil s diode failed open in this system What would happen if the solenoid coil s diode failed shorted in this system What would happen if CR1 coil s diode failed open in this system What would happen if CR1 coil s diode failed shorted in this system file 104152 24 Question 8 A form of liquid level switch called a tilt switch is often used for detecting sewage level in lift stations where sewage collected from homes via gravity is pumped out of the collection sump

INST 230 (Motor Controls), section 2 Lab Reversing three

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