Model 4614B User`s Manual
Contents
1. WATTS provides a choice on the POWER display of that individual phase watts or KW where If all three pushbuttons 1 2 3 are simultaneously depressed all four LEDS will go ON Each display then converts to The only remaining operator control is a recessed slide switch for CT PT provision on the lower left corner of the PA rear panel Programming and operating details are covered in the Chapter 7 CT PT INSTALLATION 4 Technical Description Magtrol Power Analyzers use the Three Wattmeter Method to determine true RMS and ElIcos 8 Transducing is accomplished by analog means followed by conversion to digital at 16 bit binary precision Binary data is then calibrated and converted to BCD for display and GPIB output AMPERES TRANSDUCING Manganin meter shunts comprise the current measuring circuits The schematic shows the essential elements for obtaining signals E and I either AC or DC The voltage drop across each meter shunt is analogous to line current CR1 and CR2 are normally closed shunt bypass relays They have no function in load control and act only as shunt current bypass devices This method permits automatic current control resulting in a wide measurement range transparent to the operator To establish range each applicable shunt signal is electronically selected synchronized with CRI and CR2 VOLTAGE TRANSDUCING Resistor networks on the load side form a classic Y Box where the individual resis2. is then executed No damage will result to the unit from the inadvertent selection of any push button at any time LOW FREQUENCY MEASUREMENTS Some invertor power supplies have variable low frequency control also some complex loads have slowly changing power consumption Normally as any digital readout begins to follow the line or load change the display quickly becomes useless In the AVERAGING mode the PA snapshots and integrates A V and P data at a rate of 10 readings per second As readings accumulate the display will steady down to provide an accurate measurement of the true power equal to the average A V and P from the time the function was started In the conversion of sinusoidal information to steady state RMS conversion and Watts transducing have inherent time constants Refer to ACQUISITION RATE A power pulse of short duration like a few cycles will be integrated into the data but the PA cannot analyze short term phenomenon A Digital oscilloscope is probably more appropriate POLYPHASE IMBALANCE In polyphase systems lines should be maintained balanced In most applications three phase power is very inefficient if excessively unbalanced To quantify excessively for example on an inductive load like a motor or transformer for every percent of line voltage imbalance the resulting percent current imbalance will be seven to ten times greater Excessive current in one phase results in temperature rise an
3. 0 thru 9 and W as shown is for Watts This letter changes for the mode selected and may be P for Powerfactor or K for Kilowatts Carriage return and line feed are shown cl and will not print Leading zeros maintain the string length fixed FULL Instruction Data for all three phases is supplied The string is a contiguous 68 ASCII characters A Xx XX V xxx X W xxxx xA vy yy V yyy yW yyyy yA zz zzV zzz zW zzzz zcl 13 Where x is 0 thru 9 for phase 1 y is phase 2 z phase 3 This configuration transmits only amps volts and watts If you require LINE voltage PF or KW these may be easily calculated from the data by the host computer using Data Rate The OPEN or SYNC commands affect bus timing Selection is dependant upon what other instruments are on the bus their acquisition rate and how you wish to process data OPEN Instruction If your data acquisition is random or for some reason you must not wait the 1 second period use the OPEN instruction Data will be output nearly on command depending upon the MPU status at the time of the request If multiple data requests are made within the MPU integration period 1sec you will simply receive multiple transmissions of the same data If your program is accumulating data in an array you might want to include a routine to ignore the second of any two identical words received SYNC Instruction The computer will be held by the PA until the integratio
4. For readability the display is refreshed at a rate of two per second 20 of the MPU data acquisition and conversion rate Chapter 5 SPECIFICATIONS describes resolution and accuracies There is a digit segment and decimal point check procedure See DIGIT TEST in Chapter 8 Mode pushbuttons toggle ON OFF HOLD This button stops the display updating and data accumulation in all modes of operation The HOLD button serves an additional function when used in conjunction with AVERAGING AVERAGING Full data is accumulated at a rate of 10 readings per second summed over any desired time period The running average 1s continuously calculated and displayed by dividing the summed value of each parameter by the total number of summations When the AVERAGING is stopped the data summations and sample count for each A V and P are retained in NV memory Normally as the AVERAGING push button is depressed with HOLD OFF A V and P data previously stored in memory is erased and immediate data starts accumulating However if the AVERAGING is initiated while the HOLD is ON data previously retained in memory is recalled and new data is then integrated into it The HOLD automatically goes OFF This function will allow you to exit the AVERAGING mode perform some other task then return and continue where you left off or simply retain and recall data POWER FACTOR Good line voltage balance is required for power factor mea
5. and find the trimpot marked Abal Slowly null the value for the lowest amps reading Try to locate the mechanical center of the cw ccw positions that result in the best null lowest reading Return to the Avf trimpot and set an amps reading for 0 000 to 0 001 but favor one digit Repeat the procedure for PHASE 2 and 3 WATTS BALANCE Always perform the VOLTS and AMPS balancing before adjusting WATTS null Select PHASE 1 and adjust the trimpot identified Wvf CCW until you read 0 0005 on the WATTS display Then adjust Wbal for a minimum reading Return Wvf to a minimum reading or 0 0001 If you find that the reading will not go any lower than a few digits then change the direction of rotation and readjust for a slight increase above the minimum attainable Repeat the procedure for PHASE 2 and 3 Adjustment of the Adc Vdc and Wdc trimpots will not be required If you have questions consult Magtrol Power Analyzer Customer Assistance CALIBRATION If the calibration power source is frequency adjustable 100 Hz is a good calibration frequency otherwise use 50 60Hz Wire the PA according to the diagram and apply between 125 to 150 VRMS Set up the PA 1 Select PHASE 1 2 Select ON PH VOLTS 3 Select 150 PHASE VOLTAGE RANGE The applied voltage will be identical for all three phases since they are wired in parallel On the 2nd slot from the right PHASE 1 find the 150v trimpot and match the PA reading to t
6. as pushbuttons 1 2 or 3 SPA Select phase all same as pushbuttons 1 2 and 3 simultaneously depressed LV Select to read line voltage PV Select to read phase voltage KW Select to read kilowatts W Select to read per phase watts P Select to read powerfactor I IC Averaging ON Averaging OFF H HC Hold ON Hold OFF L LC All front panel pushbuttons Lock out Lock out clear AZ Cancel auto zeroing function CT PT Cancel or enter data for current and or potential transformer calibration RES Reset instrument to power up state In addition to the standard instructions listed there are special instructions for reading and writing directly to the PA memory elements A specific program in the host computer is required Ifyou have a special situation where you want direct memory access or wish to directly alter machine functions or calibration this can be made available Contact Magtrol Software Assistance for more information PA gt COMPUTER There are two choices for A V and P data format Therefore before you execute a read statement it is necessary to instruct the PA for the data format you wish to receive The selection is retained by the PA becoming the default mode for subsequent data transmissions SGL Instruction Sets the data format to a string length of 24 ASCII characters including CR LF duplicating the digital display The data string is exactly A nn nnV nnn nW nnnn ncl Where n any number
7. line to the cabinet of the PA If this helps then the noise is in the grounding system If there is little change or the problem becomes worse then very likely the noise is coming through the 117 230 50 60Hz line cord power Suppress it with noise filters bring in a separate line or install a small isolation not auto transformer 1A 120V This should eliminate the problem or reduce it to a tolerable level If the instability is directly traceable to some specific device like other instrumentation control relays or magnetic circuit breakers try to isolate the cause If it is intrinsic to the breaker refer to the above paragraph CIRCUIT BREAKERS If it is an electromagnetic current surge from the load when a switch is closed isolate that line or soften the start In any event in electromagnetically severe environments sometimes a combination of remedial efforts are required With severe EMI most test and computing instruments are susceptible to these problems to some extent Despite internal shielding the circumstance unique to the Magtrol PA is that the current carrying power lines pass inside the instrument cabinet where all the action is You may obtain additional assistance by contacting Magtrol Power Analyzer Customer Service 3 Operation and Display DIGITAL DISPLAYS Each digit is a Light Emitting Diode seven segment high brightness 14cm display Each A V and P display is directly controlled by the system MPU
8. potential load burden is insignificant RESOLUTION Basic resolution of all parameters is 1 65535 16 bit binary precision AMPERES DISPLAY 5 0 Amp Range 001 amps 25 0 Amp Range gt gt 9 999 amps 01 amps 100 0 Amp Range gt gt 99 99 amps 1 amps VOLTS DISPLAY All Volts Ranges lt lt 10V 001 volts gt gt 10V lt lt 100V 01 volts gt gt 100V 1 volts POWER DISPLAY W KW Range dependant 01 GPIB A V amp P Identical to display resolution AUTOZERO If the A V P Reading is lt lt 1 FS of Rng the value is set to zero To disable refer to DIGIT TEST in Chapter 8 DATA ACQUISITION RATE ANALOG V A signals require AC conversion to analog according to the formula Since Watts Instantaneous ElIcos 9 active filtering is required resulting in a Time Constant For a stepped input 0 to F S any range Volts and Amps signal TC 60 milliseconds Watts signal TC 120 milliseconds Where TC 63 of final value DIGITAL Integration period 0 10 seconds Display 2 0 reading sec GPIB Synchronized 0 1 sec reading Not synchronized 04 to 07 sec reading ACCURACY The following accuracy specifications are valid under the conditions of Ambient Temperature room 72 F 10 F Waveform distortion lt lt 8 1 crest factor Power factor 0 1 to 1 0 lead or lag Frequency lt lt 4KHz REF ANSI specification C39 6 Phase Voltage E 0 2 of r
9. should all happen in 1 or 2 seconds If so assume the unit has survived shipping and is ready for service MAXIMUM RATINGS Rear panel input output lines Voltage line to line or line to ground 1000 VRMS maximum Current Per phase 100 Amps continuous 200 Amps for 6 seconds 500 Amps maximum for 2 seconds INSTALLATION Because of the use of special low contact resistance relays the PA must be mounted in a nearly horizontal position There are six 100 Amp connectors supplied Do not try to secure too small of a wire the locking screw may run out of threads and jam in the connector body SAFETY Once the line and load is wired install the connectors before power is applied All operating personnel should make a habit of the following Power input Never disconnect only one or two of the line input connectors When you disconnect any always pull all three Load output Always keep the output connectors in place when power is applied Again when you disconnect any always pull all three Transient Overloads Warning Unsuppressed inductive loads upon interruption may generate kilovolts at high energy This type of surge may be line to line and line s to ground Your Magtrol Power Analyzer is a rugged instrument designed to tolerate overloads however as with all electrical equipment it has limits Do not allow the PA to function as an arc suppressor where you repeatedly exceed the maximum
10. voltage ratings Please follow the load control arc quenching and wiring suggestions outlined in chapter 2 Short Circuits There are no fuses within the PA Short circuits at the load with the PA connected to an unlimited power source can be destructive If such a failure should occur immediately disconnect all power and refer to LINE ISOLATION in Chapter 8 before proceeding 2 Line Load Connections Always install a properly rated circuit breaker between the PA and the load Your best setup is to use two one on the input the second at the load side with a foolproof setup insuring that the load breaker always opens first SURGE PROTECTION Metal Oxide Varistors MOVs under various trade names are a good choice to connect between lines at the load for transient protection from inductive loads 3 PHASE 3 WIRE DELTA SYSTEM Since a connection to measure phase I is generally not available in a Delta system a Y box within the PA converts E line to E phase This satisfies the power conversion formula by converting line E to phase E and so incorporating the 3 factor The common point of the internal Y false neutral is accessible at the NEUTRAL terminal so identified on the rear panel This has no connection in a Delta system A detailed description of the PA method voltage transducing is covered in Chapter 4 3 PHASE 4 WIRE WYE SYSTEM Types of systems ie 3 wire or 4 wire are transparent to the PA The power conversi
11. 4 3 Operation and Display csccsseseesees 6 PROGRAMMING EXAMPLE 14 DIGITAL DISPLAYS 00 eee 6 p HOL 6 7 CT PT Installation ccccccsssesssssssseees 15 AVERAGING aneneen 6 CT PT DETECTION esses 15 POWER FACTOR cccnnionnansnunan 6 CT PT RATIO RANGE 0 esses 15 PHASE VOLTS 3 7 DIGITAL RANGE in 15 AMPERES RANGE oooi 7 GPIB CT PT PROGRAMMING 15 VOLTAGE RANGE onn 7 CHANGING REMOVING CT PT VALUES 16 PHASE SELECTION o 7 8 Calibration ccccssssssssssssssssscssseees 17 4 Technical Description ccsscccsscessseees 8 GENERAL ooo eeeceecses et ttttteeceeeecetettttnstneeeee 17 AMPERES TRANSDUCING r DIGEST esheets eater tease 17 VOLTAGE TRANSDUCING 8 EEE BEOU E aiar n ANALOG PROCESSING 8 LINE INPUT ISOLATION 17 DATA PROCESSING innn 8 OFFSET ADJUSTMENTS 1211r 18 DISPLAY RATE eccna 8 VOLTAGE BALANCE 0 0 0 0 18 PUSHBUTTONS cnan 9 AMPS BALANCE s in 18 LOW FREQUENCY MEASUREMENTS 9 WATTS BALANCE cacssizesinsscrnssbestosieem ast 19 POLYPHASEIMBALANCE r i CALIBRATION cssessssessssssesssssetenssseesensee 19 DISPLAY HELP nnan 9 AMPERES CALIBRATION 0 20 WATTS CALIBRATION oaaae 20 5 Specifications eseecedeeesedecausecssescecscsceseseesecsses 10 METER CALIBRATORS ccccceccccceececeee 21 VOLTAGE ennnen a 10 CALIBRATION PROBLEMS 21 PLEASE READ This docu
12. Magtrol 4614B User s Manual Contents 1 Introduction ccsssissssscescssccesvassasisdicssnvecsossese 2 AMPERES 2 cccescssccshstastesetescdastsseaceintaneatteaeieas 10 ABBREVIATIONS oiiaii 2 METER LOAD COMPENSATION 10 UNPACKING 0 ececccccccceeessenseeeeceeesesneas 2 RESOLUTION o i 10 INSTRUMENT POWER 2 AUTOZERO 00 ioc ccccicccecececccceseeststeeeeeesees 10 OPERATIONAL CHECK 00 ccsccscsccseeseeeeeees 2 DATA ACQUISITION RATE iae Il MAXIMUM RATINGS o i 2 ACCURACY seai riait aiaa nis 11 INSTALLATION ssssssessssseetssssseeeeeeeceeeeessee 2 6 GPIB Data Acquisition cccseeeeeees 12 SAFETY ARETE ATESTATE TAA wees eS eee TIET 3 GPIB IEEE 488 NEEE A REETA EE oe 12 Transient Overloads LE ELE LE EE IESEAN 3 GPIB COMPUTER INST ALL ATION ae 12 Short CACCUItS rrna s NENDEST 3 SOFTWARE INSTALLATION 12 2 Line Load Connections ccccccccccscssscees 4 PRIMARY ADDRESS oooccccceecececcccceee 12 SURGE PROTECTION aaiae 4 COMPUTER gt PA ja 12 3 PHASE 3 WIRE DELTA SYSTEM 4 PA gt COMPUTER o n 13 3 PHASE 4 WIRE WYE SYSTEM 4 SGL Instruction 0 0cccccceeeeeesseeeeeeeees 13 SINGLE PHASE 4 FULL Instruction 0cccccccecceeesseseseeseeseesees 13 CIRCUIT BREAKERS 2 4 Data Rate wiscssshevsier ciwnesieatishiaudinien aes 14 INSTABILITY CAUSES amp SOLUTIONS 5 OPEN TSOHO sirsiran desiit 14 SYNC InStHuCti ON eansoun 1
13. agreement If the difference is gt gt 0 005A and you are certain the difference is the PA and not your standard compensate the error by slight adjustment of Avf to trim it closer then return to the full scale value and touch up the calibration Proceed as above for PHASES 2 and 3 Then apply 25 and 100 amps selecting the appropriate range and calibrate all three phases On the higher current ranges omit the 10 FS check required only on the 5 0 amp range When your calibration is complete verify all ranges on all phases by applying a value and switch through phases 1 2 and 3 The readings should agree within 2 LS digits WATTS CALIBRATION Meter calibrators perfectly satisfactory for Volts Amps above are generally unsuitable for watts calibration The reasons are described in the paragraph METER CALIBRATORS Do not proceed with the following until you are certain of the individual VOLTS AMPS calibration accuracy Volts and amperes calibration establishes the power reading calibration on all ranges for W KW and PF however there is a single adjustment one for each phase to set the multiplier span The easiest method is to use a unity power factor single phase VOLT AMP to establish a known wattage If a non inductive lamp or ribbon heater load is used phase shift error from minor affects from small XL or XC will be negligible This is provided the frequency 100Hz and the ampere value is minimal Therefore use a po
14. d reduced efficiency Also in unbalanced polyphase systems for the above reasons true power factor is indeterminate DISPLAY HELP If the A or V displays show HELP this indicates that the maximum range of the PA is exceeded or wave form distortion high crest factor is such that a portion of the signal is exceeding the PA range If the condition lasts for only a few seconds such as a start up overload it is of no consequence However do not allow an overload to persist For example if one of three phases should open most loads will draw excessive current on the remaining lines Any phase regardless of the phase selected when overloaded causes the display to protest If you install an overload detection circuit breaker a good idea please refer to Chapter 2 for circuit location and type considerations 5 Specifications VOLTAGE Three phase line to line 920 VRMS maximum Phase voltage 630 VRMS maximum AMPERES Maximum continuous line current per phase e 100 amperes continuous e 200 amps for 6 seconds e 500 amps for 2 seconds Maximum reading capability is 105 amperes METER LOAD COMPENSATION Each current range extracts 100 millivolts from the load potential at full scale Voltage is measured on the load side therefore no compensation is required The potential measuring circuit burden is a fixed resistance drawing approximately 1 2 milliampere at a line potential of 920 volts Therefore
15. dicators are sufficient For the isolation test a HI POT tester or a source of 1200 Volts AC with leakage current measurement will be required For span calibration you must have the capability for known accurate true RMS reading of AC volts and amperes within the range of the PA Meter calibrators are very useful for A and V providing they have at least 05 accuracy of reading If you do not have a calibrator you will need a source of precision isolated and known AC voltage and current Please do not even think about using the common power line for this The shock hazard is too great and stability inadequate LINE INPUT ISOLATION With the PA OFF interconnect the output terminals according to the diagram Any terminal to the metal cabinet should read infinity resistance open circuit with an Ohmmeter With caution apply a potential of 1200 VRMS 50 60 Hz between the interconnected terminals and the uninsulated aluminum side plate of the PA for at least 10 seconds Some leakage current will be indicated It should be steady and not exceed 400 microamperes This is due to approximately 850 picofarads of distributed capacity between the input circuitry and the surrounding metal cabinet plus some capacitive coupling in the optical isolaters and PC Bd foils OFFSET ADJUSTMENTS Be sure you have performed the DIGIT TEST and have not turned the PA OFF since that procedure Allow the unit to stabilize for at least 1 2 hou
16. e Very often either a procedural change or component replacement will satisfy the problem If there has been a short circuit disaster and the unit fails the Hi Pot test do not attempt to use the instrument The only alternative is to return it to Magtrol for service Please do not hesitate to request assistance for any of the above 21 Testing Measurement and Control of Torque Speed Power Load Force Weight Tension Displacement MAGTROL INC 70 Gardenville Parkway Buffalo New York 14224 USA Phone 1 716 668 5555 Fax 1 716 668 8705 E mail magtrol magtrol com MAGTROL SA Route de Moncor 4B 1701 Fribourg Switzerland Phone 41 0 26 407 3000 Fax 41 0 26 407 3001 E mail magtrol magtrol ch Subsidiaries in e Germany e France e Great Britain e China Worldwide Network of Sales Agents www magtrol com Certified ISO 9001 2000 by Bi n 150887
17. e is substantial power dissipation a low voltage source for obtaining that current is the only efficient alternative Consider Low impedance AC voltage from a transformer and passed through the metal back panel of the 4614B albeit non ferrous nevertheless will have some inductive component If you apply Ohms law formula above using a few microhenrys for L R total circuit resistance with the PA contributing only about 001 ohms and a value for F 60Hz the result will be a phase shift of a few degrees This is enough to create a measurable error in watts calibration Some V A calibrators have an adjustable means for controlling the phase relationship of volts to amps This will be useful for watts calibration if the control is infinitely variable and if the operator remembers to adjust the phase control to peak the watts reading each time any electrical parameters are changed Instruments with stepped or switched phase controls to be useful must be calibrated for adjustment in minutes of arc Of course Ohms law applies equally to the volt amp load calibration method outlined above However with a power absorbing load the total circuit R is much higher This results in insignificant phase shift at low frequencies providing the load reactance is minimized CALIBRATION PROBLEMS If the calibration fails to achieve the results expected or you suspicion a defective part call Magtrol and ask for Power Analyzer servic
18. eading 0 2 of range lt 0 gt Line Amperes I 0 22 of reading 0 25 of range Power W or KW P 0 2 of reading 0 3 of VA range PF VA error W error Temperature Coefficient 008 C max of range Note 004 is typical Cos 0 error 4Min KHz 4KHz to 15KHz 6 GPIB Data Acquisition GPIB IEEE 488 When installing the GPIB cable the PA should be OFF This cable is normally supplied with the computer interface card It is also available from Magtrol Inc most electronic distributors or Hewlett Packard Inc GPIB COMPUTER INSTALLATION A GPIB interface requires an interface card installed in the host computer with the driver software made resident on disk There are several manufacturers for these products Magtrol has good experience with National Instruments Corp GPIB PC2A for IBM or compatible PCs SOFTWARE INSTALLATION There are a number of formatting and initialization questions to be answered the first time that the GPIB interface control software is installed in the computer You may obtain assistance in the installation and formatting procedure from Magtrol ask for GPIB software assistance All GPIB data acquisition systems require the use of termination characters to signal conclusion of a data exchange The PA uses the Hewlett Packard HPIB standard ASCII termination characters Carriage Return CR Line Feed LF in that order On a read cycle the PA looks
19. for the CR LF to signal completion of an instruction and transmits these characters upon conclusion of a data write cycle PRIMARY ADDRESS All instruments serviced on the bus have a separate primary address code The factory setting for the 4614B is fourteen 14 If you wish to change the code on the rear panel above the GPIB connector there is an opening providing access to the code selection switch The chart may help in selecting the switch combination for the address that you want Switch segment identification resulted in the binary code notation reversed from the normal convention The MSB is to the right Some PC interfaces National GPIB PC2A will access 0 to 15 4 Bit primary address numbers only Others may access up to 31 5 Bit codes even though the GPIB capability is limited to 16 instruments The 4614B code range uses the 5 bit format Before selecting a value greater than 15 check that your particular interface has 5 bit capability COMPUTER gt PA A5 A25 A100 Amperes range selection V150 V300 V600 Volts range selection AA Amps AUTO range ON VA Volts AUTO range ON FULL Sets data format to A V and W for 3 phases SGL Sets data output format to the front panel display 12 SYNC GPIB data output rate is synchronized to 0 10 second bus output rate OPEN Data output is transmitted nearly upon request SP1 SP2 SP3 Select phase 1 2 or 3 same
20. he standard Reduce the voltage to 10 of full scale about 15 0 VRMS The reading should be within 0 15 V Ifso further compensation is unnecessary If the difference is gt gt 0 15V and if you are sure the difference is the PA and not your standard compensate the difference by slight adjustment of Vyf to bring it closer then reset the applied voltage to FS and touch up the calibration Do not adjust Vvf too far this is a compromise situation Chapter 5 SPECIFICATIONS states the basic accuracies attainable Repeat the above calibration for phases 2 and 3 by selecting that phase and adjust the appropriate trimpots Calibration for the 300 and 600V ranges is accomplished by applying full scale voltage on each respective range for all three phases as above The exception is to omit the 10 of full scale check This is required only on the 150V range A good final check is to verify minimal voltage reading change on all ranges as you switch from one phase to another AMPERES CALIBRATION 1 Select PHASE 1 2 Select AMPERES RANGE 5 0 Wire the PA according to the diagram Apply a known current with a precision of at least 05 Since current is identical in each leg of a series circuit the current will be the same in all three phases On the 2nd slot from the right find the trimpot marked 5a and match the PA reading to the standard Reduce the value to 10 of full scale or about 0 500 Amps and check
21. ility for any future confusion don t forget to set the rear panel switch to OUT 8 Calibration GENERAL If you wish to perform a full scale accuracy verification check skip the section OFFSET ADJUSTMENTS With the PA outputs shorted all A V and W displays should show zero or a very small value Ifthe zero input readings are greater than 0 2 of full scale range and the unit is stable and operates normally proceed with the OFFSET ADJUSTMENTS If there appears to be excessive drift or you suspicion a component failure call Magtrol ask for Power Analyzer servicing for instructions If there are line transient induced problems resulting in display instability refer to the section INSTABILITY CAUSES AND SOLUTIONS in Chapter 2 pS Three categories of measurement and adjustment are necessary to calibrate the PA These are ISOLATION TEST OFFSET balancing and SPAN adjustment In the following all descriptions assume proper operation when stating the result of an action DIGIT TEST With the PA OFF simultaneously depress both the HOLD and SELECT PHASE 1 push buttons Turn the PA ON with the buttons depressed While maintaining the buttons IN observe all 13 digits all digit segments and decimal points should be ON When released the PA operates normally except that the AUTO ZERO function is disabled To re enable toggle the PA OFF ON normally EQUIPMENT REQUIRED For offset balancing the PA front panel in
22. ment includes text recovered from the final edition of a now obsolete manual of a discontinued Magtrol product Magtrol Inc assumes no responsibility for errors or omissions Additionally no liability is assumed for any damages that may result from the use of the information contained within this publication LAST PRINTING M ay ise FEAMAGTROL 1 Introduction ABBREVIATIONS PA Model 4614B Power Analyzer GPIB IEEE 488 Instrument Bus Standard LED front panel indicators A VandP Amperes Volts Power display MPU Microprocessor unit UNPACKING The 4614B was adequately packaged for shipping We recommend that all cartons and internal packing material be saved until the instrument is checked for proper operation In the event of damage please notify the carrier and Magtrol Customer Service INSTRUMENT POWER Instrumentation service power is 120V 50 60Hz or 230V 50 60Hz 75 watts If none was specified all domestic shipments will be supplied as 120V 60Hz The Line Cord is a detachable NEMA standard 3 wire For personnel safety please make sure with certainty that your ground line is intact and connects the cabinet to an earth ground OPERATIONAL CHECK Plug in the unit turn it on and in quick succession you should see the readouts flash then blank then read zero or a small value The RANGE indicators will start on the highest amps volts range then drop down to the lowest ranges leaving the AUTO LED s on This
23. n period is up In this mode data will always be the result of the most recent integration period However if you are using another Magtrol controller that is also operating at a 0 1 second acquisition rate like the Model 4629B the two instruments should be synchronized to avoid a timing conflict where one instrument may temporarily blank the other This is easily accomplished by the following technique Output any instruction except RES to each of the instruments only suppress the CR and LF termination characters You now have both instruments hung up at fixed program locations waiting for the CR LF Then output only the CR LF characters to both instruments in quick successive statements The instruments will slowly drift apart and not remain synchronized indefinitely If you are accessing data in batches consider executing this procedure just prior to each data input routine PROGRAMMING EXAMPLE The sample program sets PA in the SYNC mode with FULL data format The CRT displays Amperes summed for total three phase line Voltage average three phase line Power three phase kilowatts This example assumes National GPIB PC2A Interface Hardware programmed in Microsoft Quick Basic suitable for most any PC system operating under MS DOS 7 CT PT Installation Calibration of the 4614B has special provisions for readout compensation that permit the installation of Current Transformers CT and P
24. on formula is identical to the Delta system except that ina WYE system Connect the non current carrying neutral terminal to the neutral at the load Any system voltage imbalance will be accurately indicated SINGLE PHASE P EI cos 0 A number of connection configurations are possible The connection method shown opposite places the line current measurement on the PA phase 1 with unused legs tied off With this connection method set the PA mode pushbutton selections as follows AMPERE VOLT PHASE SELECT 1 ON PH VOLTS ON OFF PH WATTS OFF The readout is line current line voltage and true power in watts CIRCUIT BREAKERS If circuit breakers are electrically controlled relays if possible use D C control Place a quenching diode across the coils at the relay If you must use A C controlled breakers install a metal oxide varister or at least a 2 watt common resistor across the coil s Determine the resistor value such that the power dissipation is 1 to 1 1 2 watts The correct resistance is easily determined by 4 INSTABILITY CAUSES amp SOLUTIONS Instability of the PA can be caused by excessive voltage spikes or electromagnetic power pulses that manage to reach the high speed digital circuitry within the unit High frequency noise generating a potential between the instrumentation power line and the line cord ground is troublesome Try to determine the source by temporarily attaching an isolated earth ground
25. otential Transformers PT Reading compensation consists of multipliers installed into non volatile memory via the GPIB Standard CT s are usually rated for 5 0 Amps however current is current and any range on the PA should read correctly You may install a CT alone or a CT and PT There is no instance where you would want a PT only The schematics suggest connection methods for a three wire three phase system CT PT DETECTION During power up initialization the MPU interrogates that portion of memory where CT or PT compensation values reside If a value is found then the MPU checks to see if the recessed slide switch on the rear panel is set IN If both of these are true then normal calibration values are revised to include the CT PT multiplier Otherwise default calibration standard reading values are loaded Neither the switch nor the compensation values are interrogated again as long as the PA remains ON Therefore to remove the compensation and return to standard calibration set the switch to OUT then toggle the power switch OFF wait for a few seconds then back ON CT PT RATIO RANGE The PA compensates all display parameters for any ratio of amps CT or volts PT for any value from 0 01 to a maximum of 255 DIGITAL RANGE After CT PT installation if the resulting compensated reading is in excess of the display capability there will be no Decimal Point The reading will be correct for four A V or five W KW most
26. r then remove the top cover plate Interconnect the rear panel terminals according to the diagram and set up the front panel 1 5Amps 2 150 Volts 3 ON PH VOLTS 4 PHASE SELECT 1 5 OFF PH WATTS VOLTAGE BALANCE On an internal cover plate there are six 3 8 by 5 inch ventilation and trimpot access slots 2 for each phase Phase 1 are the two on the right as you face the front In the PHASE 1 access slot find and rotate the trimpot identified Vyf slowly CCW until the VOLTS display shows a reading about 0 100 Move left to the next slot and find the trimpot marked Vbal and slowly adjust this to obtain a minimum null reading Allow several seconds after each 1 8 turn of the pot for the reading to settle Try to locate the mechanical center of the CW CCW positions that result in the lowest reading When you are satisfied you have attained the lowest reading re adjust the trimpot Vvf CW until you obtain between 0 000 and a minimum value probably around 0 020 Leave the minimum value reading 1 Select PHASE SELECT 2 Push Button move to the set of access slots marked PHASE 2 and repeat the above 2 Select PHASE SELECT 3 and repeat AMPS BALANCE This is similar to volts above except the reading will be smaller and somewhat more sensitive Select PHASE 1 and adjust the trimpot identified Avf in the PHASE 1 access slot cew until you read about 0 005 on the AMPS display Move to the next slot to your left
27. significant digits You have a clue that the compensated value is above the display capability when the DP is missing If the integer is in excess of the maximum resolution of the GPIB data the DP cannot simply be omitted since that would alter the length of the data string Therefore an exclamation mark ASCII 033 is substituted to the right of the least significant digit to signal unknown magnitude GPIB CT PT PROGRAMMING The PA accepts either upper or lower case whole numbers or decimal numbers in any numerical format For CT installation CTnnncl For PT installation PTnnncl Where nnn 0 01 to 255 cl denotes the carriage return line feed termination characters For example ACT with 250 1 ratio CT250 cl A PT with 10 1 ratio PT10 0cl The PA will ignore any value that is out of range ie gt gt 255 or lt lt 01 In addition it will briefly flash HELP on the respective display to signal displeasure with the entry CHANGING REMOVING CT PT VALUES To change a value simply overwrite the existing value s To remove a CT or PT value output a CT cl or PT cl only To eliminate both but save the data switch the rear panel slide switch to OUT toggle the power switch OFF ON Ifyou eliminate both CT and PT reading correction data by GPIB instruction the unit will automatically reset saving the necessity to switch the power OFF ON If both CT s and PT s have been software erased to avoid the possib
28. surements of induction motors Chapter 4 contains additional information PF data cannot be averaged PF calculations are invalid when VOLTS AMPS and WATTS are separately integrated PHASE VOLTS 3 This pushbutton provides an indication of line voltage by applying the above formula It is not identified as line voltage because it is not a true line to line measurement If there is excessive line to line imbalance a difference may exist between the displayed value and an actual line to line measurement This is unavoidable since phase voltage is required for accurate power determination in balanced or unbalanced systems AMPERES RANGE When you select a specific range the AUTO LED turns OFF indicating the MANUAL range selection mode Ifthe line amperes exceeds full scale gt 105 on any phase either AUTO or manual the unit will advance uprange to avoid reading inaccuracies or overload Current over 105 AMPS on any phase results in the readout begging HELP and remaining that way until the overload is removed To return the unit to AUTO ranging mode press the AUTO pushbutton VOLTAGE RANGE Operation is identical to CURRENT RANGE described above and upranging also occurs at 105 of phase voltage range in effect If you have selected OFF PH VOLTS 3 then uprange will occur at 105 of range x 1 73 PHASE SELECTION Pushbuttons 1 2 or 3 select that specific phase for display Pushbutton ON 3PH KW OFF PH
29. tors shown are actually divider networks The resulting phase voltage signal 1s selected and amplified for conversion and processing ANALOG PROCESSING A simplified schematic shows the essential elements of the analog section and applicable conversion formulas Conversion from voltage to frequency permit the use of optical isolators to transfer signals to an earth ground related potential Balancing and calibration controls referred to in chapter 8 are identified on their respective elements DATA PROCESSING Three variable frequency signals AFo VFo and WFo represent one of three phases for a total of nine Each are integrated for a precise period of 0 1 second for digital conversion The system MPU controls functions of auto zero range control calibration conversion to BCD digital display and preparation for GPIB transmission DISPLAY RATE To avoid a nervous display the readouts update at a reduced rate of 500 milliseconds from the MPU acquisition and conversion rate of 100 milliseconds A minor software change can revise the display rate faster or slower Contact Magtrol Customer Service PUSHBUTTONS The MPU looks at the condition of all pushbuttons approximately 25 times per second If the MPU detects a pushbutton the appropriate LED is immediately turned ON OFF The MPU then locks in a program loop until the button is released On the next program cycle the action programmed for the respective push button
30. wer source and load that is stable producing 700 to 750 Watts on the 150V 5A ranges Three wiring examples are shown one for each phase Set up the PA as follows 1 SELECT 5A 150 V range 2 SELECT Phase 1 3 SET OFF PH WATTS 4 SET ON PH VOLTS Multiply Volts x Amps VA and adjust PHASE 1 Weal for a watts reading equal to that product Re wire the rear panel to the Phase 2 diagram 1 SELECT Phase 2 on the front panel and repeat the above procedure likewise for Phase 3 20 If a Standard Wattmeter is used instead of the VOLT AMP method described above calculated reading compensation will be required External potential or current fields installed anywhere in the circuit apply some load that will not be equally measured by both meters METER CALIBRATORS Unless a current potential calibration source is phase controlled specifically intended to calibrate Watts there will be no control over the phase angle between the applied voltage and applied current This difference is not dependant upon the calibrator only it is dependant upon what the calibrator sees as a load form Since the nature of the load is a factor unknown and not under control of the instrument or its manufacturer to have predictable phase compliance the instrument must phase align the potential to the current Most do not The reason for current potential phase shift is basic If you wish to generate current in terms of amperes unless ther
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