Model 721 - Chauvin Arnoux Group
Contents
1. CLAMP ON HARMONIC METER 2 AEMC ENGLISH User Manual INSTRUMENTS TABLE OF CONTENTS INTRODUCTIONA 3 1 1 Receiving Your Shipment et edi 4 1 2 Ordering Information sssss e 4 PRODUCT FEATURES T 5 2 1 Description tiere ee eee 5 2 2 Control Featutes aet et Rer ROO 7 2 3 Digital Display Features u uu 8 2 3 1 Display and Error Indications 9 SPECIFICATIONS e eren enn nnn nuum nu nun nun unu uuu an 10 3 1 Electrical Specifications ette orit 10 3 2 General Specifications 12 3 3 Mechanical Specifications 12 3 4 Safety Specifications itte ed bue 13 UNDERSTANDING ELECTRICAL HARMONICS 14 41 Detection and 20 4 2 Effects on the System tron 21 4 3 Transformer Deratifnig L ere 22 4 4 Meter Readings 23 4 5 CRESUIPACION 23 4 6 Limiting the Effects of Harmonics 24 OPERATION III III II su awwawwwswawawawanwwsawwswwwa 25 5 1 Curren2. CREST FACTOR CF Range 1 00 to 10 00 Resolution 0 01 Minimum Input 300 mA 300 mV Accuracy 40 to 450 Hz 10 3 cts Frequency Range 15 Hz to 10 kHz Display Digital CF Bargraph True RMS A or V FREQUENCY Hz Range 0 5 to 9999 Hz Minimum Input 1 Aor 1 V Accuracy 0 5 Hz to 999 9 Hz 0 1 R 1 ct 1000 Hz to 9999 Hz 0 296 1 ct Display Digital Hz Bargraph True RMS or V Harmonic Meter Model 721 11 ANALOG OUTPUT Vout Range 1 mV A 0 05 to 700 Arms or 10 mV A 0 05 to 60 Arms Basic Accuracy 3 Input 0 05 A to 999 9 A Peak Output Impedance 4 47 pF Display Digital all A and THD functions Bargraph Arms 3 2 General Specifications Power Source 9 V Alkaline battery NEDA 1604 6LF22 6LR61 Power Source Life 50 hr continuous use approx Dimensions 10 x 3 8 x 1 7 254 x 97 x 44 mm Weight 1 3 Ib 600 g Display Quadriplexed LCD with 12 5 mm digits 374 digits 9999cts Temperature Operating 14 to 131 F 10 to 55 C Storage 40 to 158 F 40 to 70 C Humidity Operating 0 to 80 RH to 40 C 50 RH 55 C Storage 0 to 95 RH Material Case Gray Lexan 920A UL 94 V2 Jaws Red Lexan 500R 10 fiberglass UL 94 VO LCD lens Crystal Lexan 920A UL 94 V1 Altitude Operating 2000 m 6500 ft Storage 5000 m 16 000 ft 3 3 Mechanical Specifications Envelope Protection IEC 529 IP 40 Drop Test IEC 68 2 32 1m Vibration IEC 68 2 6 Shoc
3. DF CF HZ PEAK SMOOTH MIN MAX recording These functions are described further in this manual see p 29 36 5 2 3 Bargraph Please note that the analog bargraph will continue to display RMS volt age values while other measurement functions are displayed e g THD DF CF Hz Min Max Smooth Peak The bargraph ranges are 60 Vrms and 600 Vrms 28 Harmonic Meter Model 721 5 3 THD Push Button Power Quality Measurements THD gives access to Power Quality measurements THD DF and CF and can be accessed while in Current or in Voltage The THD push button accesses three measurement values by sequen tially pressing the button Push Button Sequencing AorV gt THD gt DF gt CF gt Aor V 5 3 1 THD Total Harmonic Distortion THD is the Total Harmonic Distortion and referenced to the Fundamental 50 60 Hz signal The THD is expressed as a percentage and may be greater in AEMC Model 721 amplitude than the fundamental A read gt ing greater than 100 is possible The THD is also referred to as the Har monic Factor or THD F viii Mathematically the Total Harmonic Dis tortion THD is the ratio of the root MAX SMOOTH Hz RANGE THD mean square RMS of the harmonic 0 0 0 0 8 content to the root mean square RMS value of the fundamental and expressed as percentage see 16 for details Harmonic Meter Model 721 29 THD Application Example
4. In theory the maximum current that the neutral will carry is 1 73 times the phase current If not sized correctly overheating will result Higher than normal neutral current will cause voltage drops between neutral and ground which are well above normal Readings above 4 volts indicate high neutral current False tripping of circuit breakers is also a problem encountered with the higher frequencies that harmonics produce Peak sensing circuit breakers often will trip even though the amperage value has not been exceeded Harmonic current Peak values can be many times higher than sinusoidal waveforms 18 Harmonic Meter Model 721 Power factor correction capacitor failure in many cases can be directly attributed to harmonic content Capacitors appear as extremely low imped ance values and are more susceptible to harmonics Inductive reactance varies directly with frequency XL 2pfl Parallel resonance between the capacitor bank and the source impedance can cause system resonance resulting in higher than normal currents and voltages High harmonic cur rents have been known to overheat correction capacitors causing prema ture failure and sometimes resulting in explosion lt To Source of Power lt Main Service Entrance Switch Capacitors Disconnect Switch for Capacitors Power Factor Capacitors at Resonant Frequency Most harmonic problems result when the resonant frequency is close to the 5th or 7t
5. Vout is always present when in A The analog output is independent and does not interfere with the current or power quality measurements THD DF CF Hz Min Max Peak An insulated banana jack to BNC connector is supplied with the instru ment Use your BNC lead and scope In essence you have a free current harmonic transducer for oscilloscopes or hand held scopes or even rent transducer for loggers and recorders 38 Harmonic Meter Model 721 1 Disconnect the probe from all circuits and turn the meter OFF 2 Connect the insulated BNC connector to the voltage jacks red to and black to 3 Connect your BNC cable to the insulated BNC jack and to your oscil loscope 4 Turn the rotary switch to the current measurement function A Selec tion is confirmed with a short beep 5 Press the trigger to open the jaws Clamp the jaws around the con ductor The most accurate readings are obtained with the conductor aligned with the centering marks on the jaws 6 Adjust the oscilloscope range for the desired waveform size and dis play Readings from the Model 721 are also valid The analog output is preset to 1 mV A at the factory and permits current measurements from 50 mA to 700 0 Arms and to 999 9 A Peak 5 8 1 Output Level The output is preset at 1 mV A at the factory We recommend that you use the oscilloscope amplification rather than changing the 1 mV A output in order to benefit from the full 700 Arms o
6. a sinusoidal wave form If the power user connects loads to the system which are resistive such as an incandescent light bulb the resulting current waveform will also be sinusoidal However if the loads are nonlinear which is typically the case the current is drawn in short pulses and the current waveform will be distorted Total current that is then drawn by the nonlinear load would be the fundamental as well as all the harmonics N PAPAS Fundamental 3rd Harmonic Resultant Distorted Waveform Harmonic distortion can cause serious problems for the users of electric power from inadvertent tripping of circuit breakers to dangerous overheat ing of transformers and neutral conductors as well as heating in motors and capacitor failure Harmonics can cause problems that are easy to recognize but difficult to diagnose It is becoming increasingly important to understand the fundamentals of harmonics and to be able to recognize and monitor the presence of dam aging harmonics Harmonics within an electrical system vary greatly within different parts of the same distribution system and are not limited simply 14 Harmonic Meter Model 721 to the supply of the harmonic producing device Harmonics can interact within the system through direct system connections or even through capacitive or inductive coupling A harmonic may be defined as an integer multiple of a fundamental fre quency Harmonics are d
7. bargraph will continue to display present values while other measurement functions are displayed In Volts Pushing the RANGE push button will select a fixed manual range 60 Vrms first and 600 Vrms on the second push The digital display and the bargraph indicate the selected range RANGE is displayed at the top of the display indicating a manual range selection Selection is also con firmed with an audible tone To sequence back to Auto Ranging push and hold the RANGE push button for approximately 3 seconds The displayed RANGE indicator will disappear confirmed with an audible tone The bargraph ranges are 60 Vrms and 600 Vrms and are also manually selected The analog bargraph will continue to display present values while other measurement functions are displayed Harmonic Meter Model 721 33 5 5 Hz Push Button Frequency Measurement The Hz push button accesses the frequency function while in either cur rent or in voltage Frequency measurements are possible from 0 5 Hz to 9999 Hz Frequency measurements are always Auto Ranging Pushing the RANGE push button will only select a fixed range of either 60 or 600 A or V on the bargraph The RANGE indicator is displayed at the top of the digital display indicating fixed A or V range selection on the bargraph Selection is confirmed with Model 721 an audible tone HARMONIC METER To sequence back to Auto Ranging push and hold the range selection push button for ap
8. greater than 1 414 Harmonic Meter Model 721 23 4 6 Limiting the Effects Harmonics Derating certain types of electrical equipment is the easiest way to limit the effects that the increased heating has on the equipment A 25 derating for transformers and generators is commonly employed in industry Filtering is currently the most common method used to limit the effects that harmonics present to the rest of the system Filters typically consist of tuned series L C circuits Filter impedance is negligible with respect to the rest of the system limiting its interaction effects for harmonic control Filters are sized to withstand the RMS current as well as the value of cur rent for the harmonics In the future systems may be available which will offset harmonics by applying signals that are equal in amplitude but opposite in phase thereby canceling or severely limiting harmonic effects I I I I Reactor 2 Bank Single tuned shunt filter 24 Harmonic Meter Model 721 Harmonic Meter Model 721 CHAPTER 5 OPERATION 5 1 Current Measurements AEMC Model 721 HARMONIC METER MIN MAX SMOOTH Hz RANGE THD 00000 A Turn the rotary switch to the current measurement function Selection is confirmed with a short beep Press the trigger to open the jaws Clamp the
9. problem take an inventory of equipment that may generate harmonic currents e g electronic equipment fluores cent lighting fixtures with electronic ballasts variable speed motors etc List the nonlinear loads which are on each branch circuit The electrical panel is the point at which most nonlinear harmonic problems can be detected Excessive current flow on the neutral can be detected with a True RMS current meter but may also be indicated by a resonant buzzing sound or even visually with discolored connections on the neutral buss Beginning at the service entrance panel measure and record the True RMS current in each phase as well as the neutral of the distribution trans former secondary Compare this measured neutral current to the antici pated current due to phase imbalance If the phase currents are equal the vector sum of the neutral currents will add to zero If excessive amounts of triplen harmonics are present in the neutral neutral current may exceed phase current Consult the NEC for the maximum ampacity for each of the conductors that have been tested 20 Harmonic Meter Model 721 Measure each feeder for har monic content A high degree at this location is often heard as a buzzing sound A voltage THD reading is also useful at this loca tion IEEE standard 519 1992 is a guidance document for utilities and electric power users which specifies both the maximum dis tortion levels and recommended correction leve
10. 999 9 V Peak A WARNING A Though the meter can display to 999 9 V in Auto Range and in the 600 V manual range the warning symbol will be displayed above 600 Vrms and accompanied by a beeping alarm sound This indicates that the input exceeds the specified safety and operating range The displayed value is only indicative and not specified Do not continue to operate the instrument when the input value exceeds the meter safety and operating specifications OL is displayed above 1000 V peak in the Peak mode and may also be accompanied by the warning triangle if the RMS value exceeds 600 V The warning symbol may also be displayed if the input signal is too low lt 50 mV or if the fundamental is not 50 or 60 Hz 27 5 2 1 Ranging Auto Ranging is selected by default and selects the best range for the digital display and for the analog bargraph Pushing the RANGE push button will select a fixed manual range 60 Arms first and 600 Vrms on the second push The digital display and the bargraph indicate the selected range RANGE is displayed at the top of the display indicating a manual range selection Selection is also confirmed with audible tone To sequence back to Auto Ranging push and hold the RANGE push button for approximately 3 seconds The displayed RANGE indicator will disappear confirmed with an audible tone 5 2 2 Other Functions All others push button functions relating to voltage may be accessed in V THD THD
11. E 41 6 1 Cleanitig ccce 41 6 2 Battery Test amp Replacement 41 6 2 1 Battery Replacement 42 Repair CallDratlOn 43 Technical and Sales Assistance ted t pene dd 43 Limited Warranty ett ete 44 Warranty u uu da 44 CHAPTER 1 INTRODUCTION A Warning A These safety warnings are provided to ensure the safety of personnel and proper operation of the instrument Read this instruction manual completely before attempting to use or ser vice this instrument and follow all the safety information Use caution on any circuit Potentially high voltages and currents may be present and may pose a shock hazard The meter must not be operated beyond its specified operating range Safety is the responsibility of the operator Never open the back of the meter while connected to any circuit or input Always make connections from the instrument to the circuit under test Always inspect the instrument and accessory leads for serviceability prior to use and replace defective parts immediately Do not use the meter or any test leads BNC leads connectors probes or clips if they look damaged Never use the meter on electrical conductors rate
12. IN PEAK MAX SMOOTH Hz RANGE THD MAX SMOOTH Hz RANGE THD 00000 80000 8 i AEMC 721 AEMC Model 721 INSTRUMENTS HARMONIC METER HARMONIC METER MIN PEAK MAX SMOOTH Hz RANGE THD MAX SMOOTH Hz RANGE THD 0000 0000 TC cow TE Harmonic Meter Model 721 37 Recording mode is stopped manually at any time by pushing the HOLD button RECORD PAUSE will then be displayed and the record indication will no longer blink At this point recorded measurement can be read by pushing the MIN MAX push button sequentially The bargraph blinks on the MIN and the MAX values To resume recording press HOLD again When recording PEAK measurements only MAX PEAK measurement values are stored in memory and the bargraph indicates Peak values and blinking MAX Peak Before accessing any other functions you must exit MIN MAX Recording by pushing and holding the MIN MAX push button a few seconds until it beeps The beep will indicate the mode change and the displayed RECORD symbol will disappear 5 8 Vout Analog Output When measuring current or current power quality the Model 721 automati cally provides an analog output 1 mV A or 10 mV A through the voltage terminals This function enables the user to display the actual current waveform on any oscilloscope or hand held scope You can take measurements on the clamp on and visualize the signal waveform on the oscilloscope
13. It is possible to calculate total harmonic current from a THD reading when a true RMS current or voltage is also known First solve for the Fun damental current using the following example Fundamental With the value for fundamental current known we can calculate for the amount of Harmonic Current Harmonic 1 RMS Fundamental Example The Model 721 measures a RMS value of 230 Amps and THD of 13096 This means that the harmonic content is 13096 of the fundamental Calcu late for Total Harmonic current by solving the equations 230 130 Y 100 D Fundamental 19665 140 23A Fundamental Harmonic e x Fundamental 1 3 x 140 23 182A 30 Harmonic Meter Model 721 5 3 2 DF Distortion Factor DF or Distortion Factor is the Total Har Model 721 monic Distortion referenced to the total AEMC Model 21 RMS signal The Distortion Factor is expressed as a percentage and may not be greater than the fundamental The DF never exceeds 100 The DF is sometimes referred to 1 1 I as the THD R MAX SMOOTH Hz RANGE THD Please note that our DF is not the same 0 value as the Distortion Factor as expressed in the IEEE standard 519 1992 in which L e Distortion Factor is the same as THD The DF is a useful term because of the market need to quickly determine the content of Harmonics and the requirement of Harmonics as a percentage of the Total RMS
14. arrives it will be tracked and processed promptly Please write the CSA on the outside of the shipping container If the instrument is returned for calibration we need to know if you want a standard calibration or a calibration traceable to N I S T Includes calibration certificate plus recorded calibration data Chauvin Arnoux Inc d b a AEMC Instruments 15 Faraday Drive Dover NH 03820 USA Tel 800 945 2362 Ext 360 603 749 6434 Ext 360 Fax 603 742 2346 or 603 749 6309 repair aemc com Or contact your authorized distributor Costs for repair standard calibration and calibration traceable to 5 are available NOTE All customers must obtain a CSA before returning any instrument Technical and Sales Assistance If you are experiencing any technical problems or require any assistance with the proper operation or application of your instrument please call mail fax or e mail our technical support hotline Chauvin Arnoux Inc d b a AEMC Instruments 200 Foxborough Boulevard Foxborough MA 02035 USA Phone 800 343 1391 508 698 2115 Fax 508 698 2118 techsupport aemc com www aemc com NOTE Do not ship Instruments to our Foxborough MA address 43 Harmonic Meter Model 721 Limited Warranty The Model 721 is warranted to the owner for a period of one year from the date of original purchase against defects in manufacture This limited warranty is give
15. be greater than 100 Total Harmonic Distortion THD Sum of squares of amplitudes of all 100 Square of amplitude of fundamental THD current 2 03 14 Is 1 2 100 THD voltage V2 V3 V4 Vs V1 100 Wherever there are large numbers of nonlinear loads there are sure to be harmonics in the distribution system Harmonic producing equipment is found in varied locations from administrative offices to manufacturing facilities In the factory environment electronic power converters such as variable speed drives SCR drives etc are the largest contributors to har monic distortion It is not uncommon to have THD levels as high as 2596 within some industrial settings 16 Harmonic Meter Model 721 Most single phase office equipment draws nonlinear current While fluo rescent lighting with electronic ballasts and many types of office equip ment contribute to creating harmonics personal computer power supplies are the largest contributor of harmonics within the office environment Although THD levels will be lower than in an industrial setting the suscep tibility of office equipment to variations in power quality is extremely high Current Draw Computer Current Waveform In the industrial environment there can be many three phase nonlinear loads drawing high levels of load current The most prevalent harmonic frequencies are the odd integer mult
16. ct ruggedness and overall design qualities the Model 721 is built with GE Lexan and meets specific physical standards the instrument features a high level of safety The Model 721 meets IEC 1010 1 Category III for 600 V ratings Harmonic Meter Model 721 5 The Model 721 is comfortable to hold compact easy to maneuver in crowded breaker panels The hooked jaw design facilitates clamping and accommodates two 500 MCM conductors The AEMC Harmonic Meter Model 721 works as easily as a clamp on mul timeter while permitting True RMS voltage and current measurements The rotary switch selects the volt or ampere range and beneath the large LCD five push buttons provide direct access to additional key measure ment and power quality values The Model 721 high sensitivity accepts low input levels 300 mA and 300 mV permitting power quality measurements on even low power or idling equipment an advantage not common to many instruments 6 Harmonic Meter Model 721 2 2 Control Features 1 Jaw assembly Transformer jaws opens to 1 7 43 mm Accepts two 500 MCM 2 Lever Trigger Opens or closes jaws 3 Display Liquid crystal display 9999 count 4 Min Max Selects Record mode for A V THD DF CF Hz Accesses the following values Max Min AVG Harmonic Meter Model 721 10 11 Peak Smooth Accesses the following modes Smooth for 3 second averaging for easy readings on fluctuating signals Peak mea
17. ction aside from improved efficiency is that high frequency harmon ics are superimposed onto the fundamental 60 Hz frequency The harmonics are produced by the diode capacitor input section which rectifies the AC signal into DC The circuit draws current from the line only during the peaks of the voltage waveform thereby charging a capacitor to the Peak of line voltage The equipment DC requirements are fed from this capacitor and as a result the current waveform becomes distorted Harmonic Meter Model 721 15 Harmonics in the electric power system combine with the fundamental frequency to create distortion The level of distortion is directly related to the frequencies and amplitudes of the harmonic current The contribution of all harmonic frequency currents to the fundamental current is known as Total Harmonic Distortion or THD This THD value is expressed as a percentage Voltage of the fundamental current THD values of over 10 are reason for concern TE THD is calculated as the square root of the sum of the squares of all the har monics divided by the fun damental signal 50 or 60 Hz This calculation arrives at the value of distortion as a percentage of the fundamental gt E Nonlinear Current Draw Mathematically is the ratio of the root mean square RMS of the harmonic content to the root mean square RMS value of the fundamen tal 50 or 60 Hz signal THD is expressed as a percentage and may
18. d above 600Vrms International Electrical Symbols E This symbol signifies that the instrument is protected by double or reinforced insulation Use only specified replacement parts when servicing the instrument A This symbol on the instrument indicates a WARNING and that the operator must refer to the user manual for instructions before operating the instrument In this manual the symbol preceding instructions indicates that if the instructions are not followed bodily injury installation sample and product damage may result Risk of electric shock The voltage at the parts marked with this symbol may be dangerous Harmonic Meter Model 721 3 1 1 Receiving Your Shipment Upon receiving your shipment make sure that the contents are consis tent with the packing list Notify your distributor of any missing items If the equipment appears to be damaged file a claim immediately with the carrier and notify your distributor at once giving a detailed description of any damage Save the damaged packing container to substantiate your claim 1 2 Ordering Information Harmonic Meter Model 721 Cat 1208 52 Includes a 9V battery two 5 ft 1 5m leads two test probes two grip probes one insulated banana to BNC connector a user manual and a hard carrying case 4 Harmonic Meter Model 721 CHAPTER 2 PRODUCT FEATURES 2 1 Description The Harmonic Meter Model 721 combines th
19. d servicing single phase nonlinear loads such as PCs computer terminals or other office equipment For further use of the CBEMA Derating Factor contact CBEMA directly It should be noted that there is no direct or useful relationship between the CBEMA Derating Factor the and Transformer Factor IEEE 57 110 1986 Crest Factor CF Peak RMS CBEMA Derating Factor 1 414 x RMS Peak 1 414 CF 5 3 4 Bargraph Please note that the analog bargraph will continue to display Arms or Vrms while THD function measurement values 96 THD DF CF are displayed The Range button only changes the bargraph ranges while in the THD function 32 Harmonic Meter Model 721 5 4 Range Push Button Manual Ranges Pressing the RANGE push button enables you to exit the auto ranging mode and enter manual ranges RANGE operates in either current or volt age In Amps Pushing the RANGE push button will select a fixed manual range 60 Arms first and 600 Arms on the second push The digital display and the bargraph indicate the selected range RANGE is displayed at the top of the display indicating a manual range selection Selection is also con firmed with an audible tone To sequence back to Auto Ranging push and hold the RANGE push button for approximately 3 seconds The displayed RANGE indicator will disappear confirmed with an audible tone The bargraph ranges are 60 Arms and 600 Arms and are also manually selected The analog
20. e simplicity and familiarity of digital clamp ons with today s critical information on power quality and harmonics Operation is simple and direct with no menus calculations or complex analyzer procedures Select Amps or Volts on the rotary dial connect and measure The push of a button gives additional or more specific informa tion You can troubleshoot and measure power quality with the ease of using a digital clamp on simply safely and economically The Model 721 performs current and voltage measurements in True RMS and provides immediate readings of total harmonic distortion dis tortion factor DF crest factor CF and Peak of distorted currents and complex voltages It also gives the minimum maximum maximum Peak and average measurement values so you can record for over 24 hours to monitor daily fluctuations And you can measure frequency Hz through either the current or the voltage at any time In addition the instrument s analog output allows display of the current waveforms on any oscilloscope or hand held scope while measuring or the output may be used for loggers and recorders The Model 721 incorporates True RMS electronics and measurement techniques to ensure correct and accurate readings on distorted wave forms Use the Model 721 as a comprehensive tool for troubleshooting as well as for daily measurements on circuits supplying traditional and today s nonlinear loads Beyond the absolute produ
21. esignated by their harmonic number For our discussion we will focus on the 60 Hz power frequency The second har monic would be two times the fundamental or 120 Hz The third would be three times the fundamental or 180 Hz and so on Nonlinear equipment generates harmonic frequencies The nonlinear nature of a device draws current waveforms that do not follow the voltage waveform Electronic equipment is a good example While this is a broad category that encompasses many different types of equipment most of these devices have one characteristic in common They rely on an internal DC power source for their operation LOADS WHICH PRODUCE HARMONIC CURRENTS Electronic lighting ballast Adjustable speed drives Electric arc furnaces Personal computers Electric welding equipment Solid state rectifiers Industrial process controls UPS systems Saturated transformers Solid state elevator controls Medical equipment This is by no means an exhaustive list of equipment which generate har monics Any electronic based equipment should be suspected of produc ing harmonics Due to the ever increasing use of electronics the percentage of equip ment which generates harmonic current has increased significantly The harmonic problem manifests itself with proliferation of equipment using diode capacitor input power supplies This type of equipment draws cur rent in a short pulse only during the Peak of the sine wave The result of this a
22. fe It is considered good practice to replace any battery with only a few hours of life remaining Power Source 9V Alkaline battery NEDA 1604 6LF22 6LR61 Source Life 50 hr continuous use approx Harmonic Meter Model 721 41 6 2 1 Battery Replacement 1 The instrument must be OFF and disconnected from any circuit or input 2 Place the meter face down and remove the three Phillips screws on the back of the instrument ELEME 3 Remove the back cover by pulling it down and away from the instrument 4 Liftthe battery away from the case and disconnect the battery 5 Connect the new battery and position the leads so that they won t get pinched when the cover is replaced 6 Replace the back cover noting that it slips beneath the hold down lip and fits securely into position Take care to position any loose wire or circuit correctly before closing 7 Install and tighten the three screws Battery Compartment Vout Range Switch Left 1 mV A Right 10mv A 42 Harmonic Meter Model 721 Hs Repair Calibration m a To ensure that your instrument meets factory specifications we recommend that it be submitted to our factory Service Center at one year intervals for reca libration or as required by other standards or internal procedures For instrument repair and calibration You must contact our Service Center for a Customer Service Authorization Number CSA This will ensure that when your instrument
23. for a square wave and a triangular wave with 50 duty cycle at 50 or 60 Hz R refers to Reading and 5 to count s Counts may also be referred to as the least significant digits LSD CURRENT TRMS Input Range 0 05 to 700 0 Arms 4999 9 A Peak Basic Accuracy 0 3 to 99 99 A 2 R 20 cts 100 0 to 400 0 A 2 R 400 0 to 700 0 A 5 R Crest Factor gt 3 0 below 300A Frequency Range 15 Hz to 10 kHz CURRENT PEAK Input Range 0 05 to 999 9 A Peak Basic Accuracy 0 05 to 99 99 A 3 R 30 cts 100 to 600 A 3 R 600 to 999 9 8 R VOLTAGE TRMS Input Range 0 05 to 600 Vrms 1200 V Peak Basic Accuracy 0 3 to 400 0 1 5 R 4 cts 400 0 to 999 9 V 1 5 R Crest Factor gt 4 0 below 300 V Input Impedance 1 MQ 47 pF Frequency Range 15 Hz to 10 kHz 10 Harmonic Meter Model 721 Input Range 0 05 to 999 9 Peak Basic Accuracy 0 05 to 99 99 V 3 30 cts 100 to 999 9 V 3 TOTAL HARMONIC DISTORTION THD Range 0 5 to 600 0 Resolution 0 1 Minimum Input 300 mA 300 mV Basic Accuracy 50 60 Hz 3 2 cts Frequency Range Fundamental 45 to 65 Hz 25th harmonic Display Digital Bargraph True RMS A or V DISTORTION FACTOR Range 0 5 to 100 Resolution 0 1 Minimum Input 300 mA 300 mV Basic Accuracy 50 60 Hz 3 R 2 cts Frequency Range Fundamental 45 to 65 Hz 25th harmonic Display Digital Bargraph True RMS A or V
24. h harmonic These happen to be the largest harmonic ampli tude numbers that adjustable speed drives create When this situation arises capacitor banks should be resized to shift the resonant point to another frequency Another useful parameter is the Distortion Factor or DF DF is the Total Harmonic Distortion referenced to the total RMS signal The Distortion Factor is expressed as a percentage and may not be greater than 100 We provide this term because of the market need and the requirement of this value under the international standard IEC 555 Mathematically DF is the ratio of the root mean square RMS of the harmonic content to the root mean square RMS value of the total signal and expressed as a percentage Harmonic Meter Model 721 19 Distortion Factor DF Sum of squares of amplitudes of all imei 100 Total RMS DF current 02 03 Ia 15 IRMSY 100 DF voltage rasoir 100 Please note that our DF is not the same value as the Distortion Factor as expressed in the IEEE standard 519 1992 in which Distortion Factor is same as THD 4 1 Detection and Measurement Harmonic analysis is the first step in alleviating the many problems that can be encountered Field measurements are performed to identify fre quency and magnitude An important factor to remember is that most distribution systems are designed specifically to carry 60 Hz To begin identifying a possible harmonics
25. he harmonic waveform usu ally swings equally in both the positive and negative direction the even number harmonics are mitigated Heating effect causes the greatest problem in electrical equipment Many times electrical distribution equipment has overheated and failed even when operating well below the suggested rating requirements Tempera ture increase is directly related to the increase in RMS current Because harmonic frequencies are always higher than the 60 Hz funda mental frequency skin effect also becomes a factor Skin effect is a phe nomenon where the higher frequency causes the electrons to flow toward the outer sides of the conductor effectively reducing the cross sectional diameter of the conductor and thereby reducing the ampacity rating of the cable This effect increases as the frequency and the amplitude increase As a result higher harmonic frequencies cause a greater degree of heat ing in conductors On balanced three phase systems with no harmonic content the line cur rents are 120 degrees out of phase canceling each other and resulting in very little neutral current However when there is distortion in any one of the phase currents the harmonic currents increase and the cancellation effect is lessened The result is typically a neutral current that is signifi cantly higher than planned The triplen harmonics odd multiples of three are additive in the neutral and can quickly cause dangerous overheating
26. iples of the 60 Hz frequency The third harmonic 180 Hz is always the most prevalent and troublesome In general even harmonics cancel out and are negligible The largest single current draw for ballasts is the third harmonic Triplens odd multiples of the third harmonic are typically the dominant harmonics and are most common in single phase nonlinear loads The fifth and seventh harmonics are dominant generally in motor drives Large commercial buildings have many different sizes and types of loads In most installations the power is distributed with 208 120 volt transform ers in a Delta Wye configuration When multiple loads are supplied each generates triplen harmonic currents on the neutral conductor which are sent on to the transformer secondary and reflected into the delta primary These currents circulate within the delta primary causing overheating and shortened service life 480V 208V Transformer A C1 B C2 Secondary C3 C Neutral Delta Primary Circulating Current Harmonic Meter Model 721 17 Harmonics can cause variety of problems to any electrical power user For large users the problems can be intense For electronic equipment that relies on the zero crossing of the sinusoidal waveform such as clock timing devices heavy harmonic content can cause a zero crossing point offset Odd number harmonics 3rd 5th amp 7th cause the greatest concern in the electrical distribution system Because t
27. is a negative sequence harmonic causing the motor to have a backward rotation shortening the service life Harmonic Meter Model 721 21 Noise can be picked up communication equipment and telephone systems when harmonics at audio or radio frequencies are inductively or capacitively coupled into communication or data lines When induction disc watt hour meters are monitoring nonlinear loads depending on the content of the harmonics the disk may run slower or faster resulting in erroneous readings 4 3 Transformer Derating Most generators and transformers base their operating characteristics on non disturbed 60 Hz waveforms When the waveforms are rich in harmonics shortened service or complete failure is sure to follow The derating K factor can be applied specifically to transformers to ensure that dangerous heating will not result due to the transformer supplying load currents which are rich in harmonic content The K factor is determined by measuring the True RMS current of each har monic multiplied by the harmonic order and squared The total sum of this is then multiplied by the eddy current losses Transformer parasitic heating due to harmonic currents is frequency dependent higher frequency harmonic cur rents cause a higher degree of transformer heating and failure The factor can be thought of as an index of the transformer s ability to handle nonlinear load current without abnormal heating Some distribution transf
28. jaws around the con ductor The most accurate readings are obtained with the conductor aligned with the centering marks on the jaws Take the reading from the display Current measurements are pos sible from 50 mA to 700 0 Arms and to 999 9 A Peak A WARNING A Although the meter can display up to 999 9 A in Auto Range and in the 600 A manual range the warning symbol will be displayed above 700 Arms and accompanied by a beeping alarm sound This indicates that the input exceeds the specified safety and operating range The displayed value is only indicative and not specified Do not continue to operate the instrument when the input value exceeds the meter safety and operating specifications OL is displayed above 1000 A peak in the Peak mode and may also be accompanied by the warning triangle if the RMS value exceeds 700 A The warning symbol may also be displayed if the input signal is too low 50 or if the fundamental signal is 50 60 Hz 25 5 1 1 Ranging Auto Ranging is selected by default selects the best range for the digital display and for the analog bargraph Pushing the RANGE push button selects a fixed manual range 60 Arms first and 600 Arms on the second push The digital display and the bargraph indicate the selected range RANGE is displayed at the top of the display indicating a manual range selection Selection is also confirmed with audible tone To sequence back to Auto Ranging
29. ks IEC 68 2 27 12 Harmonic Meter Model 721 3 4 Safety Specifications Protection Level Double insulation IEC 1010 1 600 V Category III Pollution degree 2 Working Voltage 600 Vrms Dielectric Test 5 5 kV 50 60 Hz 1 minute Overload Protection Voltage 1 5 kV Peak permanent Current 3000 AAC permanent Analog output 1 5 kV Peak permanent Agency Approvals UL CSA GS VDE ELECTROMAGNETIC COMPATIBILITY Electrostatic Discharge IEC 801 2 No influence 4 kV class 2 Non destructive 15 kV class 4 RF IEC 801 3 No influence 3 V m class 2 Minor influence 10 V m class 3 Transients IEC 801 4 No influence 2 kV class 4 Electric shocks IEC 801 5 No influence 1 kV class 3 Harmonic Meter Model 721 13 CHAPTER 4 UNDERSTANDING ELECTRICAL HARMONICS Until fairly recently power quality referred to the ability of the electric utilities to supply electric power without interruption Today the phrase encompasses any deviation from a perfect sinusoidal waveform Power quality now relates to short term transients as well as steady state distor tions Power system harmonics are a steady state problem with danger ous results Harmonics can be present in current voltage or both Within the next few years as many as half of all electrical devices will operate with nonlinear current draw Utility companies invest millions of dollars each year to ensure that voltage supplied to their customers is as close as possible to
30. ls The harmonic distortion limit of 5 is proven to be the point where harmon ics begin to have a detrimental effect on an electrical distribution Measuring Neutral Currents system at Service Entrance Panel Harmonic current measurements define the harmonic generating charac teristics of the load so measurements should be taken at the load when possible Voltage measurements define the system response and are usu ally taken at the individual busses 4 2 Effects on the System To compound the problems that harmonic currents present to the system the nonlinear harmonic load currents also have an Ohm s Law relationship with the source impedance of the system to produce voltage harmonics Consider a heavily loaded transformer that is affected by one branch cir cuit feeding a nonlinear load the resulting voltage harmonics can then be passed down to all the remaining circuits fed by that transformer Voltage harmonics may cause havoc within the electrical system Motors are typically considered to be linear loads however when the source volt age supply is rich in harmonics the motor will draw harmonic current The result is typically a higher than normal operating temperature and short ened service life Different frequency harmonic currents can cause additional rotating fields in the motor Depending on the frequency the motor will rotate in the oppo site direction counter torque The fifth harmonic which is very prevalent
31. n A or V Aor gt Smooth gt Peak gt Aor V In THD THD function Smooth THD Function In Hz Hz Smooth Hz 5 6 1 Smooth Smooth stabilizes the digital readings when measurements are fluctuating In AEMC Model 721 this mode the Model 721 calculates and SMOOTH displays a three second average reading Smooth may be used in Volts Amps Fre quency as well as power quality functions THD DF CF Smooth may also be used while in the MIN MAX recording 08 mode The analog bargraph will not be affected by the Smooth functions and continues to display Arms or Vrms Harmonic Meter Model 721 35 5 6 2 Peak is a fast responding function which measures the instantaneous 1ms Peak values of the measured signal This function is often used for half cycle in rushing signals The Peak function is displayed in the lower right hand corner of the display next to the measurement symbol AEMC Model 721 HARMONIC METER Peak may also be accessed when record ing When recording MIN MAX depress ing PEAK gives the MAX Peak only 1 TP 2 1 1 The bargraph also indicates the Peak values When a Peak value exceeds Buono RANGE D the bargraph scale an arrow at the end of the scale gt is displayed When MAX Peak the MAX Peak value blinks while the bargraph continues to respond in Peak mode cov T GS 5 7 MIN MAX Push Button Recording Function The recordi
32. n by AEMC Instruments not by the distributor from whom it was purchased This warranty is void if the unit has been tampered with abused or if the defect is related to service not performed by AEMC Instruments For full and detailed warranty coverage please read the Warranty Cov erage Information which is attached to the Warranty Registration Card if enclosed or is available at www aemc com Please keep the War ranty Coverage Information with your records What AEMC Instruments will do If a malfunction occurs within the one year period you may return the instrument to us for repair provided we have your warranty registration information on file or a proof of purchase AEMC Instruments will at its option repair or replace the faulty material REGISTER ONLINE AT www aemc com ssnr Warranty Repairs What you must do to return an Instrument for Warranty Repair First request a Customer Service Authorization Number CSA by phone or by fax from our Service Department see address below then return the instrument along with the signed CSA Form Please write the CSA on the outside of the shipping container Return the instrument postage or shipment pre paid to Chauvin Arnoux Inc d b a AEMC Instruments Service Department 15 Faraday Drive Dover NH 03820 USA Tel 800 945 2362 Ext 360 603 749 6434 Ext 360 Fax 603 742 2346 or 603 749 6309 repair aemc com Caution To protect you
33. n the Record Mode MAX Displays maximum measurement value MIN Displays minimum measurement value Displays average measurement value THD Total Harmonic Distortion DF Distortion Factor CF Crest Factor PEAK Peak 1 ms measurement MAX Peak is available in the recording mode 2 Auto Off feature disabled Bargraph Analog bargraph for trend measurements A V and remaining battery life at power up 2 3 1 Display and Error Indications UL Input overload gt 999 9 V peak or gt 999 9 A peak vem Input signal below measurement range A Input exceeds safety measurement or operating range The warn ing triangle is accompanied by a beeping alarm Discontinue mea surement and refer to the specific function and specification section in user manual Please note that the warning triangle will also be displayed if the input signals are too low or if the fundamental signal is not 50 or 60Hz Harmonic Meter Model 721 9 3 SPECIFICATIONS 3 1 Electrical Specifications Reference Conditions Accuracies are provided under the following reference conditions Temperature 23 C 5K 45 to 75 RH battery voltage 8 5V to 9V conductor centered in the probe jaws DC magnetic field earth s field no external AC magnetic field no external electrical field sine wave 45 to 65 Hz In Peak basic accuracy is based on 1 ms samples and a signal from 10 to 500 Hz In THD and DF the basic accuracy is provided
34. ng feature allows the user to record the Minimum MIN Maxi mum MAX Average AVG and Maximum Peak MAX Peak measure ment values By pressing the MIN MAX push button sequentially the measurements are displayed Recording is possible in A V THD DF CF and HZ If SMOOTH is selected prior to RECORDING the smoothed values are recorded Push Button Sequencing In A or V Aor V Max gt Min gt Avg gt Aor V In A or V Peak A or V Peak Max Peak gt A or V Peak In THD Functions THD Function Max Min gt Avg gt THD Function In Hz Hz 5 Max gt Min gt Avg gt Hz Note The same operations apply with SMOOTH turned on Recording is initiated with the MIN MAX push button during the selected measurement function RECORD indication will blink 1 second during the record mode Control is verified with a short beep 36 Harmonic Meter Model 721 Recording is possible for up to 24 hours when using a fresh battery and limited to 8 hours in THD and DF During record mode a beep indicates the capture of each new minimum and maximum value When recording current or voltage measurement information specific segments on the analog bargraph will blink indicating the current status of the MIN and MAX values In MIN MAX Recording the bargraph indicates Arms or Vrms The MIN and MAX values are also indicated and blink EMC Model 721 AEMC Model 721 INSTRUMENTS HARMONIC METER INSTRUMENT HARMONIC METER MIN PEAK M
35. ormers today are being designed with magnetic cores and windings to accommodate harmonic contents K rated transformer is specifically designed to handle nonlinear loads The higher the K factor value the better the ability of the transformer to handle nonlinear loads IEEE C57 110 1986 is a prescribed procedure used to derate the transformer loading based on the specific harmonic content Each specific electrical appli cation is unique in type and amount of harmonic interaction IEEE C57 12 00 1987 has proposed a limit of 5 for transformer harmonic current factor An alternate method for derating transformers is available for buildings which supply single phase 120 V receptacles This method is established by The Computer amp Business Equipment Manufacturers Association 1 414 CBEMA Derating Factor Crest Factor 22 Harmonic Meter Model 721 4 4 Meter Readings Harmonic problems can be analyzed more easily with the proper test equip ment The term True 5 or Root Mean Square relates to the equivalent DC heating value of the current or voltage waveform If for example we apply a pure sine wave and a distorted sine wave to a resistive load the point where they both create the same heating value is the point where they both have the same RMS value True RMS capability is required to accurately measure systems where har monic current is present Average responding instrumen
36. perating range The 10 mV A is limited to 60 Arms Analog output may be switched internally to either 1 mV per A or 10 mV per A The selection is made internally by a mini switch located under the input terminal circuit card found on the base of the instrument refer to the diagram on p 42 Extreme care should be exercised when changing the mini switch selec tion to avoid damaging internal components or wires This procedure should only be performed by qualified service personnel 5 9 Summary of Accessible Functions Harmonic Meter Model 721 39 5 10 Auto Off Feature The Model 721 will automatically shut itself off after 10 minutes during the following conditions No push button action e No rotary switch action No measurement change Not in Record Min Max mode A short beep will be heard prior to shutdown Any control action will re power the instrument The Auto Off feature may be disabled by holding down the RANGE push button while turning the rotary selection switch from OFF to either Amps or Volts vill be displayed in the upper left hand corner of the LCD when the Auto Off feature has been disabled The Auto Off feature will be reset when the Model 721 is turned off 5 11 Troubleshooting From time to time a minor malfunction may occur due to normal operating events Below are common events and solutions which should help you troubleshoot your Model 721 Symptom Recommended Action Instrumen
37. proximately 3 seconds Displayed RANGE indicator will disappear firmed with an audible tone PEAK SMOOTH push button is active in 0 0 8 0 0 Hz but only the Smooth feature is avail able Peak does not exist in Hz mea cow t surements see PEAK SMOOTH Push Button 8 5 6 MIN MAX is active in Hz see MIN MAX Push Button 8 5 7 If while measuring frequency on a 60 Hz system the Model 721 indicates 180 Hz then the third harmonic is dominant and exceeds the fundamental in magnitude This may occur in office settings on single phase loads or on lighting ballasts The Model 721 measures the frequency of the signal with the greatest amplitude The analog bargraph will continue to display Arms or Vrms depending upon which input function is selected The HZ function must be exited in order to select another measurement function Hz is exited by pressing the Hz push button briefly A brief beep will be emitted 34 Harmonic Meter Model 721 5 6 Peak Smooth Push Button Peak Smooth functions are accessed with this push button Control is veri fied with a short beep Peak and Smooth functions may be used for volt age and current measurements In THD functions and Hz measurement mode only Smooth is active The PEAK and SMOOTH are reached by sequentially pressing the push button Smooth and Peak are selected by sequentially pressing the Peak Smooth push button Push Button Sequencing I
38. push and hold the RANGE push button for approximately 3 seconds The displayed RANGE indicator will disappear confirmed with an audible tone 5 1 2 Analog Output Vout In the Current Measurement mode the Analog Output Vout is always acti vated in A see 5 8 and the 10 mV A or 100 mV A signal is present at the voltage terminals 5 1 3 Other Functions All others push button functions relating to current may be accessed in A e THD THD DF CF HZ PEAK SMOOTH MIN MAX recording These functions are described further in this manual see p 16 24 5 1 4 Bargraph Please note that the analog bargraph will continue to display RMS cur rent values while other measurement functions are displayed e g DF CF Hz Min Max Smooth Peak The bargraph ranges are 60 Arms and 600 Arms 26 Harmonic Meter Model 721 5 2 Voltage Measurements Harmonic Meter Model 721 AEMC Model 721 HARMONIC METER iann v v MIN PEAK MAX SMOOTH Hz RANGE THD 00000 t Turn the rotary switch to the voltage measurement function Selection is confirmed with a short beep Insert the red test lead into the jack and the black test lead into the jack Select the appropriate termination test probes or clips Touch or connect the voltage test leads to the circuit under test Take the reading from the display Voltage measurements are pos sible from 50 mV to 600 Vrms and to
39. rself against in transit loss we recommend you insure your returned material NOTE All customers must obtain a CSA before returning any instrument 44 Harmonic Meter Model 721 EJAEMC INSTRUMENTS 11 03 99 MAN 100066 v2 Chauvin Inc d b a Instruments 15 Faraday Drive Dover NH 03820 USA Phone 603 749 6434 Fax 603 742 2346 www aemc com www chauvin arnoux com
40. surement values 1 ms for A and V Hold Data Hold Freezes last measured value on display Does not freeze bargraph or analog output Rotary selection switch OFF Amps Vout Volts Hz Selects frequency measurement A or V input THD Accesses in A or V the following measurement modes THD Total Harmonic Distortion referenced to the fundamental Distortion Factor THD referenced to RMS CF Crest Factor Range Selects Auto Ranging or Manual Ranging measurement ranges A or V Voltage Jacks and Analog Output Vout COM black red 2 3 Digital Display Features SMOOTH RANGE RECORD PAUSE MAX MIN AVG pp RMS LI LI LI LI AV Freak 0 4 2 3 4 5 600 The combination digital analog display gives measurements a large 9999 count 3 digit LCD display A fast responding analog bargraph display provides indications for trends or surges A V 8 Displayed when instrument is measuring TRMS amperes Displayed when instrument is measuring TRMS voltage Harmonic Meter Model 721 sg Indicates that internal battery requires replacement SMOOTH Indicates three second measurement averaging to smooth fluctuating signals RANGE Displayed during manual range selection HOLD Displayed when Hold function is activated RECORD Blinks 1 second during record mode PAUSE Interrupts recording mode when Hold is activated i
41. t Measurements 25 54 1 Ranging creto oer ps 26 5 1 2 Analog Output VOU sioe 26 5 1 3 Other 5 cocco tea dere eae oe Pena 26 5 14 Bargtapbi i terit esee 26 5 2 Voltage Measurements 2n rx rep RE 27 5241 JRANGING zie 28 52 2 Other FUnctlons c RR SR 28 0 2 0 Bargraplicis ce 28 5 3 THD Push Button Power Quality Measurements 29 5 3 1 THD Total Harmonic Distortion 29 5 3 2 DE Distortion Factor 31 5 3 3 CF Crest deiade 32 5 3 4 DBargraBhu u uu t ine ac deor a 32 5 4 Range Push Button Manual Ranges 33 5 5 Hz Push Button Frequency 34 56 Peak Smooth Push Bultton dete 35 5 0 1 Smooth cie ca eds pdt a d 35 502 nte Sagan 36 5 7 MIN MAX Push Button Recording Function 36 58 Vout Analog Output ee 38 58 1 Output Level oet ERR 39 5 9 Summary Accessible 39 9 10 Auto Off Feature e teret 40 5 11 Troubleshooting tete eee 40 6 MAINTENANGCG
42. t will not turn on Low battery replacement required Missing or inaccurate readings Check that minimum input level is present Check that the transformer mating surfaces are clean No function control action Exit current mode with push button High frequency beep s Instrument may be beyond safety or operating range 40 Harmonic Meter Model 721 6 MAINTENANCE A WARNING To avoid electrical shock do not attempt to perform any servicing unless you are qualified to do so To avoid electrical shock and or damage to the probe do not get water or other foreign agents into the case Turn the Model 721 OFF and discon nect the meter from all circuits and inputs before opening the case 6 1 Cleaning Wipe the case and jaw covers with a damp cloth and mild detergent Do not use abrasives or solvents If rusted sand with very fine sandpaper then lightly oil Wipe off excess oil to prevent it from dripping into the case 6 2 Battery Test amp Replacement To determine useful battery life a self test may be initiated by holding down any push button while turning the rotary selector from the OFF posi tion to Amps or Volts All indicators will light up The Battery symbol as well as battery segment indi cator will blink indicating useful battery life remaining A full bargraph display represents 60 hours of useful battery life Each bar segment represents approximately two hours of battery li
43. ts will yield erroneous measurement results from 25 40 below the actual value when harmonic distortion is present Many instruments on the market measure average or Peak values of a waveform and internally multiply by 1 11 or 707 respectively to indicate RMS values These devices work well when measuring a pure sine wave Instruments with True RMS converters sample the waveform at many different points and provide accurate readings on distorted waveforms Microproces sor based circuits sample digitize and square each sample add it to the pre vious sample squared and take the square root of the total This process will yield a True RMS value regardless of the amount of distortion 4 5 Crest Factor The crest factor is the ratio of the Peak value of the sinusoidal waveform to its RMS value Peak Value Crest Factor CF RMS value Crest factor indicates the level of peaking Peak value that an instrument can handle without errors RMS value in the measurement For a perfect sine wave Average value the crest factor would be 1 414 This relates to the Peak amplitude that an instrument is capable of measuring accurately Typi cal crest factor ratings are from 2 0 to 6 0 The higher the factor the more capable the instrument of measuring a complex waveform correctly When harmonics are present crest RMS Avg Peak factors may be less than CF of a square Relationship on Sine Wave wave 1 or
44. under the international standard IEC 555 and possibly other standards Mathematically the Distortion Factor or DF is the ratio of the root mean square RMS of the harmonic content to the RMS value of the total signal and expressed as a percentage see p 20 for details DF Application Example The Model 721 measures an RMS value of 100 A and a DF of 30 The math ematics below show how to figure out the Harmonic and Fundamental current 2 Fundamental DE Harmonic TUS x RMS Using the measured values of RMS 100A and a DF of 30 we can com pute the Harmonic and Fundamental current 2 Fundamental S Fundamental 9100 954A Harmonic ae 100 0 3 x 100 30A Harmonic Meter Model 721 31 5 3 3 Crest Factor Crest Factor is the ratio of the Peak value of a waveform to its RMS value A perfect AEMC Model 721 sine wave has a crest factor of 1 414 In xxx distorted waveforms the crest factor is typically greater than 1 414 and gives an 1 71 indication of the harmonic content 4 2 3 lt Inmnmnmmm 0 1 I IIIIIIIIII The CF may also be used to determine MIN PEAK the CBEMA Computer amp Business Equip M s SS IHE ment Manufacturers Association Derat 0 0 0 0 8 ing Factor The CBEMA Derating Factor is used for evaluating the survivability of T existing conventional transformers in ser m vice an
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