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In Tune with Power Harmonics Fluke Corporation 1

Application Note

In Tune withPower Harmonics

Basic troubleshooting usingmultimeters and current clamps

What’s all the noiseabout harmonics?A mystery is occurring intoday’s office buildingsand manufacturing plants.Transformers supplyingseemingly average loadsare overheating. Neutralconductors in balancedcircuits are overheatingfrom excessive loads.Circuit breakers aretripping for no apparentreason.

Yet the standardtroubleshooting proce-dures show everything tobe normal. So what’s theproblem?

In one word—harmonics.

New technology introducesnew challengesHarmonics are the by-products ofmodern electronics. They are es-pecially prevalent wherever thereare large numbers of personalcomputers, adjustable speeddrives and other types of equip-ment that draw current in shortpulses.

This equipment is designed todraw current only during a con-trolled portion of the incomingvoltage waveform. While this dra-matically improves efficiency, itcauses harmonics in the load cur-rent. And that causes overheatedtransformers and neutrals, andtripped circuit breakers.

If you were to listen to an ordi-nary 60 cycle power line, you’dhear a monotone hum. When har-monics are present, you hear adifferent tune, rich with highnotes.

The problem is even more evi-dent when you look at the waveform. A normal 60 cycle powerline voltage appears on the oscil-loscope as a near sine wave(Figure 1) When harmonics arepresent, the waveform is distorted(Figure 2A and 2B). These wavesare described as non-sinusoidal.The voltage and current wave-forms are no longer simplyrelated—hence the term“non-linear.”

Getting to the rootof the problemFinding the problem is relativelyeasy once you know what to lookfor and where to look. Harmonicssymptoms are usually anythingbut subtle. This application notewill give you some basic pointerson how to find harmonics andsome suggestions of ways to ad-dress the problem. However, youshould call a consultant to ana-lyze your operation and design aplan for your specific situation.

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Figure 1. Near sine wave

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Figure 2A. Distorted current waveform

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Figure 2B. Distorted voltage waveform

2 Fluke Corporation In Tune with Power Harmonics

Work safelyThe high voltages and currentspresent in electrical power sys-tems can cause serious injury ordeath by electrocution. Conse-quently, testing and modifica-tion of electrical systems shouldbe performed by only trained,experienced electricians whohave knowledge of electricalsystems in general and theequipment under test.

Fluke cannot anticipate allpossible precautions that youmust take when performing themeasurements described in thisapplication note. At a minimum,however, you should:• Use appropriate safety equip-

ment such as safety glasses,insulating gloves, insulatingmats, etc.

• Be sure that all power hasbeen turned off, locked out,and tagged in any situationwhere you will be in directcontact with circuit compo-nents, and be certain that thepower can’t be turned on byanyone but you.

• Read and understand all ofthe applicable manuals be-fore using the application in-formation in this applicationnote. Take special note of allsafety precautions and warn-ings in the instructionmanuals.

This application note is a gen-eral guide to understandingharmonics. It is not intended tosubstitute for the services of aprofessional electrical systemsconsultant. Before you take anymeasures to diagnose or ad-dress your potential harmonicsproblems you should have youroperation thoroughly analyzedby a professional.

This application note is notintended as a tutorial on electri-cal theory. It assumes basicelectrical and electronic knowl-edge on the part of the reader.

Work Safely Sources of Harmonics

Defining the problemHarmonics are currents or volt-ages with frequencies that areinteger multiples of the funda-mental power frequency. Forexample if the fundamental fre-quency is 60 Hz, then the sec-ond harmonic is 120 Hz, thethird is 180 Hz, etc.

Harmonics are created bynon-linear loads that draw cur-rent in abrupt pulses ratherthan in a smooth sinusoidalmanner. These pulses cause dis-torted current wave shapeswhich in turn cause harmoniccurrents to flow back into otherparts of the power system.

The inside storyThis phenomenon is especiallyprevalent with equipment thathas diode-capacitor inputpower supplies, i.e., personalcomputers, printers and medicaltest equipment.

Electrically what happens isthe incoming ac voltage is dioderectified and is then used tocharge a large capacitor. After afew cycles, the capacitor ischarged to the peak voltage ofthe sine wave (e.g. 170V for a120V ac line). The electronicequipment then draws currentfrom this high dc voltage topower the rest of the circuit.

The equipment can draw thecurrent down to a regulatedlower limit. Typically, beforereaching that limit, the capacitoris recharged to the peak in thenext half cycle of the sine wave.This process is repeated overand over. The capacitor basi-cally draws a pulse of currentonly during the peak of thewave. During the rest of thewave, when the voltage is be-low the capacitor residual, thecapacitor draws no current.

The diode/capacitor powersupplies found in office equip-ment are typically single phasenon-linear loads. In industrialplants the most common causesof harmonic currents are three-phase non-linear loads whichinclude electronic motor drives,and uninterruptible power sup-plies (UPS).


Office buildings andplants—harmonicsare on the riseSymptoms of harmonics usuallyshow up in the power distribu-tion equipment that supportsthe non-linear loads. There aretwo basic types of non-linearloads—single-phase and three-phase. Single-phase non-linearloads are prevalent in offices,while three-phase loads arewidespread in industrial plants.

Each component of thepower distribution systemmanifests the effects of harmon-ics a little differently. Yet all aresubject to damage and ineffi-cient performance.

Neutral conductorsIn a 3-phase, 4-wire system,neutral conductors can beseverely affected by non-linearloads connected to the 120Vbranch circuits. Under normalconditions for a balanced linearload, the fundamental 60 Hzportion of the phase currentswill cancel in the neutralconductor.

In a 4-wire system withsingle-phase non-linear loads,certain odd-numbered harmon-ics called triplens—odd multi-ples of the third harmonic: 3rd,9th, 15th etc.—do not cancel,but rather add together in theneutral conductor. In systemswith many single-phase non-linear loads, the neutral currentcan actually exceed the phasecurrent. The danger here is ex-cessive overheating becausethere is no circuit breaker in theneutral conductor to limit thecurrent as there are in thephase conductors.

Excessive current in theneutral conductor can alsocause higher than normal volt-age drops between the neutralconductor and ground at the120V outlet.

Effects of Harmonic CurrentsVoltage harmonicsThe power line itself can bean indirect source of voltageharmonics.

The harmonic currentdrawn by non-linear loadsacts in an Ohm’s law rela-tionship with the source im-pedance of the supplyingtransformer to produce volt-age harmonics. Source im-pedance includes the sup-plying transformer andbranch circuit components.For example, a 10A har-monic current being drawnfrom a source impedance of0.1Ω will generate aharmonic voltage of 1.0V.

Any loads sharing atransformer or a branch cir-cuit with a heavy harmonicload can be affected by thevoltage harmonics gener-ated.

The personal computercan be affected by voltageharmonics. The performanceof the diode/capacitorpower supply is criticallydependent on the magni-tude of the peak voltage.Voltage harmonics cancause “flat topping” of thevoltage waveform loweringthe peak voltage (see Figure2B). In severe cases, thecomputer may reset due toinsufficient peak voltage.

In the industrial environ-ment, the induction motorand power factor correctioncapacitors can also be seri-ously affected by voltageharmonics.

Power correction capaci-tors can form a resonant cir-cuit with the inductive partsof a power distribution sys-tem. If the resonant fre-quency is near that of theharmonic voltage, the re-sultant harmonic currentcan increase substantially,overloading the capacitorsand blowing the capacitorfuses. Fortunately, the ca-pacitor failure detunes thecircuit and the resonancedisappears.

Circuit breakersCommon thermal-magnetic cir-cuit breakers use a bi-metallictrip mechanism which respondsto the heating effect of the cir-cuit current. It is designed torespond to the true-rms value ofthe current waveform andtherefore will trip when it getstoo hot. This type of breaker hasa better chance of protectingagainst harmonic currentoverloads.

A peak sensing electronic tripcircuit breaker responds to thepeak of current waveform. As aresult it won’t always respondproperly to harmonic currents.Since the peak of the harmoniccurrent is usually higher thannormal this type of circuitbreaker may trip prematurely ata low current. If the peak islower than normal the breakermay fail to trip when it should.

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Figure 3B. Three phase non-linear loadcurrent waveform

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Figure 3A. Single phase non-linear loadcurrent waveform


Effects of Harmonic Currents

Bus bars andconnecting lugsNeutral bus bars and connectinglugs are sized to carry the fullvalue of the rated phase cur-rent. They can become over-loaded when the neutral con-ductors are overloaded with theadditional sum of the triplenharmonics.

Electrical panelsHarmonics in electrical panelscan play a lively tune. Panelsthat are designed to carry 60 Hzcurrents can become mechani-cally resonant to the magneticfields generated by higherfrequency harmonic currents.When this happens, the panelvibrates and emits a buzzingsound at the harmonicfrequencies.

TelecommunicationsTelecommunications systemsoften give you the first clue to aharmonics problem. Telecom-munications cable is commonlyrun right next to power cables.To minimize the inductive inter-ference from phase current,telecommunications cables arerun closer to the neutral wire.Triplens in the neutral conduc-tor commonly cause inductiveinterference which can beheard on a phone line. This isoften the first indication of aharmonics problem and givesyou a head start in detectingthe problem before it causesmajor damage.

TransformerCommercial buildings commonlyhave a 208/120 volt transformerin a delta-wye configuration.These transformers commonlyfeed receptacles in a commer-cial building. Single phase non-linear loads connected to thereceptacles produce triplen har-monics which algebraically addup in the neutral. When thisneutral current reaches thetransformer it is reflected intothe delta primary windingwhere it causes overheatingand transformer failures.

Classification of harmonicsEach harmonic has a name, frequency and sequence. The sequence refers tophasor rotation with respect to the fundamental (F), i.e., in an induction motor,a positive sequence harmonic would generate a magnetic field that rotated inthe same direction as the fundamental. A negative sequence harmonic wouldrotate in the reverse direction. The first nine harmonics along with their effectsare listed below:

Name F 2nd* 3rd 4th* 5th 6th* 7th 8th* 9th

Frequency 60 120 180 240 300 360 420 480 540

Sequence + — 0 + — 0 + — 0

*Even harmonics disappear when waves are symmetrical (typical for electrical circuits)

Sequence Rotation Effects (from skin effect, eddy currents, etc.)

Positive Forward Heating of conductors, circuit breakers, etc.

Negative Reverse Heating as above + motor problems

Zero** None Heating, + add in neutral of 3-phase, 4-wire system

**Zero sequence harmonics (odd multiples of the 3rd) are called “Triplens” (3rd, 9th, 15th, 21st, etc.)

Another transformer problemresults from core loss and cop-per loss. Transformers are nor-mally rated for a 60 Hz phasecurrent load only. Higher fre-quency harmonic currents causeincreased core loss due to eddycurrents and hysteresis, result-ing in more heating than wouldoccur at the same 60 Hz current.These heating effects demandthat transformers be derated forharmonic loads or replaced withspecially designed transformers.

GeneratorsStandby generators are subjectto the same kind of overheatingproblems as transformers. Be-cause they provide emergencybackup for harmonic producingloads such as data processingequipment they are often evenmore vulnerable. In addition tooverheating, certain types ofharmonics produce distortion atthe zero crossing of the currentwaveform which causes inter-ference and instability for thegenerator’s control circuits.01

02

03

120V

Bra

nch

Circ

uits

208/480 Volt Transformer

SecondaryPrimary

Neutral

A

B

C


Survey the situationA harmonic survey will giveyou a good idea whether or notyou have a harmonic problemand where it is located. Hereare a few guidelines to follow.1. Load inventory—Make a

walking tour of the facilityand take a look at the typesof equipment in use. If youhave a lot of personal com-puters and printers, adjust-able-speed motors, solid-state heater controls andcertain types of fluorescentlighting, there’s a goodchance that harmonics arepresent.

2. Transformer Heat Check—Locate the transformersfeeding those non-linearloads and check for exces-sive heating. Also make surethe cooling vents areunobstructed.

3. Transformer SecondaryCurrent—Use a true-rmsmeter to check transformercurrents.• Verify that the voltage rat-

ings for the test equipmentare adequate for the trans-former being tested.

• Measure and record thetransformer secondarycurrents in each phaseand in the neutral (if used).

• Calculate the kVA deliv-ered to the load and com-pare it to the nameplaterating.Note: If harmonic currents arepresent, the transformer canoverheat even if the kVA deliv-ered is less than the nameplaterating.

• If the transformer second-ary is a 4-wire system,compare the measuredneutral current to thevalue predicted from theimbalance in the phasecurrents. (The neutral cur-rent is the vector sum ofthe phase currents andwould normally be zeroif the phase currents arebalanced in both ampli-tude and phase.) If theneutral current is unex-pectedly high, triplen har-monics are likely and thetransformer may need tobe derated.

• Measure the frequency ofthe neutral current. 180 Hzwould be a typical readingfor a neutral current con-sisting of mostly 3rdharmonic.

4. Sub-Panel Neutral CurrentCheck—Survey the sub-pan-els that feed harmonic loads.Measure the current in eachbranch neutral and comparethe measured value to therated capacity for the wiresize used. Check the neutralbusbar and feeder connec-tions for heating or discolor-ation. A non-contact infraredtemperature probe is usefulfor detecting excessive over-heating on busbars andconnections.

5. Receptacle Neutral-to-Ground Voltage Check—Neu-tral overloading in receptaclebranch circuits can some-times be detected by measur-ing the neutral-to-groundvoltage at the receptacle.Measure the voltage whenthe loads are on. Two volts orless is about normal. Highervoltages can indicate troubledepending on the length ofthe run, quality of connec-tions, etc. Measure the fre-quency. 180 Hz would sug-gest a strong presence ofharmonics. 60 Hz would sug-gest that the phases are outof balance.

Pay special attention to undercarpet wiring and modularoffice panels with integratedwiring that uses a neutralshared by three phase conduc-tors. Because the typical loadsin these two areas are computerand office machines they areoften trouble spots for over-loaded neutrals.

Finding Harmonics

In search of harmonicsHere’s a simple way to determinethe extent of harmonic distortioncaused by single phase non-linearload input circuits:

Make two separate currentmeasurements:1. Using an average responding

current clamp or meter with aclamp-on, e.g. Fluke 27 and80i-600.

2. Using a true-rms current clampmeter, such as the Fluke 32, 33or 36 or a true-rms meter with aclamp-on, e.g. Fluke 87 and80i-600.

Divide the results of the first mea-surement by the second measure-ment. This gives you the A/Rratio. A ratio of 1.0 would indicatelittle or no harmonic distortion.A ratio of 0.50 would indicatesubstantial harmonic distortion.

The A/R ratio method is not asubstitute for a harmonic analyzer,but it is a simple practical way todetermine whether there’s a prob-lem in single phase branch cir-cuits. Once you know harmonicsare present you can use a FlukeModel 39 or Model 41B to deter-mine the extent of the problem.Note: The A/R ratio method is useful forsingle phase branch circuit currents onlyand should not be used on three phaseloads.

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Troubleshooting Tools

True-rms metersgive you a headstartHaving the proper tools is cru-cial to diagnosing harmonicsproblems. The type of equip-ment you use varies with thecomplexity of measurementsyou need.

To determine whether youhave a harmonics problem youneed to measure the true-rmsvalue and the instantaneouspeak value of the wave shape.For this you need a true-rmsclamp meter like the Fluke 32,33 or 36, or a handheld digitalmultimeter that makes true-rmsmeasurements and has a highspeed (1 ms) peak hold circuitsuch as a Fluke 87.

Getting the true picture“True-rms” refers to the root-mean-square, or equivalentheating value of a current orvoltage wave shape. “True”distinguishes the measurementfrom those taken by “averageresponding” meters. The vastmajority of low cost portableamp clamp meters are averageresponding. These instrumentsgive correct readings for puresine waves only, and will typi-cally read low when confrontedwith a distorted current wave-form. The result is a readingthat can be up to 50% low.

True-rms meters give correctreadings for any wave shapewithin the instrument’s crestfactor and bandwidthspecifications.

Know your crest factorThe crest factor of a waveformis the ratio of the peak value tothe rms value. For a sine wave,the crest factor is 1.414. A true-rms meter will have a crest fac-tor specification. This spec re-lates to the level of peaking thatcan be measured without errors.

A quality true-rms handhelddigital multimeter has a crestfactor of 3.0 at full scale. This ismore than adequate for mostpower distribution measure-ments. At half scale the crestfactor is double. For example, inthe 400 volt ac range, the Fluke87 has a crest factor spec of 3.0when measuring 400V ac, anda crest factor of 6.0 when mea-suring 200V ac.Note: Most true-rms meters cannot beused for signals below 5% of scale dueto the measurement noise problem. Usea lower range if it is available.

Using a true-rms meter witha “Peak” function—like the Fluke87—or a “Crest” function—likethe Fluke 33—the crest factorcan be easily calculated. A crestfactor other than 1.414 indicatesthe presence of harmonics. Intypical single phase cases,the greater the differencefrom 1.414, the higher the har-monic content. For voltage har-monics, the typical crest factoris below 1.414, i.e. a “flat top”waveform. For single phasescurrent harmonics, the typicalcrest factor is much above 1.414.Three phase current waveformsoften exhibit the “double hump”waveform shown in Figure 3B,therefore the crest factor com-parison method should not beapplied to three phase loadcurrent.

After you’ve determined thatharmonics are present, you canmake a more in-depth analysisof the situation with a harmonicanalyzer such as Fluke models39 or 41B.

Multimeter Measuring Sine Wave Square Wave Distorted WaveType Circuit Response* Response* Response*

Average RectifiedCorrect 10% High Up to 50% LowResponding Average x 1.1

True-rms RMS Calculatingconverter.

Correct Correct CorrectCalculatesheating value.

*Within multimeter’s bandwidth and crest factor specifications

Multimeter performance comparisonaverage responding vs. true-rms


The following are some sugges-tions of ways to address sometypical harmonics problems.Before taking any such mea-sures you should call a powerquality expert to analyze theproblem and design a plantailored to your specificsituation.

In overloaded neutralsIn a 3-phase 4-wire system,the 60 Hz portion of the neutralcurrent can be minimized bybalancing the loads in eachphase. The triplen harmonicneutral current can be reducedby adding harmonic filters atthe load. If neither of thesesolutions are practical, you canpull in extra neutrals—ideallyone neutral for each phase. Oryou can install an oversizedneutral shared by three phaseconductors.

In new construction, under-carpet wiring and modularoffice partitions wiring shouldbe specified with individualneutrals and possibly an iso-lated ground separate from thesafety ground. (Reference FIPSPub 94, Guideline on ElectricalPower for ADP Installations,*and 1990 NEC Article 250-74exception No. 4.)

Derating transformersOne way to protect a trans-former from harmonics is to limitthe amount of load placed on it.This is called “derating” thetransformer. The most rigorousderating method is described inANSI/IEEE standard C57.110-1986. This method is somewhatimpractical because it requiresextensive loss data from thetransformer manufacturer plus acomplete harmonic spectrum ofthe load current.

The Computer & BusinessEquipment Manufacturers Asso-ciation (CBEMA), recently rec-ommended a second method

Solving the Problem

*Copies of this publication are for saleby the National Technical InformationService, U.S. Dept. of Commerce,Springfield, VA 22161. When ordering,refer to Federal Information ProcessingStandards Publication 94 and give title.

Note: National Electrical Code and NECare registered trademarks of theNational Fire Protection Association.

that involves several straightfor-ward measurements that youcan get with commonly avail-able test equipment. It appearsto give reasonable results for208/120 Y receptacle transform-ers that supply low frequencyodd harmonics (3rd, 5th, 7th)commonly generated by com-puters and office machinesoperating from single phasebranch circuits.

The test equipment you usemust be capable of taking boththe true-rms phase current, andthe instantaneous peak phasecurrent for each phase of thesecondary.

Derating factorTo determine the derating factor for the transformer, take the peak andtrue-rms current measurements for the three phase conductors. If thephases are not balanced, average the three measurements and plug thatvalue into the following formula:

HDF = Harmonic Derating Factor= (1.414)(true-rms Phase Current)

(Instantaneous Peak Phase Current)

This formula generates a value between 0 and 1.0, typicallybetween 0.5 and 0.9. If the phase currents are purely sinusoidal(undistorted) the instantaneous peaks are 1.414 times thetrue-rms value and the derating factor is 1.0. If that is the caseno derating is required.

However, with harmonics present the transformer rating is the product ofthe nameplate kVA rating times the HDF.

kVA derated = (HDF) x (kVA nameplate)

For example: 208/120 Y transformer rated at 225 kVA:

Conductor True-rms InstantaneousName Current Amps Peak Current

01 410A 804A02 445A 892A03 435A 828A

I phase avg. = 410 + 445 + 435 = 430A

3

I pk avg. = 804 + 892 + 828 = 841A

3

HDF = (1.414) (430) = 72.3%

841

The results indicate that with the level of harmonics present the transformershould be derated to 72.3% of its rating to prevent overheating.

Load currents were measuredwith a Fluke Model 87 and an80i-600 ac current probe toproduce the following results:


Case Study

SituationA modern office building dedi-cated primarily to computersoftware development con-tained a large number of per-sonal computers and otherelectronic office equipment.These electronic loads were fedby a 120/208V transformerconfigured with a delta primaryand a wye secondary. The PCswere fairly well distributedthroughout the building, exceptfor one large room that con-tained several machines. ThePCs in this room, used exclu-sively for testing, were servedby several branch circuits.

The transformer and mainswitch gear were located in aground floor electrical room.Inspection of this room immedi-ately revealed two symptoms ofhigh harmonic currents:• The transformer was gener-

ating a substantial amount ofheat.

• The main panel emitted anaudible buzzing sound. Thesound was not the chattercommonly associated with afaulty circuit breaker, butrather a deep resonant buzzthat indicated the mechani-cal parts of the panel itselfwere vibrating.

Ductwork installed directly overthe transformer to carry offsome of the excess heat keptthe room temperature withinreasonable limits.

Defining the problemTransformer—Current measure-ments (see Table 1) were takenon the neutral and on eachphase of the transformer sec-ondary using both a true-rmsmultimeter and an average-re-sponding unit. A 600A clamp-on current transformer acces-sory was connected to eachmeter to allow them to makehigh current readings. The cur-rent waveshapes are shown inFigures 4 and 5.

The presence of harmonicswas obvious by comparison ofphase current and neutral cur-rent measurements. As Table 1shows, the neutral current wassubstantially higher than any ofthe phase currents, even thoughthe phase currents were rela-tively well balanced. The aver-age-responding meter consis-tently took readings approxi-mately 20% low on all thephases. Its neutral current read-ings were only 2% low.

The waveforms explain thediscrepancy. The phase currentswere badly distorted by largeamounts of third harmonic cur-rent, while the neutral currentwas nearly a pure sinewave atthe third harmonic frequency.The phase current readingslisted in Table 1 demonstrateclearly why true-rms measure-ment capability is required toaccurately determine the valueof harmonic currents.

The next step was to calcu-late the “harmonic derating fac-tor” or HDF (Refer to “DeratingTransformer” section on theprevious page.)

The results indicated that,with the level of harmonicspresent, the transformer shouldbe derated to 72.3% of itsnameplate rating to preventoverheating. In this case thetransformer should be deratedto 72.3% of its 225 kVA rating,or derated to 162.7 kVA.

The actual load was calcu-lated to be 151.3 kVA. Althoughthat figure was far less than thenameplate rating, the trans-former was operating close toits derated capacity.

Subpanel—Next a subpanelwhich supplied branch circuitsfor the 120V receptacles wasalso examined. The current ineach neutral was measured andrecorded (see Table 2).

When a marginal or over-loaded conductor was identi-fied, the associated phase cur-rents and the neutral-to-groundvoltage at the receptacle werealso measured. When a check ofneutral #6 revealed 15 amperesin a conductor rated for 16A, thephase currents of the circuits(#25, #27, and #29) thatshared that neutral were alsomeasured (Table 3). Note thateach of the phase currents ofthese three branch circuits wassubstantially less than 15A, andalso the same phase conductorshad significant neutral-to-ground voltage drops.

Table 1. Current readings at the receptacle transformer secondary

AverageTrue-rms responding Instantaneous

Conductor multimeter multimeter peak currentname (amps) (amps) (amps)

Phase 1 410 328 804

Phase 2 445 346 892

Phase 3 435 355 828

Neutral 548 537 762


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Figure 5. Neutral current

In the branch circuits whichhad high neutral current, therelationship between the neu-tral and the phase currents wassimilar to that of the transformersecondary. The neutral currentwas higher than any of the as-sociated phase currents. Thedanger here is that the neutralconductors could become over-loaded and not offer the warn-ing signs of tripped circuitbreakers.

Recommendations1. Refrain from adding addi-

tional loads to the receptacletransformer unless steps aretaken to reduce the level ofharmonics.

2. Pull in extra neutrals to thebranch circuits that areheavily loaded.

3. Monitor the load currentson a regular basis usingtrue-rms measuring testequipment.

Neutral-to-groundCircuit Phase current voltage drop at

number (amps) receptacle

25 7.8 3.75V27 9.7 4.00V29 13.5 8.05V

Table 3. Phase currents and neutral-to-ground voltage for neutral #06

Neutralconductor Currentnumber (amps)

01 5.002 11.303 5.004 13.105 12.406 15.0*07 1.808 11.709 4.510 11.811 9.612 11.513 11.314 6.715 7.016 2.317 2.6

Table 2. Subpanel branch circuit neutral currents


The ABCs of Digital Multimeter Safety• Length: 20 minutes• Topics covered:

• Overvoltage categories• Proper work procedures and equipment• What to look for in a meter

Fluke 87• Volts, ohms, current,

frequency, dutycycle and diode test

• Analog/Digitaldisplay

• True-rms, backlitdisplay, 4 digitmode

• Auto/manualranging

• Automatic TouchHold®

• Continuity beeper• MIN/MAX/AVG• 1 msec peak hold

for crest factorcalculation

• Holster/Flex-StandTM

• 400 hour batterylife (alkaline)

• 3 year warranty• CAT I II-1000• UL 3111 Listed• CSA, CE, DVE

Understanding and Managing Harmonics• Length: 30 minutes• Topics covered:

• Definition of harmonics• Causes of harmonics• Effects of harmonics• Diagnosis of harmonics• Selection of test tools• Planning for harmonics

Fluke 39• Direct 3Ø/three-

phase readouts fromsimple single-phase measurements

• True-rms voltagefrom 10V to 600V

• True-rms currentfrom 1A to 500A(1000A withoptional probe)

• Peak, dc, and crestfactor

• Total harmonicdistortion (%THDFand %THDR)

• Active power from10W to 300 kW(600 kW withoptional probe)

• Apparent power(kVA)

• Total power factor(PF)

• Displacement powerfactor (DPF)

• K-factor• Frequency from

6 Hz to100 Hz(fundamental)

• Harmonics to 31st• Phase angle of

fundamental andharmonics

• Waveform andspectrum displays

• Record mode – MIN,MAX and AVG

• Zoom mode• 48-hour battery life

(4 “C” cells)• Handheld, 1 kg (2 lb)• Surge protection,

6 kV per IEC 1010-1CAT III-600V

• Marks – CE,CSANRTL, TÜV/GS

• Includes 500Acurrent clamp and“Managing ElectricalPower Systems”

Fluke Products

Fluke 41B• Direct 3Ø/three-

phase readouts fromsimple single-phase measurements

• True-rms voltagefrom 10V to 600V

• True-rms currentfrom 1A to 500A(1000A withoptional probe)

• Peak, dc, and crestfactor

• Total harmonicdistortion (%THDFand %THDR)

• Active power from10W to 300 kW(600 kW withoptional probe)

• Apparent power(kVA)

• Total power factor(PF)

• Displacement powerfactor (DPF)

• K-factor• Frequency from

6 Hz to100 Hz(fundamental)

• Harmonics to 31st• Phase angle of

fundamental andharmonics

• Waveform andspectrum displays

• Record mode – MIN,MAX and AVG

• Zoom mode• 48-hour battery life

(4 “C” cells)• Handheld, 1 kg (2 lb)• Surge protection,

6 kV per IEC 1010-1CAT III-600V

• Marks – CE,CSA NRTL, TÜV/GS

• Includes 500Acurrent clamp and“Managing ElectricalPower Systems”video

• Memory for eightcomplete data sets

• Optically isolatedRS-232 interface

• FlukeView™ PCsoftware forWindows® and DOSincluded

• New data loggingsoftware now

Fluke 36• 2000 count digital

display• 2% of reading,

basic accuracy forac current

• 1.9% of reading,basic accuracy fordc current

• One-year warranty• Max hold• Manual ranging• Ohms• Sleep mode• True-rms ac

measurement, crestfactor ≤3

Fluke 76• Volts, ohms,

resistance• True-rms,

smoothing• Analog/Digital

display• Capacitance from

99.99 nF to 9999µF

• Frequency ofvoltage from 1 Hz to20 kHz

• Lo ohms range to0.01Ω

• Continuity beeper• Sleep mode• Holster/Flex-StandTM

• 400 hour batterylife (alkaline)

• CAT I II-600V• UL Listed• CSA, TÜV, CE,

100ms AVG H

k

400 1 2 3 54 6 7 8 9 0

87 TRUE RMS MULTIMETER

MIN MAX RANGE HOLD H

REL Hz

mAA

A

mV

V

V

OFF

!

A COM VmA A

1000V MAX

400mA MAXFUSED

10A MAXFUSED

PEAK MIN MAX

Hz

VOFF

A

76 TRUE RMS MULTIMETER

mV H

V H

H

40

2000 400 600 800 1000Hz

FUSED

CAT

AUTORANGE,

V

RANGEPRESS

600V

40

TOUCH HOLD( )

10A COM

1 SEC

2 SEC

40mA

POWER METER39®

POWER HARMONICSANALYZER41B®

CAT

200A

200V

OFF

200

600V

600A1000A

MAX

600V 600A

1000A

CLAMP METER36

COM V

600VTRUE RMS

DC / ACZEROA

DC

Fluke Videos


80i-1000s• 1 to 1000 ampere

ac clamp-on currentprobe foroscilloscope

• Works with Model39 or 41B PowerMeters

80i-600• 1 to 600 ampere ac

clamp-on currentprobe formultimeters

80i-500s• 1 to 500 ampere ac

clamp-on currentprobe foroscilloscope

• Included withModel 39 or 41BPower Meters

80i-400• 1 to 400 ampere ac

clamp-on currentprobe formultimeters

80T-IR InfraredTemperature Probe• Non-contact

temperatureaccessory for DMMs

• Range: 0°F to 500°For -18°C to 260°C

Fluke 33• Combination

digital/analogdisplay

• 4000 count digitaldisplay (current);10,000 count digitaldisplay (frequency)

• True-rms• AC current 0.3A to

400A• Frequency• Display hold• Crest/instantaneous

peak• MIN/MAX/AVG

record mode• Crest factor ≤2.5• Sleep mode to

preserve battery life• SmoothingTM

displays a 3 secondrunning average ofcurrent orfrequency

33TRUE RMS CLAMP METER

HHOLD

MINMAX Hz

SMOOTHCREST RANGE

ONOFF

0 1 2 3 40 A

RECORD MAXSMOOTH

AUTO

RMSA

H


Fluke CorporationPO Box 9090, Everett, WA USA 98206

Fluke Europe B.V.PO Box 1186, 5602 BDEindhoven, The Netherlands

For more information call:U.S.A. (800) 443-5853 orFax (425) 356-5116Europe/M-East (31 40) 2 678 200 orFax (31 40) 2 678 222Canada (905) 890-7600 orFax (905) 890-6866Other countries (425) 356-5500 orFax (425) 356-5116Web access: http://www.fluke.com

©1997 Fluke Corporation. All rights reserved.Windows is a registered trademark of MicrosoftCorporation.Printed in U.S.A. 8/97 B0221UEN Rev F

Printed on recycled paper.

Fluke. Keeping your worldup and running.

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