AshraeMoncton2009.pptx
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AshraeMoncton2009.pptx
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,VariableFrequencyDrives&MotorsintheHVACIndustry,ASHRAENBPEIChapterMay12,2009,1,HVACVariableFrequencyDrives,PumpsFansTowers,2,3,ControlHPSaveEnergy,FlowSpeedHPSpeed3At50%Speed,HP=12.5%,CentrifugalLoads,Usedtobethemaintopic,4,AffinityLaws,FlowvsSpeedQ1/Q2=S1/S2HeadvsSpeedH1/H2=S12/S22HPvsSpeedbhp1/bhp2=S13/S23,5,TypicalHVACVFDApplications,FansAHU(SupplyAirFans)ReturnAirExhaustCoolingTowersEvaporativeCondensersPumpsChilledWaterCondenser,6,7,8,EnergySavings,Head,Head,Power,Power,Throttling(ridingthecurve),VFD(varyingthespeed),Speed1,Speed2,9,VariableFrequencyDrives,Over25yearsofHVACapplicationsFundamentalprincipalremainsunchangedConvertlinevoltage&frequencytocontrollablevaluesandapplytoinductionmotorsFora4polemotor:
60Hz=1800rpm30Hz=900rpm,Thepreferredchoicetoachievevariableflowcontrol,10,VariableFrequencyDrives,Numerousadvancementsoverthe25yrsPowerdevicesevolved:
Thyristor(SCR)GTOBipolarTransistortopresentdayIGBTdevicesIGBT(InsulatedGateBipolarTransistor):
FasterSwitching/HigherperformanceLowerlosses/HigherefficiencySmallerpackagingRobust/Increasedreliability,11,VariableFrequencyDrives,Numerousadvancementsoverthe25yrsMicroprocessorpower:
BettercontrolandaccuracyEnhancedfirmwareHighspeedcurrentlimit“Tripless”RegenAvoidanceBuilt-inPLCFunctionPIDcontrolloopNetworkcommunications:
BACnetMSTP,BACnetIP,FLN,N2,LonWorks,ModbusRTU,ModbusTCP/IPTodayVFDsareratedfor100kAinterruptcapacity,12,KeypadStoreMultipleParameterSetsUpload/DownloadParametersDownloadParameterswithoutpoweringuptheVFD,13,HighSpeedUSBporttocaptureoscilloscopetypedatatraces,14,15,InputLine,FilterCapacitor,Inverter,Rectifier,ACMotor,TypicalPWMVFD,575/3/60,ACtoDC,DCtoAC,0-575V0-60Hz,SpeedHz,TorqueV/Hz,DCBus,PWMOutput,16,Motors,ManufacturedtoNemaMG1standardPart30GeneralPurposenotgenerallyassociatedwithVFDapplicationsInsulationratedfor1000V/2msecrisetime(majorityofqualitymotorsratedforwithstandvoltageof1200Vto1400V),NotethatspecssuchasClassBorFrelatetotemperatureclassesnotvoltagewithstandrating.Similarlyefficiencyratingsalsodonotrelatetovoltagewithstandratings.,17,Motors,ManufacturedtoNemaMG1standardPart31DefinitePurposeInverterDutyInsulationratedfor1600V/0.1msecrisetime,NotethatspecssuchasClassBorFrelatetotemperatureclassesnotvoltagewithstandrating.Similarlyefficiencyratingsalsodonotrelatetovoltagewithstandratings.,18,Motors,ManufacturedtoNemaMG1standardPart31DefinitePurposeInverterDutyInsulationratedfor1600V/0.1msecrisetimeNewermotordesignsratedfor2000VSpeedTurndownrangeCT10:
1VT100:
15YearWarranty,19,Motors,CommentsandRecommendationsThevoltagewithstandratingrelatestothevoltagewaveformappliedtothemotorwindingsWhenconnectedtothelineanormalsinewavehasapeakvoltageofapprox800VPWMoutputwithvoltagereflectionduetofastrisetime(0.1msec)andlongcablecanapproachtwotimesthepeakvoltage(1600V).RecommendusingaNemaMG1Part31motorfornewinstallationsForretrofitinstallationsuseanoutputLRCdv/dtfilterSomeinstallationswithshortcablescanusealoadreactor.,20,ComponentVFDvsPackagedSystem,StandAloneComponentVFDVFDmountedandindividuallyconnectedtoexternalcomponents(intheirownenclosures)suchas:
DisconnectsorCircuitBreakersFusesReactorsand/orfiltersBypasscomponentsPackagedSystemVFDandcomponentsmountedandwiredinaNema1wallorfloormountenclosure,21,ComponentVFDvsPackagedSystem,APackagedSystemprovidesthefollowingbenefits:
MorecosteffectivevsFieldmountingandinterconnectingLessspacerequiredAvoidsfingerpointingrewarrantyissuesReducesmaterialmanagementonsite,22,SystemComponents,FusedDisconnect,LineReactororHarmonicFilter,VFD,LoadReactororLRCfilter,Bypass,O/L,23,Manydevicesaredefinedasnon-linearand“draw”currentfromthelineinsuchamannerastoinducecurrentharmonics.Examplesare:
AdjustableSpeedDrives(AC&DC)UPSSwitch-modepowersupplies(computers)ElectronicballastsPhaseconverters,Harmonics,24,WhatAreHarmonics,Basicpowersourceis575/3/60Baseorfundamentalfrequencyis60Hz-SinusoidalWewillseethatVFDlinecurrentisadistortedwaveformArepeating,distortedwaveformcanbeexpressedastheFundamental+multiplesofthefundamental,25,Mostcommonloadsdonotcauseharmonicse.g.IncandescentlightbulbsBaseboardheatersMotorsTheseareknownasLinearLoadsThecurrenttheydraw“follows”thevoltage,LoadsWithoutHarmonics,26,TheseareknownasNon-LinearLoadsThecurrenttheydrawdoesnot“follow”thevoltage,LoadsWithHarmonics,27,Harmonics,Voltage,Current,LinearLoadFund.Current,Non-LinearLoadFund.Current+Harmonics,28,Harmonics,Non-LinearLoadHighHarmonicContent,Non-LinearLoadReducedHarmonicContent,29,WhatareHarmonics?
Fundamental(60Hz),2ndHarmonic(120Hz),3rdHarmonic(180Hz),30,Fundamental,7thHarmonic,5thHarmonic,Harmonics,Fundamental+5thHarmonic+7thHarmonic,Note:
Lowestharmonicin6pulseVFDsisthe5th,31,EffectsofHarmonics,PreviousslidesreferredtoCurrentDistortionCurrentDistortionresultsinVoltageDistortionPotentialforoverheatingofTransformers,MotorsHarmonicresonanceHighneutralcurrents(1ph-3rdharm.),32,IEEE519,Originallyintroducedin1981toplacelimitsofVoltageDistortiononthepowerutilityatapointofcommoncouplingbetweenusersattheUtilitylevel.The1992revisionaddedlimitsofCurrentDistortionrelativetothesysteminwhichnon-linearloadsareutilized.,33,6&12PulseConfiguration,6Pulse,12Pulse,+,+,-,-,34,IEEE519,Asimplifiedsummaryofthe1992revisioncanbeexpressedas:
A“small”non-linearloadinstalledinalargeorstiffsystemwillnotresultinexcessiveharmonicdistortion.Astheratioofnon-linearloadsvssystemcapacityincreases,mitigationofharmoniclevelsmaybenecessary.,35,IEEE519-1992,current(fundamentalfrequencycomponent)atPCC.,Currentdistortionsthatresultinadcoffset,e.g.,half-waveconverters,arenotallowed.,36,IEEE519PCC,Xfmr1,Xfmr2,M,M,M,M,VFD,xxMVA69kV/13.8kV,xxkVA13.8kV/480V,PCC-1,PCC-2,“X”,37,IEEE519-PCC,Fromthepreviousslide:
TheintentofIEEE519isnotto“define”thePCCaspoint“X”butratheraspointsPCC1or2dependingontheUtilitymeteringpoint.(TDDappliedhere)IfXfmr1hasalargeMVAvaluetheISCwillbelargeaswellleadingtoagreaterISC/ILvaluethusahigherallowableTDD.,38,IEEE519-PCC,Fromthepreviousslide:
Thepracticesuggestedistoreducetheharmonicdistortionatpoint“X”butmeasuretheresultsatthePCCwhichistheintentofIEEE519SpecifyingthatTDDbemetatpoint“X”canleadtoexpensivesolutionsandmaynotbepossible.,39,IEEE519-PCC,Fromthepreviousslide:
IfcalculatedlevelsofbothCurrentandVoltagedistortionarerequiredatthequotationstagethefollowingmustbemadeavailable:
AsinglelinediagramTransformerdetailstocalculateIscLoaddetailstocalculateILAspecifiedPCC,40,HarmonicSolutions,ReduceHarmonicLevelsby:
AddingLineReactors12,18.PulseConfigurationAddTunedFilterTrapsAddPassiveBroadbandFiltersAddActiveFiltersAddActiveFrontEnd,IftheIEEE519levelsatthePCCcannotbemet,thenharmonicmitigationmustbeemployed.,41,HarmonicSolutions,A6pulseVFDwithoutanyfilteringwilltypicallyhaveacurrentdistortionlevelofapproximately75%Addinglinereactorswillreducethisto35-40%atalowcostMidlevelfilteringor12pulsesystemscanachievelevelsof9-15%atincreasedcost,Thevarioussolutionswillreducecurrentdistortionvaluesinvaryingdegrees,42,HarmonicSolutions,Highlevelfilteringor18+pulsesystemscanreducethecurrentdistortionleveldowntoapproximately5%atafurtherincreaseincost,43,Summary,ThesolutionshavelimitationsToleranceofVoltageunbalanceLeadingpowerfactorsatlightloadCompareefficiencyComparesize,44,45,NotephysicalsizeofHarmonicFiltersrelativetoDrivePanelsbesidethem,46,BypassPackagewithInputandOutputReactors,47,Summary,TherearevarioussolutionsSpecifyperformancenotthemethod,48,
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