AshraeMoncton2009

1VariableFrequencyDrives&MotorsintheHVACIndustryASHRAENBPEIChapterMay12,20092HVACVariableFrequencyDrivesPumpsFansTowers34ControlHP–SaveEnergyFlowSpeedHPSpeed3At50%Speed,HP=12.5%CentrifugalLoads5AffinityLawsFlowvsSpeed–Q1/Q2=S1/S2HeadvsSpeed–H1/H2=S12/S22HPvsSpeed–bhp1/bhp2=S13/S236TypicalHVACVFDApplicationsFansAHU(SupplyAirFans)ReturnAirExhaustCoolingTowersEvaporativeCondensersPumpsChilledWaterCondenser7TypicalCentrifugalFanSystem02040608010012030405060708090100%Flow%InputPowerTheoreticalFanCurveVFDOutletDamperVariableInletVane100%Flow8TypicalCentrifugalLow-Head,Low-FrictionPumpSystem0204060801001202030405060708090100%Flow%InputPowerTheoreticalPumpCurveVFDThrottlingValveRecirc/Bypass9EnergySavingsHeadHeadPowerPowerThrottling(ridingthecurve)VFD(varyingthespeed)Speed1Speed210VariableFrequencyDrivesOver25yearsofHVACapplicationsFundamentalprincipalremainsunchanged–Convertlinevoltage&frequencytocontrollablevaluesandapplytoinductionmotors–Fora4polemotor:60Hz=1800rpm30Hz=900rpmThepreferredchoicetoachievevariableflowcontrol11VariableFrequencyDrivesNumerousadvancementsoverthe25yrs–Powerdevicesevolved:Thyristor(SCR)GTOBipolarTransistortopresentdayIGBTdevicesIGBT(InsulatedGateBipolarTransistor):–FasterSwitching/Higherperformance–Lowerlosses/Higherefficiency–Smallerpackaging–Robust/Increasedreliability12VariableFrequencyDrivesNumerousadvancementsoverthe25yrs–Microprocessorpower:BettercontrolandaccuracyEnhancedfirmwareHighspeedcurrentlimit–“Tripless”RegenAvoidanceBuilt-inPLCFunctionPIDcontrolloop–Networkcommunications:BACnetMSTP,BACnetIP,FLN,N2,LonWorks,ModbusRTU,ModbusTCP/IP–TodayVFDsareratedfor100kAinterruptcapacity13Keypad•StoreMultipleParameterSets•Upload/DownloadParameters•DownloadParameterswithoutpoweringuptheVFD14HighSpeed–USBporttocaptureoscilloscopetypedatatraces1516InputLineFilterCapacitorInverterRectifierACMotorTypicalPWMVFD575/3/60ACtoDCDCtoAC0-575V0-60HzSpeedHzTorqueV/HzDCBusPWMOutput17MotorsManufacturedtoNemaMG1standard–Part30GeneralPurpose–notgenerallyassociatedwithVFDapplicationsInsulationratedfor1000V/2msecrisetime(majorityofqualitymotorsratedforwithstandvoltageof1200Vto1400V)NotethatspecssuchasClassBorFrelatetotemperatureclassesnotvoltagewithstandrating.Similarlyefficiencyratingsalsodonotrelatetovoltagewithstandratings.18MotorsManufacturedtoNemaMG1standard–Part31DefinitePurpose–InverterDutyInsulationratedfor1600V/0.1msecrisetimeNotethatspecssuchasClassBorFrelatetotemperatureclassesnotvoltagewithstandrating.Similarlyefficiencyratingsalsodonotrelatetovoltagewithstandratings.19MotorsManufacturedtoNemaMG1standard–Part31DefinitePurpose–InverterDutyInsulationratedfor1600V/0.1msecrisetimeNewermotordesignsratedfor2000VSpeedTurndownrange–CT10:1–VT100:15YearWarranty20MotorsCommentsandRecommendations–ThevoltagewithstandratingrelatestothevoltagewaveformappliedtothemotorwindingsWhenconnectedtothelineanormalsinewavehasapeakvoltageofapprox800VPWMoutputwithvoltagereflectionduetofastrisetime(0.1msec)andlongcablecanapproachtwotimesthepeakvoltage(1600V).RecommendusingaNemaMG1Part31motorfornewinstallationsForretrofitinstallationsuseanoutputLRCdv/dtfilterSomeinstallationswithshortcablescanusealoadreactor.21ComponentVFDvsPackagedSystemStandAloneComponentVFD–VFDmountedandindividuallyconnectedtoexternalcomponents(intheirownenclosures)suchas:DisconnectsorCircuitBreakersFusesReactorsand/orfiltersBypasscomponentsPackagedSystem–VFDandcomponentsmountedandwiredinaNema1wallorfloormountenclosure22ComponentVFDvsPackagedSystemAPackagedSystemprovidesthefollowingbenefits:–MorecosteffectivevsFieldmountingandinterconnecting–Lessspacerequired–Avoidsfingerpointingrewarrantyissues–Reducesmaterialmanagementonsite23SystemComponentsFusedDisconnectLineReactororHarmonicFilterVFDLoadReactororLRCfilterBypassO/L24Manydevicesaredefinedasnon-linearand“draw”currentfromthelineinsuchamannerastoinducecurrentharmonics.Examplesare:–AdjustableSpeedDrives(AC&DC)–UPS–Switch-modepowersupplies(computers)–Electronicballasts–PhaseconvertersHarmonics25WhatAreHarmonicsBasicpowersourceis575/3/60Baseorfundamentalfrequencyis60Hz-SinusoidalWewillseethatVFDlinecurrentisadistortedwaveformArepeating,distortedwaveformcanbeexpressedastheFundamental+multiplesofthefundamental26Mostcommonloadsdonotcauseharmonicse.g.–Incandescentlightbulbs–Baseboardheaters–MotorsTheseareknownasLinearLoadsThecurrenttheydraw“follows”thevoltageLoadsWithoutHarmonics27TheseareknownasNon-LinearLoadsThecurrenttheydrawdoesnot“follow”thevoltageLoadsWithHarmonics28HarmonicsVoltageCurrentLinearLoadFund.CurrentNon-LinearLoadFund.Current+Harmonics29HarmonicsNon-LinearLoadHighHarmonicContentNon-LinearLoadReducedHarmonicContentVoltageCurrent30WhatareHarmonics?-100-80-60-40-20020406080100090180270360Fundamental(60Hz)2ndHarmonic(120Hz)3rdHarmonic(180Hz)31-100-80-60-40-20020406080100090180270360Fundamental7thHarmonic5thHarmonicHarmonics•Fundamental+5thHarmonic+7thHarmonicNote:Lowestharmonicin6pulseVFD’sisthe5th32EffectsofHarmonicsPreviousslidesreferredtoCurrentDistortionCurrentDistortionresultsinVol