变频器制动电阻选择和计算方法课件

SizingDynamicBrakeResistors

andChopperModulesDynamicBrakeModuleCircuitUsingaDynamicBrakeorChopperIngeneral,themotorpowerrating,speed,torque,anddetailsoftheregenerativedutycycleneedtobeknown.Generally,adynamicbrakecanbeusedwheneverregenerativeenergyisdissipatedonanoccasionalorperiodicbasis.Ifthedrivewillconsistentlyberegenerating,seriousconsiderationshouldbegiventoreturningthepowertotheACutility.GathertheInformationFirstThenameplatepowerratingofthemotorinwatts,kilowatts,orhorsepower.Thenameplatespeedratingofthemotorinrpm,orrps.Themotorinertiaandloadinertiainkilogram-meters2,orlb-ft2.Thegearratio,ifagearispresentbetweenthemotorandload,GR.Themotorshaftspeed,torque,andpowerprothedriveapplication.ExampleSpeed,Torque,andPowerProfiletttHowtoChooseaDynamicBrake/ChopperCalculatethetotalinertiaofthesystemCalculatethepeakregenerativepoweryouneedtodissipate.ThiswilldeterminethemaximumallowableresistancevalueoftheDBresistor.CalculatetheaveragepowerdissipationThiswilldeterminetheaveragepowerdissipationcapacityneededintheDBresistor.Third,checktoseethatthepeaktemperatureofthedynamicbrakingresistordoesnotexceeditscapacity.PlottheAverageLoadandPeakLoadonthecurveinthesizingguide.Thisisnecessaryonlyonthedynamicbrakemodules!Dynamicbrakemodulesshouldonlybeusedondrives75HPandsmaller.HowtoSizeADynamicBrakeModuleStep1-TotalInertiaJT=totalinertiareflectedtothemotorshaft,kilogram-meters2(kg-m2)orpound-feet2(lb-ft2)Jm=motorinertia,kilogram-meters2(kg-m2)orpound-feet2(lb-ft2)GR=thegearratioforanygearbetweenthemotorandload,dimensionless.2:1=0.5JL=loadinertia,kilogram-meters2(kg-m2)orpound-feet2(lb-ft2)Note:1.0lb-ft2=0.04214011kg-m2DBModuleStep2-PeakRegenerativePowerJT=totalinertiareflectedtothemotorshaft,kg-m2wb=maxangularrotationalspeed,Rad/s=2pNb/60wo=angularrotationalspeed,lessthanratedspeed(canbezero)Rad/sNb=maximumapplicationspeedinRPMt3-t2=totaltimeofdecelerationfromwbtowo,secondsPb=peakbrakingpower,wattsNote:1.0HP=746wattsDBModuleStep3-MaximumDBResistorValueVd=thevalueofDCBusvoltagethatthechoppermoduleregulatesat.Thisvaluewillbe375VDCor750VDCor937.5VDCPb=peakbrakingpowercalculatedinstep2Rdb1=themaximumallowablevalueforthedynamicbrakeresistorResistortolerancescouldbebuiltinhere.+/-10%DBModuleStep4-ChoosetheCorrectDBModuleKA005-28ohms,666wattsKA010-13.2ohms,1650wattsKA050-10.5ohms,7000wattsKB005-108ohms,1500wattsKB010-52.7ohms,2063wattsKB050-10.5ohms,7000wattsKC005-108ohms,1500wattsKC010-52.7ohms,2063wattsKC050-15.8ohms,8000wattsDBModuleCopyright©2006RockwellAutomation,Inc.Allrightsreserved.Step5-EstimatetheAveragePowerPav=averagedynamicbrakeresistordissipation,wattst3-t2=elapsedtimetodeceleratefromwbspeedtowospeed,secondst4=totalcycletime,secondsPb=Peakbrakingpower,wattswb=maximummotorspeed,Rad/swo=aslowermotorspeed,Rad/sDBModuleStep6-PercentAverageLoadStep7-PercentPeakLoadAL=AverageLoadinpercentofDynamicBrakeResistorPav=Averagedynamicbrakeresistordissipationcalculatedinstep5,wattsPdb=SteadystatepowerdissipationcapacityoftheselecteddynamicbrakemodulePL=PeakLoadinpercentofDynamicBrakeResistorPav=Peakbrakingpowercalculatedinstep2,wattsPdb=SteadystatepowerdissipationcapacityoftheselecteddynamicbrakemoduleDBModuleStep8-PlotALandPLonCurvesDBModuleHowtoSelectaChopperModuleandDynamicBrakingResistorStep1-TotalInertiaJT=totalinertiareflectedtothemotorshaft,kilogram-meters2(kg-m2)orpound-feet2(lb-ft2)Jm=motorinertia,kilogram-meters2(kg-m2)orpound-feet2(lb-ft2)GR=thegearratioforanygearbetweenthemotorandload,dimensionless.2:1=0.5JL=loadinertia,kilogram-meters2(kg-m2)orpound-feet2(lb-ft2)Note:1.0lb-ft2=0.04214011kg-m2ChopperStep2-PeakRegenerativePowerJT=totalinertiareflectedtothemotorshaft,kg-m2wb=maxangularrotationalspeed,Rad/s=2pNb/60wo=angularrotationalspeed,lessthanratedspeed(canbezero)Rad/sNb=maximumapplicationspeedinRPMt3-t2=totaltimeofdecelerationfromwbtowo,secondsPb=peakbrakingpower,wattsNote:1.0HP=746wattsChopperStep3-MaximumDBResistorValueVd=thevalueofDCBusvoltagethatthechoppermoduleregulatesat.Thisvaluewillbe375VDCor750VDCor937.5VDCPb=peakbrakingpowercalculatedinstep2Rdb1=themaximumallowablevalueforthedynamicbrakeresistorResistortolerancescouldbebuiltinhere.+/-10%ChopperStep4-ChoosetheCorrectChopperModuleId1=theminimumcurrentflowingthroughthechoppermoduletransistorVd=thevalueoftheDCbusvoltage,seestep3Rdb1=themaximumallowablevalueforthedynamicbrakeresistorChopperCopyright©2006RockwellAutomation,Inc.Allrightsreserved.Step5-MinimumDBResistorValueStep6-ChoosingDBResistorValueRdb2=theminimumvalueofthedynamicbrakeresistorVd=thevalueoftheDCbusvoltage,seestep3Id2=thevalueofthecurrentratingforthechoppermoduleChopperAboutDutyCycleChopperGiventhataresistorcoolsoffinabout15minutes,ifcycletimeminusthedeceltimeexceeds900thenusingthelargercycletimecan’tbeusedforcalculatingaveragepower.Let’ssaythatIdecelin10secondseveryhour.Thatwouldbe10/3600or0.002777timesthepeakpower.WhatifIdecelin50secondsonceaday?Or60secondsonceaweek?Copyright©2006RockwellAutomation,Inc.Allrightsreserved.Step7-EstimateResistorWattagePav=averagedynamicbrakeresistordissipation,wattst3-t2=elapsedtimetodeceleratefromwbspeedtowospeed,secondst4=(adjusted)totalcycletime,secondsPb=Peakbrakingpower,wattswb=maximummotorspeed,Rad/swo=aslowermotorspeed,Rad/sChopperStep8–CalculateWatt-SecondsPws=requiredwatt-secondsoftheresistort3-t2=elapsedtimetodeceleratefromwbspeedtowospeed,secondsPb=Peakbrakingpower,wattsChopperCopyright©2006RockwellAutomation,Inc.Allrightsreserved.HowtoSizearesistorforPowerFlex70/700PowerFlex70/700Copyright©2006RockwellAutomation,Inc.Allrightsreserved.Step1-TotalInertiaJT=totalinertiareflectedtothemotorshaft,kilogram-meters2(kg-m2)orpound-feet2(lb-ft2)Jm=motorinertia,kilogram-meters2(kg-m2)orpound-feet2(lb-ft2)GR=thegearratioforanygearbetweenthemotorandload,dimensionless.2:1=0.5JL=loadinertia,kilogram-meters2(kg-m2)orpound-feet2(lb-ft2)Note:1.0lb-ft2=0.04214011kg-m2PowerFlex70/700Copyright©2006RockwellAutomation,Inc.Allrightsreserved.Step2-PeakRegenerativePowerJT=totalinertiareflectedtothemotorshaft,kg-m2wb=maxangularrotationalspeed,Rad/s=2pNb/60wo=angularrotationalspeed,lessthanratedspeed(canbezero)Rad/sNb=maximumapplicationspeedinRPMt3-t2=totaltimeofdecelerationfromwbtowo,secondsPb=peakbrakingpower,wattsNote:1.0HP=746wattsPowerFlex70/700Copyright©2006RockwellAutomation,Inc.Allrightsreserved.Step3-MaximumDBResistorValueVd=thevalueofDCBusvoltagethatutilizesthefullcapabilityofthedrive.395VDCor790VDCor987VDCPb=peakbrakingpowercalculatedinstep2Rdb1=themaximumallowablevalueforthedynamicbrakeresistorResistortolerancesarebuiltintotheminimumresistancesforeachindividualdriveCopyright©2006RockwellAutomation,Inc.Allrightsreserved.AboutDutyCycleGiventhataresistorcoolsoffinabout15minutes,ifcycletimeminusthedeceltimeexceeds900thenusingthelargercycletimecan’tbeusedforcalculatingaveragepower.Let’ssaythatIdecelin10secondseveryhour.Thatwouldbe10/3600