異步電動機起動的方法和問題畢業(yè)論文外文翻譯

1、英文原文INDUCTIONMOTSTARTINGMETHODSISSUESAbstractManymethodscanbeusedtostartlargeACinductionmots.ChoicessuchasfullvoltagereducedvoltageeitherbyautotransfmerWyesDeltaasoftstarterusageofanadjustablespeeddrivecanallhavepotentia

2、ladvantagestradeoffs.Reducedvoltagestartingcanlowerthestartingtquehelppreventdamagetotheload.Additionallypowerfactcrectioncapacitscanbeusedtoreducethecurrentbutcaremustbetakentosizethemproperly.Usageofthewrongcapacitscan

3、leadtosignificantdamage.Choosingtheproperstartingmethodfamotwillincludeananalysisofthepowersystemaswellasthestartingloadtoensurethatthemotisdesignedtodelivertheneededperfmancewhileminimizingitscost.Thispaperwillexamineth

4、emostcommonstartingmethodstheirrecommendedapplications.IndexTerms:motstarting.ReducedvoltagestartautotransfmerwyesdeltapowerfactcrectionI.INTRODUCTIONThereareseveralgeneralmethodsofstartinginductionmots:fullvoltagereduce

5、dvoltagewyesdeltapartwindingtypes.Thereducedvoltagetypecanincludesolidstatestartersadjustablefrequencydrivesautotransfmers.Thesealongwiththefullvoltageacrossthelinestartinggivethepurchaseralargevarietyofautomotiveswhenit

6、comestospecifyingthemottobeusedinagivenapplication.Eachmethodhasitsownbenefitsaswellasperfmancetradeoffs.Properionwillinvolveathoughinvestigationofanypowersystemconstraintstheloadtobeacceleratedtheoverallcostoftheequipme

7、nt.Inderftheloadtobeacceleratedthemotmustgenerategreatertquethantheloadrequirement.Ingeneraltherearethreepointsofinterestonthemotsspeedtquecurve.Thefirstislockedrottque(LRT)whichistheminimumtquewhichthemotwilldevelopatre

8、stfallangularpositionsoftherot.Thesecondispulluptque(PUT)whichisdefinedastheminimumtquedevelopedbythemotduringtheperiodofaccelerationfromresttothespeedatwhichbreakdowntqueoccurs.Thelastisthebreakdowntque(BDT)whichisdefin

9、edastheInductionmotstypicallyhaveverylowpowerfactduringstartingasaresulthaveverylargereactivepowerdraw.SeeFig.2.Thiseffectonthesystemcanbereducedbyaddingcapacitstothemotduringstarting.Thelargereactivecurrentsrequiredbyth

10、emotlagtheappliedvoltageby90electricaldegrees.Thisreactivepowerdoesntcreateanymeasurableoutputbutisrathertheenergyrequiredfthemottofunction.TheproductoftheappliedsystemvoltagethisreactivepowercomponentcanbemeasuredinVARS

11、(voltamperereactive).Thecapacitsacttosupplyacurrentthatleadstheappliedvoltageby90electricaldegrees.Theleadingcurrentssuppliedbythecapacitscancelthelaggingcurrentdemedbythemotreducingtheamountofreactivepowerrequiredtobedr

12、awnfromthepowersystem.Toavoidovervoltagemotdamagegreatcareshouldbeusedtomakesurethatthecapacitsareremovedasthemotreachesratedspeedintheeventofalossofpowersothatthemotwillnotgointoageneratmodewiththemagizingcurrentsprovid

13、edfromthecapacits.Thiswillbeexpedoninthenextsectionintheappendix.B.PowerFactCrectionCapacitscanalsobeleftpermanentlyconnectedtoraisethefullloadpowerfact.Whenusedinthismannertheyarecalledpowerfactcrectioncapacits.Thecapac

14、itsshouldneverbesizedlargerthanthemagizingcurrentofthemotunlesstheycanbedisconnectedfromthemotintheeventofapowerloss.Theadditionofcapacitswillchangetheeffectiveopencircuittimeconstantofthemot.Thetimeconstantindicatesthet

15、imerequiredfremainingvoltageinthemottodecayto36.8%ofratedvoltageafterthelossofpower.Thisistypicallyonetothreesecondswithoutcapacits.Withcapacitsconnectedtotheleadsofthemotthecapacitscancontinuetosupplymagizingcurrentafte

16、rthepowertothemothasbeendisconnected.Thisisindicatedbyalongertimeconstantfthesystem.IfthemotisdrivingahighinertialoadthemotcanchangeovertogeneratactionwiththemagizingCurrentfromthecapacitstheshaftdrivenbytheload.Thiscanr