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外文翻译--异步电动机起动的方法和问题.doc

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外文翻译--异步电动机起动的方法和问题.doc

中国地质大学长城学院本科毕业论文外文资料翻译系别工程技术系专业机械设计制造及其自动化姓名学号年月日外文翻译AsynchronousMotorStartingMethodAndProblemsAbstractThelargecapacityofcommunicationasynchronousmotorhasavarietyofstartmethod.Choiceofsuchastotalpressureofthepressuredropandstartstartup,autoformertransformerstart,startriangleconversionstart,softstart,orusingspeeddriveshavepotentialadvantageandchoice.Stepdownstartcanreducestarttorque,canpreventdamagetotheload.Inaddition,thepowerfactorcorrectioncapacitorcanbeusedtoreduceelectricitybutchoosemodelmustbeappropriate,orwillcauseseriousdamageofcapacitor.Chooseasuitableforamotorstartupmethod,needanalysispowersystemsandstartloadtoensurethatmeettheperformanceandcostmotoratleast.Thispaperwilldiscussthemostcommonseveralstartmethodandtheirapplication.keywordsMotorstartup,stepdownstart,Autoformertransformer,Startriangle,Powerfactorcorrection.1.Introductionstart,stepdownstart,startriangleconversionstartandpartofthewindingtypeetc.Stepdownstartincludingsolidstarter,frequencyconversionstartandselfcouplingtransformerstart.Thesealongwithallthepressureordirectstart,whenmotorapplicationsisdeterminedtogivethebuyerafteratypeofchange.Eachmethodhasitsownadvantages,andtradeperformance.Thereasonablechoiceofelectricpowersystemincludingthoroughstudyoftheaccelerationoftheloadandthefullcostofequipment.Inordertomaketheloadcanbegoodacceleration,motormustproduceloaddemandmorethanthetorque.GeneraltoSaid,inthemechanicalcharacteristiccurvefocusonthefollowingthreeareas.ThefirstpointisstuckaroundmomentLRTandmakemotorrotatebystatictotheminimumtorque.Thesecondistheminimumstarttorqueandmakemotorfromthestaticacceleratedtoappearbrakingtorqueyestheminimumtorque.Thelastpointisastreettorque,isthelargestmotorcanproducetorque.Ifanysectionofthedottedlineintheloadcurve,themotorcantstart.Motorsaccelerationtimebyinertiaandtheloadisthemotortorquespeedcharacteristiccurveandloadcharacteristicscurveofthedifferencebetweenthedecision.Ingeneral,theaccelerationofmotorthelongerthearticlecopper,endofmotorrotorstatorwindingring,thequantityofheatofgenerationarealsomore.Theheatwillgivethesepartsadditionalpressureevenaffecttheservicelifeofthemotor.2.ThevoltageAllthepressureofthemethodisalsocalledthestartdirectlystarted,isthefirstusedmethods,andtheequipmentisthelowestcostthemostreliablework.ThismethodUSESacontrollertomotorcurrentcontactdevicethetotalpressureoftheinput.Thismethodallowsmotorproducethemaximumstarttorquetoacceleratetheshortesttime.Becauseofusingthismethodthechancetostarttostartcurrentmotorratedcurrentofsixtoseventimes,sothemethodalsoistobringthegreatestpowersupplysystemofthemethodofpressure.Ifpowersupplysystemisrelativelyweakpowermotorsuddenlystartwillnotonlymakethemotorvoltageinstantaneousdown,andtotheentirebusvoltageofthemotorpowersupplydrop.Voltagedropswillmakethemotorstarttorqueandworkatthesamebusthemotortorqueonthedecline.Asynchronousmotortorqueaboutandthescaleoftheinputvoltagechangingproportionofthesquare.Therefore,becauseofadeclineinvoltageworkthepowersupplysystemofmotormayparking.Manyothercontrolsystemmonitorsworkinginlowvoltagemotoroffline.Andbusvoltagechangeofdirectstartanotherproblemdrivingequipmentwassuddenlyloading.Becauseoftheinstantaneoustorquecanbemorethan600oftherotorbrakingtorque,theshockloadwillincreaseequipmentwearandtear,ifnotinherittheloadbymotorstartproducetorqueandwillcausecatastrophicfailure.2.1,CapacitorandstartAsynchronousmotorpowerfactorisusuallylow,soinhaveaseriousperceptualreactive.Inthestartupthroughincreasedtomotorcapacitortoreducetheinfluenceofthesystem.Motorneedalotofreactivecurrentlagsbehindtheinputvoltageis90degrees.Thisreactivepowerdoesnotproduceanyout,butitisnecessarytothemotorrunning.Theinputvoltageproducereactivepowerandthereactivepowercanbecomposedofreactivepowermetertomeasurethepower.Asacapacitortoprovidealeading90degreesofcurrent.Producedbycapacitoradvancecurrentcancelledmotorneedthelagofthecurrent,reducethepowersupplysystemoftheinputfromperceptualreactivepower.Avoidovervoltageandmotordamageshouldbecarefultoensurecapacitorberemovedwhenthemotorreachingtheratedspeed,otherwiseduetothelossofpower,byusingthemotorcapacitorofmagnetizationcurrentwillprovidenotintothepowermode.Thiswillbeinthenextparagraphandappendixdetails.2.2,PowerfactorcorrectionCapacitorcanalsobeleftwithapermanentincreasepowerfactor,whenusingthisapproachiscalledpowerfactorcorrectioncapacitors.Thiskindofcapacitorcapacityisnotgreaterthanthecurrentmotorexcitation,unlesswhenpowerreductiontheycanandmotorseparation.Additionalcapacitorswillchangethemotorringopeningtimeconstant,timeconstantsaidwhenthepowervoltagemotorattenuationto36.8bythetimeneededto,nocapacitanceofthetypicalvaluesistwotothreeseconds.Duetothefrontendofthemotorcapacitorandconnected,inthemotoroffthepowercapacitorscancontinuetoprovideafterexcitercurrent.Thisshowsthatthesystemoftimeconstantisbigger.Ifmotordrivehighinertialload,theelectriccapacitanceofthechancetouseprovideexcitercurrentandloadthedrivingintopowerstate.Thismayresultinattheendofthemotorofthevoltageupto50oftheratedvoltage.Ifthevoltageviolentattenuationenergizedagainbeforeitwillcauseabigswitchcurrentandtorque,cancausemotorandthedriveequipmentbadlydamaged.3,Fallvoltage

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