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AsynchronousMotorStartingMethodAndProblemsAbstract:Thelargecapacityofcommunicationasynchronousmotorhasavarietyofstartmethod.Choiceofsuchastotalpressureofthepressuredropandstartstart-up,autoformertransformerstart,startriangleconversionstart,softstart,orusingspeeddriveshavepotentialadvantageandchoice.Step-downstartcanreducestarttorque,canpreventdamagetotheload.Inaddition,thepowerfactorcorrectioncapacitorcanbeusedtoreduceelectricitybutchoosemodelmustbeappropriate,orwillcauseseriousdamageofcapacitor.Chooseasuitableforamotorstartupmethod,needanalysispowersystemsandstartloadtoensurethatmeettheperformanceandcostmotoratleast.Thispaperwilldiscussthemostcommonseveralstartmethodandtheirapplication.keywords:Motorstartup,step-downstart,Autoformertransformer,Startriangle,Powerfactorcorrection.1.Introductionstart,step-downstart,startriangleconversionstartandpartofthewindingtypeetc.Step-downstartincludingsolidstarter,frequencyconversionstartandselfcouplingtransformerstart.Thesealongwithallthepressureordirectstart,whenmotorapplicationsisdeterminedtogivethebuyerafteratypeofchange.Eachmethodhasitsownadvantages,andtradeperformance.Thereasonablechoiceofelectricpowersystemincludingthoroughstudyoftheaccelerationoftheloadandthefullcostofequipment.Inordertomaketheloadcanbegoodacceleration,motormustproduceloaddemandmorethanthetorque.GeneraltoSaid,inthemechanicalcharacteristiccurvefocusonthefollowingthreeareas.ThefirstpointisstuckaroundmomentLRTandmakemotorrotatebystatictotheminimumtorque.Thesecondistheminimumstarttorqueandmakemotorfromthestaticacceleratedtoappearbrakingtorqueyestheminimumtorque.Thelastpointisastreettorque,isthelargestmotorcanproducetorque.Ifanysectionofthedottedlineintheloadcurve,themotorcantstart.Motorsaccelerationtimebyinertiaandtheloadisthemotortorque-speedcharacteristiccurveandloadcharacteristicscurveofthedifferencebetweenthedecision.Ingeneral,theaccelerationofmotorthelonger:thearticlecopper,endofmotorrotorstatorwindingring,thequantityofheatofgenerationarealsomore.Theheatwillgivethesepartsadditionalpressureevenaffecttheservicelifeofthemotor.2.ThevoltageAllthepressureofthemethodisalsocalledthestartdirectlystarted,isthefirstusedmethods,andtheequipmentisthelowestcostthemostreliablework.ThismethodUSESacontrollertomotorcurrentcontactdevicethetotalpressureoftheinput.Thismethodallowsmotorproducethemaximumstarttorquetoacceleratetheshortesttime.Becauseofusingthismethodthechancetostarttostartcurrentmotorratedcurrentofsixtoseventimes,sothemethodalsoistobringthegreatestpowersupplysystemofthemethodofpressure.Ifpowersupplysystemisrelativelyweak-powermotorsuddenlystartwillnotonlymakethemotorvoltageinstantaneousdown,andtotheentirebusvoltageofthemotorpowersupplydrop.Voltagedropswillmakethemotorstarttorqueandworkatthesamebusthemotortorqueonthedecline.Asynchronousmotortorqueaboutandthescaleoftheinputvoltagechangingproportionofthesquare.Therefore,becauseofadeclineinvoltageworkthepowersupplysystemofmotormayparking.Manyothercontrolsystemmonitorsworkinginlowvoltagemotoroffline.Andbusvoltagechangeofdirectstartanotherproblemdrivingequipmentwassuddenlyloading.Becauseoftheinstantaneoustorquecanbemorethan600%oftherotorbrakingtorque,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,timeconstantsaidwhenthepowervoltagemotorattenuationto36.8%bythetimeneededto,nocapacitanceofthetypicalvaluesistwotothreeseconds.Duetothefrontendofthemotorcapacitorandconnected,inthemotoroffthepowercapacitorscancontinuetoprovideafterexcitercurrent.Thisshowsthatthesystemoftimeconstantisbigger.Ifmotordrivehighinertialload,theelectriccapacitanceofthechancetouseprovideexcite