外文翻译永磁牵引电机的崛起Word文档格式.docx
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外文翻译永磁牵引电机的崛起Word文档格式.docx
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外文原文
TheRiseOfThePermanent-magnetTractioMotor
Technologyofferingbenefitsintermsofmass,sizeandenergyconsumption,thepermanent-magnetsynchronousmachineisincreasinglybeingadoptedfortractiondrives,despitetheneedforcomplexcontrolsystemsandpotentialfailuremodes.
Inthepastcoupleofyears,manyofthebidsfornewrollingstockplacedwithmajorinternationalsuppliershaveproposedtheuseofpermanent-magnetsynchronoustractionmotors,whicharesmallerandlighterthanthethree-phaseinductionmotorsthathavedominatedthemarketinrecenttimes.
Permanent-magnetmotorsfirstcametoprominencewiththeuseoftwopoweredbogiesfromAlstom'
sAGVintheV150trainsetwhichbroketheworldspeedrecordonApril32007,buttheyhavesubsequentlybeenusedinavarietyofapplications,rangingfromtheCitadis-Dualistram-traintoSBB'
sTwindexxdouble-deckinter-citytrainsets(TableI).
Althoughrailwayoperatorsareoftenviewedasconservativeintheadoptionofnewtechnologies,thedesignersandmanufacturersofrailtractionsystemstendtocapitaliseonthelatestdrivetechnologies,whicharerapidlydeployedinserviceiftheypromisesignificantperformanceimprovements.Thiswasthecasefortheearlychopperssupplyingseries-connectedDCtractionmotors,separately-excitedDCmotors,synchronousACmotorsanddrives(asusedonthefirstgenerationsofTGVs)andforthevariousgenerationsofasynchronous(squirrel-cage)three-phasedrives.Astechnologymovedforward,tractiondrivesbecamemoreefficientandmorecontrollable,allowingbetteruseofavailableadhesionwhilereducingenergyconsumption.
Thepermanent-magnetsynchronousmachine,withitsassociatedcontrolelectronics,representsthelatestsuchadvanceintractiontechnology.MillionsofsmallPMSMsarealreadybeingusedinthetransmissionsofhybridcars,thankstotheirlowmassandgoodcontrollability.Largermachinesofferasimilarpotentialtoenhancetheoverallperformanceoftherailwaytractionpackage.Thetechnologyisnowbeginningtobeintroducedintoavarietyofnewrollingstock,buttheintegrationofPMSMsintotractionpackagespresentssomesignificanttechnicalchallengeswhichmustbeovercome.
Fundamentalrequirements
Petrolanddieselenginesforautomotiveapplicationsgenerallyrequirecomplexgearboxestoallowtheprimemovertooperateintheoptimumspeedband.Bycontrast,electricmotorsforrailtractionareexpectedtooperateeffectivelyandefficientlyovertheentirespeedrange,allowingapermanentcouplingtotheaxlesandwheels,eitherdirectlyorviaasingleratiogearbox.Thismechanicallyelegantsolutionresultsinhighlyreliabledriveswhichneedrelativelylittlemaintenance.
Thusthefirstrequirementplacedonthedesignoftractionmotorsistheabilitytoprovidetorqueortractiveeffortoverawidespeedrange,suchasfrom0to320km/h.
Whilstitisessentialforthetractionmotortooperatereliably,itisequallyimportantfromthedriver'
sandrailwayoperator'
sperspectivethatmoderntractionsystemscontrolthetorqueaccuratelyandsmoothlythroughoutthespeedrange.Excellenttorquecontrolresultsinoptimumuseofavailableadhesionbetweenwheelandrail,alongwithsmoothaccelerationandtheabilitytocruiseataconstantspeedandtobrakethetrainelectrically(dynamicbraking).
Tractiveeffort,powerandspeed
Thetorqueproducedinatractionmotoristranslatedintoalinearforceatthewheel-railinterface.Thisforce,whichcausesthetraintoaccelerateorbrakedynamically,isnormallyreferredtoasthetractiveeffort.Fig1showstheTEcurveofatypicaldrivesystem,togetherwiththeassociatedtrainorvehicleresistancecurve.TheTEcurveintersectstheresistancecurveattheso-calledbalancingspeed,thatis,thetheoreticalmaximumspeed.Closetothisspeed,thereisonlyaverysmallamountoftractiveeffortavailabletoacceleratethetrain,asindicatedbytheredarrowinFig1.Fig2showsthepowerproducedbythedriveandthepropulsionpowerrequired,whichistheproductofspeedandtractiveeffort.
Tractionmotorsaregenerallydesignedtomatchaparticularduty.Themotormustproducetherequiredfulltorqueatzerospeedandsustainthistorqueuptotheso-calledbasespeed,throughoutregion1oftheTEcurve.Abovethisspeed,themachineoperatesatitsmaximumpoweroutput,andinregion2thetractiveeffortisthereforeinverselyproportionaltothespeedv.Inthethirdregion,tractiveefforthastoreduceininverseproportiontov²
becauseofmachinelimitations.
Torquecontrol
Atlowspeeds,themotorcanintheoryprovideatorquethatisgreaterthanthatwhichcanbetransmittedbymeansoftheadhesionavailableatthewheel-railinterface.However,thiswouldoverloadthemotorbeyondthenormallyaccepted
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