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外文翻译---电力绞车的控制VIP免费

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英文原文ElectricalWinchControlsbyTomYoungTheformofmotorcontrolweallknowbestisthesimplemanualstationwithupanddownpushbuttons.Whilethesestationsmaystillbetheperfectchoiceforcertainapplications,adizzyingarrayofmoresophisticatedcontrolsisalsoavailable.Thisarticleaddressesthebasicelectricalrequirementsofthemotorsanduserinterfaceissuesyouwillneedtoaddressbeforespcifying,buildingorbuyingwinchcontrols.beginwith,themanualcontrolstationsshouldbeofthehold-to-runtype,sothatifyoutakeyourfingeroffofthebuttonthewinchstops.Additionally,everycontrolstationneedsanemergencystop(E-stop)thatkillsallpowertothewinch,notjustthecontrolcircuit.Thinkaboutit—ifthewinchisn’tstoppingwhenitshould,youreallyneedafailsafewaytokillthelinepower.It’salsoagreatideatohaveakeyoperatedswitchoncontrolstations,especiallywhereaccesstothestationsisnotcontrolled.Safeoperationbyauthorizedpersonnelmustbeconsideredwhendesigningeventhesimplestmanualcontrols.ControllingFixedSpeedMotorsTheactualcontrollingdeviceforafixedspeedwinchisathreephasereversingstarter.ThemotorisreversedbysimplyswitchingthephasesequencefromABCtoCBA.Thisisaccomplishedbytwothree-polecontactors,interlocked,sotheycan’tbothbeclosedatthesametime.TheNECrequiresbothoverloadandshortcircuitprotection.Toprotectthemotorfromoverheatingduetomechanicaloverloadsathermaloverloadrelayisbuiltintothestarter.Thishasbi-metallicstripsthatmatchtheheatingpatternofthemotorandtripscontactswhentheyoverheat.Alternatively,athermistorcanbemountedinthemotorwindingtomonitorthemotortemperature.Shortcircuitprotectionisgenerallyprovidedbyfusesratedforusewithmotors.Aseparatelinecontactorshouldbeprovidedaheadofthereversingcontactorforredundancy.Thiscontactoriscontrolledbythesafetycircuits:E-stopandovertravellimits.Thisbringsustolimitswitches.Whenyougettothenormalendoftravellimitthewinchstopsandyoucanonlymoveitintheoppositedirection(awayfromthelimit).Therealsoneedstobeanovertravellimitincase,duetoanelectricalormechanicalproblem,thewinchrunspastthenormallimit.Ifyouhitanovertravellimitthelinecontactoropenssothereisnowaytodriveoffofthelimits.Ifthisoccurs,acompetenttechnicianneedstofixtheproblemthatresultedinhittingtheovertravellimit.Then,youcanoverridetheovertravelsusingthespringreturntoggleswitchinsidethestarter—asopposedtousingjumpersorhandshootingthecontactors.VariableSpeedRequirementsOfcourse,thesimplefixedspeedstartergetsreplacedwithavariablespeeddrive.Here’swherethingsstarttogetinteresting!Attheveryleastyouneedtoaddaspeedpottothecontrolstation.Ajoystickisabetteroperatorinterface,asitgivesyouamoreintuitivecontrolofthemovingpiece.Unfortunately,youcan’tjustorderanyoldvariablespeeddrivefromyourlocalsupplierandexpectittoraiseandlowerequipmentsafelyandreliablyoverkidsonstage.Mostvariablespeeddriveswon’t,astheyaren’tdesignedforlifting.Thedriveneedstobesetupsothattorqueisdevelopedatthemotorbeforethebrakeisreleased,and(whenstopping)thebrakeissetbeforetorqueistakenaway.FormanyyearsDCmotorsanddrivesprovidedapopularsolutionastheyallowedforgoodtorqueatallspeeds.ThelargeDCmotorsrequiredformostwinchesareexpensive,costingmanytimeswhatacomparableACmotorcosts.However,theearlyACdriveswerenotveryuseful,astheyhadaverylimitedspeedrangeandproducedlowtorqueatlowspeeds.Morerecently,astheACdrivesimproved,thelowcostandplentifulavailabilityofACmotorsresultedinatransitiontoACdr...

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外文翻译---电力绞车的控制

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