外文翻译---电力绞车的控制VIP免费

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...