2023年全國碩士研究生考試考研英語一試題真題（含答案詳解+作文范文）_第1頁
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1、1英文題目：Electricmotcontrol中文題目：電動機控制ELECTRICMOTGENERALPRINCIPLESOFELECTRICMOTCONTROLTherearecertainconditionsthatmustbeconsideredwheningdesigninginstallingmaintainingelectricmotcontrolequipment.Thegeneralprinciplesarediscu

2、ssedtohelpunderstingtomotivatestudentsbysimplifyingthesubjectofelectricmotcontrol.Motcontrolwassimpleproblemwhenmotwasusedtodriveacommonlineshafttowhichseveralmachineswereconnected.Itwassimplynecessarytostartstopthefewti

3、mesaday.Howeverwithindividualdrivethemotisnowalmostanintegralpartofthemachineitisnecessarytodesignthemotcontrollertofittheneedsofthemachinetowhichitisconnected.Motcontrolisabroadtermthatmeansanythingfasimpletoggleswitcht

4、oacomplexsystemwithcomponentssuchasrelaystimersswitchesthecommonfunctionofallcontrolshoweveristocontroltheoperationofanelectricmot.Asaresultwhenmotcontrolequipmentisedinstalledmanyfactsmustbeconsideredtoinsurethatthecont

5、rolwillfunctionproperlyfthemotthemachinefwhichitised.1MotControlInstallationConsiderations.Whenchoosingaspecificdevicefaparticularapplicationitisimptanttorememberthatthemotmachinemotcontrollerareinterrelatedneedtobeconsi

6、deredasapackage.Ingeneralfivebasicfactsinfluencetheioninstallationofacontroller.1.ElectricalServiceEstablishwhethertheserviceisdirect(dc)alternatingcurrent(ac).Ifacdeterminethefrequency(hertz)numberofphasesinadditiontovo

7、ltage.2.MotThemotshouldbematchedtotheelectricalservicecrectlysizedfthemachineloadinhsepowerrating(hp).Otherconsiderationsincludemotspeedtque.Toproperprotectionfthemotitsfullloadcurrentrating(FLC)servicefact(SF)timerating

8、(duty)otherpertinentdata——asshownonthemotnameplate─mustbeused.3.OperatingacteristicsofControllerThefundamentaltasksofamotcontrolleraretostartstopthemottoprotectthemotmachineproductoperat.Thecontrollermayalsobecalledupont

9、oprovidesupplementaryfunctionssuchasreversingjogginginchingpluggingoperatingatseveralspeedsatreducedlevelsofcurrentmottque.4.EnvironmentControllerenclosuresservetoprovidesafetyprotectionfoperatingpersonnelbypreventingacc

10、identalcontactwithliveparts.Incertainapplicationsthecontrolleritselfmustbeprotectedfromavarietyofenvironmentalconditionswhichmightinclude:WaterrainsnowsleetDirtnoncombustibledustCuttingoilscoolantlubricantsBothpersonnelp

11、ropertyrequireprotectioninenvironmentsmadehazardousbythepresenceofexplosivegasescombustible3operatsfromunsafeconditions.ProtectionfromDamagePartoftheoperationofanautomaticmachineistoprotectthemachineitselfthemanufactured

12、processedmaterialsithles.Fexampleacertainmachinecontrolcanreversestopslowdowhateverisnecessarytoprotectthemachineprocessedmaterials.MaintenanceofStartingRequirementsOnceproperlyinstalledadjustedmotstarterswillprovidereli

13、ableoperationofstartingtimevoltagescurrenttquefthebenefitofthedrivenmachinethepowersystem.TheNationalElectricalCodesupplementedbylocalcodesgovernstheionofthepropersizesofconductsstartingfusescircuitbreakersdisconnectswit

14、chesfspecificsystemrequirements3ManualControlAmanualcontrolisonewhoseoperationisaccomplishedbymechanicalmeans.Theefftrequiredtoactuatethemechanismisusuallyprovidedbyahumanoperat.Themotmaybecontrolledmanuallyusinganyoneof

15、thefollowingdevices.ToggleSwitchAtoggleswitchisamanuallyoperatedelectricswitch.Manysmallmotsarestartedwithoggleswitches.Thismeansthemotmaybestarteddirectlywithouttheuseofmagicswitchesauxiliaryequipment.Motstartedwithtogg

16、leswitchesisprotectedbythebranchcircuitfusecircuitbreaker.Thesemotsgenerallydrivefansblowersotherlightloads.SafetySwitchInsomecasesitispermissibletostartamotdirectlyacrossthefulllinevoltageifanexternallyoperatedsafetyswi

17、tchisused.Themotreceivesstartingrunningprotectionfromdualelementtimedelayfuses.Theuseofasafetyswitchrequiresmanualoperation.Asafetyswitchtherefehasthesamelimitationscommontomostmanualstarters.DrumControllerDrumcontroller

18、sarerotarymanualswitchingdeviceswhichareoftenusedtoreversemotstocontrolthespeedsofacdcmotsTheyareusedparticularlywherefrequentstartstopreverseoperationisrequired.Thesecontrollersmaybeusedwithoutothercontrolcomponentsinsm

19、allmotsgenerallythosewithfractionalhsepowerratings.Drumcontrollersareusedwithmagicstartersinlargemots.FaceplateControlFacecontrollershavebeeninusefmanyyearstostartdomots.Theyarealsousedfacinductionmotspeedcontrol.Theface

20、platecontrolhasmultipleswitchingcontactsmountedneararmonthefrontofaninsulatedplate.Additionalresistsaremountedonthereartofmacompleteunit.Theuseoffaceplatestartersoffersadvantagesfeaturesnotabstainedwithothermanualcontrol

21、lers.Theyarealsocheapertopurchasethanautomaticcontrols.3.1.4RemoteAutomaticControlThemotmaybecontrolledbyremotecontrolusingpushbuttonswhenpushbuttonremotecontrolisusedwhenautomaticdevicesdonothavetheelectricalcapacitytoc

22、arrythemotstartingrunningcurrentsmagicswitchesmustbyincluded.Magicswitchcontrolisonewhoseoperationisaccomplishedbyelectromagicmeans.Theefftrequiredtoactuatetheelectromagissuppliedbyelectricalenergyratherthenbythehumanope

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