电工基础考试试题.docx

电工基础考试试题.docx

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电工基础考试试题

电工基础考试试题（BasicexaminationquestionsofElectricalEngineering）

2007fallsemesterelectricianfoundationfinalexampaper

Fillintheblanks（eachemptypart）

1.Thecircuitisaclosedloopconsistingof,,etc..

2.Theelectricityusedinhouseholdlifeisalternatingcurrent,andthevoltageeffectivevalueisvolts.

3.Thesafetyvoltageisvolts.

4,R1=5,R2=3,iftworesistorsareconnectedinseries,thetotalresistanceisomega.

5,withmultimetertestresistance,everytimechangeratefiles,shouldbere.

6、constantvoltagesourceisprovided,constantcurrentsourceisprovided.

7transformermainlyconsistsoftwoparts.Thecoreislaminated.

8.Themotorconsistsoftwobasicparts.

9,three-phasealternatingcurrentreferstowhatthree-phase?

,.

Two,multiple-choicequestions（eachsubjectpoints）

1,theratedvoltageofanelectricapplianceis220V,anditshouldbeconnectedtothepowervoltageof380V.

Aseriescapacitor,Bseriesresistor,Cshuntresistor,Dshuntcapacitor

2,ingeneral,diodes,transistors,resistors,pinsare.

A233B332C232D222

3.Thesamebattery.Thelightbulbispoweredbytwobatteriesconnectedinseries.Thelightsecondispoweredbytwobatteriesinparallel,andthetwolamp.

AisasbrightasB,alightison,CBislight,Disnotsure

4,thefollowingcomponents,withfilteringfunctionis.

Aresistor,Binductor,Ccapacitor,Ddiode

5,electricitycanproducemagnetism,andwhenthecurrentisthesame,whichofthefollowingsetsproducesthegreatestmagneticfieldstrength?

.

Astraightwire,Bsinglecoil,Ccorelesssolenoid,Dwithironcoresolenoid

6,windingpartsofthetransformercannotbeusedbelowwhatkindofwindingsystem?

.

AenameledwireBlineCDbarecopperwire.

7,three-phasealternatingcurrent,thelinevoltageandphasevoltagearerespectivelyhowmanyvolts?

.

A220220B220380C380220D380380

8,theclosedwireforcuttingmagneticinductionlinemovementcanproducecurrent,thecurrentsizeandwhatfactorsareirrelevant.

Amagneticfieldstrength,Btraversespeed,Cwirelengthinmagneticfield,Dwiremovementtime

Three,Janeanswer（eachsubjectpoints）

1,drawingandexplainshowtoapplythedoubleswitchinthetwocontrollamp?

2,drawthreephaseloadtriangle,starconnection,andsayaboutthisdifferentconnection,plusthevoltageontheloadeachforhowmuch?

Four,thecalculationquestions（eachsubjectpoints）

1.Theresistanceofanelectricapplianceis5,andthevoltageatbothendsis10V.HowmuchisthesizeofthecurrentthroughitandhowmanyMaisit?

2,apoweruseof2kilowatts,3hoursafterthenormalwork,howmuchelectricity?

3,anodehasfourbranchconnections,includingI1=2A,I2=3A,I3=1A,inwhichI1andI2

Theinflownode,I3andI4,flowsintothenode.HowmuchisthesizeoftheI4?

4,transformerprimarywindingN1=500,twowindingN2=800,

IfthevoltageaddedtotheN1is100V,howmuchistheoutputvoltageattheN2endV?

Electricianclassthreeexaminationquestions,2008,02,Thursday,14,22:

28,fillintheblanks

1.TherotorofDCmotoriscomposedofarmaturecore,windingcommutator,rotatingshaftandfanblade.Itisanimportantpartofenergyconversion.

2,theexcitationmodeofDCmotorcanbedividedintoitsexcitation,shuntexcitation,seriesexcitationandcompoundexcitation.

3,DCmotorundertheratedloadoperation,the#levelshouldnotexceed1.5level.

4.Theratedcapacityofthree-phasetransformeristhemaximumapparentpowerthatisallowedtooutputwhentheratedvoltageofthewindingisnothigherthantheratedvalue.Itisequaltotwotimestheproductofwindingratedvoltageandcurrenttick3times.

5,intheoperationofthetransformer,thelosscausedbythethermaleffectofthewindingcurrentisusuallycalledthecopperloss;losscausedbyalternatingmagneticfieldinthecorecanbedividedintohysteresislossandeddycurrentloss,collectivelyknownastheironloss.

6,becausethetransformershort-circuittestcurrentislarger,butthevoltageisverylow,sogenerallyinthehighpressuresidepressure,sothatthelowvoltagesideshortcircuit.

7.Thepartofthemotorwindingunitembeddedintheslotiscalledtheeffectivepart,andthepartoutsidetheslotiscalledthepart.

8,three-phaseasynchronousmotorrotatingmagneticfieldisdecidedbythepowerofthephasesequence,inoperation,iftherotationoftherotatingmagneticfieldchanged,therotor'ssteeringwillchange.

9,YseriesACmotorinsulationlevelisBlevel.

10,synchronousmotorrotorwithconvexpoleandhiddenpoleoftwokinds,

Therotorofdieselgeneratorandsynchronousmotorusedingeneralfactoryisconvextype.

11,three-phaseasynchronousmotorspeeddependsonthemagneticfield,thepolenumberP,slipSandpowerfrequencyf.

12,windingdryingoftenadoptsthefollowingthreemethods:

dryingroom,dryingmethod,bulbdryingmethod,currentdryingmethod.

13,arcgenerationisduetothegapinthegasisfree,producealargenumberofelectronsandions,sothattheinsulatinggasintoaconductor.Theelectricenergyconsumedbythecurrentpassingthroughthisfreezoneischangedintoheatandlightenergy,sotheeffectoflightandheatisemitted.

14,RL1seriesspiralfuse,themeltisfilledwithquartzsand.Whencuttingoffanelectriccurrent,thequartzsandrapidlyextinguishesthearc.

15.Theopeningdistanceofcontactorcontactistheshortestdistancebetweenthestaticanddynamiccontactpointswhenthecontactpointiscompletelyseparated.

16、themaincontactoftheDCcontactorisdifficulttoextinguishbecauseofanalyzingthearcgeneratedbytheDCcircuitthantheACarc,sothearcextinguishingdeviceisusuallyused.

17,thepurposeofsettingupzeroprotectionforbridgecraneistopreventtheaccidentofmotorstartingwhenthecontrollerisnotinthezeropositionandissentagainafterthepowerhasbeencutoff.

18、thefixedpartsofmagneticelectronicinstrumentmainlyinclude,and,andtherotorpart,mainlybytheneedle,pointerandcomposition.

19,intheRLCseriescircuitisequalto,whenthecurrentinthecircuitreachesthemaximumvalue,thisphenomenoniscalled.

20.Theprincipleofthree-phaseloadconnectedtothree-phasepowersupplylineisthatiftheratedvoltageoftheloadisequaltothevoltageofthepowerline,theloadshouldbeconnectedbydelta;

Iftheratedvoltageoftheloadisequaltothesupplyphasevoltage,theloadshouldbeYconnected.

21,themostbasiclogicaloperationsrefertoand/or,ornot,threeoperations.

22,transformercoolingmethodsareoilimmersed,selfcooled,oilimmersedair-cooled,strongoilair-cooled.

23,inputno-loadtransformerwillproduceinrushcurrent,itsvaluecanreachtheratedcurrentof6~8times.

24.Theparalleloperationofthetransformershallmeetthreeconditionsofequalchangeratio,sameconnectiongroupandshortcircuitvoltage.

25,whenmeasuringinsulationresistance,thefactorsaffectingaccuracyaretemperature,humidityandthedegreeofdirtontheinsulationsurface.

26.Theabsorptionofinsulatingmediumistheratiooftheinsulationresistancein60secondstotheinsulationresistancein15seconds.

27、themaincircuitfortheDCsystemtoprovidepowersupplyisthemainswitchingcircuit,thecontrolandprotectioncircuit,theaccidentlightingcircuit,thesignalcircuitandsoon.

28,thestoragecapacityofNiCdbatteriesisdeterminedbytheterminalvoltageofthebattery,notbytherepetition.

29,over-currentprotectionactioncurrentaccordingtoavoidmaximumloadcurrenttoadjust.

30,gasprotectionisbasedonthetransformerinternalfaultwillproduceanddecomposethegascharacteristicsoftheset.

31,whentherunningvoltageexceeds1.1timestheratedvoltageofcapacitor,thecapacitorshallberunoutofoperation.Theratedvoltageofthecapacitoris.

32、workinelectricalequipment,

Toensurethesafetyoftheorganizationmeasuresworkticketsystem,operationticketsystem,inventorysiteandcomprehensiveworksystem,workpermitsystem,worksystem,workandworkcontinuouslymonitoringthetransfersystemandtheworkingendandpowertransmissionsystem.

33,thedefectsofsubstationoperationequipmentaredividedintothreecategories,namely,generaldefects,seriousdefectsandcriticaldefects.

34,highvoltageequipmentgroundingfaultoccurs,indoorpersonnelshouldbefromthefaultpointisgreaterthan4metersoutside,outdoorpersonnelshouldbefromthefaultpointisgreaterthan8meters.

Two、judgmentquestions

1.Theratedpowerofatransformeristhemaximumpoweroutputallowedonthetwosidewhenthetemperatureriseisnothigherthantheallowabletemperaturerisewhentheratedvoltageisappliedtotheprimaryside.（x）

2.Whenthetransformerisinuse,thecorewillgraduallyoxidizeandrust.Therefore,thevacuumcarryingcurrentwillgraduallydecreaseaccordingly.（x）

3,three-phaseasynchronousmotorspeeddependsonthepowerfrequencyandthenumberofpoles,andnothingtodowiththeslip.（x）

4,three-phaseasynchronousmotorrotorspeedislower,themotorslipratioisbigger,therotorelectromotiveforcefrequencyishigher.（V）

5,theuseofshortcircuittestertocheckwhetherthethree-phaseasynchronousmotorwindingisonephaseshort-circuit,formultiplewindingorshuntwinding,youmustfirstdisassemblethebranches.（V）

6,regardlessofthenatureoftheloadtransformer,aslongastheloadcurrentcontinuestoincrease,theoutputvoltagewillinevitablydecrease.（x）

7、everycontactorwitharcextinguishingcovermustbeequippedwitharcextinguishingcover,andthem