电气工程及其自动化专业英语

电气工程及其自动化专业英语SpecializedEnglishforElectricalEngineering ItsAutomation戴文进主编杨植新副主编 Contents Part1ElectricsandElectronicsPart2ElectricMachineryPart3ElectricalEngineeringPart4ModernComputerControlTechniques Unit1SpecializedEnglishWords circuitcomponents电路元件circuitparameters电路参数thedielectric电介质storagebattery蓄电池electriccircuit电路wire导线electricaldevice电气设备electricenergy电能energysource电源primarycell原生电池secondarycell再生电池energyconverter电能转换器e m f electromotiveforce电动势unidirectionalcurrent单方向电流circuitdiagram电路图loadcharacteristic负载特性terminalvoltage端电压externalcharacteristic外特性Conductor导体loadresistance负载电阻generator发电机heatingappliance电热器direct current D C circuit直流电路magneticandelectricfield电磁场time invariant时不变的self ormutual induction自 互 感displacementcurrent位移电流voltagedrop电压降conductance电导volt amperecharacteristics伏安特性metal filamentlamp金属丝灯泡carbon filamentlamp碳丝灯泡non linearcharacteristics非线性特性 Unit1CircuitElementsandParameters Anelectriccircuit ornetwork isaninterconnectionofphysicalelectricaldevices Thepurposeofelectriccircuitsistodistributeandconvertenergyintosomeotherforms Accordingly thebasiccircuitcomponentsareanenergysource orsources anenergyconverter orconverters andconductorsconnectingthem 连接它们的 Anenergysource aprimaryorsecondarycell ageneratorandthelike convertschemical mechanical thermalorsomeotherformsofenergyinto 将 转换成 electricenergy Anenergyconverter alsocalledload suchasalamp heatingapplianceorelectricmotor convertselectricenergyintolight heat mechanicalworkandsoon Eventsinacircuitcanbedefinedintermsof 用 根据 e m f orvoltage andcurrent Whenelectricenergyisgenerated transmittedandconvertedunderconditionssuchthatthecurrentsandvoltagesinvolvedremainconstantwithtime oneusuallyspeaksofdirect current D C circuits Withtime invariantcurrentsandvoltages themagneticandelectricfieldsoftheassociatedelectricplantarealsotime invariant Thisisthereasonwhynoe m f sofself ormutual induction 自感或互感 appearinD C circuits norarethere 倒装结构 anydisplacementcurrents 位移电流 inthedielectricsurroundingtheconductors 导体周围的电介质 Fig 1 1showsinsimplifiedformahypotheticalcircuitwithastoragebatteryasthesourceandalampastheload Theterminalsofthesourceandloadareinterconnectedbyconductors generallybutnotalwayswires Asisseen thesource loadandconductorsformaclosedconductingpath Thee m f ofthesourcecausesacontinuousandunidirectionalcurrenttocirculateroundthisclosedpath Thissimplecircuitmadeupofasource aloadandtwowiresisseldom ifever metwithinpractice PracticalcircuitsmaycontainalargenumberofsourcesandloadsinterconnectedinavarietyofwaysFig 1 1 按不同方式连接的 Tosimplifyanalysisofactualcircuits itisusualtoshowthemsymbolicallyinadiagramcalledacircuitdiagram whichisinfactafictitiousor rather idealizedmodelofanactualcircuitofnetwork Suchadiagramconsistsofinterconnectedsymbolscalledcircuitelementsorcircuitparameters TwoelementsarenecessarytorepresentprocessesinaD C circuit Theseareasourceofe m f Eandofinternal orsource resistanceRS andtheloadresistance whichincludestheresistanceoftheconductors R Fig 1 2 Fig 1 2 Whateveritsorigin thermal contact etc thesourcee m f E Fig 1 2 a isnumericallyequaltothepotentialdifferencebetweenterminals1and2withtheexternalcircuitopen thatis whenthereisnocurrentflowingthroughthesourceE 1 2 V12 1 1 Thesourcee m f isdirectedfromtheterminalatalowerpotentialtothat 代替terminal atahigherone 代替potential Ondiagram thisisshownbyarrows 箭头 Whenaloadisconnectedtothesourceterminals thecircuitisthensaidtobeloaded andthecircuitisclosed acurrentbeginstoflowroundit Nowthevoltagebetweensourceterminals1and2 calledtheterminalvoltage isnotequaltoitse m f becauseofthevoltagedropVSinsidethesource thatis acrossthesourceresistanceRSVS RSI Fig 1 3showsatypicalso calledexternalcharacteristicV 1 2 V I ofaloadedsource henceanothernameistheloadcharacteristicofasource Asisseen increaseofcurrentfromzerotoI I1causestheterminalvoltageofthesourcetodecreaselinearlyV12 V E VS E RSI Fig 1 3 Inotherwords thevoltagedropVSacrossthesourceresistancerisesinproportiontothecurrent Thisgoesonuntilacertainlimitisreached Thenasthecurrentkeepsrising theproportionalitybetweenitsvalueandthevoltagedropacrossthesourceisupset andtheexternalcharacteristicceasestobe 不再是 linear Thisdecreaseinvoltagemaybecausedbyareductioninthesourcevoltage byanincreaseintheinternalresistance orboth Thepowerdeliveredbyasourceisgivenbytheequality 等式 PS EI 1 2 wherePSisthepowerofthesource Itseemsrelevantatthispointtodispelacommonmisconceptionaboutpower Thusonemayhearthatpowerisgenerated delivered consumed transmitted lost etc Inpointoffact however itisenergythatcanbegenerated delivered consumed transmittedorlost Powerisjusttherateofenergyinputorconversion thatis thequantityofenergygenerated delivered transmittedetcperunittime So itwouldbemorecorrecttousethetermenergyinsteadofpowerintheabovecontext Yet wewouldratherfallinwiththetradition TheloadresistanceRasageneralizedcircuitelement givesanideaabouttheconsumptionofenergy thatis theconversionofelectricenergyintoheat andisdefinedasP RI2 1 3 Inthegeneralcase theloadresistancedependssolelyonthecurrentthroughtheload whichinfactissymbolizedby 用符号 thefunctionR I ByOhm slaw thevoltageacrossaresistanceisV RI 1 4 Incircuitanalysis useisoftenmadeofthereciprocaloftheresistance termedtheconductance whichisdefinedasg 1 RInpracticalproblems oneoftenspecifiesthevoltageacrossaresistanceasafunctionofcurrentV I ortheinverserelationI V havecometobeknownasvolt amperecharacteristics Fig 1 4showsvolt amperecurvesforametal filamentlampV1 I andforacarbon filamentlampV2 I Asisseen therelationbetweenthevoltageandthecurrentineachlampisotherthanlinear Theresistanceofthemetal filamentlampincreases andthatofthecarbon filamentlampdecreaseswithincreaseofcurrent Fig 1 4 Electriccircuitscontainingcomponentswithnon linearcharacteristic 含有非线性特性元件的 arecallednon linear Ifthee m f andinternalresistancesofsourcesandassociatedloadresistancesareassumedtobeindependentofthecurrentandvoltage respectively theexternalcharacteristicV I ofthesourcesandthevolt amperecharacteristicV1 I oftheloadswillbelinear Electriccircuitscontainingonlyelementswithlinearcharacteristicarecalledlinear Fig 1 5 Mostpracticalcircuitsmaybeclassedaslinear Therefore astudyintothepropertiesandanalysisoflinearcircuitsisofboththeoreticalandappliedinterest ofinterest interesting Unit2SpecializedEnglishWords idealsource理想电源seriesandparallelequivalentcircuit串并联等值电路internalresistance内阻doublesubscript双下标idealvoltagesource理想电压源activecircuitelements有源电路元件passivecircuitelements无源电路元件powertransmissionline输电线sendingend发送端receivingend接收端leakagecurrent漏电流idealcurrentsource理想电流源 Unit2IdealSourcesSeriesandParallelEquivalentCircuits Consideranelementarycircuitcontainingasinglesourceofe m f EandofinternalresistanceRS andasingleloadR Fig 2 1 Theresistanceoftheconductorsofthistypeofcircuitmaybeneglected Intheexternalportionofthecircuit thatis intheloadR thecurrentisassumedtoflowfromthejunctiona whichisatahigherpotentialsuchthat a 1 tothejunctionb whichisatalowerpotentialsuchthat b 2 Thedirectionofcurrentflowmaybeshowneitherbyahollowarrowheadorbysupplyingthecurrentsymbolwithadoublesubscriptwhosefirstdigitidentifiesthejunctionatahigherpotentialandthesecond 省略了identifies thejunctionatalowerpotential ThusforthecircuitofFig 2 1 thecurrentI Iab WeshallshowthatthecircuitofFig 2 1containingasourceofknowne m f EandsourceresistanceRmayberepresentedbytwotypesofequivalentcircuits Asalreadystarted theterminalvoltageofaloadedsourceislowerthanthesourcee m f byanamountequaltothevoltagedropacrossthesourceresistanceV 1 2 E VS E RSI 2 1 Ontheotherhand thevoltageacrosstheloadresistanceRis Fig 2 1 Since 1 aand 2 b fromEqs 2 1 and 2 2 itfollowsthatE RsI RI orE RSI RI 2 3 AndI E RS R V a b RI 2 2 Fromthelastequationweconcludethatthecurrentthroughthesourceiscontrolledbyboththeloadresistanceandthesourceresistance Therefore inanequivalentcircuitdiagramthesourceresistanceRmaybeshownconnectedinserieswith 与 串联 theloadresistanceR Thisconfigurationmaybecalledtheseriesequivalentcircuit usuallyknownastheTheveninequivalentsource 戴维宁等效电源 DependingontherelativemagnitudeofthevoltagesacrossRsandR wecandeveloptwomodificationsoftheseriesequivalentcircuit 串联等效电路 Fig 2 2 IntheequivalentcircuitofFig 2 2 a Viscontrolledbytheloadcurrentandisdecidedbythedifferencebetweenthesourcee m f EandthevoltagedropV IfRS Rand forthesamecurrent VS V thatis ifthesourceisoperatingunderconditionsverycloseto 接近 no loadoranopen circuit wemayneglecttheinternalvoltagedrop putVS RI 0 verynearly andobtaintheequivalentcircuitofFig 2 2 b Whatwehavegotisasourcewhoseinternalresistanceiszero R 0 Itiscalledanidealvoltagesource Indiagramsitissymbolizedby 用 符号表示 acirclewith with结构 anarrowinsideandtheletterEbesideit Whenappliedtoanetwork itiscalledadrivingforceoranimpressedvoltagesource Theterminalvoltage 端电压 ofanidealvoltagesourceisindependentoftheloadresistanceandisalwaysequaltothee m f Eofthepracticalsourceitrepresents Itsexternalcharacteristicisastraightlineparalleltothex axis 与X轴平行的 thedottedlineabinFig 1 3 TheotherequivalentcircuitinFig 2 3maybecalledtheparallelequivalentcircuit usuallyknownastheNortonequivalent 诺顿等效电路 Itmayalsohavetwomodifications Toprovethis wedividetheright andleft handsidesofEq 2 3 byRSE RS I V RS I VgSorJ I IS 2 4 whereJ E RS currentwiththesourceshort circuited withR 0 IS V RS VgS currentequaltotheratiooftheterminalsourcevoltagetothesourceresistance 与 的比率 I V R Vg loadcurrent Eq 2 4 issatisfiedbytheequivalentcircuitofFig 2 3 a inwhichthesourceresistanceRSisplacedinparallelwith 与 并联 theloadresistanceR IfgS Rand forthesamevoltagesacrossRSandR thecurrentIS I thatis ifthesourceisoperatingunderconditionsapproachingashort circuit wemayputIS VgS 0 verynearly andgettheequivalentcircuitofFig 2 3 b Fig 2 3 Whatwehavegotisasourceofzerointernalconductance gS 0 RS Itiscalledanidealcurrentsource Whenappliedtoacircuit itiscalledadrivingforceofanimpressedcurrentsource ThecurrentofanidealcurrentsourceisindependentoftheloadresistanceRandisequaltoE RS Theexternalcharacteristicofanidealcurrentsourceisastraightlineparalleltothey axis 平行于Y轴的 thedottedlinecdinFig 1 3 ThuswhetherarealenergysourcemayberepresentedbyanidealvoltagesourceoranidealcurrentsourcedependsontherelativemagnitudeofRSandR Arealsource though mayberepresentedbyanidealvoltageorcurrentsourcealsowhenRSiscomparablewithR Insuchacase eitherRS orgS 1 RS Fig 2 2 a andFig 2 3 a respectively shouldberemovedfromthesourceandlumpedwithRorg 1 R Idealvoltageandcurrentsourcesareactivecircuitelements 有源电路元件 whileresistancesandconductancearepassiveelements 无源元件 Indevelopinganequivalentcircuit itisimportanttotakeintoaccount asmuchaspracticable 实际上 theknownproperties 已知的特性 ofeachdeviceandofthecircuitasawhole 整体上 Letusdevelopanequivalentcircuitforatwo wirepowertransmissionline 输电线 oflengthI diagrammaticallyshown 用图形表示 inFig 2 4 a Thereisageneratorofe m f EandofsourceresistanceRSatthesendingendandaloadofresistanceR2atthereceivingendoftheline Fig 2 4 Itisobviousthatthereceivingendvoltagewillbelessthanthesendingendonebyanamountequaltothevoltagedropacrosstheresistanceofthelineconductors Thecurrentatthereceivingendwillbesmallerthanthatatthesendingendbyanamountequaltotheleakagecurrent 漏电流 duetoimperfectinsulation 绝缘不完善 AlessthanBbyanamount whichis equalto A比B少 LeteachlineconductorhavearesistanceR0 2andaconductanceg0perunitlengthoftheline Wedividethelineintolengthelementsdx Fig 2 4 a Theneachlengthelementwillhaveassociatedwithitthecombinedresistanceofthe go and return wires R0dx R0 2 dx R0 2 dxandaconductanceg0dx 这样 一长度元将含有与其相关的 含有 去 与 来 两段组合的电阻即R0dx R0 2 dx R0 2 dx 和电导g0dx Accordingly theentirelinemayberepresentedbyanetworkofelementseachofresistanceR0dxandconductanceg0dx Fig 2 4 b Thesendingendgeneratorinthisnetworkisrepresentedbyavoltagesource ofe m f EandofsourceresistanceRS Fromthisequivalentcircuitwecanfind 计算出 thevoltageandcurrentatanypointonthelineintermsofspecifiedvoltageandcurrent 根据给定的电压和电流 atthesendingorreceivingend Iftheleakagecurrentofthelineisonlyasmallfractionof 只占小部分 theloadcurrent wemayneglectitandremoveallconductanceg0dxfromthenetwork 把所有的电导从网络中移开 Thiswillleaveuswithasimple single loopnetworkwithoneandthesamecurrentineachofitselements suchasshowninFig 2 5 wherethelineresistanceRline R0lisconnectedinserieswithRSandR2 ThenetworkofFig 2 5maybeusedforanalysisoflineperformancewithoutaconsiderationof 不考虑 leakagecurrents 漏电流 Fig 2 5 Ittakessomepracticetolearntodevelopequivalentcircuitssuchaswillreflectthebehaviorofphysicalprototypesinthemostfaithfulmannerandmeettherequirementsoftheproblemathand 遇到的 此句的主句是Ittakessomepracticetolearntodevelopequivalentcircuits 其中tolearntodevelopequivalentcircuits是不定式短语做主语 只是由于其太长 若放在句首会给人头重脚轻的感觉 其次要了解此句是 Ittakessomething time money 的句型 此处practice的意思是 要花一些时间 实践 要花一些工夫的 即 要学会画 这样的 等值电路是要花一番工夫的 那么是什么样的等值电路呢 后面整个都是由suchas that 引导的定语从句 修饰equivalentcircuits 意为 既能以最可靠的方式反映实际电路的运行情况 又能满足常常遇到的实际问题需要的这样一种等值电路 Unit4AlternatingcurrentSpecializedEnglishWords alternatingcurrent交流电definition定义instantoftime瞬时frequency频率instantaneousvalueofcurrent电流瞬时值symbolizedby用符号表示harmonic orsinusoidal current正弦电流over voltage过电压communicationcircuit通信电路remotecontrol遥控period周期modulatedby 由U 调制periodiccurrent周期电流pole pairs极对数non salientpole隐 非凸 极mechanicalstrength机械强度heat treatment热处理induction heating感应发热peakvalue 交变量的 最大值semiconductoroscillator半导体振荡器 amplitude 交变量的 幅值phase相位initialphase初相位epochangle初相角pulsatance谐振常数角频率angularvelocity角频率inquadrature正交A C generator交流发电机stator 电机 定子rotor 电机 转子magneticpole磁极slip ring滑环slot槽stackedup叠装electrical sheetsteel电工钢片magneticinduction磁感应强度activelength有效长度distributionofB磁场分布phaseshift phasedisplacement相位移laginphasebehind 相位 落后inphase同相anti phase反相 Unit4AlternatingCurrent BasicDefinitionsAnalternatingcurrentisonewhichvariesinthecircuitwithtime 随时间变化 Thevalueofthecurrentatanygiveninstantoftimeistermed called theinstantaneousvalueofcurrent symbolizedbyi Theinstantaneousvalueofcurrentiisdeemed 认为是 positiveforonedirectionofflowthroughthecross sectionofaconductor andnegativefortheoppositedirection 省略了成分 Acurrentisfullyspecified ifoneknowsitsinstantaneousvaluesasafunctionoftime i F t anditspositivedirection Currentswhosevaluesrecurforequalincrementsoftimearecalledperiodic andtheleastincrementoftimeforwhichthisrecurrencetakesplaceiscalledtheperiodT Foraperiodiccurrenti F t F t T Fig 4 1showsanexampleoftherelationshipi F t foraperiodiccurrent Thearrowinthediagramindicatesthepositivedirectionofcurrentflow 电流正方向 Thedottedarrowsshowtheactualdirectionsofcurrentflowattheinstantsoftimewheni 0andi 0 ThesegmentsofthecurvebetweenpointsaandborOandccoveracompletecycleofcurrentalternationsoveroneperiod Fig 4 1 Thenumberofcyclesorperiodspersecondisthefrequencyofaperiodiccurrent Itisreciprocalofitsperiodf 1 TItisusuallytospecifythefrequencyofanyperiodicquantityincyclespersecond 每秒周数 Thusthefrequencyofaperiodiccurrentwillbe1cyclepersecond ifitsperiodis1second or1cycle sec Adirectcurrentmayberegardedasaspecialcaseofaperiodiccurrentwhoseperiodisinfinitelylong 无穷大 andthefrequencyisthuszero Theterm 术语 alternatingcurrentisoftenusedinthenarrowsenseofaperiodiccurrentwhoseconstant direct current componentiszero orThefrequenciesofalternatingcurrentencounteredinpractice 在实际中遇到的 rangeover 涉及 verywidevalues Themainsfrequencyis50HzintheSovietUnionandEurope and60HzintheUnitedStates Someindustrialprocessesusefrequenciesfrom10Hzto2 5 109Hz inradiopractice 在无线电应用中 frequenciesupto3 1010Hzareemployed Thedefinitionsforcurrentsjustintroduced and indeed thosethatwillbeintroducedshortly fullyapplytoperiodicvoltages e m f s magneticfluxesandanyotherelectricalandmagneticquantities Someadditionalremarksareonlyneededwithregardtothesignofalternatingvoltagesande m f s AnalternatingvoltagebetweentwopointsAandB determinedalongaspecifiedpathl periodicallychangessign sothatifitisassumedtobepositiveinthedirectionfromAtoB 沿A到B的方向 itwillbenegativeinthedirectionfromBtoAatthesameinstantoftime 1 Thisiswhyitisimportanttolabelwhichofthetwodirectionsisassumedpositive Indiagrams suchadirectionislabeledeitherbyarrowsorsubscriptsinthesymbolsforvoltagesandisregardedtobethepositivereferencedirectionofavoltage orofane m f Electricalengineeringusesthesimplestandcommonesttypeofalternatingcurrent theonewhichvariessinusoidallywithtime 按正弦规律变化 hencetheterm iscalled termed aharmonicorasinusoidalcurrent Thepreferenceforsinusoidalcurrentsisexplainedbythefactthatnon sinusoidalcurrentsentailincreasedenergylosses inducedover voltages andexcessiveinterferencewith 对 的干扰 communicationscircuits Thetransmissionofinformationoveradistance wireorradiocommunicationscircuits remotecontrol etc alsousessinusoidalcurrentsmodulatedbythesignalinamplitude frequencyorphase Periodicnon sinusoidalcurrentsmaylikewisebetreatedascomposedofsinusoidalcurrentsatavarietyoffrequenciesoccurringsimultaneously Thisiswhythoroughofsinusoidal currentcircuitsisofprimaryimportance TheA C GeneratorAnA C generatorconsistsofastationarypart thestator andarevolvingpart therotor Asaruletherotorcarriesmagneticpoleswithcoilsaroundthem Thesearethefieldcoilsofthegenerator becausetheyestablishamagneticfieldinthemachine Theyareenergizedwithdirectcurrentthroughslipringsandbrushes Theslotsofthestatorstackedupfromelectrical sheetsteelpunchingsreceivethecoilsofthestatorwinding 2 Thestatorcoilsareconnectedinseries asshownbythefullanddottedlinesinthedrawing Thee m f inducedinastatorconductorisgivenbyE BlvwhereB magneticinductionofthefieldmovingrelativetotheconductor l activelengthoftheconductor v speedwithwhichthemagneticfieldmovesrelativetotheconductor Sincelandvareconstant theinducede m f willvaryexactlyasBvaries Iftheinducede m f istobesinusoidal whichisusuallysought thedistributionofBaroundthecircumferenceofthestatorshouldbeasclosetosinusoidalaspracticable Withppole pairsontherotor thee m f willundergopcyclesofchangeseveryrevolution Ifthespeedoftherotorisrevolutionsperminute r min thisworksouttopncyclesperminute andthefrequencyoftheinducede m f isf pn 60 Forf 50Hz therotorofageneratorwithonepairofpolesshouldrunat3000r min andwithtwopole pairs at1500r min Withspeedslikethis rotorsareusuallyfabricatedwithnon salientpilesforgreat