专外考前复习重点.docx

专外考前复习重点.docx

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专外考前复习重点

P1U1A

1passivenetwork无源网络2activenetwork有源网络

3passivecircuitelements无源电路元件

4therateofchangewithtimeofthecurrent电流随时间的变化率

5proportionalityconstant比例常数6differentialequation微分方程

7voltagesource电压源currentsource电流源

8thesecond-orderdifferentialequation二阶微分方程

9.loopanalysis回路分析法10.voltagedrop电压降11.loopcurrent回路电流

12Notethatconventionalcurrentflowisused;hencethecurrentineachelementisshowninthedirectionofdirectionofdecreasingvoltage.

注意，图中电流的参考方向为惯用的参考方向，因此流过每一个元件的电流方向与电压降的方向一致。

13Intheiridealform,voltagesourcesgenerateaconstantvoltageindependentofthecurrentdrawnfromthesource.Theaforementionedbatteryandgeneratorareregardedasvoltagesourcessincetheirvoltageisessentiallyconstantwithload.Ontheotherhand,currentsourcesproduceacurrentwhosemagnitudeisindependentoftheloadconnectedtothesource.

在理想状态下：

电压源产生恒定的电压，它与从电压源中流出的电流无关。

因为负载变化时电压基本恒定，所以上述电池和发电机被认为是电压源。

另一方面，电流源产生电流，电流的大小与电源连接的负载无关。

14.Anelectricalcircuitornetworkiscomposedofelementssuchasresistors,inductors,andcapacitorsconnectedtogetherinsomemanner.Ifthenetworkcontainsnoenergysources,suchasbatteriesorelectricalgenerators,itisknownasapassivenetwork.Ontheotherhand,ifoneormoreenergysourcesarepresent,theresultantcombinationisanactivenetwork.

15.Inthecaseofaresistor,thevoltage-currentrelationshipisgivenbyOhm’slaw,whichstatesthatthevoltageacrosstheresistorisequaltothecurrentthroughtheresistormultipliedbythevalueoftheresistance.

16.ThevoltageacrossapureinductorisdefinedbyFaraday’slaw,whichstatesthatthevoltageacrosstheinductorisproportionaltotherateofchangewithtimeofthecurrentthroughtheinductor.

17.Activeelectricaldevicesinvolvetheconversionofenergytoelectricalform.Fromitsstoredchemicalenergy.Theelectricalenergyofageneratorisaresultofthemechanicalenergyoftherotatingarmature.

18.Activeelectricalelementsoccurintwobasicforms:

voltagesourcesandcurrentsource.

19.Ontheotherhand,currentsourcesproduceacurrentwhosemagnitudeisindependentoftheloadconnectedtothesource.

20.Acommonmethodofanalyzinganelectricalnetworkismeshorloopanalysis.Thefundamentallawthatisappliedinthismethodiskirchhoff’sfirstlaw,whichstatesthatthealgebraicsumofthevoltagesaroundaclosedloopis0,or,inanyclosedloop,thesumofthevoltagerisesmustequalthesumofthevoltagedrops.

分析电气网络的一般方法是网孔分析法或回路分析法。

应用于此方法的基本定律是基尔霍夫第一定律，基尔霍夫第一定律指出：

一个闭合回路中的电压代数和为0，换句话说，任一闭合回路中的电压升等于电压降。

P1U1B

1positivehalf-cycle正半周2phasesequence相序

3linevoltage线电压

4armaturecoil电枢绕组

5three-wireorfour-wirethree-phasesystem三线或四线三相系统

6wye-connection星（Y）形联结

7delta-connection三角形（）联结

8phasordiagram相量图

9powerfactor功率因数

10Athree-phaseelectriccircuitisenergizedbythreealternatingemfsofthesamefrequencyanddifferingintimephaseby120electricaldegrees.

三相电路可由三个频率相同、在时间相位上相差120电角度的电动势供电。

11Three-phasemachineryandcontrolequipmentaresmaller,lighterinweight,andmoreefficientthansingle-phaseequipmentofthesameratedcapacity.Inadditiontotheabove-mentionedadvantagesofferedbyathree-phasesystem,thedistributionofthree-phasepowerrequiresonlythreefourthsasmuchlinecopperasdoesthesingle-phasedistributionofthesameamountofpower.

三相供电的机械和控制设备与相同额定容量的单相供电的设备相比：

体积小，重量轻，效率高。

三相系统除了具有上述优点，三相电的传输所需要的铜线仅仅是单相电传输同样功率所需铜线的3/4。

13.Atunitypowerfactor,thepowerinasingle-phasecircuitiszerotwiceeachcycle．

在功率因数为1时，单相电路里的功率值每个周波有两次为零。

14.Viewedinthislight,itwillbefoundthattheanalysisofthree-phasecircuitsislittlemoredifficultthanthatofsingle-phasecircuits.

这样看来，三相电路的分析比单相电路的分析难不了多少。

15.Thesewindingsaresospacedonthearmaturesurfacethattheemfsgeneratedinthemare120apartintimephase.

这些绕组在电枢表面上是按它们产生的电动势在时间相位上相差120分布的。

16ItishelpfulwhendrawingcircuitdiagramsofwyeconnectiontoarrangethethreephasesintheshapeofaYasshowninFig.

将三相绕组排列成如图所示的Y形有助于Y形联接电路图的绘制。

17

ItshouldbenotedthatifthepolarityofpointAwithrespecttoN（）isassumedforthepositivehalf-cycle,thenwhenusedinthesamephasordiagramshouldbedrawnoppositeto,or180outofphasewith,.

应该注意，如果把A点相对于N点的极性（）定为正半周，那么在用于同一相量图中时就应该画得同相反，即相位差为180。

18

ThecurrentflowingouttothelinewiresfromthegeneratorterminalsA,BandCmustflowfromtheneutralpointN,outthroughthegeneratorcoils.

从发电机接线端A、B和C（图1-1B-2）流到线路导线的电流必定从中性点N中流出，并流过发电机线圈。

19.three-phasecircuit三相电路20.single-phasecircuits单相电路

21.Inasingle-phasecircuit,thepowerisofapulsatingnature

22.powerfactor功率因数

23.Althoughthepowersuppliedtoeachofthethreephasesofathree-phasecircuitispulsating,itmaybeprovedthatthetotalthree-phasepowersuppliedabalancedthree-phasecircuitisconstant.Becauseofthis,thecharacteristicsofthree-phaseapparatus,ingeneral,aresuperiortothoseofsimilarsingle-phaseapparatus.

24.Thecoilendsmayallbebroughtoutofthegeneratortoformthreeseparatesingle-phasecircuits.However,thecoilsareordinarilyinterconnectedeitherinternallyorexternallytoformathree-wireorfour-wirethree-phasesystem.

25.Therearetwowaysofconnectingthecoilsofthree-phasegenerators,andingeneral,therearetwowaysofconnectingdevicesofanysorttoathree-phasecircuit.Thesearethewye-connectionanddelta-connection.Mostgeneratorsarewye-connected,butloadsmaybeeitherwye-connectedordelta-connected.

26.ThevoltagesgeneratedineachphaseofanACgeneratorarecalledthephasevoltages（symbolEp）.

27.ThevoltagebetweenanytwoofthethreelineterminalsA,B,orCiscalledline-to-linevoltageor,simply,alinevoltage（symbolEL）.

28.ItshouldbenotedinFig.1-1B-2thateachphasorisletteredwithtwosubscripts.

29.Thetwolettersindicatethetwopointsbetweenwhichthevoltageexists,andtheorderofthelettersindicatestherelativepolarityofthevoltageduringitspositivehalf-cycle.

30.Forexample,thesymbolEANindicatesavoltagebetweenthepointsAandNwiththepointAbeingpositivewithrespecttopointNduringitspositivehalf-cycle.

31.Therefore,inabalancedwye-connectionEL=1.73EP

因此，用平衡星型连接:

EL=1.73EP

32.InawyeconnectionIL=IP

用星型连接:

IL=IP

P1U2A

1two-portsystem双端口系统

2outputresistance输出阻抗

3integratedcircuit（IC）集成电路

4innerworkings工作原理6gainfactor增益系数

5filtercircuit滤波电路7gatheringterms综合上述等式

8theconnectionofthecircuitryinsidetheOp-Amp.

运算放大器的内部电路结构。

9Thismakesdesigndifficultsincetheseparametersusuallyvaryfromdevicetodevice,aswellaswithtemperature.

器件之间参数的分散性和温度漂移特性给设计工作增加了难度。

10Variouscurrentsaredefinedinpartbofthefigure.

各个电流定义如b图所示。

11Eachismeasuredwithrespecttogroundpotential.

每一个电压均指的是相对于接地管脚的电位。

12NotshownareotherconnectionsnecessarytoruntheOp-Ampsuchasitsattachmentstopowersuppliesandtogroundpotential.让运算放大器正常运行所必需的其它一些管脚，诸如电源管脚、接地管脚等并未画出。

13ThisisoneofthekeyfeaturesofOp-Ampdesign---theactionofthecircuitonsignalsdependsonlyupontheexternalelementswhichcanbeeasilyvariedbythedesignerandwhichdonotdependuponthedetailedcharacteroftheOp-Ampitself.

这是运算放大器设计的重要特征之一—在信号作用下，电路的动作仅取决于能够容易被设计者改变的外部元件，而不取决于运算放大器本身的细节特性。

14Insomesense,byusinganOp-Ampwetradeoff“power”for“control”.

从某种意义上说，使用运算放大器是以“能量”为代价来换取“控制”。

15Integratedcircuittechnologyasconstructionofmanyamplifiercircuitsonasinglecomposite“chip”ofsemiconductormaterial.

集成电路技术使得在非常小的一块半导体材料构成的复合“芯片”上可以安装许多放大器电路。

16.Theoperationalamplifier运算放大器

17.Operationalamplifiersaredifferentialdevices.Bythiswemeanthattheoutputvoltagewithrespecttogroundisgivenbytheexpression

UO=A（U+-U-）

whereAisthegainoftheOp-AmpandU+andU-thevoltagesatinputs.Inotherwords,theoutputvoltageisAtimesthedifferenceinpotentialbetweenthetwoinputs.

18.First,wenotethatthevoltageatthepositiveinput,U+,isequaltothesourcevoltage,U+=Us.

19.ThisshowsthatifAisverylarge,thenthegainofthecircuitisindependentoftheexactvalueofAandcanbecontrolledbythechoiceofR1andR2.

20.ThefirstlawstatesthatinnormalOp-Ampcircuitswemayassumethatthevoltagedifferencebetweentheinputterminalsiszero,thatis,

U+=U-

21.ThesecondlawstatesthatinnormalOp-Ampcircuitsbothoftheinputcurrentsmaybeassumedtobezero:

I+=I-=0

22.ThefirstlawisduetothelargevalueoftheintrinsicgainA.Forexample,iftheoutputofanOp-Ampis1VandA=100,000,then（U+-U-）=10-5V.Thisissuchasmallnumberthatitcanoftenbeignored,andwesetU+=U-.ThesecondlawcomesfromtheconstructionofthecircuitryinsidetheOp-Ampwhichissuchthatalmostnocurrentflowsintoeitherofthetwoinputs.

P1U2B

1.electronsormobilenegativecharges（N-type）：

自由电子

2.“holes”orpositivecharges（P-type）：

正电荷3.bipolartransistor:

双向晶体管

4.forwardbias:

正偏5.theemitter:

发射极6.thecollector:

集电极

7.thebase:

基极8.commonemitterconfiguration:

共射极连接

9.Theparticularadvantageofferedbythiscircuitisthatarelativelysmallbasecurrentcancontrolandinstigateaverymuchlargercollectorcurrent（or,morecorrectly,asmallinputpoweriscapableofproducingamuchlargeroutputpower）.Inotherwords,thetransistorworksasanamplifier.

电路特性就是一个相对小的基极电流能够控制和激发一个非常大的集电极电流（或者更准确地说，一个小的输入功率能够产生一个大的输出功率）。

换句话说，晶体管起放大器的作用。

10.reversebiased:

反向偏置11.workingprinciples:

工作原理

12.threeleads:

三根引线13.integratedcircuits:

集成电路

14.powertransistors:

功率晶体管