WuhanInstituteofShipbuildingTechnologyLesson28ParallelingOperationofAlternatorsThreephasealternators(三相交流发电机)arrangedfor(准备)paralleloperation(并车运行)require(需要)aconsiderableamountof(很多的)instrumentation(仪表).三相交流发电机的并车运行需要很多仪表。Thiswillincludeammeters(电流表),watt-meters(功率表),voltmeters(电压表),frequencymeters(频率表)andasynchronizingdevice(同步指示装置).包括电流表、功率表、电压表、频率表和同步指示装置。Reversepowerprotection(逆功率保护)isprovidedtoalternatorssincecurrentprotection(电流保护)cannotbeused.因不能采用逆电流保护，所以发电机装设了逆功率保护。Alternatively(或者)varioustrips(跳闸装置)maybeprovidedintheeventof(万一)primemover(原动机)failure(故障)toensure(确保)thatthealternator(交流发电机)doesnotactas(作为)amotor(电动机).或者装设各种跳闸机构，万一在原动机故障时，确保交流发电机不能按电动机工作。Theoperation(运行)ofparalleling(并车)twoalternators(交流发电机)requires(需要)thevoltagestobeequal(相等的)andalsoinphase(同相).两台交流发电机并车运行需要电压相等且同相。Thealternatingcurrentoutput(交变电流输出)ofanymachinesisalwayschanging,sofar(因此)twomachinestooperate(运行)togethertheirvoltagesmustbechangingatthesamerate(变化率)orfrequency(频率),andmustbereachingtheirmaximum(最大值)(oranyothervalue)together.交变电流输出总是在改变，因此，对欲并车的两台发电机而言，它们的电压必须以相同的变化率即频率变化，并且必须同时达到最大值(或其他值)。Theyarethensaidtobe"inphase".此时我们就说它们“同相”。Useisnowadays(目前)madeofasynchroscope(同步指示仪)whenparalleling(vt.并联)twoA.C.machines(alternatingcurrentgenerators,交流发电机).目前，并联两台交流发电机时采用同步指示仪。Thesynchroscope(同步指示仪)hastwowindings(绕组)whichareconnectedonetoeachsideoftheparallelingswitch(联络开关).同步指示仪有两组绕组，每组与联络开关相连。Apointer(指针)isfree(自由的)torotate(转动)andismovedbythemagneticeffect(磁效应)ofthetwowindings(绕组).同步指示仪指针可自由转动并且受两组绕组的磁效应而动作。Whenthetwovoltagesuppliesareinphase(同相)thepointer(指针)isstationary(不动的)inthe12o'clockposition.当两组输出电压同相时，指针停在12点位置不动。Ifthepointerisrotatingthenafrequency(频率)differenceexistsandthedial(表盘)ismarked(标明)forclockwiserotation(顺时针旋转)FASTandanti-clockwiserotation(逆时针旋转)SLOW,thereference(参考)beingtotheincoming(引入的)machinefrequency(频率).若指针在转动，则频率不相同，在表盘上标明顺时针转、快，逆时针转、慢，其参考是入网频率。Toparallel(并联)anincoming(引入的)machinetoarunning(正在运行的)machinetherefore(因此)itisnecessarytoensure(确保)