WuhanInstituteofShipbuildingTechnologyUnit3MarineElectrizationandAutomatizationLesson27MarineGeneratorDirectcurrentgenerators直流发电机Alternatingcurrentgenerators交流发电机Emergencygenerator(supply)应急发电机（供给）Directcurrentgenerators直流发电机Thecurrentproducedmaybeincreasedbytheuseofmanyturns(转数)ofwire(线圈)andadditionalmagneticfields(磁场).通过增加线圈的转数或增加磁场来增大所产生的电流。Withmanycoils（线圈，这里特指线路）connectedtothecommutator(换向器),sparking(火花)willoccur（产生）asthecurrentcollectingbrushes（电刷）moveacross（滑动）theinsulatedsegments（绝缘部件）.当一些线路连接到换向器上，随着电刷在绝缘部件上滑动，电流汇聚以后会产生火花。Commutatingpoles(换向极)orinterpoles(中间极)areusedtoreducethissparking(火花).使用换向极或中间极以减少火花。Theyareinfact(事实上)electromagnets(电磁铁)havingapolarity(极性)thesameasthemainpole(主磁极)whichfollows(vi.跟随)inthedirection(方向)ofrotation(旋转).事实上，它们是与主磁极同性的电磁铁，并且转向相同。Themagneticfield(磁场)betweenthepoles(电磁极)isproducedbywhatareknownas(称为，就是所谓的)"fieldcoils“(励磁线圈).电磁极之间产生的磁场就是所谓的“励磁线圈”。Thesecoils(特指“励磁线圈”)areexcited(激励)orenergized(供电)bythecurrentproducedinthemachine(特指“发电机”).这些励磁线圈由发电机自身产生的电流励磁或供电。Thesoftironcore(软铁芯)ofthefieldcoils(励磁线圈)retains(保留、含有)somemagnetism(磁性)whichenablesapreliminary(初始的)currentgeneration(产生)tobuildup(建立)eventually(最终)tothefull(所有的)machine(特指“发电机”)output(输出功率).励磁线圈的软铁含有磁性，以便建立初始的励磁电流并均匀分配至所有发电机功率。Thefieldwindings(磁场励磁绕组)canbeconnectedtotheoutputcurrent(输出电流)inanumberofways–shunt(并激励),series(串激励)orcompound(混合激励).磁场励磁绕组有多种方式从输出电流供电——并激励，串激励或混合激励。Thecompoundwound(混合激励)arrangement(搭配)isusualsince(因为)itprovidesthebest(最佳的)voltagecharacteristics(n.特性).联合励磁即混合激励是常见的，因为它可提供最佳的电压特性。Thecompoundwoundgeneratorhastwosets(两组)offieldcoils(励磁线圈).混合激励的发电机有两组励磁线圈。Theshuntcoil(并激励线圈)hasmanyturnsoffine(细的)wire(金属线圈)andtheseriescoil(串激励线圈)hasafewturnsofheavy(粗的)wire.并激励线圈有许多圈细金属线圈，而串激励线圈只有几圈粗金属线圈。Theshuntfield(并励磁场)producesfullvoltageonno-load(空载)whichfallsoff(减少)astheloadcurrent(负载电流)increases.并励磁场产生全部空载电压，并随负载电流的增加逐渐减少。Theseriesfield(串励磁场)creates(引起)anincreaseinvoltageastheloadincreases.串励磁场随负载增大增加电压。Properly（适当地）combined(联合励磁)orcomp