轮机英语ppt第27课.ppt

Wuhan Institute of Shipbuilding Technology Power Engineering Department Unit 3Marine Electrization and Automatization 第3单元 船舶电气及自动化 Lesson 27 Marine Generator 第27课 船舶发电机 Direct current generators 直流发电机 Alternating current generators 交流发电机 Emergency generator (supply) 应急发电机（供给） Direct current generators直流发电机 A current is produced when a single coil(单匝线圈) of wire is rotated in a magnetic field(磁场). 一个金属线圈在磁场中转动就会产生电流。 When the current is collected using a ring which is split into(分成) two halves(两部分), that is, a commutator(换向器), a direct or single direction current(直流电) is produced. 当电流汇集在一个分成两部分的环，也就是换向器上，就会有直流电输出。 The current produced may be increased by the use of many turns(转数) of wire(线圈) and additional magnetic fields(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。 With many coils（线圈，这里特指线路） connected to the commutator(换向器), sparking(火花) will occur（产生） as the current collecting brushes（电刷） move across（滑动） the insulated segments（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。 Commutating poles(换向极) or interpoles(中间极) are used to reduce this sparking(火花). 使用换向极或中间极以减少火花。 They are in fact(事实上) electromagnets(电磁铁) having a polarity(极性) the same as the main pole(主磁极) which follows(vi.跟随) in the direction(方向) of rotation(旋转). 事实上，它们是与主磁极同性的电磁铁，并且转向相同。 The magnetic field(磁场) between the poles(电磁极) is produced by what are known as(称为，就是所谓的) field coils“(励磁线圈). 电磁极之间产生的磁场就是所谓的“励磁线圈”。 These coils(特指“励磁线圈”) are excited(激励) or energized(供电) by the current produced in the machine(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。 The soft iron core(软铁芯) of the field coils(励磁线圈) retains(保留、含有) some magnetism(磁性) which enables a preliminary(初始的) current generation(产生) to build up(建立) eventually(最终) to the full(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。 The field windings(磁场励磁绕组) can be connected to the output current(输出电流) in a number of ways – shunt(并激励), series(串激励) or compound(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。 The compound wound(混合激励)arr