電力專業(yè)英語(yǔ)第九講

1、山東交通學(xué)院電氣系 張建軍 詞匯 AC = alternating-current 交流電 rotate v. 旋轉(zhuǎn) convert v. 使轉(zhuǎn)變； 兌換，換算; 侵占 DC = direct-current 直流電 turbine n. 渦輪機(jī)；氣輪機(jī)；水輪機(jī) coil kl n. 線圈； 卷，（一）盤(pán); 盤(pán)卷之物; 紛亂，糾纏不清; pole n. 磁極；電極 桿; 物 極點(diǎn)，頂點(diǎn); vt.用篙撐船，擺船 brush n. 電刷；刷子，畫(huà)筆; 灌木叢; 小沖突 insulate nsjuletv. 使絕緣；使隔離，使孤立; 使隔熱; energizeendaz v. 給予.電壓；勵(lì)磁；加強(qiáng)

2、，給與以活力; 使活躍; 物 給與能量 efficient fnt a. 有效力的；能干的；收效大的 excitation eksaten n. 勵(lì)磁；激發(fā)（過(guò)程）; 激動(dòng); couple v. 連接 n. 對(duì)，雙; 配偶，夫妻; kilowatt n. 千瓦 positivepztv a. （電）陽(yáng)；正的；積極的; 確實(shí)的，肯定的; negative negtv a. （電）負(fù)的，陰的；反抗性的; 無(wú)預(yù)期結(jié)果的;消極性 magnet mgnt n. 磁石，磁鐵 ；有吸引力的人或物; 物 磁體 magnetomgni:t n. 磁電機(jī)，永磁發(fā)電機(jī) in the case of 就.來(lái)說(shuō)；至于.

3、 課文內(nèi)容 Generators AC Generators An alternating-current generator is a rotating machine for converting mechanical energy into alternating- current electric power. As in the case of a dc generator, the rotating part of the machine is driven by a source of rotating power external to the machine itself.

4、An alternating-current generator交流發(fā)電機(jī) dc generator直流發(fā)電機(jī); Alternating-current generators, also called “alternators”, can be divided into three types according to the type of drive or prime mover. There are direct- connected engine-driven (steam or internal combustion) ac generators, water-wheel ac ge

5、nerators, turbine-driven ac generators. alternator:ltnet(r)交流發(fā)電機(jī); according to the type of drive or prime mover根據(jù)原動(dòng) 機(jī)驅(qū)動(dòng)類型不同 steam or internal combustion蒸汽機(jī)或內(nèi)燃機(jī) water-wheel ac generators水輪發(fā)電機(jī) turbine-driven ac generators渦輪驅(qū)動(dòng)交流發(fā)電機(jī) Operation Basically, the alternator operates on the principle of genera

6、tor action-voltage is set up in coils of wire when they are moved in a magnetic field in such a way as to cut the magnetic lines of force. operates on the principle of generator基于發(fā)電機(jī)的 工作原理運(yùn)行 action-voltage 動(dòng)作電壓，工作電壓，感應(yīng)電壓 coils of wire繞組線圈 when they are moved in a magnetic field in such a way as to c

7、ut the magnetic lines of force當(dāng)他們?cè)诖?場(chǎng)中以切割磁力線的方式移動(dòng)時(shí) This is the same principle on which the dc generator operates. But there is a basic difference between dc generators and alternators in accomplishing the relative motion between coils and field. in accomplishing the relative motion between coils and

8、 field在磁場(chǎng)和繞組線圈間實(shí)現(xiàn)相對(duì)運(yùn)動(dòng) In a dc generator, the magnetic field is set up by placing electro-magnetic field poles around the inside of the housing or stator. Coils are placed on the rotor so that when the rotor rotates, the coils are cutting across the magnetic lines of force set up by the poles and vol

9、tage is produced in the rotor coils. by placing electro-magnetic field poles around the inside of the housing or stator通過(guò)把電磁場(chǎng)的磁極放在 外殼或定子內(nèi)部 the coils are cutting across the magnetic lines of force set up by the poles and voltage is produced in the rotor coils線圈切割由定子中磁極所產(chǎn)生的磁力線，隨之在 轉(zhuǎn)子中產(chǎn)生出電壓 By the use

10、of a commutator and brushes, voltage is taken from the rotor. In an ac generator, the electro-magnetic fieldthe source of the magnetic lines of forceis generally placed on the rotor and the coils in which the voltage is to be generated are mounted around the inside of the stator. By the use of a com

11、mutator and brushes通過(guò)使用換向 器和電刷 the electro-magnetic fieldthe source of the magnetic lines of force電磁場(chǎng)-磁力線的來(lái)源 and the coils in which the voltage is to be generated are mounted around the inside of the stator. 用來(lái)產(chǎn)生電壓的線圈被安裝在定子內(nèi)部 In this case, the rotating field sweeps the lines of magnetic force across

12、 the stationary coils and produces the voltage in them. In this case在這種情況下; 既然如此; 這樣的話; the rotating field sweeps the lines of magnetic force across the stationary coils旋轉(zhuǎn)的磁場(chǎng)使得磁力線掃過(guò) 靜止的線圈 and produces the voltage in them并且在線圈中產(chǎn)生電 壓 Alternators with stationary coils (or stationary armature, as it is

13、sometimes described) have distinct advantages over alternators with rotating coils and are the most common type. stationary coils 靜止的（固定的）繞組線圈靜止的（固定的）繞組線圈 stationary armature靜止的電樞靜止的電樞 have distinct advantages over alternators with rotating coils 對(duì)于對(duì)于那些旋轉(zhuǎn)的繞組那些旋轉(zhuǎn)的繞組線圈而言，有明線圈而言，有明 顯的優(yōu)勢(shì)顯的優(yōu)勢(shì) and are the

14、 most common type并且是最常見(jiàn)的類并且是最常見(jiàn)的類 型型 If the generator coils are placed on the rotor, two or more slip rings must be used for conducting the ac power to the external circuit which the generator feeds. Such rings are a frequent source of trouble, particularly at the high voltage put out by standard al

15、ternators. two or more slip rings must be used必須要使用 兩個(gè)或 更多的滑環(huán) for conducting the ac power to the external circuit which the generator feeds用來(lái)把交流電能引導(dǎo)到發(fā)電機(jī) 所供電的外部電路 Such rings are a frequent source of trouble這一類的滑環(huán) 是頻繁出現(xiàn)的故障源 particularly at the high voltage put out by standard alternators. 特別是由標(biāo)準(zhǔn)發(fā)電機(jī)的高壓

16、所引起 If stationary coils are used, the generated ac power can be taken directly from the coil leads to output bus bars. Also, if the coils are on the rotor, it is more difficult to properly insulate them, and they are subjected to heavy centrifugal forces and vibrations. the generated ac power can be

17、 taken directly from the coil leads to output bus bars發(fā)出的交流電能可以直接 由線圈引導(dǎo)到母線 Also另外 it is more difficult to properly insulate them很難使它 們可靠絕緣 and they are subjected to heavy centrifugal forces and vibrations并且它們還要受到嚴(yán)重的離心力和振動(dòng)的影 響 When the electro-magnetic field is placed on the rotor, as in most commerc

18、ial alternators, the direct current necessary to energize the field must be conducted to and from the rotor by the use of slip rings. as in most commercial alternators像大多數(shù)商用 發(fā)電機(jī)那樣 the direct current necessary to energize the field must be conducted to and from the rotor by the use of slip rings用于勵(lì)磁的

19、直流電流必須要由滑 環(huán)來(lái)流經(jīng)轉(zhuǎn)子 However, the voltage seldom exceeds 250 volts and the amount of power involved is so small as to cause no particular difficulties. WindingsIn general, windings for alternators are the same as for dc generators. Single-phase windings are almost never used in alternators. the voltage

20、seldom exceeds 250 volts 電壓很少超過(guò)250伏 and the amount of power involved is so small as to cause no particular difficulties并且所涉及的電能非常少，因 此不會(huì)帶來(lái)問(wèn)題 Single-phase windings are almost never used in alternators在交流發(fā)電機(jī)中幾乎從來(lái)不用單相繞組 Generators for single-phase railroad supply are the exceptions. Usually, alternator

21、 windings are arranged to provide three-phase output of ac electric power, such an arrangement is most efficient and economical. Single-phase power can be taken from a three-phase alternator. Generators for single-phase railroad supply are the exceptions用于單相軌道供電的發(fā)電機(jī)屬于例外 such an arrangement is most e

22、fficient and economical 這樣的安排是最有效和經(jīng)濟(jì)的 Actually, three-phase windings in alternators are simply three single-phase windings properly spaced in the stator slots. three-phase windings in alternators 發(fā)電機(jī)中的三相繞 組 are simply three single-phase windings properly spaced in the stator slots是三個(gè)單相繞組在定子凹槽 中適當(dāng)?shù)姆胖?/p>

23、 Field ExcitationGenerally, current is supplied to the field windings on the rotor by an individual exciter which may be driven directly or through a gear reduction. Excitation voltage varies between 120 and 250 volts. Excitation voltage is also often obtained from exciters coupled directly to the a

24、lternator shaft or from a bank of batteries. Field Excitation勵(lì)磁，場(chǎng)激勵(lì); by an individual exciter由單獨(dú)的勵(lì)磁機(jī) which may be driven directly or through a gear reduction 它可以直接驅(qū)動(dòng)或經(jīng)過(guò)齒輪減速后驅(qū)動(dòng) a bank of batteries蓄電池 DC Generators A direct-current generator is a rotating machine for converting mechanical energy into

25、direct-current electric power. A dc generator is driven by mechanical means, such as a steam engine, diesel engine or electric motor. Direct-current generators are rated in kilowatts, sizes range from a fraction of a watt to several thousand watts. A dc generator is driven by mechanical means直流發(fā) 電機(jī)由

26、機(jī)械方式驅(qū)動(dòng) such as a steam engine, diesel engine or electric motor 像是蒸汽機(jī)，柴油機(jī)，電動(dòng)機(jī) are rated in kilowatts額定功率為千瓦 sizes range from a fraction of a watt to several thousand watts型號(hào)從幾分之一瓦到幾千瓦 Operation The basic electrical principle underlying operation of dc generators is called “generator action”. If a len

27、gth of wire is moved through a magnetic field in such a way that the wire cuts between the North and South poles producing the magnetic field, an electric voltage will be set up in the wire . principle underlying operation基本操作原理 generator action發(fā)電機(jī)效應(yīng) If a length of wire is moved through a magnetic f

28、ield in such a way that the wire cuts between the North and South poles producing the magnetic field如果一定長(zhǎng)度 的導(dǎo)線在N極和S極之間以切割磁力線的方式移動(dòng) Of course, the voltage set up in a single length of wire would be small. But if a large number of wires were connected end to end and rotated in the magnetic field, the v

29、oltage set up in the series of wire lengths would be equal to the sum of voltages set up in the individual lengths wire. “Generator action” is the effect whereby the voltage is set up in a moving conductor. Of course, the voltage set up in a single length of wire would be small. 當(dāng)然，在單根一定長(zhǎng)度的導(dǎo)線中產(chǎn)生的電壓將

30、很 小。 But if a large number of wires were connected end to end and rotated in the magnetic field但是假如大量的導(dǎo)線首尾 相接并且在磁場(chǎng)中旋轉(zhuǎn) in the series of wire lengths 在這一系列的導(dǎo)線長(zhǎng)度中 whereby借以; 通過(guò); 與一致; Generator action” is the effect whereby the voltage is set up in a moving conductor發(fā)電機(jī)效應(yīng)就是通過(guò)在移動(dòng)的導(dǎo)體中 建立電壓的效應(yīng) In dc genera

31、tors, the conductors are wound into coils and mounted in slots on the armature or rotating element within the units housing. The ends of each coil of conductors are brought out to one end of the armature where they are connected to individual insulated bars in an assembly of such bars, which is moun

32、ted around the armature shaft. In dc generators, the conductors are wound into coils and mounted in slots on the armature or rotating element within the units housing在直流發(fā)電機(jī)中，導(dǎo) 體被繞成線圈并安裝在機(jī)殼內(nèi)的電樞或旋轉(zhuǎn)部分的凹 槽中。 This assembly is called the “commutator”, which is required to provide direct-current output fro

33、m the generator. The wires that come out of the generator, one for the positive side of the dc output and one for the negative side, are connected within the generator to carbon brushes which ride on the commutator. The brushes pick up the electric current from the commutator and pass it to the circ

34、uit being fed by the generator. The magnetic field required for generator action is produced in three ways: By permanent magnets, in which case the machine is called a magneto. Magnetos are generally small in size and capacity due to the limited strength of permanent magnets. Magnetos are used for v

35、arious speed indicating devices. The magnetic field required for generator action is produced in three ways用于發(fā)電機(jī)效應(yīng)的磁場(chǎng)可以由三種 方式產(chǎn)生 Magneto永磁發(fā)電機(jī) Magnetos are used for various speed indicating devices.永磁磁電機(jī)用于各種速度 的指示裝置 By electromagnets excited by a direct-current source independent of the generator itself. In such cases, magnetic pole pieces are parts of the stator (stationary housing of the generator in which the armature r