電氣工程及其自動化專業(yè)英語 課件 -Chapter 1 Power Generation System

目錄Introduction1.1GeneratingElectricCurrents1.2ElectricPowerStation1.3SynchronousGeneratorVoltageControl1.4MotorApplicationsinPowerPlants1.5Chapter1PowerGenerationSystem 1.1Introduction1. electricitygeneration[??lek?tr?s?ti?d?en??re??n]n.發(fā)電2. electricitytransmission[??lek?tr?s?titr?nz?m??n]n.輸電3. reciprocatingengine[ri'sipr?keiti??end??n]n.往復(fù)式引擎4. permanentmagnet[?p??m?n?nt?m?ɡn?t]n.永久磁鐵Generator[?d?en?re?t?(r)]n.發(fā)電機(jī)photoelectric[,f?ut?ui'lektrik]adj.光電的7. ironcore[?a??nk??(r)]n.鐵芯8. turbine['t?:bain,-bin]n.渦輪機(jī)9. thermalenergy[?θ??m(?)l]n.熱能10. condense[k?n'dens]v.使凝結(jié)11. component[k?m'p?un?nt]n.元件、器件If

youbring

a

（）

near

a

compass

and

move

it

around,thecompasswillreact.

permanent

magnetironcorereciprocatingenginePowerfactorABCD提交單選題1分12. Turbine-Generator[?t??ba?nd?en?re?t?(r)]n.渦輪發(fā)電機(jī)13. hydroelectric[,haidr?ui'lektrik]adj.水力發(fā)電的14. excitation[,eksi'tei??n]n.勵磁15. synchronous['si?kr?n?s]adj.同步的16. overload[,?uv?'l?ud,'?uv?l?ud]n.過載17. exciter[ik'sait?]n.勵磁機(jī)18. regulator['reɡjuleit?]n.調(diào)節(jié)器19. amplidyne['?mplidain]n.電機(jī)放大機(jī)20. alternator['?:lt?neit?]n.交流發(fā)電機(jī)21. separatelyexcited[?sepr?tli?k?sa?t?d]adj.他勵的22. armature['ɑ:m?,tju?,-t??]n.電樞Thethermallimitshavetime-dependentcharacteristics,andtheshort-term（）capabilityofthegeneratorsmayextendfrom15to60seconds.No-loadOverloadShort-circuitmanufacturingABCD提交單選題1分23. air-gapn.氣隙24. servo-controln.伺服控制25. fieldwindingn.勵磁繞組26. magneticfieldn.磁場27. polarity[p?u'l?r?ti]n.極性28. commutator['k?mjuteit?]n.換相器29. series-wound['si?ri(:)zwaund,'si:r-]n.串勵30. shunt-wound['??ntwaund]n.并勵31. compound-wound['k?mpaund'waund]n.復(fù)勵32. brush[br??]n.電刷33. horsepower['h?:s,pau?]n.馬力

The

winding

through

which

a

current

ispassedto

produce

the

primary

sourceof

flux

in

the

machine

iscalled

the

().

field

windingstatorwindingprimarywindingsecondarywindingABCD提交單選題1分34. demagnetization['di:,m?ɡnitai'zei??n,-ti'z-]n.去磁，失磁35. rheostat['ri:?ust?t]n.變阻器36. fieldcurrentn.勵磁電流37. cumulativecompound['kju:mju,leitiv]n.積式復(fù)勵38. differentialcompound[,dif?'ren??l]n.差分復(fù)勵39. shortshunt[??nt]n.短復(fù)勵40. Long-shuntn.長復(fù)勵41. ferromagneticmaterialn.鐵磁材料42. squirrel-cagen.鼠籠式43. wound-rotor[wu:nd]n.繞線式44. statorwindingn.定子繞組56. bearing['bε?ri?]n.軸承57. fieldvoltagen.勵磁電壓58. electricalmotorn.電機(jī)59. Single-Quadrant['kw?dr?nt]n.單象限60. fieldfluxn.勵磁磁通61. referencesignaln.參考信號、給定信號62. powerfactorn.功率因數(shù)63. startingcurrentn.啟動電流64. overloadprotectionn.過載保護(hù)65. time-delayrelayn.時間繼電器66. under-voltageprotectionn.欠壓保護(hù)The

input

()

ofthe

converter

isabout0.99.

power

failurepower

factorharmoniccontentpercentreactanceABCD提交單選題1分45. three-phaseinductionmotorn.三相感應(yīng)電機(jī)46. low-reluctance[ri'l?kt?ns]n.低磁阻47. magneticfluxn.磁通48. doublyexcitedn.雙勵49. slipringn.滑環(huán)50. regenerativebrakingn.回饋制動51. eddycurrentbrakingn.渦流制動52. dynamicbrakingn.能耗制動53. reversecurrentbrakingn.電流反向接制動54. variable-frequencyn.變頻55. copper['k?p?]n.銅Ahybrid‘s

battery

isreplenished

constantly

by

the

engine

aswellas

bythe

vehicle‘s

（）

system.

dynamicbrakingeddycurrentbrakingregenerative

brakinghard

brakingABCD提交單選題1分67. slipn.滑差68. Adjustable-Frequencyn.調(diào)頻69. DClinkn.直流環(huán)節(jié)目錄Introduction1.1GeneratingElectricCurrents1.2ElectricPowerStation1.3SynchronousGeneratorVoltageControl1.4MotorApplicationsinPowerPlants1.51.1IntroductionElectricitygenerationistheprocessofgeneratingelectricenergyfromotherformsofenergy.Thefundamentalprinciplesofelectricitygenerationwerediscoveredduringthe1820sandearly1830sbytheBritishscientistMichaelFaraday.Hisbasicmethodisstillusedtoday:electricityisgeneratedbythemovementofaloopofwire,ordiscofcopperbetweenthepolesofamagnet.發(fā)電是利用其他形式的能量產(chǎn)生電能的過程。發(fā)電的基本原理是在19世紀(jì)20年代和30年代初由英國科學(xué)家邁克爾·法拉第發(fā)現(xiàn)的。他的基本方法至今仍在使用:電是由磁鐵兩極之間的線圈或銅片的運(yùn)動產(chǎn)生的。Forelectricutilities,itisthefirstprocessinthedeliveryofelectricitytoconsumers.Theotherprocesses,electricitytransmission,distribution,andelectricalpowerstorageandrecoveryusingpumpedstoragemethodsarenormallycarriedoutbytheelectricpowerindustry.對于電力公司來說，這是向用戶輸送電力的第一個過程。其他過程，電力傳輸，配電，以及使用抽水蓄能方法的電力儲存和回收通常由電力工業(yè)進(jìn)行。備注：電力工業(yè)（electricpowerindustry)是將煤炭、石油、天然氣、核燃料、水能、海洋能、風(fēng)能、太陽能、生物質(zhì)能等一次能源經(jīng)發(fā)電設(shè)施轉(zhuǎn)換成電能,再通過輸電、變電與配電系統(tǒng)供給用戶作為能源的工業(yè)部門。生產(chǎn)、輸送和分配電能的工業(yè)部門。包括發(fā)電、輸電、變電、配電等環(huán)節(jié)。

Electricityismostoftengeneratedatapowerstationbyelectromechanicalgenerators,primarilydrivenbyheatenginesfueledbychemicalcombustionornuclearfissionbutalsobyothermeanssuchasthekineticenergyofflowingwaterandwind.Therearemanyothertechnologiesthatcanbeandareusedtogenerateelectricitysuchassolarphotovoltaicsandgeothermal

power.電能通常由發(fā)電廠中機(jī)電能量轉(zhuǎn)換的發(fā)電機(jī)產(chǎn)生。發(fā)電機(jī)主要由采用化學(xué)燃燒或核裂變產(chǎn)熱的熱機(jī)驅(qū)動，但也有利用水和風(fēng)的動能等其他方式驅(qū)動。還有許多其他技術(shù)可以用來發(fā)電，如太陽能光伏發(fā)電和地?zé)岚l(fā)電。Electricityismostoftengeneratedatapowerstationbyelectromechanicalgenerators,primarilydrivenbyheatenginesfueledbychemicalcombustionornuclearfissionbutalsobyothermeanssuchasthekineticenergyofflowingwaterandwind.Therearemanyothertechnologiesthatcanbeandareusedtogenerateelectricitysuchassolarphotovoltaicsandgeothermalpower.電通常由發(fā)電站的發(fā)電機(jī)產(chǎn)生，主要由化學(xué)燃燒或核裂變?nèi)剂系臒釞C(jī)驅(qū)動，但也通過其他方式，如流動的水和風(fēng)的動能。還有許多其他技術(shù)可以用來發(fā)電，如太陽能光伏發(fā)電和地?zé)岚l(fā)電。備注：此處的“electromechanicalgenerators”泛指使用機(jī)械能轉(zhuǎn)換成電能的機(jī)械設(shè)備，就是《電機(jī)學(xué)》中的發(fā)電機(jī)。因此翻譯為“發(fā)電機(jī)”，略去“機(jī)電”。Centralisedpowergenerationbecamepossiblewhenitwasrecognisedthatalternatingcurrentpowerlinescantransportelectricityatverylowcostsacrossgreatdistancesbytakingadvantageoftheabilitytoraiseandlowerthevoltageusingpowertransformers.當(dāng)人們認(rèn)識到交流電線路可以利用電力變壓器提高和降低電壓的能力，（實(shí)現(xiàn)）以極低的成本遠(yuǎn)距離送電時，集中發(fā)電成為可能。Electricityhasbeengeneratedatcentralstationssince1881.Thefirstpowerplantwererunonwaterpowerorcoal,andtodaywerelymainlyoncoal,nuclear,naturalgas,hydroelectric,andpetroleumwithasmallamountfromsolarenergy,tidalharnesses,windgenerators,andgeothermalsources.自1881年以來，中心站就開始發(fā)電。第一個發(fā)電廠使用的是水力或煤炭，而今天我們主要依靠煤炭、核能、天然氣、水力發(fā)電和石油，還有少量太陽能、潮汐能、風(fēng)力發(fā)電機(jī)和地?zé)豳Y源。Therearesevenfundamentalmethodsofdirectlytransformingotherformsofenergyintoelectricalenergy:將其他形式的能量直接轉(zhuǎn)化為電能的基本方法有7種:1）Staticelectricity,fromthephysicalseparationandtransportofcharge(examples:triboelectriceffectandlightning)靜電，從物理上分離和傳輸電荷(例如:摩擦電效應(yīng)和閃電)2）Electromagneticinduction,whereanelectricalgenerator,dynamooralternatortransformskineticenergy(energyofmotion)intoelectricity2)電磁感應(yīng)，即發(fā)電機(jī)、發(fā)電機(jī)或交流發(fā)電機(jī)將動能(運(yùn)動的能量)轉(zhuǎn)化為電能3）Electrochemistry,thedirecttransformationofchemicalenergyintoelectricity,asinabattery,fuelcellornerveimpulse.電化學(xué)，將化學(xué)能直接轉(zhuǎn)化為電能，如在電池、燃料電池或神經(jīng)沖動中。4）Photoelectriceffect,thetransformationoflightintoelectricalenergy,asinsolarcells.光電效應(yīng)，即光轉(zhuǎn)化為電能，如在太陽能電池中5）Thermoelectriceffect,directconversionoftemperaturedifferencestoelectricity,asinthermocouples,thermopiles,andthermionicconverters.熱電效應(yīng)，溫差直接轉(zhuǎn)化為電能，如在熱電偶、熱電堆和熱離子轉(zhuǎn)換器中6）Piezoelectriceffect,fromthemechanicalstrainofelectricallyanisotropicmoleculesorcrystals6)壓電效應(yīng)，來自電各向異性分子或晶體的機(jī)械應(yīng)變7）Nucleartransformation,thecreationandaccelerationofchargedparticles(examples:betavoltaicsoralphaparticleemission)7)核轉(zhuǎn)化，帶電粒子的產(chǎn)生和加速(例如:β電或α粒子發(fā)射)Staticelectricitywasthefirstformdiscoveredandinvestigated,andtheelectrostaticgeneratorisstillusedeveninmoderndevicessuchastheVandeGraaffgeneratorandMHDgenerators.Electronsaremechanicallyseparatedandtransportedtoincreasetheirelectricpotential.靜電是發(fā)現(xiàn)和研究的第一種形式，即使在現(xiàn)代設(shè)備中，如范德格拉夫發(fā)電機(jī)和MHD發(fā)電機(jī)，靜電發(fā)生器仍在使用。電子通過機(jī)械分離和傳遞來增加它們的電勢。（為了加深最后一句話的理解，請查閱范德格拉夫起電機(jī)的原理。推薦視頻網(wǎng)址：/s?__biz=MzUxNTc5ODc5NQ==&mid=2247500491&idx=2&sn=3a9f850a3b19a5aa91f7f8308da670d4&chksm=f9b3a0afcec429b9ab8396da061746598633e0d2e32665cef9222eb93a8cce8cd9955fbdbedf&scene=27）請注意該視頻取自網(wǎng)絡(luò)，非作者版權(quán)，轉(zhuǎn)載請注明出處Almostallcommercialelectricalgenerationisdoneusingelectromagneticinduction,inwhichmechanicalenergyforcesanelectricalgeneratortorotate.Therearemanydifferentmethodsofdevelopingthemechanicalenergy,includingheatengines,hydro,windandtidalpower.幾乎所有的商業(yè)發(fā)電都是利用電磁感應(yīng)來完成的，在電磁感應(yīng)中，機(jī)械能迫使發(fā)電機(jī)旋轉(zhuǎn)。有許多不同的方法來開發(fā)機(jī)械能，包括熱機(jī)，水力發(fā)電，風(fēng)力發(fā)電和潮汐能。Thedirectconversionofnuclearpotentialenergytoelectricitybybetadecayisusedonlyonasmallscale.Inafull-sizenuclearpowerplant,theheatofanuclearreactionisusedtorunaheatengine.Thisdrivesagenerator,whichconvertsmechanicalenergyintoelectricitybymagneticinduction.通過β衰變將核勢能直接轉(zhuǎn)化為電能的方法只在很小的范圍內(nèi)使用。在一個通常大小的（標(biāo)準(zhǔn)的）核電站中，核反應(yīng)的熱量被用來驅(qū)動熱機(jī)。熱機(jī)驅(qū)動發(fā)電機(jī)，發(fā)電機(jī)通過磁感應(yīng)將機(jī)械能轉(zhuǎn)化為電能。Mostelectricgenerationisdrivenbyheatengines.Thecombustionoffossilfuelssuppliesmostoftheheattotheseengines,withasignificantfractionfromnuclearfissionandsomefromrenewablesources.Themodernsteamturbine(inventedbySirCharlesParsonsin1884)currentlygeneratesabout80percentoftheelectricpowerintheworldusingavarietyofheatsources.大多數(shù)發(fā)電是由熱機(jī)驅(qū)動的?；剂系娜紵秊檫@些發(fā)動機(jī)提供了大部分熱量，其中很大一部分來自核裂變，還有一些來自可再生能源。現(xiàn)代蒸汽輪機(jī)(由查爾斯·帕森斯爵士于1884年發(fā)明)目前使用各種熱源產(chǎn)生世界上約80%的電力。目錄Introduction1.1GeneratingElectricCurrents1.2ElectricPowerStation1.3SynchronousGeneratorVoltageControl1.4MotorApplicationsinPowerPlants151.2GeneratingElectricCurrentsInthissection,wewillseethatachangeinthemagneticfluxpassingthroughatransformer’ssecondarycoilcausescurrenttoflowinthatcoil.Sincethemagneticfluxthroughthesecondarycoilchangeswheneverthecurrentthroughtheprimarycoilchanges,analternatingcurrentinthetransformer’sprimarycoilinducesanalternatingcurrentinitssecondarycoil.在本節(jié)中，我們將看到通過變壓器次級線圈的磁通量的變化導(dǎo)致電流在該線圈中流動。因?yàn)橥ㄟ^次級線圈的磁通量隨著通過初級線圈的電流的變化而變化，所以變壓器初級線圈中的交流電在次級線圈中產(chǎn)生交流電。1.2GeneratingElectricCurrentsButthere’sanotherwaytochangethemagneticfluxpassingthroughacoilofwire:movethemagneticflux.That’showageneratorworks.Wheneveramagnetmovespastacoilofwireoracoilofwiremovespastamagnet,thefluxthroughthecoilchangesandcurrentflowsinthecoilanditscircuit.但是還有另一種方法可以改變通過線圈的磁通量:移動磁通量。這就是發(fā)電機(jī)的工作原理。每當(dāng)磁鐵經(jīng)過一圈電線或一圈電線經(jīng)過磁鐵時，通過線圈的磁通就會發(fā)生變化，電流就會在線圈及其電路中流動。1.2GeneratingElectricCurrents大多數(shù)發(fā)電機(jī)使用旋轉(zhuǎn)運(yùn)動來發(fā)電。圖1.1a和圖1.1.b所示的發(fā)電機(jī)有一個在兩個固定線圈之間旋轉(zhuǎn)的永磁體。Mostgeneratorsuserotarymotiontoproduceelectricity.ThegeneratorshowninFigs.1.1aand1.1.bhasapermanentmagnetthatspinsbetweentwofixedcoilsofwire.Fig.1.1-(a)Astherotatingmagnetofageneratorturns,itperiodicallyalignswithironcoresinsidethegenerator’scoilsandtemporarilymagnetizesthosecores.Thechangingfluxthroughthecoresandcoilsinducescurrentsinthecoilandgenerateselectricity.(b)Withouttheironcores,fewfluxlinesfromtherotatingmagnetwouldpassthroughthegenerator’scoils.1.2GeneratingElectricCurrentsAsthemagnetspins,itsmagneticfluxlinessweepthroughthetwocoilsanddriveacurrentthroughthem.Thiscurrentexperiencesavoltageriseasitpassesthroughthecoilsandavoltagedropasitpassesthroughthelightbulb,soittransferspowerfromthegeneratortothelightbulb.當(dāng)磁鐵旋轉(zhuǎn)時，它的磁通量線掃過兩個線圈并在線圈內(nèi)產(chǎn)生電流。電流通過線圈時電壓上升，通過燈泡時電壓下降，這樣它將能量從發(fā)電機(jī)傳遞到燈泡。1.2GeneratingElectricCurrentsTheironcoreinsideeachcoilextendsthemagnet’sfluxlinessothattheyaresuretosweepthroughthecoileachtimeapoleofthemagnetpassesby.Thesecoresaretemporarilymagnetizedbythenearbymagnetandeffectivelyincreaseitslength(Fig.1.1a).Withouttheironcores,mostoftherotatingmagnet’sfluxlineswouldbendaroundbeforepassingthroughtheentirecoil(Fig.1.1b)andthegeneratorwouldbelesseffectiveinproducingelectricity.每個線圈內(nèi)的鐵芯延長了磁鐵的磁通線，以便每次磁鐵的極點(diǎn)經(jīng)過時，它們都肯定會掃過線圈。這些磁芯被附近的磁體暫時磁化，有效地增加了磁體的長度(圖1.1a)。如果沒有鐵芯，大多數(shù)旋轉(zhuǎn)磁鐵的磁通線在通過整個線圈之前就會彎曲(圖1.1b)，發(fā)電機(jī)的發(fā)電效率就會降低。1.2GeneratingElectricCurrentsAgeneratorofthistypeproducesanalternatingcurrentinthecircuititpowers.Thiscurrentflowsinonedirectionasthemagnet’snorthpoleapproachesacoilandintheoppositedirectionasthesouthpoleapproachesit.Togeneratethe60HzalternatingcurrentusedintheUnitedStates,thegeneratormustturn60timeseachsecondsothatthecurrentcompletesonefullcycleofreversalsevery1/60thofasecond.這種類型的發(fā)電機(jī)在其供電的電路中產(chǎn)生交流電。當(dāng)磁鐵的N極接近線圈時電流沿一個方向流動，當(dāng)磁鐵的S極接近線圈時沿相反的方向流動。在美國，為了產(chǎn)生60Hz的交流電，電機(jī)必須每秒轉(zhuǎn)60圈，這樣電流每1/60秒內(nèi)完成一個周期。1.2GeneratingElectricCurrentsInEurope,thegeneratormustturn50timeseachsecondtosupply50Hzalternatingcurrent.Thegeneratorsthroughoutthecontinent-widepowerdistributionnetworksallturntogetherinperfectsynchronization.Thatway,powercanberedirectedwithineachnetworksothatanygeneratorcanprovidethepowerconsumedbyanyuser.在歐洲，發(fā)電機(jī)必須每秒轉(zhuǎn)50次才能提供50赫茲的交流電。整個大陸配電網(wǎng)絡(luò)的發(fā)電機(jī)都以完全的同步方式運(yùn)轉(zhuǎn)。這樣，電力可以在每個電網(wǎng)中重新分配，以便任何發(fā)電機(jī)都可以提供任何用戶消耗的電力。1.2GeneratingElectricCurrentsSomedevicesrequiredirectcurrentelectricpower.Theautomobileisagoodexample.ItgeneratesDCelectricpowertochargeitsbatteryandtorunitsheadlights,ignitionsystem,andotherelectriccomponents.WhilethispowerisactuallyproducedbyanACgeneratororalternator,thecarusesspecialelectronicswitchestosendcurrentfromthealternatoronewaythroughitselectricsystem.Whilethecurrentinthealternator’scoilsreverses,thecurrentthroughthecar’selectricsystemalwaystravelsinonedirection.有些設(shè)備需要直流電。汽車就是一個很好的例子。系統(tǒng)產(chǎn)生直流電，為電池充電，驅(qū)動車頭燈、點(diǎn)火系統(tǒng)和其他電子元件。雖然這種電力實(shí)際上是由交流發(fā)電機(jī)或交流發(fā)電機(jī)產(chǎn)生的，但汽車使用特殊的電子開關(guān)將交流發(fā)電機(jī)產(chǎn)生的電流通過其電力系統(tǒng)單向輸送。當(dāng)交流發(fā)電機(jī)線圈中的電流反向時，流經(jīng)汽車電氣系統(tǒng)的電流總是沿一個方向傳輸。1.2GeneratingElectricCurrentsBecauselargepermanentmagnetsareextremelyexpensive,mostindustrialgeneratorsactuallyuseiron-coreelectromagnetsinstead.Theserotatingelectromagnetsdrivecurrentsthroughgeneratorcoilsjustaseffectivelyaspermanentmagnetswould.Althoughtheseelectromagnetsconsumesomeelectricpower,theyaremuchmorecosteffectivethanrealpermanentmagnets.由于大型永磁體極其昂貴，大多數(shù)工業(yè)發(fā)電機(jī)實(shí)際上使用有鐵芯的電磁鐵代替。這些旋轉(zhuǎn)的電磁鐵驅(qū)動電流通過發(fā)電機(jī)線圈，就像永久磁鐵一樣有效。雖然這些電磁鐵消耗一些電力，但它們比真正的永久磁鐵更具成本效益。1.2GeneratingElectricCurrentsSincetheelectriccurrentextractsenergyfromthegenerator,somethingmustdoworkonittokeepitturning.WecanseewhythisworkisneededbylookingatFig.1.2.Asthepermanentmagnetturnsitsnorthpoletowardtheironcoreaboveit,thatcoretemporarilybecomesmagneticwithitssouthpoledown.由于電流從發(fā)電機(jī)中汲取能量，因此必須有工作保持發(fā)電機(jī)運(yùn)轉(zhuǎn)。我們可以通過圖1.2看到為什么需要這樣。當(dāng)永磁體將其N極轉(zhuǎn)向其上方的鐵芯時，該核暫時變得具有磁性，此時其S極朝下。Fig.1.2-Ageneratorworksbysweepingmagneticfluxthroughwirecoils.Herearotatingmagnetmovesitsfluxpasttwocoilsandprovidespowertotheelectriccircuitandthelightbulb.1.2GeneratingElectricCurrentsOppositepolesarethennearoneanotherandthepermanentmagnetisattractedtowardtheironcore.Thisattractiondoes(positive)workontheturningpermanentmagnetasthetwopolesapproachbutitalsodoesnegativeworkonthepermanentmagnetasthetwopolesseparate.Overall,theironcoredoeszeronetworkonthepermanentmagnet.相反的兩極然后彼此靠近，永磁體被吸引朝向鐵芯。當(dāng)兩個磁極靠近時，這個吸引對轉(zhuǎn)動的永磁體做功(正)，但當(dāng)兩個磁極分開時，它也對永磁體做功(負(fù))?？偟膩碚f，鐵芯對永磁體的凈功為零。1.2GeneratingElectricCurrentsButwhenthegenerator’scoilsareconnectedaspartofacompletecircuit,thecurrentsinducedinthosecoilsmakethemmagnetic,too.AsrequiredbyLenz’slaw,eachmagnetizedcoilrepelstheapproachingpermanentmagnet.Thiseffectisidenticaltotheoneweobservedinelectrodynamicallylevitatedtrains.但是，當(dāng)發(fā)電機(jī)的線圈作為一個完整電路的一部分連接起來時，這些線圈中產(chǎn)生的電流也使它們具有磁性。根據(jù)楞次定律，每個被磁化的線圈排斥靠近的永磁體。這種效應(yīng)與我們在電動懸浮列車上觀察到的效果相同。1.2GeneratingElectricCurrentsAnapproachingmagnetisalwaysrepelledbythecurrentsitinduces.Whileamagnetizedcoilrepelstheturningpermanentmagnet,bothasitapproachesandasitleaves,thenetworkdonebythisrepulsionisn’tnecessarilyzero.Ifthecurrentpassingthroughthecoilsdiminishesduringthetimebetweenthepermanentmagnet’sapproachanditsdeparture,thecoilwillrepelthepermanentmagnetmorestronglyasitapproachesthanasitleavesandthenetworkdoneonthepermanentmagnetwillbenegative.靠近的磁鐵總是被它所產(chǎn)生的電流排斥。當(dāng)一個被磁化的線圈排斥旋轉(zhuǎn)的永磁體時，無論是當(dāng)它接近還是離開時，這種排斥所做的凈功不一定是零。如果在永磁體接近和離開之間的時間內(nèi)通過線圈的電流減小，線圈將在永磁體接近時比離開時更強(qiáng)烈地排斥永磁體，并且對永磁體所做的凈功將是負(fù)的。1.2GeneratingElectricCurrentsSomeofthepermanentmagnet’senergywillbetransferredtotheelectriccurrent,whichwilldeliverittothedevicesinthecircuit.Themorepowerthesedevicesextractfromthecircuit,themoreworkthepermanentmagnetmustdotokeepthecurrentflowing.Butinsteadofderivingtheirpowerfromburningaviationfuel,powerplantturbinesoperateonsteam(Fig.1.3).永磁體的一些能量將轉(zhuǎn)化為電流，將其輸送到電路中的設(shè)備中。這些設(shè)備從電路中提取的能量越多，永磁體就必須做更多的功來保持電流的流動。但是，發(fā)電廠的渦輪機(jī)不是通過燃燒航空燃料來獲得動力，而是依靠蒸汽運(yùn)行(圖1.3)。目錄Introduction1.1GeneratingElectricCurrents1.2ElectricPowerStation1.3SynchronousGeneratorVoltageControl1.4MotorApplicationsinPowerPlants1.51.3.1SteamGeneratorSincethepermanentmagnetlosesenergytotheelectriccurrent,somethingmustexertatorqueonittokeepitturning.Whilesmallgeneratorsareoftenturnedbyhandcranks,pedals,orinternalcombustionengines,mostlargepowerplantgeneratorsaredrivenbysteamturbines.由于永磁體因產(chǎn)生電流而失去能量，因此必須對其施加轉(zhuǎn)矩以使其保持轉(zhuǎn)動。雖然小型發(fā)電機(jī)通常由手搖曲柄、踏板或內(nèi)燃機(jī)驅(qū)動，但大多數(shù)大型發(fā)電廠的發(fā)電機(jī)由蒸汽輪機(jī)驅(qū)動。1.3.1SteamGeneratorFig.1.3-Asteamturbineextractsworkfromsteamasthatsteamflowsfromahigh-pressureboilertoalow-pressurecoolingtower.Thecoolingtowercondensesthesteamintohotwater,whichisthenpumpedbackintotheboiler.1.3.1SteamGeneratorAturbineresemblesafanrunbackward.Whileafanusesrotarymotiontopushairfromlowpressuretohighpressure,aturbineusestheflowofsteamfromhighpressuretolowpressuretopropelarotarymotion.High-pressuresteamexertsunbalancedpressuresontheturbinebladesandthosebladesrotateawayfromthesteam.渦輪機(jī)類似于反向運(yùn)轉(zhuǎn)的風(fēng)扇*1。當(dāng)風(fēng)扇利用旋轉(zhuǎn)運(yùn)動將空氣從低壓推向高壓時，渦輪機(jī)使用從高壓到低壓的蒸汽流來推動旋轉(zhuǎn)運(yùn)動。高壓蒸汽對渦輪葉片施加不平衡的壓力，使葉片遠(yuǎn)離蒸汽旋轉(zhuǎn)。*1意思即蒸汽的方向和渦輪機(jī)的運(yùn)動方向是相反的。1.3.1SteamGeneratorSincethesteam’sforceandthedirectionofmotionarebothinapproximatelythesamedirection,thesteamdoesworkontheturbineandprovidestheorderedenergyneededtospinthegenerator’spermanentmagnet.Thisorderedenergycomesfromthesteam’sthermalenergy.由于蒸汽的力和運(yùn)動方向大致相同，所以蒸汽對渦輪機(jī)做功，并提供旋轉(zhuǎn)發(fā)電機(jī)永磁體所需的有序能量。這種有序的能量來自于蒸汽的熱能。1.3.1SteamGeneratorThermalenergycan’tbeconverteddirectlyintoorderedenergy.Thesteamturbinemustanddoesoperateasaheatengine,convertingalimitedamountofthermalenergyintoorderedenergyasheatflowsfromahotterobjecttoacolderobject.Inthesteamturbine,thehotterobjectisthehigh-pressuresteamandthecolderobjectistheoutsideairorwater.熱能不能直接轉(zhuǎn)化為有序的能量。當(dāng)熱量從較熱的物體流向較冷的物體時，汽輪機(jī)必須并且確實(shí)作為熱機(jī)運(yùn)行，將有限的熱能轉(zhuǎn)換成有序的能量。在汽輪機(jī)中，較熱的物體是高壓蒸汽，較冷的物體是外界空氣或水。1.3.1SteamGeneratorAsthesteam’sheatflowstowardthecolderworldaround,natureandthermodynamicsallowustoextractsomeofthatheatasorderedmechanicalenergy.Asteamturbineisideallysuitedtoelectricpowergenerationbecausebothinvolverotarymotions.Theshaftoftheturbine,onwhichitsbladesarefastened,experiencesatorquefromthesteamandtransfersthattorquetothegenerator.當(dāng)蒸汽的熱量流向周圍更冷的世界時，自然和熱力學(xué)允許我們提取一些熱量作為有序的機(jī)械能。蒸汽輪機(jī)非常適合發(fā)電，因?yàn)閮烧叨忌婕靶D(zhuǎn)運(yùn)動。渦輪機(jī)的葉片固定在軸上，軸受到來自蒸汽的扭矩，并將該扭矩傳遞給發(fā)電機(jī)。1.3.1SteamGeneratorTheturbineandthegenerator’spermanentmagnetrotatetogether,withpowerflowingfromthehigh-pressuresteam,totheturbineblades,totheshaft,tothepermanentmagnet,andfinallytotheelectriccurrentflowingthroughthegenerator(Fig.1.4).Theturbinespinsatasteady,regulatedratetoproduce60HzalternatingcurrentintheUnitedStatesand50HzinEuropeandChina.渦輪和發(fā)電機(jī)的永磁體一起旋轉(zhuǎn)，能量從高壓蒸汽流向渦輪葉片、軸、永磁體，最后成為流經(jīng)發(fā)電機(jī)的電流(圖1.4)。渦輪機(jī)以穩(wěn)定、可調(diào)節(jié)的速率旋轉(zhuǎn)，在美國產(chǎn)生60赫茲的交流電，在歐洲和中國產(chǎn)生50赫茲的交流電。1.3.1SteamGeneratorFig.1.4Ahigh-pressuresteamturbinedrivesthiselectricgenerator,producingroughly66MWofelectricpower.備注：照片中男士身高1.75米1.3.1SteamGeneratorSteamisproducedinaboiler,wherethermalenergyisaddedtoliquidwateruntilitsmoleculesseparateintoadense,high-pressuregas.Thehotterthesteam,thehigheritspressureandthemoreeffectiveitisatspinningtheturbine.Thisthermalenergycancomefromburnedfossilfuels,fromnuclearreactors,orfromsunlight.蒸汽是在鍋爐中產(chǎn)生的，在鍋爐中，熱能被添加到液態(tài)水中，直到液態(tài)水分子分離成致密的高壓氣體。蒸汽溫度越高，壓力就越高，使渦輪機(jī)旋轉(zhuǎn)的效率就越高。這種熱能可以來自燃燒的化石燃料、核反應(yīng)堆或陽光。1.3.1SteamGeneratorAsthesteamflowsthroughtheturbineanddoesworkontherotatingblades,itspressureandtemperaturedrop.Bythetimethesteamleavestheturbine,ithascooledconsiderablyanditspressureisonlyslightlyaboveatmospheric.It’stimetoreturnittotheboilerforreuse.Butthesteammustfirstbeconvertedbackintowaterbecausetheworkrequiredtopumpsteamintotheboilerisproportionaltoitsvolume.Turningthesteamintodenseliquidwaterreducesthatworkenormously.當(dāng)蒸汽流經(jīng)渦輪機(jī)并對旋轉(zhuǎn)葉片做功時，其壓力和溫度下降。當(dāng)蒸汽離開渦輪機(jī)時，它已經(jīng)大大冷卻，其壓力僅略高于大氣。是時候把它送回鍋爐重新使用了。但是蒸汽必須首先轉(zhuǎn)化為水，因?yàn)閷⒄羝萌脲仩t所需的功與鍋爐的體積成正比。把蒸汽變成致密的液態(tài)水大大減少了這種工作量。1.3.1SteamGeneratorThelow-pressuresteamflowsthroughacoolingtower,whereitgivesupheattothesurroundingair.Oftenthatheatisusedtoevaporateadditionalwater,whichthencondensesinthecoolerairabovethetowerasaplumeofwhitemist.Oncethesteamhasgivenupenoughheat,itcondensesintowaterandcanbereturnedtothe低壓蒸汽流經(jīng)冷卻塔，將熱量散發(fā)給周圍的空氣。通常，這些熱量被用來蒸發(fā)額外的水，然后在塔上方較冷的空氣中凝結(jié)成一縷白霧。一旦蒸汽釋放出足夠的熱量，它就會凝結(jié)成水，并可以返回鍋爐。1.3.1SteamGeneratorManypowerplantsarebuiltnearlargebodiesofwater,whichalsoreceivesomeofthesteam’swasteheat.Andafewmodernpowerplantsusethiswasteheatforotherindustrialorcommercialpurposessuchasheatingbuildings.許多發(fā)電廠建在大片水域附近，這些水域也接收了一些蒸汽的余熱。一些現(xiàn)代發(fā)電廠將這些廢熱用于其他工業(yè)或商業(yè)目的，如為建筑物供暖。1.3.1SteamGeneratorMostelectricPowerPlantsarethermalpowerplants.Theyhaveanumberofcomponentsincommonandareaninterestingstudyinthevariousformsandchangesofenergynecessarytoproduceelectricity.大多數(shù)發(fā)電廠都是火力發(fā)電廠。它們有許多共同的組成，研究發(fā)電所需的各種形式和能量的變化是一項(xiàng)有趣的研究。1.3.1SteamGeneratorBoilerUnit:Almostallofpowerplantsoperatebyheatingwaterinaboilerunitintosuperheatedsteamatveryhighpressures.Thesourceofheatfromcombustionreactionsmayvaryinfossilfuelplantsfromthesourceoffuelssuchascoal,oil,ornaturalgas.鍋爐機(jī)組:幾乎所有的發(fā)電廠都是通過將鍋爐機(jī)組中的水加熱成高壓的過熱蒸汽來運(yùn)行的。在化石燃料工廠中，燃燒反應(yīng)產(chǎn)生的熱源可能與煤、石油或天然氣等燃料的熱源不同。1.3.1SteamGeneratorBiomassorwasteplantpartsmayalsobeusedasasourceoffuels.Insomeareassolidwasteincineratorsarealsousedasasourceofheat.Allofthesesourcesoffuelsresultinvaryingamountsofairpollution,aswellas,thecarbondioxide(agasimplicatedinglobalwarmingproblems).Inanuclearpowerplant,thefissionchainreactionofsplittingnucleiprovidesthesourceofheat.生物質(zhì)或廢棄的植物部分也可用作燃料的來源。在一些地區(qū)，固體廢物焚燒爐也被用作熱源。所有這些燃料來源都會導(dǎo)致不同程度的空氣污染，以及二氧化碳(一種與全球變暖問題有關(guān)的氣體)。在核電站中，分裂核的裂變鏈?zhǔn)椒磻?yīng)提供了熱源。1.3.1SteamGeneratorTurbine-Generator:Thesuperheatedsteamisusedtospinthebladesofaturbine,whichinturnisusedinthegeneratortoturnacoilofwireswithinacirculararrangementofmagnets.Therotatingcoilofwireinthemagnetsresultsinthegenerationofelectricity.渦輪發(fā)電機(jī):過熱的蒸汽用來旋轉(zhuǎn)渦輪機(jī)的葉片，渦輪葉片又用來在發(fā)電機(jī)中轉(zhuǎn)動圓形磁鐵排列中的線圈。磁鐵中旋轉(zhuǎn)的線圈產(chǎn)生了電。1.3.1SteamGeneratorCoolingWater:Afterthesteamtravelsthroughtheturbine,itmustbecooledandcondensedbackintoliquidwatertostartthecycleoveragain.Coolingwatercanbeobtainedfromanearbyriverorlake.Thewaterisreturnedtothebodyofwater10-20degreeshigherintemperaturethantheintakewater.Alternatemethodistouseaverytallcoolingtower,wheretheevaporationofwaterfallingthroughthetowerprovidesthecoolingeffect.冷卻水:蒸汽通過渦輪機(jī)后，必須冷卻并冷凝回液態(tài)水，重新開始循環(huán)。冷凝用水可以從附近的河流或湖泊中獲得。給水的溫度比補(bǔ)給水高10-20度。另一種方法是使用一個非常高的冷卻塔，在那里蒸發(fā)的水通過塔提供冷卻效果。目錄Introduction1.1GeneratingElectricCurrents1.2ElectricPowerStation1.3SynchronousGeneratorVoltageControl1.4MotorApplicationsinPowerPlants1.54．Thebasicrequirementisthattheexcitationsystemsupplyandautomaticallyadjustthefieldcurrentofthesynchronousgeneratortomaintaintheterminalvoltageastheoutputvarieswithinthecontinuouscapabilityofthegenerator.最基本要求是，勵磁系統(tǒng)為同步發(fā)電機(jī)提供并自動調(diào)節(jié)勵磁電流，當(dāng)輸出功率在發(fā)電機(jī)容量范圍內(nèi)變化時，維持端電壓恒定。5．Theexcitationsystemsofthiscategoryutilizedcgeneratorsassourcesofexcitationpowerandprovidecurrenttotherotorofthesynchronousmachinethroughsliprings.這種勵磁系統(tǒng)利用直流發(fā)電機(jī)作為勵磁電源，通過滑環(huán)為同步發(fā)電機(jī)轉(zhuǎn)子提供勵磁電流。Theuseofelectricalmotorshasincreasedforhomeappliancesandindustrialandcommercialapplicationsfordrivingmachinesandsophisticatedequipment.電機(jī)在在家用電器以及工業(yè)和商用的驅(qū)動電機(jī)和復(fù)雜裝置方面的應(yīng)用更廣泛了。目錄Introduction1.1GeneratingElectricCurrents1.2ElectricPowerStation1.3SynchronousGeneratorVoltageControl1.4MotorApplicationsinPowerPlants1.57．EachofthetypesofDCmotorsaresimilarinconstructiontothetypeofDCgeneratorthatcorrespondstoit.Theonlydifference,inmostcases,isthatthegeneratoractsasavoltagesourcewhilethemotorfunctionsasamechanicalpowerconversiondevice.每種類型的直流電動機(jī)和相應(yīng)的直流發(fā)電機(jī)的結(jié)構(gòu)是相似的。大多數(shù)情況下，唯一的區(qū)別在于，發(fā)電機(jī)做為一個電壓源使用而電動機(jī)作為一個機(jī)電轉(zhuǎn)換設(shè)備使用。8.Thespeedofaseriesmotorvariesfromveryfastatnoloadtoveryslowathe