MarineEngineeringEnglish《輪機英語》APracticalCourseforEngineersWorkingonBoardShips

MarineElectricalSystemandAutomatizationLesson25ParallelingOperationofAlternators第25課交流發(fā)電機并車LearningObjectives:1.Graspsomeusefulwordsandexpressionsinthewholetext.2.Afterstudyingthelesson,heorshewillhaveabetterunderstandingofParallelingOperationofAlternators.3

4part1

NewWordsandExpressions5part2

TextAnalysisLesson25ParallelingOperationThreephasealternatorsarrangedforparalleloperationrequireaconsiderableamountofinstrumentation.#三相交流發(fā)電機的并車操作需要很多儀表。Lesson25ParallelingOperationThiswillincludeammeters,watt-meters,voltmeters,frequencymetersandasynchronizingdevice.#包括電流表、功率表、電壓表、頻率表和同步指示裝置。Lesson25ParallelingOperationReversepowerprotectionisprovidedtoalternatorssincecurrentprotectioncannotbeused.#因不能采用逆電流保護，所以發(fā)電機裝設了逆功率保護。Lesson25ParallelingOperationAlternativelyvarioustripsmaybeprovidedintheeventofprimemoverfailuretoensurethatthealternatordoesnotactasamotor.#或者裝設各種脫扣機構，萬一在原動機故障時，確保發(fā)電機不能按電動機工作。Lesson25ParallelingOperationTheoperationofparallelingtwoalternatorsrequiresthevoltagestobeequalandalsoinphase.#發(fā)電機并車運行需要電壓相等且同相。Lesson25ParallelingOperationThealternatingcurrentoutputofanymachinesisalwayschanging,sofartwomachinestooperatetogethertheirvoltagesmustbechangingatthesamerateorfrequency,andmustbereachingtheirmaximum(oranyothervalue)together.#交流輸出總是在改變，因此，對欲并車的兩臺發(fā)電機而言，它們的電壓必須以相同的變化率或頻率變化，并且必須同時達到最大值(或其它值)。Lesson25ParallelingOperationTheyarethensaidtobe“inphase”.#此時我們就說它們“同相”。Lesson25ParallelingOperationUseisnowadaysmadeofasynchroscopewhenparallelingtwoACmachines.#現(xiàn)今，當進行并車時使用同步指示器。Lesson25ParallelingOperationThesynchroscopehastwowindingswhichareconnectedonetoeachsideoftheparallelingswitch.#同步指示器有兩組繞組，每組與并車開關一側相連。Lesson25ParallelingOperationApointerisfreetorotateandismovedbythemagneticeffectofthetwowindings.#同步指示器指針可自由轉(zhuǎn)動并且受兩個繞組的磁效應而動作。Lesson25ParallelingOperationWhenthetwovoltagesuppliesareinphasethepointerisstationaryinthe12o’clockposition.#當兩組輸出電壓同相時，指針停在12點位置不動。Lesson25ParallelingOperationIfthepointerisrotatingthenafrequencydifferenceexistsandthedialismarkedforclockwiserotationFASTandanti-clockwiserotationSLOW,thereferencebeingtotheincomingmachinefrequency.#若指針在轉(zhuǎn)動，則頻率不相同，在表盤上標明順時針轉(zhuǎn)“快”，逆時針轉(zhuǎn)“慢”，其參考是待并機頻率。Lesson25ParallelingOperationToparallelanincomingmachinetoarunningmachinethereforeitisnecessarytoensurefirstlythatbothvoltagesareequal.#為了將一臺發(fā)電機并入正在運行的發(fā)電機電網(wǎng)，首先必須確保兩者電壓相等。Lesson25ParallelingOperationVoltmetersareprovidedforthispurpose.Secondlythefrequenciesmustbebroughtintophase.#為此設有電壓表。其次，頻率必須同相。Lesson25ParallelingOperationInpracticethesynchroscopeusuallymovesslowlyintheFASTdirectionandtheparallelingswitchisclosedasthepointerreachedthe11o’clockposition.在實際操作中，通常在同步指示器指針按“快”的方向緩慢轉(zhuǎn)動到11點位置時合閘。

Lesson25ParallelingOperationThisresultsintheincomingmachineimmediatelyacceptingasmallamountofload.這導致待并發(fā)電機能立即承擔少量負荷。Lesson25ParallelingOperationAsetofthreelampsmaybeprovidedtoenablesynchronizing.#也可用一組三個指示燈實現(xiàn)同步操作。23燈光明暗法

Introduction(Backgroundknowledge)

24燈光旋轉(zhuǎn)法

Introduction(Backgroundknowledge)

Lesson25ParallelingOperationThesequencemethodoflampconnectionhasakeylampconnectedacrossonephasewithtwootherlampscrossconnectedovertheotherphases.#指示燈連結的順序是，其中主燈跨接于同名相，而另兩個燈分別連接于異名相。Lesson25ParallelingOperationIfthefrequenciesofthemachinesaredifferentthelampswillbrightenanddarkeninrotation,dependingupontheincomingfrequencybeingFASTorSLOW.#若發(fā)電機頻率不同，則燈泡按轉(zhuǎn)向發(fā)生明暗變化，取決于待并機頻率的快慢。Lesson25ParallelingOperationThecorrectmomentforsynchronizingiswhenthekeylampisdarkandtheothertwoareequallybright.#并車操作的正確時機是當主燈變暗而其它兩燈等亮的時候。Lesson25ParallelingOperationIfthetwomachineshavebeenoperatedinparallel,thespeed-controllingswitchofthe“in-coming”

machine

willbehandledslightlytomakeit

runwithsomeload.#如果兩臺機組并聯(lián)運行，待并機的速度控制開關將被輕輕操作，以使其帶有一些負載運行。Lesson25ParallelingOperationThedivisionofthekilowattloadbetweentwoalternatorsoperatinginparalleliscontrolledbythesettingsandcharacteristicsof

their

primemovers’governors.#并聯(lián)運行的兩臺交流發(fā)電機之間的有功負荷分配由其原動機調(diào)速器的設置和特性控制。Lesson25ParallelingOperationWhen

itisnecessarytomakeonemachine

removefromtheparalleloperation,thefirststepinde-parallelingistoremovetheloadfrom“off-going”

machine.#當需要從并聯(lián)運行中移除一臺發(fā)電機時，解列的第一步是移除待解列機組上的負載。Lesson25ParallelingOperationItisimportanttolowertheloadofthe“off-going”

machine

andraisetheloadoftherunningmachine

stepbystepandatthesametimethefrequencyof

thebusbar

iskeptconstant.#重要的是要逐步降低待解列機組的負載，提高運行機組的負載，同時保持母線的頻率恒定。Lesson25ParallelingOperationWhentheload

ofthe“off-going”

machineislowerthan10%ratedvalue,theload-shiftingwillbestopped,pressthe“OPEN”button.Thenthe“off-going”

machinewillberemovedfromtherunning

machine.#當待解列機組的負載低于10%額定值時，負載轉(zhuǎn)移將停止，按下“分閘”按鈕。然后，將從運行機上移除解列機。part3

Exercise&ExaminationHandheldphasesequenceindicatorsareusefulwhen_____.A.preparingtoparallelalternators B.connectinglightingbranchcircuitsC.troubleshootingDCmotorsD.connectingshorepowerlinestotheshipWhenparallelingtwoalternatorsusingthreesynchronizinglamps,theflickeringofallthreelampsbecomesprogressivelyslowerandslower.Thismeansthe_____.A.frequencyoftheincominggeneratorisapproachingthatofthebusB.frequencyoftheincomingalternatorislessthanthatofthebusC.phaserotationoftheincomingalternatorsisoppositetothatofthebusD.terminalvoltageoftheincomingalternatorisapproachingthatofthebusEqualizationofthepowerfactorsoftwoalternatorsoperatinginparallelisaccomplished_____.A.manually,byadjustingthegovernorcontrolsB.automatically,byautomaticvoltageregulatorsC.manually,adjustingtheoutputofcurrenttransformersD.automatically,bythede