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《机电专业英语 教学课件 作者 杨寿智 刘水平 机电专业英语.Lesson 25.ppt》由会员上传分享，免费在线阅读，更多相关内容在应用文档-天天文库。
1、Lesson25AdcGeneratorTextFigure25.1showsasimplifieddcgeneratorconsistingofasingleloopofwireinapermanentmagneticfield.Noticethateachendoftheloopisconnectedtoasplit-ringarrangement.Thisconductivemetalringiscalledacommutator.Astheloopisrotatedinthemagneticfi
2、eld,thesplitcommutatorringalsorotates.Eachhalfofthespiltringrubsagainstthefixedcontacts,calledbrushes,andconnectsthelooptoanexternalcircuit.Asthelooprotatesthroughthemagneticfield,it“cuts”throughthefluxlinesatvaryingangles,asillustratedinFigure25.2①.Atpo
3、sitionAinitsrotation,theloopofwireiseffectivelymovingparallelwiththemagneticfield.Therefore,atthisinstant,therateatwhichitiscuttingthroughthemagneticfluxlinesiszero.AstheloopmovesfrompositionAtopositionB,itcutsthroughthefluxlinesatanincreasingrate.Atposi
4、tionB,itismovingeffectivelyperpendiculartothemagneticfieldandthusiscuttingthroughamaximumnumberoflines.AsthelooprotatesfrompositionBtopositionC,therateatwhichitcutsthefluxlinesdecreasestominimum(zero)atC.FrompositionCtopositionD,therateatwhichtheloopcuts
5、thefluxlinesincreasestoamaximumatDandthenbacktoaminimumagainatA.Asyoupreviouslylearned,whenawiremovesthroughamagneticfield,avoltageisinduced,andbyFaraday’slaw,theamountofinducedvoltageisproportionaltothenumberofloops(turns)inthewireandtherateatwhichitism
6、ovingwithrespecttothemagneticfield②.Nowyouknowthattheangleatwhichthewiremoveswithrespecttothemagneticfluxlinesdeterminestheamountofinducedvoltage,becausetherateatwhichthewirecutsthroughthefluxlinesdependsontheangleofmotion③.Figure25.3Operationofabasicdcg
7、eneratorFigure25.3illustrateshowavoltageisinducedintheexternalcircuitasthesinglelooprotatesinthemagneticfield.Assumethattheloopisinitsinstantaneoushorizontalposition,sotheinducedvoltageiszero.Astheloopcontinuesinitsrotation,theinducedvoltagebuildsuptoama
8、ximumatpositionB,asshowninPart(a)ofthefigure.Then,astheloopcontinuesfromBtoC,thevoltagedecreasestozeroatC,asshowninPart(b).Duringthesecondhalfoftherevolution,showninPart(c)and(d),thebrushesswitchtooppositecommutatorsection
