地铁客运服务英语课件第六单元教材课件moban.ppt

地铁客运服务英语课件第六单元教材课件moban.ppt

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Unit6PowerSupplySystem,地铁供电系统,TranslatethefollowingwordsintoEnglish:

（BrownisaCanadianEngineer.HeishavingaconversationwithasubwaystaffmemberJohn.）Brown:

Howmanycomponentsdoespowersupplysystemhaveinthesubway?

John:

Basicallywehavecityelectricity,LVdistributor,UPS,computercontrolledSmartUPSandsubsystems.Brown:

Whydoesthesignalsystemhavetwopowersupplies?

John:

Thisisbecausesignalsystemarethelifelineofsubwayoperation.Outofpowermaycausehugeaccidents,casualtiesandeconomicloss.Twopowersuppliescanensureitsreliablerunning.Brown:

Well,LVdistributorhastwopowersupplies,isitbecauseofthesamereason?

John:

Absolutely.Brown:

WhatisUPS?

John:

ThefullnameofUPSisUninterruptiblePowerSupplywhichimprovesthereliabilitiesofsubwaypowersupplies.Brown:

WhatisthemodeofpowersupplyfortheMetro?

John:

Usuallytherearetwomodes,thirdrailandoverheadwires.Itisdifferentfromcitytocity.Brown:

Isee.Ihavelearnedalottoday.,PartCText,AlthoughtheinitiallinesofwhatbecametheLondonUndergroundusedsteamengines,mostmetrotrains,bothnowandhistorically,areelectricmultipleunits,withsteelwheelsrunningontwosteelrails.Powerforthetrains,referredtoastractionpower,iscommonlysuppliedbymeansofasinglelivethirdrail（asinNewYork）at600to750volts,butsomesystemsusetwoliverails（notablyLondon）andthuseliminatethereturncurrentfromtherunningrails.Overheadwires,allowinghighervoltages,aremorelikelytobeusedonmetrosystemswithoutmuchlengthintunnel,asinAmsterdam;buttheyalsooccuronsomethatareunderground,asinMadrid.BostonsGreenLinetrainsderivepowerfromanoverheadwire,bothwhiletravelinginatunnelinthecentralcityandatstreetlevelinthesuburbanareas.SystemsgenerallyuseDCpowerratherthanAC,eventhoughthisrequireslargerectifiersforthepowersupply.DCmotorswereformerlymoreefficientforrailwayapplications,andonceaDCsystemisinplace,convertingittoACisgenerallyconsideredtoolargeaprojecttocomplete.,1.Pleaselisttwomodesofpowersupplyformetro.thirdrailandoverheadwires2.Pleaselistthenameofeachpartofthepowersupplysystem.Thirdrail:

alivethirdrail,operationalrailoverheadwires:

wires,pantograph3.Whatsthecharacteristicofpowersupplysystem?

Tractionpowerissuppliedbymeanisofasinglelivethirdrailoroverheadwires.,