《轮机英语轮机长大管轮》_Lesson 37 Switchboards.pptVIP

NewWordsandExpressionsopentype开式dead-fronttype表面不带电式live[liv]adj.带电的sustain[s??stein]v.承受wind[wind]v.绕线latch[l?t?]n.锁闭装置reversepowerrelay逆功率保护继电器earthed[?:θt]adj.接地的NewWordsandExpressionsenergize[?en??d?a?z]v.供给…能量polarity[p???l?r?ti:,p?-]n.极性Switchboardsmaybeoftheopentypeinwhichalltheessentialswitchgearsareexposedonthefrontofthepanel,orofthedead-fronttypeinwhichallthelivepartsareinstalledbehindthepanelsandonlytheoperatinghandlesandinstrumentsareonthefront.Theswitchboardsfora.c.systemsdifferfromthed.c.switch-gearinthattheopentypepanelsaregenerallynotpermissible(用于交流电系统的配电板与用于直流电系统的配电板不同之处是前者一般不允许采用开式).Dead-frontboardscanbeeitheroftwopatterns,onehavingmanually-operatedswitchesandcircuit-breakerswiththehandlesonthefrontofthepanelsandallthelivepartsattherear;andtheotherhavingelectricallyoperatedcircuit-breakersoperatedbypush-buttonsonthefrontofthepanels.Usuallythepanelsareinterlockedwithisolators,sothatthedevicescanbemadedeadbeforethedoorsareopened.Thevoltagesmostcommonlyadoptedfora.c.systemsareeither440Vor220Vthree-phase.Ford.c.switchboards,thereareammeters,voltmeters,circuit-breakers,tippingdevicesandsoon,buta.c.requiresadditionalequipmentascomparedwithd.c.,suchasfrequencymeters,synchroscopes,watt-meters,voltageandcurrenttransformers,ammeterswitches,voltageregulators,etc.Circuitbreakersandswitcheswillbethree-poleascomparedwithtwo-poleford.c.However,inspiteoftheadditionalequipmentana.c.switchboardisusuallysmallerandlighterthanthecorrespondingd.c.boardbecauseofthehighervoltageandlowercurrentandsmallerbus-bars,etc(然而，尽管使用了额外设备，交流配电板通常比相应的直流配电板尺寸要小、重量要轻。这是因为它采用高电压、低电流的输送方式，母线尺寸较小等原因).Electricalsupplyisalwaysneeded,evenifonlyforlighting.Soafterashipgoesintose