电气毕业设计外文翻译.doc

《电气毕业设计外文翻译.doc》由会员上传分享，免费在线阅读，更多相关内容在工程资料-天天文库。

1、TransformerOneofthemostvaluableapparatusinelectricpowersystemisthetransformer,foritenablesustoutilizedifferentvoltagelevelsacrossthesystemforthemosteconomicalvalue.Generationofpoweratthesynchronousmachinelevelisnormallyatarelativelylowvoltage，whichismostdesirableeconomicall

2、y．Steppingupofthisgeneratedvoltagetohighvoltage，extra-highvoltageoreventoultra-highvoltageisdonethroughpowertransformerstosuitthepowertransmissionrequirementtominimizelossesandincreasethetransmissioncapacityofthelines．Thistransmissionvoltagelevelisthensteppeddowninmanystage

3、sfordistributionandutilizationpurposes．Atransformerisastaticdevicefortransferringelectricenergyfromonecircuittoanotherelectromagnetically，thatis，byinductioninsteadofbyconduction．Itsusualfunctionistotransferenergybetweencircuitsofdifferentvoltage．Atransformerhasamagneticcore

4、onwhichtherearetwoormorewindings．Thesewindingsareinsulatedfromeachotherandfromground．Inautotransformers，however，thewindingsareconnectedtogether．Theassemblyofcoreandcoilsisnormallyinsulatedandcooledbyimmersioninmineraloilorothersuitableliquidwithinanenclosingtank．Connectiont

5、othewindingsisbymeansofinsulatingbushings，usuallythroughthecover.The“ratiooftransformation”isdeterminedbytherelativenumberofturnsineachofhewindings．Thisisknownasthe“turnratio”anditistheratiooftheno-loadvoltages．Whentheunitiscarryingload,theratiooftheactualvoltagesisslightly

6、differentbecauseofthedropcausedbytheflowof1oadcurrentthroughtheimpedanceofthetransformerwindings．Atratedload,thisdropisknownasthe"voltageregulation".Theamountofvoltagedropvarieswiththepowerfactoroftheoutputevenwhenthekilovolt-amperesremainconstant．Practicallyallpowertransfo

7、rmersandmanydistributiontransformershavetapsinoneormorewindingsforchangingtheturnratio．Changingtheratioisdesirablefortworeasonstocompensateforvaryingvoltagedropinthesystemandtoassurethatthetransformeroperatesasnearlyaspossibleatthecorrectcoredensity．Forthelatterpurpose,thet

8、apsshouldbeinthewindingsubjecttothevoltagevariation.De-energizedtapchangersareused