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1、电力电气的基础常识()Basicknowledgeofpowerandelectrica1.Txt2007,06,24Sunday,23:001,thermalrelayisaprotectiverelayoperatedbycurrenteffect2,inductaneeisdividedintomutualinductanceandselfinductsneeoftwo3atransformerconsistsofacoilandanironcorethatisusedtochangethevoltageTheformulais:primaryvoltag
2、e(Ul)/secondaryvoltage(U2)=primaryturns/secondaryturns,transformercanonlychangevoltage,notincreasepower・1.1voltage:Voltage,alsoknownaspotentialdifference,referstothecurrentfromthehighpotentisltothelowpotential,thedifferencebetweenthetwopotentia1.Alsoknownasvoltage.InalphabeticalU,the
3、unitisvoltsandisrepresentedbytheletter〃V〃・Ofwhich:IV二1000mV=1000000,V,lmV=1000,VThevoltageisalsoACandDC,representedbyAC,V,andDCV,respective!y.DCvoltageinthemeasurementshouldpayattentionto+-一points.1.1resistor:Theresistancethatcurrentflowsthroughanobjectiscalledresistanceandisexpresse
4、dinR.Amongthem,IM二lOOOK二1000000IK二1000Therearemanykindsofresistors,suchascarbonresistance,carbonfilmresistance,windingresistanceandsoon.Intheformoffixedresistors,variableresistorsandpotentiometers・Resistancetemperaturecoefficient:whenthecurrentflowsthroughtheresistor,thetemperaturein
5、creases,anditsresistancechanges・Theratiooftheresistancevaluetotheoriginalresistanceiscalledthetemperaturecoefficientoftheresistance・Theresistanceofthemetalmaterial,theresistanceincreaseswiththeincreaseoftemperature,positivetemperaturecoefficient;ongraphiteandcarbon,theresistancedecre
6、asedwiththeincreaseintemperature,negativetemperaturecoefficient・Thesmallerthecoefficientoftemperatureis,themorestabletheresistanceis.Thetemperaturesensoroftheairconditionerisalsoakindofresistance,whichiscalledathermistor,anditsresistanceisdecreasedwiththeincreaseoftemperature・Ratedpo
7、werpoints1/&1/4,1/2,1,2,3,5,10,20Wandotherspecifications・Whenmeasuringtheresistancewithapointertypemultimeter,payattentiontoselectingtheappropriategearandtheshiftmustbezero.1.1capacitor:Anycombinationoftwoconductorsseparatedbyinsulationiscalledcapacitance・WiththeletterC,theunitisFala
8、,represented