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EXCITATION&CONTROL.ppt

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POWERFACTORCORRECTIONOUTLINE DEFINITION: Powerfactor(P.F)istheratiobetweenactualpowertotheapparentpower. Actualpower/Apparentpower. P.F=Kw/Kva. Forapurelyresistiveloadthepowerfactorisunity.ActiveandreactivepoweraredesignatedbyP&Qrespectively.Theaveragepowerinacircuitiscalledactivepowerandthepowerthatsuppliesthestoredenergyinreactiveelementsiscalledreactivepower. ActivePower: Alsoknownas“realpower”orsimply“power.”Activepoweristherateofproducing,transferring,orusingelectricalenergy.Itismeasuredinwattsandoftenexpressedinkilowatts(KW)ormegawatts(MW).Theterms“active”or“real”powerareusedinplaceoftheterm“power”alonetodifferentiateitfrom“reactivepower.POWERFACTORDEFINITIONConsideracanalboatbeingpulledbyahorse. Ifthehorsecouldwalkonwaterthentheangle(Phi)ØwouldbezeroandCOSINEØ=1.Meaningallthehorsepowerisbeingusedtopulltheload.Howevertherelativepositionofthehorseinfluencesthepower.Asthehorsegetsclosertothebarge,angleØ1increasesandpoweriswasted,but,asthehorseispositionedfurtheraway,thenangleØ2getsclosertozeroandlesspoweriswasted. CAUSESOFLOWPOWERFACTORCAUSESOFLOWPOWERFACTORPOWERFACTORCORRECTION AsreactivepowerisusuallymeasuredinthousandstheletterKisusedforthousand.thecapacitorKVARratingthenshowshowmuchreactivepowerthecapacitorwillsupply.Eachunitofthecapacitor'sKVARwilldecreasetheinductivereactivepowerdemand. POWERFACTORCORRECTIONAllinductiveloadsrequiretwokindsofpowertooperate: Activepower(KW)-toproducethemotiveforce Reactivepower(KVAR)-toenergizethemagneticfield Theoperatingpowerfromthedistributionsystemiscomposedofbothactive(working)andreactive(non-working)elements.Theactivepowerdoesusefulworkindrivingthemotorwhereasthereactivepoweronlyprovidesthemagneticfield.POWERFACTORCORRECTIONKVARCORRECTIONItisnotusuallynecessarytoreachunity,i.e.PowerFactor1,sincemostsupplycompaniesarehappywithaPFof0.95to0.98.Byinstallingsuitablysizedswitchedcapacitorsintothecircuit,thePowerFactorisimprovedandthevaluebecomesnearerto1thusminimisingwastedenergyandimprovingtheefficiencyofaplantorpowerfacto