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**amit kulkarni said: **

hi can u help me @ transformer (3 phase) losses any formulae or thumb rules.if the transformer is 50 % loaded there are some losses but how to calculate? how we to calculate % of transformer loading?

WE HAVE TWO TYPES OF LOSSES IN TRANSFORMER…..ie….iron loss and copper loss…one which will be constant for every loads…and the one which vary with bthe loading conditions respectively…..iron loss occurs all the time whether the transformer is loaded or unloaded and hence also called constant loss…and the other occurs only when it is loaded…and vary with the loads..and hence also called variable loss….an open circuit test in which rated voltage is applied to the primary winding and secondary winding is open circuited(test will be carried out in the low voltage side)is used for determining ironloss…..here the wattmeter gives the iron loss…bcos copper loss at no load conduction is negligible…..and the copper loss could be datemined by short circuit test in which rated current is made to flow through the primary winding and secondary winding will be short circuited….here the wattmeter reading gives full load copper loss…and to determine copper loss at x(FULL LOAD) the below formula can be used…

W(cu,xfl)=X*X*W(cu,fl) where W(cu,fl) is the full load copper loss…… and the total transformer loss will be iron loss+copper loss