# Re: transformer losses

#12120
Spir Georges GHALI
Participant

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?

Dear Amit ;

there are 2 kinds of losses : Iron Losse & Cupper losse, the iron loose is not affected by the load, but the cupper load si affected by the load.

Normally, on the name plate of any transformer there's a percentage value ” i % ” that's the percentage current of the nominal current for the iron losse, so, if we have it we can calculate the iron losse. and also on the name plate there is a value of cupper losse on full load in ” watt “, by whici we can calculate the ” R ” of the transformer then accordingly the load's current and the value of R we can calculate the cupper losse, notint taht the formula by which we calculate the ” R ” of any transformer is : R = Pcu/3 . In2  ; where :

– Pcu : is the full load cupper losse

– In2 : is the square on the transformer nominal current

Regards.