What is the condition to obtain maximum efficiency in a single-phase transformer?

The efficiency of a transformer changes with changing load. To understand this, first we have to remember that what is efficiency?

So efficiency = output/(output + losses),

When the transformer is on no load, there is only core losses because at no load copper losses are almost negligible. But ad load increases, copper loss in the system also increases, so efficiency varies with load.

The transformer will give the maximum efficiency when their copper loss is equal to the iron loss.

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