Question

What are the power loss in a transformer

Answer 1

In any electrical machine, 'loss' can be defined as the difference between input power and output power. An electrical transformer is an static device, hence mechanical losses ( friction losses) are absent in it. A transformer only consists of electrical losses (iron losses and copper losses).

Answer 2

The main causes for power loss in a transformer are:-
~ Copper Loss in the form of heat
~ Eddy Current Loss in the form of heat
~ Hysteresis Loss in the form of heat
~ Flux Leakage, i.e., flux produced in primary coil does not pass fully to the secondary coil 
~ Humming Loss in the form of a humming sound due to magnetostriction.

Hope it helps you. :D