There are two losses in a transformer.
a. Iron losses.
b. Copper losses.
Iron losses – Iron losses constitutes of two losses.
a. Eddy current losses, these are due to the induced emf in the core, which constitutes a current in the core. These will heats up the core.
Eddy current losses can be minimised by using laminated core immersed in varnish. This provides a high resistance between the laminations and thus eddy current in reduced.
b. Hysterisis losses, these are due to the magnetic reversal of current by which there is friction between molecules of core and heat is generated.
Hysterisis losses can be minimised by selecting proper magnetic material, like silicon steel.
Copper losses – these losses are due to the resistance of the winding, which is equal to I2 rt (calories). These losses are depends on load. That is the losses are increased to the square of the load current.
I – current through winding.
r – resistance of winding.
t – time duration.