LOSSES IN A TRANSFORMER

The losses that occur in an actual transformer are core or iron losses and copper losses.

1. Core or iron losses: When AC supply is given to the primary winding of a transformer, an alternating flux is set up in the core; therefore, hysteresis and eddy current losses occur in the magnetic core.
   1. Hysteresis loss: When the magnetic material is subjected to reversal of flux, power is required for the continuous reversal of molecular magnets. This power is dissipated in the form of heat and is known as hysteresis loss (P_h = K_hV f ). This loss can be minimized by using silicon steel material for the construction of core.
   2. Eddy current loss: Since flux in the core of a transformer is alternating, it links with the magnetic material of the core itself also. This induces an emf in the core and circulates eddy currents. Power is required to maintain these eddy currents. This power is dissipated in the form of heat and is known as eddy current loss (P_e = K_eV f² t²). This loss can be minimized by making the core of thin laminations.
   It is already seen in article−8 that the flux set up in the core of the transformer remains constant from no-load to full load. Hence, iron loss are independent of the load and are known as constant losses.
2. Copper losses: Copper losses occur in both primary and secondary windings due to their ohmic resistance. If I₁, I₂ are the primary and secondary currents and R₁, R₂ are the primary and secondary resistances, respectively.

Then, total copper losses 

The currents in the primary and secondary winding vary according to the load, and therefore, these losses vary according to the load and are known as variable losses.