# Transformer losses, efficiency and voltage reduction

Transformers also consume a certain amount of energy, resulting in iron and power heat losses. Iron losses are not affected by the transformer’s load, but the resistive losses increase as the flow increases.

The Iron losses (PR) are Hystereesihäviöiden (Ph) and the sum of the Eddy current losses (PR ).

Current heat losses (copper losses PK) are the power losses consisting of the resistance of the Transformer’s primary (r1) and secondary windings (R2) in the primary and secondary currents (I1 and I2).

They can be defined by the formula:

Pk = (i12 x r1) + (i22 x r2)

The power efficiency describes what the power transformer gives and what it takes, i.e. the ratio of the output p2and the inputpower p1.

The power efficiency of the transformer η is:

η = P2 /P1

The transformer’s secondary voltage is indicated by the nominal load. If the second load is lower than the nominal load, the resistive losses of the transformer are lower and the secondary voltage is higher than the nominal secondary voltage. In other words, the transformer generates the highest secondary voltage in idle conditions.

The difference between the idling voltage and the current voltage under rated power depends on the size of the transformer and its structure. The difference varies between 5-25. For small transformers, the difference between the idling voltage and the laden voltage is greater than that of the larger transformers. The Transformers are defined by standards that provide a certain range of idling voltage. When designing a transformer for a specific purpose, can be idle voltage and nominal load voltage differential minimized.