What will happen to the operation of Transformer if the frequency of operation is changed?

Change in frequency affects the operation of a transformer in the following ways:

i. Iron Loss – Increases with a decrease in frequency. A 60 Hz transformer will have nearly 11% higher losses, when worked on 50 Hz instead of 60 Hz. However, when a 25 Hz transformer is worked on 60Hz, iron losses are reduced by 25%.

ii. Cu Loss – In distribution transformer, it is independent of frequency.

iii. Efficiency- Since Cu loss is unaffected by change in frequency, a given transformer efficiency is less at a low frequency than at a higher one.

iv. Regulation – Regulation at unit power factor is not affected because IR drop is independent of frequency. Since reactive drop is affected, regulation at low power factor decreases with decrease in frequency and vice versa. For example, the regulation of a 25 Hz transformer when operated at 50 Hz and low power factor is much poorer.

v. Heating – Since total loss is greater at a lower frequency, the temperature is increased with decrease in frequency.