By operating at higher frequencies, transformers can be physically more compact without reaching saturation, and a given core is able to transfer more power. However, other properties of the transformer, such as losses within the core and skin-effect, also increase with frequency. Generally, operation of a transformer at its designed voltage but at a higher frequency than intended will lead to reduced magnetising current. At a frequency lower than the designed value, with the rated voltage applied, the magnetising current may increase to an excessive level.
A transformer designed for 50Hz will work at 60Hz; however a transformer designed for 60Hz may be damaged if required to work at 50Hz.