Operation at Non-Rated Voltages and Frequencies

Author: E.E. Kimberly

Transformers may be operated at voltages or frequencies within 10 per cent of the rated values. If a 60-cycle transformer be connected to a 25-cycle line of its rated voltage, it will draw excessive exciting current, the core will overheat, and the result will be generally unsatisfactory. A 25-cycle transformer may be used on a 60-cycle line of its rated voltage, but with much higher voltage regulation than normal. It may be stated as a general rule that, within the breakdown limits of its insulation, a transformer may be operated at any frequency satisfactorily if the ratio of the applied voltage to the frequency for which it was designed is maintained approximately.