What is the duty cycle of a transformer?

Duty cycle is the amount of load over set periods of time. Transformers are designed to run continuously at full load without exceeding the insulation temperature limits provided that parameters such as ambient temperature, harmonic distortion, power factor, etc., are met. Transformers can also be designed to run for short term duty cycles which may result in a smaller unit. Short term duty cycles will need lower or no-load periods to aid in cooling. High load duty cycles can affect parameters such as impedance and voltage regulation.