How is duty cycle taken into consideration?
In many applications, a transformer will not be called upon to provide the maximum amount of current required by a system on a continuous basis. Just like motors which are rated by a duty cycle calculation, a transformer rated for continuous duty will be bigger and more expensive than one rated for partial duty. In typical machine tool application, for example, a duty cycle of 50% is assumed. By calculating the percentage of full-load use required you can properly size both the transformer and motor in a system. The square root of the duty cycle times the full-load KVA requirement gives the effective KVA rating required for the transformer. For example, take a 50% duty cycle for which the square root is .71. Thus, the transformer will have to be 71% of the full-load rating.
