Transformer Impedence

In general, the use of Z% is related to fault currents. It provides an easy measure of how much fault current the transformer will try to pass when the secondary is shorted. For example, suppose you had a Z 20% transformer with a rated secondary current of 100A. The maximum short-circuit secondary current would then be 100A/0.20 = 500A.

Obviously this is not a very useful characteristic for, say, an audio output transformer where indeed the impedance might be given in Ohms.

Thanks alot. That was easy and very helpfull. Thanks.