Short circuit current in transformer
I have 1 kVA, single phase, 250/125 V transformer.


If you can adjust the primary voltage so that the input current is 4 amps RMS when the secondary is shorted, the secondary current will be 8 amps for a 2:1 step-down transformer.

NB - you will probably find that the easiest way to do this is use the output of a variac and raise the primary voltage carefully whilst noting the primary current. Typically the variac output will only need to be around 10V RMS to get full primary current with secondary shorted out.

The primary-secondary turns ratio determines both step-down voltage ratio and step-up current ratio.