# Short circuit current in transformer

When transformer secondary is short circuited, what would be the value of current flowing through short circuited side? Shouldn't it be infinity ideally? If yes, is it only due to large cross-section & highly conductive copper wires that wires don't get melted?

For e.g. suppose I have 1 kVA, single phase, 250/125 V transformer. Now if I short circuit 125V side and set full load primary current i.e. 1000/250 = 4 A in primary then what would be value of secondary current?

• Are you interested in what happens when you operate the transformer within its ratings, or what happens when you exceed its ratings? 4 amps, 250V input into a 1000VA rated transformer is no issue. But if you short circuit the secondary, then apply 250V to the input, you will get a lot more than 4 amps. Commented Mar 17, 2015 at 8:07
• Actually I was interested in both the cases. Your explanation is made it clear, thanks.
– Deep
Commented Mar 17, 2015 at 12:54
• To add to your understanding - if you short circuit a transformer and apply full voltage to the input - the current will be limited not just by the resistance and inductance of the transformer, but also by the magnetic saturation of the iron core. Commented Mar 17, 2015 at 12:56
• Oh, I kinda forgot the core saturation thing. Thanks :)
– Deep
Commented Mar 17, 2015 at 13:03
• No, core saturation, or lack thereof, is determined by the volt-seconds applied to the primary per half-cycle. Secondary current does not cause core saturation. If anything, by causing voltage droop, it causes the H field in the core to be weaker. Commented Mar 15, 2021 at 1:21