The purpose of a short-circuit test is to determine the series branch parameters of the equivalent circuit of a transformer.

The test is conducted on the high-voltage (HV) side of the transformer where the low-voltage (LV) side (or the secondary) is short-circuited. A wattmeter is connected to the primary side. An ammeter is connected in series with the primary winding. A voltmeter is optional since the applied voltage is the same as the voltmeter reading. Now with the help of a variac, the applied voltage is slowly increased until the ammeter gives a reading equal to the rated current of the HV side. After reaching the rated current of the HV side, all three instruments reading (Voltmeter, Ammeter, and wattmeter readings) are recorded. The ammeter reading gives the primary equivalent of full load current I_L. As the voltage applied for full load current in short circuit test on transformer is quite small compared to the rated primary voltage of the transformer, the iron losses in the transformer can be taken as negligible here.

${\displaystyle W}$ is the full-load copper loss

${\displaystyle V_{1}}$ is the applied voltage

${\displaystyle I_{1}}$ is the rated current

${\displaystyle R_{01}}$ is the resistance as viewed from the primary

${\displaystyle {Z_{01}}}$ is the total impedance as viewed from the primary

${\displaystyle {X_{01}}}$ is the reactance as viewed from the primary