Short Circuit Test:

This test is performed to find out the copper losses and the series parameters (R_eq and X_eq) of the equivalent circuit of the transformer. This test is conducted on the HV winding side and LV winding in short circuited. The connection diagram is illustrated in Figure. A very low voltage (5-8% of the rated voltage) is enough to circulate the full load current under short circuit. The shunt branch parameters m,ay be neglected in this case as the I₀ is very small (0.1 to 0.5%) under the condition of very low voltage. Whereas conducting the SC test, the voltage on HV winding side is slowly raised from zero to till the value transformer draws full load current. Record the meter readings.

Figure:  Connection Diagram for Short Circuit Test

Voltmeter reading = V_sc volts

Ammeter reading = I_sc  Amps

Power input     = P_sc Watts

The wattmeter reads the copper losses (P_sc), watts

Z_eq = V_sc /I _sc

R _eq =   V_sc/ (I _sc )²

R_eq and X_eq are the ohmic values referred to the HV winding side.

Therefore short circuit test and open circuit test gives the parameters of the equivalent circuit of the transformer and also the efficiency and voltage regulation of the transformer.