Consider the following losses for short circuit test on a transformer:

1. Copper loss

2. Copper and iron losses

3. Eddy current and hysteresis losses

4. Friction and windage losses

Which of the above is/are correct?

Short circuit test:

It is done by shorting one of the winding terminals (usually low voltage terminal) and applying a small voltage across the other winding terminals (high voltage terminal because the current in HV terminal will be less and easy to handle) and using a wattmeter to measure the power dissipated in the LV terminal. Wattmeter will indicate the full load copper loss.

Short circuit test is done to find

• The full load copper loss
• Short circuit current

Open circuit test:

It is done by keeping one of the windings open (without load, usually high voltage winding is open) and applying rated voltage to other winding (usually low voltage winding because it is easier to apply rated voltage).

The current drawn from this terminal is the no-load current corresponding to core loss component. Since the no-load current is very small it doesn’t contribute to the copper loss. Core loss is calculated by multiplying the applied voltage and no-load current.

It is used to find

• The core loss of the transformer
• The no-load current
• Equivalent resistance referred to metering side