AC MACHINES-1 (66761) Theory

PROCEDURE OF POLARITY TEST OF TRANSFORMER

1. Connect the circuit as shown above with a voltmeter (V_a) across primary winding and another voltmeter (V_b) across the secondary winding.
2. If available, take down the ratings of the transformer and the turn ratio.
3. We connect a voltmeter (V_c) between primary and secondary windings.
4. We apply some voltage to the primary side.
5. By checking the value in the voltmeter (V_c), we can find whether it is additive or subtractive polarity.

If additive polarity – V_c should be showing the sum of V_a and V_b.
If subtractive polarity – V_c should be showing the difference between V_a and V_b.
Caution: Be careful that the max. measuring the voltage of voltmeter V_c should be greater than the sum of V_a (Primary winding) and V_b (Secondary winding) otherwise during the additive polarity, the sum of V_a and V_b comes across it.