how to test the polarity of a transformer?

To test the polarity of a transformer, you can use the “dot convention” method. First, connect a low-voltage AC source to the primary winding. Then, measure the voltage across the secondary winding. If the voltage is in phase with the primary voltage, the polarity is correct. Alternatively, you can use a voltmeter to check the phase relationship between the primary and secondary outputs. Ensure safety precautions are followed during testing.