how to test transformer polarity?

To test transformer polarity, use a simple method involving a voltmeter. First, connect the primary winding to an AC power source. Then, connect the voltmeter across the secondary winding. If the voltmeter reads a positive voltage when the primary is energized, the transformer is in phase, indicating correct polarity. If the reading is negative, the polarity is reversed. Always ensure safety precautions are followed when working with electrical equipment.