how to check polarity of 3 phase transformer?

To check the polarity of a three-phase transformer, you can use the polarity test method. Connect a low-voltage AC supply to one winding and measure the voltage across the other winding. If the voltage readings are in phase, the transformer is in the same polarity; if they are out of phase, the polarity is opposite. Alternatively, you can use a phase rotation meter to verify the phase sequence and ensure correct polarity alignment.