Which test would you perform to check if transformer windings are connected in phase?

To determine if transformer windings are connected in phase, the transformer polarity test is the appropriate choice. This test assesses the relative polarity of the transformer windings, helping to confirm whether they are connected correctly to ensure that the voltages at the output are additive or subtractive as intended in the application.

During the polarity test, a small voltage is applied to one winding, and the results are measured from the other winding. By comparing the phase relationships of the voltages, the technician can ascertain how the windings are related to each other. If they are in phase, the voltages will reinforce each other; if they are out of phase, they will oppose each other, which can lead to operational issues in the system.

The other tests mentioned have different purposes. The insulation resistance test evaluates the integrity of the insulation around windings, ensuring there are no leaks that could lead to short circuits. The winding resistance test focuses on measuring the resistance of the windings themselves, which helps detect issues like loose connections or burnt windings, but it does not provide information about the phase relationship. Similarly, the power factor test assesses the efficiency and health of the transformer under load conditions rather than its phase connections.