how to test winding resistance of transformer?

To test the winding resistance of a transformer, use a digital multimeter (DMM) set to the resistance (ohms) mode. Disconnect the transformer from the power supply and any load. Measure the resistance across the primary winding terminals and then across the secondary winding terminals. Record the values. Compare the readings to the manufacturer’s specifications to ensure they are within acceptable limits, indicating the windings are in good condition and free from short circuits or open circuits.