If a motor has to have heat applied to get the megger reading up, then it will need a rewind eventually as the insulation is either tracking to ground or absorbing moisture. On a good motor, a megger reading between phases will show a short. Another test we might do is called a Polarization Index test. It is like taking a 10 minute megger reading.. Some DC motor controllers can either give false readings or become damaged by the reversal of current flow into the control mechanism of the high testing voltage. Step 2. Set the DC motor on an insulated pad or piece of wood so the frame is not in contact with any metal surface. If there is a short in the motor wiring and the frame of the motor.
Disconnect the motor from the power source and discharge any stored electrical energy (many 1-phase AC motors have a starting capacitor). A disconnect or motor starter can be an easy location to disconnect supply power. Select the Megger Instrument: Choose an appropriate megger instrument based on the motor's voltage rating. Meggers are.. Connect the megger leads between one stator terminal and motor body. Step-3. Apply twice the motor operating voltage between one phase and the motor body. If Motor rated voltage is 440 volts, apply voltage 880 volts. We should test the older motor at less voltage( about 80% of the twice operating voltage).