TESTING A WOUND ROTOR MOTOR
Because the stator winding of the wound rotor motor is the same as the squirrel-cage motor, the same test procedure can be followed. Testing the rotor of a wound rotor motor is very similar to testing the stator. The rotor can be tested for an open winding with an ohmmeter by checking the continuity between each of the slip rings, Figure 16–6. The resistance readings should be the same between each pair of slip rings. To test the rotor for a ground, connect one ohmmeter lead to the shaft, and connect the other lead to each one of the slip rings, Figure 16–7. The ohmmeter should show no continuity between the rotor windings and ground. Like the stator winding, the rotor is difficult to test for a shorted winding. To test the rotor for a shorted winding it is generally necessary to use equipment that will measure the inductance of the winding instead of its resistance.
