Testing (On Bench): Rotor

Test for grounds with a I 10 volt test lamp. Place one test probe on slip ring and other test probe on rotor core. Lamp should not light. If lamp lights, rotor winding is grounded.
Test for shorted winding with a fully charged battery connected in series to ammeter and rheostat and connect one test lead to each of the slip rings, connect voltmeter across slip rings. Adjust battery voltage to specified voltage and check current draw as indicated on ammeter (see Field Current Specifications), excessive current draw indicates shorted turns in field winding.