Bench Testing: Rotor

Inspect rotor for stripped threads or damage at pulley end. Inspect for scored bearing surfaces, scuff marks on the pole fingers, or dirty or contaminated slip rings. Measure resistance across rotor slip rings. If resistance is not 2-6 ohms, replace rotor. Measure insulation resistance between individual slip rings and rotor shaft. If continuity exists, rotor windings are grounded. Replace rotor.