Visual inspection of a rotor is likely the first step in the diagnosis of a possible rotor defect. When a rotor is pulled from the stator, it should be inspected for obvious faults. Common visible defects, such as those listed below, should trigger further testing of the rotor.
- Visible cracks in bar-to-end-ring joint
- Visible points of contact with stator
- Isolated discoloration of rotor surface
- Excessive concentration of balance weights
- Cracked end rings
- Shifted or separated rotor laminations