Direct flux monitoring technique for locating rotor cage defects-how well does it work?

Several methods were developed to detect rotor bar failures in running motors. Those methods have three shortcomings: none are infallible; neither exact number nor exact location of defects are disclosed; bars not completely broken are unlikely to be detected. Other fault localization methods must then be used when the motor is not running and the rotor has been removed for inspection. One such method involves electromagnetically energizing the entire cage to search for faults not readily visible. A discussion is presented of that procedure in light of a variety of results obtained on large machines up to 6000 HP.<>