Air gap flux analysis for cage rotor diagnosis

The relationship between the magnetomotive force distribution of a three-phase induction motor and various cage rotor faults, such as broken bars and end rings, is discussed in detail. Search coil output and its harmonic components are analyzed to allow the determination of faults from the air-gap flux density. The results obtained in tests on a motor into which faults were intentionally introduced confirm the effectiveness of this method of analysis.