Eccentricity Diagnosis of Electric Machines Using Harmonic Ratio-Based Indices From Resolvers

Timely diagnosis of rotor eccentricity is essential for the safe, stable, and high-performance operation of electric machines. This article introduces novel indices for eccentricity detection, based on the output voltage signals of variable-reluctance resolver. The method utilizes the amplitude ratio between the dominant harmonics under healthy conditions and the additional dominant harmonics introduced under eccentric conditions as the diagnostic index. These indices exhibit a direct proportionality to the eccentricity level and account for various excitation modes, pole configurations, and eccentricity types. The proposed method is noninvasive, highly accurate, and suitable for both offline and real-time online applications. Through analytical modeling, finite element analysis, and experimental validation, the effectiveness of the approach for real-time eccentricity monitoring is demonstrated.