Detection of air-gap eccentricity in induction machines using multi-position magnetic field measurement approach

This paper presents a multi-position magnetic field measurement approach to detect air-gap eccentricity in induction machines, including static, dynamic and mixed eccentricity. Using this method, the position of minimum air gap of static eccentricity also can be detected. The sideband components around the fundamental frequency of magnetic flux leakage in stator yoke is particularly analyzed based on magnetic circuit. The magnitudes of induced voltage harmonics in search coils are also investigated by finite element method. The algorithm is implemented for a 4-pole three-phase cage induction machine with static, dynamic and mixed eccentricity. It is highlighted that dynamic eccentricity can be detected by any one of the search coils, static eccentricity and the position of minimum air gap can be detected by the magnitudes of induced voltages in all the search coils. The theoretical results have been validated by finite element method.