A Comprehensive Method for the Modeling of Axial Air-gap Eccentricities in Induction Motors

Abstract — When speaking about the diagnostic and reliability of induction motor (IM), it is important to note that the modeling is a main step permitting to study the evolution laws of the faults related harmonics. This is the aim of many previous works, but only few attempts on axial air-gap eccentricity modeling can be found. This paper deals with a new model of axial air-gap eccentricity faults in IM. This model is based on a variant of the modified winding function approach (MWFA) which allows the axial nonuniformity to be taken into account by considering that the eccentricity levels rise linearly along the rotor shaft. The model proves very useful to study the most documented IM faults without any need for Fourier series developments of turns and permeance functions in case of axial eccentricity. Knowing that the skew factor can be applied only under axial air-gap uniformity, the proposed model offers an accurate way in order to include the slots permeance and skewing effects even under axial eccentricity. The analysis is completed by a simulation tests on a 2-pole IM. Index Terms — Induction motor, space harmonics, skew, slot permeance effect, axial air-gap eccentricity