A new model of rotor eccentricity in induction motors considering the local air-gap over-flux concentration

Abstract

This paper proposes a novel analytical model of air-gap eccentricity in induction motors (IMs) by allowing teeth saturation due to the local air-gap over-fluxing to be taken into account. The approach takes into account the magnetic saturation by means of a fictive permeance variation while supposing that, under air-gap eccentricity conditions, the saturation factor must be revaluated in function of the varying air-gap length. The well-known 2D-modified winding function approach (2D-MWFA) is used to get the formalism of the inductances by assuming a partial uniform rise of the saturation factor with respect to the air-gap length. We show that applying the new approach confirms that the magnetic saturation reduces the asymmetry of the air-gap flux distribution due to rotor eccentricity. In contrast to the harmonic and flux models, the proposed one allows us to proceed with a full dynamic simulation without any need for the experimental data. Thanks to a fast convolution-based technique of inductance calculation, we demonstrate that the 2D-MWFA preserves its major qualities even with these new extensions. The study is supported by simulation and experimental results.