Effect of static eccentricity in back-EMF of Axial Flux Permanent Magnet Machines

This paper studies the effects of static eccentricity on back-EMF of Axial Flux Permanent Magnet Machines (AFPMM). Effect of static eccentricity on back-EMF of AFPMs has not been studied before. Many studies have demonstrated that accurately assessing the behavior of Axial Flux PM Machines is not an easy task. Use of numerical modeling makes it possible to precisely study the eccentricity in these types of machines. Recently, modeling of AFPMs has been done by finite-element (FE) analysis. Most of the models are based on the reduction of the 3D problem to a 2D problem that is not accurate. In this paper a surface mounted axial flux permanent magnet (AFPM) motor with a core of soft magnetic composite (SMC) material is modeled using 3-D finite element method. The proposed model in this paper takes into account MMF harmonics, stator and rotor core. 3-D electromagnetic finite element method (FEM) is used to calculate flux density in the air-gap, rotor back iron, and stator iron and to simulate the electromotive force (back EMF). This study indicates that static eccentricity has noticeable effects on back-EMF of coils of a phase and it introduces a good criterion for fault detection.