Study on the Axial Leakage Magnetic Flux in a Spoke Type Permanent Magnet Synchronous Motor

A spoke type permanent magnet synchronous motor generates axial leakage magnetic flux due to its flux-concentrating rotor structure, and therefore degrades the motor performance. Although a three-dimensional finite element method (3-D FEM) can be used to estimate the axial leakage magnetic flux, it requires a significant amount of time for analysis. In this article, a calibration coefficient is proposed to estimate the axial leakage magnetic flux using the two-dimensional finite element method (2-D FEM) instead of 3-D FEM. This calibration coefficient is expressed in terms of the major geometric parameters of a motor and can be calculated using the material information of the permanent magnet and the bridge of the rotor core in 2-D FEM. The validity of the proposed equation is verified through 3-D FEM and other tests.