A study on the axial leakage magnetic flux in a spoke type permanent magnet synchronous motor

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