Influence of Salient Effect on Air-Gap Flux Density Distribution of Interior Permanent-Magnet Synchronous Machines

Abstract

Interior permanent magnet synchronous machines (IPMSMs) are widely used in electric vehicles due to their high power density, high efficiency, and wide speed range. Compared with surfacemounted PMSMs, the salient effect of IPMSMs causes a significant difference between quadrature-axis and direct-axis flux paths, which can increase the harmonic components of the air-gap field and affect the operation of the machine. Herein, taking a 6-poles 36-slots PMSM as an example, this paper analyzes the influence of salient effect on the air-gap flux density. Based on salient effect function, the analytical model of air-gap flux density considering the salient effect is established, and the influence of the salient effect on the spatial-temporal distribution characteristics of air-gap flux density excited by permanent magnets and armature reaction are derived, which are verified by the finite element method (FEM). Both simulation and experiment results of the prototype show good agreement, and the sources of salient effect are found with finite element model and equivalent magnetic circuit. Further, different current excitations are applied to analyze the influence of the salient effect on different magnetic fields. The results show that the salient effect has a more significant influence on the direct-axis armature reaction magnetic field, which increases the harmonics components with the temporal orders of 3ka (ka=1,2,3…).INDEX TERMS IPMSMs, salient effect, quadrature-axis and direct-axis flux paths, spatial-temporal distribution, equivalent magnetic circuit, FEM.