Semi-Analytical Model for Spoke-Type PM Motor Nonlinear Magnetic Field Calculation With Irregular Magnetic Pole Shape

The optimization of the motor magnetic pole shape has been shown to improve the motor's electromagnetic performance; however, the irregular shape makes the analytical calculation of the magnetic field difficult. In this article, the harmonic model (HM) method is used for spoke-type permanent magnet (PM) motor magnetic field calculation; considering the influence of irregular magnetic pole shape on the magnetic field, an equivalent method with a single-layer subdomain for irregular magnetic poles is proposed based on the principle of magnetoresistance equivalence. The modulation effect of the irregular magnetic pole on the magnetic field is equaled by the equal-thickness fan-shaped regular micro-slices with the permeability varying along the circumference. By this way, the standard boundary conditions requirement of the analytical method can be satisfied. Besides, the low rank of the coefficient matrix in boundary conditions of HM method results in a time-consuming inverse calculation of the coefficient matrix. To address this issue, the dimension-reduced harmonic model (DRHM) adapted to the tangential PM structure of a spoke-type motor is derived. The saturation effect of tooth-tip, tooth-slot, and magnetic pole region is considered by iterative calculations. Finally, the finite-element model (FEM) of 12S/10P dual three-phase spoke-type PM motor with the eccentric magnetic pole is built, and then, the effectiveness of the irregular magnetic pole equivalent method and DRHM method is verified.