Improved Complex Relative Permeance Model for Slotted Surface-Mounted Permanent Magnet Motor

Abstract

This article presents a novel analytical model that significantly enhances the characterization of the magnetic field within the air gap of slotted surface-mounted permanent magnet (SPM) motors. The model, based on complex relative permeance (CRP), not only improves the accuracy but also accelerates the computation of the magnetic field in comparison to the existing CRP models and traditional numerical methods. The model denoted as improved CRP (ICRP) model is derived from the governing equations for magnetic scalar potential functions across various domains of the motor elements, diverging from traditional methodologies, such as conformal mapping. The application of the ICRP model ensures the incorporation of precise boundary conditions reflective of the permanent magnet's (PM) geometry, its angular orientation, and magnetic polarity. It proves applicable across a spectrum of motor design aspects, including pole-slot combinations, the geometry of the slotted iron core, the rotational angle of the rotor, and other critical parameters, such as the stator core slot opening angle, the pole-arc to pole-pitch ratio, and the air-gap length in 2-D spatial framework. The ICRP has been applied to the magnetic field analysis of three distinct motor designs, covering both slotless and slotted configurations, where it precisely assesses the effects of slotting through the relative permeance (RP) functions of the slotted core. The accuracy and computational efficiency of the ICRP are shown through comparative analyses with finite element analysis (FEA) and existing CRP models, focusing on scalar potential, RP, and magnetic flux density within the air-gap region. The results validate the model's superior capability, suggesting its utility in the design process of three different SPM motors.