Analytical Evaluation of Permeance Harmonics Effects in Permanent Magnet Machines Using Improved Winding Function Theory

Abstract

Permanent magnet motors (PMMs) are a good choice for many applications due to their merits. These motors include synchronous motors (SMs) and flux modulation motors (FMMs). Their principles of operation depend on the air-gap permeance harmonics. Permeance harmonics are one of the main factors influencing the performance characteristics of PMMs, including torque, back-electromotive force (EMF), power factor, flux-linkage, phase inductance, and flux-weakening capability. This paper investigates the effect of air-gap permeance harmonics on PMM performance. For this purpose, the winding function theory (WFT) and the Fourier series are used and various PMM structures having different effective permeance harmonics are presented. Since it is not possible to analyse all these structures, four structures of conventional PMMs are selected as representatives of all the structures. In this paper, the improved analytical modelling of WFT is used, in which the turn function is modified to include the saturation and slot effects. Also, it is possible to calculate the leakage inductance between two stator teeth. Ansys Maxwell software is applied to verify the analytical modelling. Finally, two designs of FMM with different air-gap permeances are analysed and compared. The superior structure of this FMM is fabricated and tested to confirm the simulation results.