Analytical field model of segmented Halbach array permanent magnet machines considering iron nonlinearity

Abstract

The permeability of the iron is usually assumed to be infinite by the linear subdomain technique, leading to the neglect of magnet saturation. This study presents an analytical model of a segmented Halbach array permanent magnet machine by considering the iron B-H curve and saturation effects. Firstly, the entire field problem is divided into six regions in the radial direction according to the excitation source. Then, Poisson's and Laplace's equations are solved in each region to obtain the magnetic vector potential. Specifically, in our approach, the teeth and slots' permeability variation is solved by Cauchy's product theorem. An iterative algorithm incorporates the nonlinearity of the iron. Subsequently, the electromagnetic performance, such as air-gap magnetic flux density, electromagnetic torque, and unbalanced magnetic force, is predicted by the analytical method. The analytical results are shown in line with those obtained from finite element analysis, and a prototype was fabricated to further verify the accuracy of the analytical method. Besides, the proposed method can also be used to evaluate the performance of the Halbach array machines with any number of segmented magnets.