Modeling And Optimization Of Brushless Permanent Magnet Machines With Unequal Thickness Halbach Array

Permanent magnet(PM)machines are widely used in the fields of industry and agriculture for their simple structure,high efficiency and power density.The performance of PM machines mainly depends on the shape of magnets.Therefore,the investigation of magnet shapes and electromagnetic properties of PM machines is of great significance.First,the analytical models for PM machines with from two to N segmented magnets are presented.The air gap flux density waveforms in PM machines have been derived.The correctness of the analytical method is verified by a finite element method.Second,a novel structure of combined unequal thickness magnets is presented,which is composed of segmented magnets with different magnetized directions.The air-gap flux density of slotless and slotted PM machines is analytically obtained by solving the Laplacian and quasi-Poissonian equations.Besides,the back electromotive force(EMF) and electromagnetic torque are obtained.In addition,the air-gap flux density of the presented machine is optimized.The optimal magnetization angles of side magnets for slotless and slotted PM machines are analytically obtained.Finally,the correctness of the analytical model is verified by a finite element method(FEM).The presented method and results are helpful for the optimization of both slotless and slotted PM machines.Third,a structure of combined unequal thickness and asymmetrical magnets is presented,which is composed of segmented magnets with different materials and magnetized directions.The air-gap flux density and magnet utilization are analyzed in terms of the pole number.Compared with the conventional structure,the machine with combined unequal thickness magnets and asymmetrical magnets can improve the performance and save the PM material.