Analytical Modeling And Magnetic Field Analysis Of A Permanent Magnet Brushless Machine With Novel Magnetic Poles

With the implementation of the "13th Five-Year Plan" in China,energy development is becoming more and more high efficiency,economical and sustainable.Brushless permanent magnet(PM)machines have the characteristics of simple structure,small size,high power density and low maintenance rate,and they are widely used in ship,aviation,appliances,medical,public life and other fields.Therefore,it is of great theoretical significance and practical engineering value to study the structure and electromagnetic characteristics of PM machines.The change of magnetic pole structure and magnetization orientation will directly influence the distribution of air-gap flux density in PM machines.First of all,the model of unequal-thickness magnetic pole structure is built,and the expression of air-gap flux density of a slotless PM machine is obtained by permanent magnet segmentation modeling,and the other electromagnetic parameters are derived by presenting relative permeability for the ideal rectangular slot PM machine;Secondly,the electromagnetic characteristics of a novel two-segment Halbach magnet array and combination double-layer Halbach magnet array are analyzed by superposition principle,on this basis,in terms of the magnet thickness ratio,pole embrace of middle magnet and magnetization angle of side magnets,the air-gap flux densities for the double-layer structure are optimized.In addition,the proposed analytical technique can also predict the no-load induced back-electromotive force(EMF)and electromagnetic torque.Finally,predicted results have been validated by finite-element analysis for a 8-pole PM machine.On this basis,the stator slot change also has some affect on the performance of the motor.In this thesis,the air-gap flux density,the induced back-electromotive force(EMF)and electromagnetic torque in the slotted PM machine are calculated by a modified Carter's coefficient for the novel two-segment Halbach magnet array and combination double-layer Halbach magnet array.The validity of the presented method is verified by the finite element method.Therefore,the presented methods and results are helpful for the optimization design of the PM machines.