Design And Optimization Of Permanent Magnet Assisted Synchronous Reluctance Motor With Magnetic Pole Offset

In recent years,benefiting from the advantages of wide speed range,high power density and low cost,permanent magnet assisted synchronous reluctance motor(PMa-SynRM)has become one of the research hotspots at home and abroad.It is widely used in electric vehicles,household appliances and other fields.To optimize the performance of PMa-SynRM will help promote the development of the above fields.The output electromagnetic torque of traditional PMa-SynRM is composed of permanent magnet torque and reluctance torque.However,in the traditional PMa-SynRM,the current phase angle corresponding to the maximum average value of the output reluctance torque and the permanent magnet torque is quite different,which leads to the low utilization rate of the two torque components in the traditional PMa-SynRM.To solve this problem,a PMa-SynRM with magnetic pole offset is designed in this paper.Through the offset distribution of permanent magnet and barrier in the magnetic pole,the flux path is changed and the air gap magnetic density distribution is adjusted,so as to change the amplitude of the average value of permanent magnet torque and reluctance torque corresponding to the current phase angle.The amplitude of the average value of the two torque components can be superimposed at the same current phase angle to increase the total output electromagnetic torque.The main contents of this paper are as follows:Firstly,the PMa-SynRM with magnetic pole offset topology is designed based on the traditional PMa-SynRM.The electromagnetic torque equation of PMa-SynRM with magnetic pole offset is derived by combining with the space vector diagram,and the electromagnetic torque formula of PMa-SynRM with magnetic pole offset is analyzed theoretically.And the design basis for PMa-SynRM to achieve that reluctance torque and permanent magnet torque amplitude appear at the same current phase angle is derived.The inductance characteristics,stator magnetomotive force,back electromotive force and cogging torque of PMa-SynRM with magnetic pole offset are analyzed under different pole-slot combination.The effects of different stator tooth width,yoke height,rotor barrier layer and rib width on the electromagnetic torque,cogging torque,efficiency and loss of PMa-SynRM with magnetic pole offset are analyzed,and the optimal size parameters are determined for the purpose of improving the motor performance.After the design is completed,the effects on motor performance under the structure characteristics of magnetic pole offset are analyzed.Secondly,the influences of different connected barrier width and connected barrier position on the electromagnetic torque and torque ripple of PMa-SynRM with magnetic pole offset is first analyzed to optimize the width and position of the upper and lower connected barrier.After that,genetic algorithm is used to optimize the barrier width of each layer and the relative position between barriers of the PMa-SynRM with magnetic pole offset.Under the premise of not increasing the total amount of permanent magnet,maximum electromagnetic torque and minimum torque ripple are taken as the optimization objectives to further improve the operating performance of PMa-SynRM with magnetic pole offset.The model before and after optimization is compared and analyzed to verify the feasibility of optimization.Thirdly,the no-load performance,load performance and inductance characteristics of the PMa-SynRM with magnetic pole offset topology obtained after optimization are analyzed.Then the basic equations of field weakening are derived to analyze the influence of motor parameters transformation on field weakening capability.And the speed range of constant power operation of PMa-SynRM with magnetic pole offset is analyzed.Finally,the vibration and noise characteristics of the PMa-SynRM with magnetic pole offset are analyzed.The radial magnetic density of the air gap of PMa-SynRM with magnetic pole offset under rated condition is analyzed,so as to obtain the radial electromagnetic force density applied to the stator tooth surface at a certain moment and the whole electric cycle,and its two-dimensional fourier decomposition is analyzed.Then,the stator modal characteristics of PMa-SynRM with magnetic pole offset are analyzed,and the modes of each order stator-shell and corresponding natural frequencies are obtained.The vibration and noise characteristics of PMa-SynRM with magnetic pole offset are analyzed under the whole speed range of constant power.