Optimal Design And Flux-weakening Characteristics Analysis Of Interior Permanent Magnet Synchronous Motor

Compared with Surface Permanent Magnet Synchronous Motor,Internal Permanent Magnet Synchronous Motor(IPMSM)has different d-axis and q-axis inductances,it can make full use of the magnetoresistance torque to obtain larger output torque,and also has a wider range of flux-weakening speed-expansion,so it is widely used in electric vehicles,CNC machine tools,rail locomotives and other aspects.However,the problems of IPMSM,such as large cogging torque,high torque ripple and difficulty of flux-weakening,seriously restrict its application in high speed,high precision and other occasions.Therefore,this paper takes IPMSM as the research object,and studies the optimal design and flux-weakening characteristics of IPMSM,trying to make the cogging torque effectively weakened,torque ripple effectively reduced and the range of flux-weakening speed-expansion wider.The main work and achievements are as follows:(1)The finite element simulation model of IPMSM is established and analyzed,including static field simulation analysis and transient field simulation analysis of IPMSM.Among them,the static field simulation analysis of IPMSM includes the static magnetic field distribution and static characteristics analysis.The transient field simulation analysis of IPMSM includes the analysis of no-load and load characteristics.(2)The method of cogging torque reduction of IPMSM based on permanent magnet segmenting optimization is studied and obtained.Firstly,the influence of permanent magnet segmenting on the cogging torque is analyzed by analytical calculation.Then,three different permanent magnet segmenting methods,i.e.uniform segmenting,nonuniform segmenting and non-uniform segmenting,are analyzed in detail.Finally,by comparing and analyzing the finite element simulation results of these three different permanent magnet segmenting methods,it is verified that the effect of permanent magnet with unequal thickness and non-uniform segmenting on cogging torque is the best.(3)The torque ripple optimization design of IPMSM based on Taguchi method and magnetic pole shifting is studied and obtained.On the one hand,the whole optimal design process of Taguchi method is introduced in detail;on the other hand,the principle and method of weakening cogging torque by magnetic poles shifting are also introduced in detail,and a new magnetic pole shifting method is proposed based on two existing magnetic poles shifting methods.The new magnetic poles shifting method and Taguchi method are combined to optimize the torque ripple of IPMSM,which not only reduces the number of orthogonal experiments and design time,but also effectively reduces the torque ripple of the motor.(4)According to the stator current control strategies of IPMSM,including constant torque control and general flux-weakening control,a stator current control program for calculating the torque characteristics and power characteristics of IPMSM is designed.By using the program,the influence of the flux-weakening parameters,such as the salient rate and the demagnetization rate,on the flux-weakening performance of IPMSM is studied.In addition,a more accurate finite element method(FEM)is used to analyze the fluxweakening characteristics of IPMSM,including its low-speed and high-speed characteristics.At last,the Segmented IPMSM is been adopted to improve the fluxweakening performance,and the flux-weakening speed-expansion principle of Segmented IPMSM is explained from the perspective of magnetic circuit analysis.The best design scheme is obtained by comparing the finite element simulation results of four different designs of Segmented IPMSM.