Research On Torque Ripple Suppression And Related Performance Optimization Of Permanent Magnet Synchronous Motor

Compared with the traditional induction motor,permanent magnet synchronous motor(PMSM)has higher torque density,power factor,keep high efficiency in wide operating range and many other advantages.It has been used widely in all walks of life.But the existence of the permanent magnet makes the torque ripple of PMSM larger than the traditional electric excitation motor,the torque ripple will affect the stability of the motor system,and cause the vibration and noise.Aiming at the problem of large torque ripple of PMSM,this paper studies the causes of torque ripple,and puts forward several economic and effective suppression methods.The work is mainly divided into the following aspects:1.The background of this project is explained in a more comprehensive way,and the current situation of industrialization development of permanent magnet motor at home and abroad and the existing gap in China are introduced.Starting from the two factors causing torque ripple,namely cogging torque and ripple torque,the methods of suppressing torque ripple proposed by scholars at home and abroad is expounded,and the advantages and disadvantages of each method and its application scope are analyzed.2.The mechanism of torque ripple is analyzed by analytical method.Firstly,the cause and influence factors of ripple torque are deduced by PMSM's voltage mathematical model and torque equation,which provides a theoretical basis for correlation suppression method.Then,the analytical expression of cogging torque is analyzed by the energy method,and the methods of reducing cogging torque can be obtained from the analytical formulas.3.Based on theoretical analysis,puts forward the axial permanent magnet combination method to reduce the cogging torque of Surface-mounted PMSM,the validity of the method is proved by analytical method,and the specific size of the combined permanent magnets is calculated by the derived formula.The correctness of the derivation is verified by finite element software,and the best combination is obtained through simulation comparison.Then,comparing the performances of optimized motor with the original motor,including the fundamental amplitude of the flux density and the permanent magnet consumption,economy and effectiveness of this method can be proved.In addition,the change of other performances of the motor are analyzed after the optimization,including the content of the back EMF harmonic and the loss of the motor.4.The change of torque ripple of inset PMSM after notching the auxiliary slots on the core is studied.The variation of the air gap magnetic field of the motor is analyzed by the magnetic force multiplied by the magnetic field theory.Combined with the second chapter,the output torque of motor is analyzed.Fourier transform method is used to compare the variation of the amplitude of the harmonics and the influences on the ripple torque with and without the auxiliary slot.The auxiliary slot can also affect the magnetic conductivity of the motor,so that the d-q axis inductance will be changed.This will affect the flux-weakening performance of the motor.The generation mechanism of the torque ripple and the suppressing methods are systematically studied in this paper.Based on theoretical analysis method,some methods for reducing torque ripple are proposed.The effectiveness and related performance changes of each method are analyzed by finite element software.The methods adopted in this paper are relatively simple and practical,which can provide reference for PMSM optimization design and torque ripple suppression.