Analysis And Suppression Of Air-gap Harmonics In Permanent Magnet Synchronous Machine

Permanent magnet synchronous motor(PMSM)has the advantages of high efficiency,low noise,convenient structure and anti-interference.It has important applications in new energy vehicles,military engineering,high-speed train,mechanical material processing,agroforestry equipment and other fields.However,the existence of harmonic in the magnetic field of permanent magnet synchronous motor not only affects the torque ripple of the motor,but also restricts its application in high precision and high efficiency.This makes the analysis and suppression of harmonics in permanent magnet motor become an important research topic.Based on the optimization design of the surface attached PMSM,the analysis and optimization method of air gap harmonic in PMSM is studied.The influence of different magnetic pole shape and magnetization mode on the motor harmonics is discussed,and the following work is done.Through the theory of electromagnetic field and electromotor,the winding function of the motor,the air gap function of the motor and the density function of the air gap magnetic field are calculated and deduced,and the relation formula of the motor flux,induction electromotive force,magnetic electromotive force and electromagnetic torque on the above physical quantities is established,and then the harmonic composition is calculated by Fu Liye decomposition.The correlation between the harmonic and the magnetic field parameters of the motor is obtained.The three magnetization modes of permanent magnet motor magnetic pole-parallel magnetization,radial magnetization and Halbach array magnetization are compared.Their advantages and disadvantages are analyzed and their applicable situations are analyzed.The magnetic density and harmonic in the air gap of the motor under three kinds of magnetization are analyzed by the finite element method.The simulation results will affect the air gap magnetic density and harmonics of the motor,and the Halbach array magnetization method is more suitable for permanent magnet synchronous motor.On the basis of traditional Halbach array,a new double-layer pole shape is proposed and magnetized by Halbach array.Compared with the single layer Halbach array,the gas gap magnetic density base wave content is large and the waveform sine is good.It can improve the magnetic field intensity,reduce the harmonic,restrain the torque ripple,improve the running stability,and further optimize the design parameters of the new double layer Halbach array.A surface mounted permanent magnet synchronous motor with magnetic pole segmented outer arc eccentricity is presented.The inner and outer arcs of each pole of the motor have different centers.The magnetic density,cogging torque and back EMF waveform of motor air gap under different eccentricity and polar arc coefficient are compared.By optimizing the eccentricity and polar arc coefficient,it can effectively reduce the air gap magnetic density harmonic,reduce the back EMF harmonics and suppress the torque ripple.The magnetic pole structure can reduce the amount of permanent magnet material and improve the electromagnetic performance of the motor.