Research On The Influence Of Different Pole-cutting Methods Of Surface-mounted Permanent Magnet Motors On The Air Gap Magnetic Field

Permanent magnet synchronous motor has the characteristics of high efficiency,small and light,etc.It is widely used in the occasions with high control accuracy and high reliability requirements.At the same time,because the air gap magnetic field of surface mount permanent magnet motor contains space harmonics,the air gap magnetic field is not an ideal sine wave,therefore,electromagnetic torque ripples are generated,causing vibration noise.With the goal of improving the sine degree of the air gap magnetic flux density waveform,this topic studied the optimization effect of different pole cutting methods of surface mount permanent magnet motor on air gap magnetic field,provide a theoretical basis for reducing the vibration noise of the permanent magnet motor and optimizing the performance of the motor.The main research contents are as follows:The distribution function of the air gap flux density of the motor with respect to the rotor position under no-load is analytically derived.The most commonly used permanent magnets for surface mount permanent magnet motors are divided into tile and bow shapes.In this paper,the geometric analysis of the magnetic pole structure of the two shapes of permanent magnets when different pole cutting methods are used,the expressions of permanent magnet thickness and air gap length with respect to the rotor position are obtained,and then the distribution function of air gap magnetic flux density is obtained.According to this,the air gap magnetic flux density waveform is obtained through programming,and the correctness of the analytical derivation is verified by the finite element method.The finite element method is used to simulate and optimize the tile-shaped eccentric and sine magnetic poles respectively.The air gap magnetic flux density waveform was obtained by finite element simulation calculation,and the Fourier decomposition of the air gap magnetic density waveform obtained the fundamental wave value and harmonic content.The optimization is aimed at reducing the harmonic content and increasing the sine of the air gap magnetic field waveform.The optimization ideas are: First determine the influence law of single pole geometry parameters on the air gap magnetic field,and then determine the influence law of the combination of pole parameters on the air gap magnetic field.Finally,the simulation results are verified experimentally based on the existing prototype.By comparing the back-EMF waveform,the fundamental wave value and the harmonic content,it is confirmed that the experimental results are consistent with the simulation results,and the accuracy of the simulation analysis is verified.Further through the finite element simulation,the influence rule of the bow-shapedmagnetic pole parameters on the air-gap magnetic field is analyzed,and the bow-shaped magnetic pole is optimized.Analog analysis process and optimization steps of tile-shaped magnetic poles.By evaluating the fundamental wave value and harmonic content of the air gap magnetic density,the influence rule of the bow eccentric and sinusoidal magnetic pole parameters on the air gap magnetic field was determined.Finally,the optimization results of tile-shaped and bow-shaped magnetic poles are summarized,and it can be determined that the bow-shaped and tile-shaped magnetic pole parameters have basically the same influence law on the air gap magnetic field.The work of this article has laid the foundation for further research on the pole cutting technology of permanent magnet motors.