Research On Magnetic Field Design For Claw-pole Hybrid Excitation BSG Motor

As the world is facing both environmental problems and energy crisis,the State Council promulgated <Chinses Manufacture 2025> for the automotive industry,which puts forward strict requirements on the fuel consumption of automobiles.With the advantages of small modification,low cost,mass production,energy saving and emission reduction,micro-hybrid vehicle has a good application prospect and research value.In this paper,the magnetic field design of BSG motor in the Belt-driven Starter Generator(BSG)system is studied.Aiming at the problems of low air gap flux density,narrow magnetic field adjustment range,poor power generation performance and low speed output performance in the current claw-pole hybrid excitation BSG motor design,the motor is optimized.Firstly,the structural characteristics and magnetic field adjustment principle of the motor are introduced.After that,the thickness of the permanent magnet,the size of the air gap and the width of the stator slot are optimized by the three-dimensional finite element method.The performance of the motor before and after optimization were compared.The optimized structure has the characteristics of high flux density,good waveform quality,good power generation performance and large starting torque.Finally,the prototype test was designed and manufactured.The results of prototype test was consistent with the finite element analysis results.The accuracy of the finite element simulation is verified,and the correctness of the analysis is further proved.And the following conclusions are obtained:(1)Under the same excitation current,there is an optimal design value for the thickness of permanent magnet.If the thickness of permanent magnet is too small,the magnetization effect of permanent magnet is not obvious;If the thickness of the permanent magnet is too large,the material utilization rate of the permanent magnet is not high.Because with the increase of the thickness of permanent magnet,the leakage coefficient will increase,which limits the large increase of the air gap magnetic density of the motor.(2)With the decrease of air gap,the leakage flux decreases,which causes the increase of the amplitude of back EMF and the distortion rate of voltage waveform.(3)The width of the notch has little influence on the amplitude of the back electromotive force,which mainly affects its voltage waveform distortion rate.With the increase of the notch,the voltage waveform distortion rate is gradually increased and eventually stable.