Research And Optimization Design Of Flux Modulated Permanent Magnet Motor With Unequal Width Permeability Modulation On Torque Performances

In recent years,with the rapid development of modern agriculture,there has been an increasing demand for agricultural electrification and intelligence.Electric tractors have received a lot of attention from researchers at home and abroad due to their low noise level,high efficiency,energy efficiency and environmental friendliness.However,as electric tractors are required to operate under complex and changing working conditions for long periods of time,higher demands are placed on the drive motors in the electric tractor drive system.Due to the characteristics of low speed and high torque,magnetic field modulated permanent magnet(FMPM)motor can meet the high torque output requirements of electric tractors in different operating environments.Therefore,magnetic field modulated motor has become the potential application object of electric tractor drive motor.However,the harmonic content of the air-gap magnetic density of FMPM motors is complex and the correlation between harmonics and motor output torque and torque ripple needs further study.Therefore,based on the performance requirements of electric tractors,how to study the intrinsic correlation between air gap magnetic density harmonic distribution and motor torque characteristics from the perspective of FMPM motor harmonic distribution,to further improve the output torque and suppress torque pulsation,has become a hot and difficult research topic in the field of electric tractor drive motor research.In this thesis,a Split-tooth V-shape Flux-Modulated Permanent Magnet(SPV-FMPM)motor was taken as the research object.By studying the unequal width modulation of the permeability,A comprehensive improvement method of torque performance with non-equal width permeability as design variable was proposed.This method takes air gap harmonics as a bridge to study the relationship between the design of unequal width permeability and torque performance,explore the permeability design law of high output torque and low torque ripple motor,and realize the comprehensive improvement of torque performances.The main work in this thesis is summarised as follows:1.This thesis summarizes the development history of electric tractor drive motor.It also summarizes the current status of research on FMPM motors at home and abroad,and describes the research methods for increasing output torque and reducing torque pulsation from the perspective of the "three elements" of FMPM motors.2.Based on the principle of magnetic field modulation,the influence of unequal-width modulation on the harmonic distribution of permanent magnetic field and armature magnetic field is discussed.Maxwell’s stress tensor method has been used to investigate the relationship between the air gap magnetic density harmonics and torque performances,and derive the equations for the output torque generated by each harmonic and the torque pulsation.On this basis,the relationship between unequal width distributed permeability and torque performance is further derived,and a comprehensive improvement method of torque performance with non-equal width permeability as design variable is proposed.3.In order to meet the performance requirements of electric tractor drive motors with high output torque and low torque pulsation,this thesis examines the key air-gap magnetic density harmonics that contribute to torque performance from the perspective of air-gap harmonics,and uses sensitivity analysis to determine highly sensitive magnetic conductivity design parameters.On this basis,the response surface algorithm was used to determine the optimal design to effectively increase the output torque and reduce the torque ripple.4.After determining the optimal structural parameters,use the finite element analysis software to simulate the performance of the SPV-FMPM motor model.The no-load performance and load performance of the motor have been analyzed and compared.The no-load performance includes magnetic field distribution,back potential and cogging torque.The load performance includes air gap flux density and its harmonic distribution,torque performance,motor loss and efficiency.5.According to the selected non-equal width permeability design variables.A SPV-FMPM motor prototype was fabricated and its corresponding experimental platform and control system have been built.The no-load back potential,steady-state torque,starting response characteristics,variable speed response characteristics and variable load response characteristics of the SPVFMPM motor are tested.By comparing the simulation results with the experimental results,the rationality and reliability of the design of SPV-FMPM motor are verified,and the effectiveness of the proposed comprehensive improvement method of torque performances with unequal width permeability as the design variable is verified.