Characteristic Harmonic Analysis And Topology Design Of Double-Air-Gap Flux-Modulated Permanent Magnet Motor

In recent years,a class of double air-gap permanent magnet motor has been widely concerned,because of its high torque density and more compact structure.Generally speaking,a reasonable topology design of a double air-gap motor can significantly improve the utilization rate of the magnetic field.However,the interaction between the inner and outer air-gap magnetic fields leads to the inevitable phenomenon of "magnetic field coupling",which increases the complexity of motor design and analysis to a certain extent.In this study,a double air-gap permanent magnet motor is proposed.By means of the analysis method of "air-gap field modulation",the magnetic field coupling phenomenon between the two air-gaps of the motor is fully considered,and the formation of the motor air-gap flux density and output torque is analyzed from the dimension of coupling characteristics.The characteristic harmonic is defined,and the analysis method of the characteristic harmonic is proposed as the theoretical guidance for the topological design and harmonic design of the motor.The specific content is summarized as follows:(1)Based on the basic principle of magnetic field modulation,the magnetic field coupling phenomenon of proposed Double-Air-gap Flux-Modulated Permanent Magnet(DA-FMPM)is analyzed from the perspective of air gap harmonics.The coupling characteristic magnetic density is defined,and the characteristic harmonics are screened out from the coupling characteristic magnetic density harmonics,which are used as the factors to analyze the magnetic field coupling.The comprehensive characteristic harmonic factor is proposed as an evaluation method to quantify the characteristic harmonic coupling characteristics.The correlation between characteristic harmonic characteristics and motor structure and performance is analyzed,which provides theoretical basis for topology design and harmonic design.(2)The permanent magnet topology is determined according to the internal resistance consuming magnetic potential.Through the comprehensive analysis of characteristic harmonic and motor performance,the relative angle of inner and outer rotor of motor is determined,so as to maximize the positive effect of characteristic harmonic.Finally,the topology structure of DA-FMPM motor is obtained.(3)Based on the analysis method of characteristic harmonics,the representative harmonic design schemes in three sections are selected respectively.The characteristic harmonic and performance of the motor under the three schemes are comprehensively analyzed.The results show that the motor using case III has better comprehensive performance,and the effectiveness of the characteristic harmonic design is verified.(4)According to the results of characteristic harmonic design,a prototype of DA-FMPM motor is manufactured,and the related performances of the motor are measured.The experimental results show that the DA-FMPM motor has stable torque output capacity and good dynamic response characteristics.In addition,the agreement between experimental results and simulation data verifies the validity of the characteristic harmonic design method and the rationality of motor machining.