The Electromagnetic Design And Analysis Of A New Type In-Wheel Motor With Novel Synthetic Slots For Electric Vehicles

Electric vehicles(EVs)have the advantages of low carbon and environmental protection.Since the 18 th national congress of the communist party of China,the electric vehicle industry has been booming,and new energy vehicles have grown rapidly in the pas t five years.The four wheels of the hub motor can be independently controlled.Hub motors can simplify the vehicle structure.Hub motors have the advantages of wide speed range,quick torque response and large output torque.Therefore,hub motors are wide ly used in electric vehicles.In this paper,the electromagnetic design and analysis of the Synthetic Slots Flux-Modulated Permanent-Magnet(SSFMPM)are carried out.Permanent magnets are installed in the rotor and stator of the SSFMPM.The stator slot adopts the synthetic slots structure.The motor is based on the principle of bidirectional flux modulating effect.The harmonic coupling with the same pole number and rotation speed improves the torque density.The working principle of coaxial magnetic gear(MG)is analyzed theoretically and the formula is deduced.The magnetic gear was modeled by Ansoft Maxwell software.Through the powerful post-processing function of the software,the air gap magnetic density distribution diagram,magnetic field line distribution diagram and torque angle curve of the magnetic gear are obtained.The simulation results verify the correctness of the theoretical derivation.On this basis,the principle of bilateral magnetic field modulation is analyzed,and the distribution of effective magnetic field harmonics is obtained.Two driving modes of hub motor are introduced.According to the requirements of the size and power of the hub motor,some structural parameters of the motor are preliminary set.The magnetic circuit method and finite element method(FEM)are combined to complete the electromagnetic design and analysis of the motor.Firstly,the main structural parameters of the motor are obtained by the magnetic circuit method.Motor modeling and analysis by finite element anal ysis software.The structural parameters of the motor are corrected according to the analysis results of the motor's structural parameters on the torque density.The magnetic circuit method is used again to calculate the structure parameters which meet the design requirements.Finally,the no-load magnetic flux density distribution diagram,no-load counter potential distribution diagram,load magnetic force line distribution diagram,rated torque curve,and the relationship curve between magnetization direc tion of permanent magnet and motor torque were obtained.The influence of the q axis current and the straight axis current on the inductance parameters of the motor is analyzed by the parametric scanning method.Set up the experiment platform and complete the motor test.The results show that the waveform of no-load counter potential is basically consistent with the simulation data.The motor can respond quickly and run smoothly under variable load.