| As global energy shortage and environmental pollution going increasingly severe,electric vehicles,a NEV of excellent performance and relatively completed technology,have received support from governments globally and gained a sound development.The motor is one of the three key technologies of electric vehicles.Hub motor has been a hotspot in the research field of electric vehicles for it is built in the wheel hub and directly drives the wheels,which has light weight and advantages of integration.With the need for higher performance of electric vehicles,society requires higher standards of hub motors.Therefore,it is necessary to research the power density of hub motors.This paper studies the power density and heat dissipation of hub motor using the method of finite element and experiment.Based on the basic structure and parameters of the motor studied in this paper,the ontology finite element model was established in the finite element software Maxwell;then,_di=0 external circuit model of double closed-loop control under SVPWM strategy was built in Simplorer,and the field-circuit coupling co-simulation was carried out to study the dynamic performance of the motor body model under various working conditions of no-load start,load start and steady-state operation loading,which preliminarily verifies the correctness of the motor body model.After that,the efficiency measurement experiment was carried out through the performance bench experiment of the hub motor.Through the comparison between the experimental results and the simulation efficiency map diagram,the correctness of the established finite element model of the motor body was verified,and the two-dimensional finite element model of the motor body was carried out to evaluate the initial performance of the original motor under no-load and load working conditions.To improve the power density performance of the motor,the influence of the block Halbach array with permanent magnet structure on the performance of the motor was studied,and multiple performances of Halbach array motors with different blocks per pole were calculated.The results show that the appropriate number of blocks per pole improves the performance of the Halbach array on the output torque and other performances of the motor.Finally,the optimal number of blocks per pole of the Halbach array of this motor was determined.Based on this structure,the influences of permanent magnet material,permanent magnet thickness,air gap width,and stator slot opening width on the performance of the motor were studied.To optimize the output torque,cogging torque,and torque fluctuation,Taguchi local optimization algorithm was used to study the influence ratio of each parameter on motor performance,and the parameters were optimized;then the two-dimensional finite element simulation model of the optimized motor was established and simulated.By comparing the simulation results with that of the original motor,it was found that the back electromotive force,sine flux linkage,the rated output torque and efficiency were improved.The fundamental amplitude of air gap magnetic density would was increased,and the harmonic distortion rate was reduced with a few negative impacts on the quality the optimized motor.Additionally,compared with the original motor,the power density was improved.Because of the heat dissipation problem resulted from the special position of the hub motor,a three-dimensional simulation model of the cooling system and temperature field of the optimized motor was established and the flow field analysis and temperature field analysis were carried out based on the Ansys Workbench simulation software.Through the distribution of temperature field,it can be seen that the highest temperature of the motor appeared in the stator winding,and its average temperature was also higher than other components,but lower than the highest upper limit of the motor,which showed that the temperature rise of the motor under the cooling system was reasonable and the optimized motor can run smoothly. |
PDF Full Text Request