Optimization And Analysis Of Asymmetrical Hybrid Pole Permanent Magnet Motor For Electric Vehicle

With the advantages of low-carbon and environmental protection,electric vehicles have gained the key attention of many domestic and foreign automotive companies and research scholars.The power source of electric vehicles mainly relies on the drive motor,therefore,the drive motor characteristics directly determine the driving performance of electric vehicles.With the advantages of high efficiency,high power density,and reliable operation,pure rare earth permanent magnet motors have been widely used in the field of electric vehicle drive motors.However,the decrease in rare earth resources reserves has caused the price of rare earth materials to soar,resulting in the rising cost of pure rare earth permanent magnet motors,and the traditional pure rare earth permanent magnet motors have problems such as excessive cogging torque and poor sinusoidal of the no-load counter potential waveform.In this paper,a new asymmetric hybrid pole permanent magnet(AHPPM)motor is proposed.On the one hand,it improves the electromagnetic performance of the motor,and on the other hand,it reduces the consumption of rare earth materials while meeting the power requirements of the drive motor for electric vehicles.Firstly,this paper has determined the overall dimensions of the motor according to the motor design requirements for electric vehicles,established the motor equivalent magnetic circuit model,analyzed the effective flux distribution in the motor,and studied the interrelationship between the pole clamping angle and motor slot torque based on the energy method and Fourier decomposition method to verify the structural advantages of the motor.The electromagnetic performance of the motor under different pole-slot matching methods has been compared by the finite element method,and the pole-slot matching scheme of 8poles and 48 slots has been determined.On this basis,a suitable stator slot structure has been selected,and the initial design of the AHPPM motor structure has been completed.Secondly,to further improve the overall performance of the motor and reduce the consumption of rare-earth materials used in the motor,a parametric model of the AHPPM motor has been established,and the torque ripple,cogging torque,and no-load back EMF harmonic distortion rate have been selected as the optimization objectives,with the average output torque as the constraint,and a multi-objective hierarchical optimization method has been used for optimization.Sensitivity analysis was conducted on the studied motor parameters,and the optimization parameter stratification has been completed.The highsensitivity parameters were optimized using the response surface method,and the lowsensitivity parameters were optimized using the single-scan method,and the optimal motor parameters were obtained to achieve a comprehensive optimum among the optimization objectives.After optimization,the motor torque ripple is significantly reduced,the no-load back EMF waveform sinusoidality is improved,and the output performance of the whole machine is significantly improved.Then,a traditional pure rare earth permanent magnet(TPREPM)motor of the same size has been used as a reference motor,and the electromagnetic performance of the two motors has been compared and analyzed by finite element simulation.The demagnetization resistance has also been analyzed for ferrite materials.The results show that the AHPPM motor reduces the use of rare earth permanent magnet materials by 18.5% compared to the TPREPM motor and has better electromagnetic performance with guaranteed output torque.The analysis results verify the feasibility of this motor research method and optimization method.Meanwhile,the thermal analysis,structural strength,and motor vibration of the AHPPM motor have been analyzed to ensure the stability of the motor during operation.Finally,a 5k W AHPPM motor prototype has been fabricated according to the final dimensional parameters of the motor,and a prototype experimental platform has been built to verify the no-load and load characteristics of the prototype.The experimental results show that the experimental results measured by the experimental platform are consistent with the finite element simulation results,which further verifies the rationality and feasibility of the new structure proposed in this paper.