Research On The Design Of FSCW-PMSM For Electric Vehicle Based On Tangential Hybrid Magnet Rotor Structure

Fractional-slot concentrated-winding permanent magnet synchronous motors(FSCW-PMSMs)have been widely used in the field of electric vehicles(EVs)due to their high-power density,high efficiency,short end turns,low cogging toque,good flux weakening capability and so on.However,these machines usually exhibit high amount of magneto-motive force(MMF)harmonics.Under high-speed conditions,it will produce very serious eddy current loss on the magnet,particularly in Nd Fe B magnets which has high conductivity.Therefore,this paper proposes a new type of PMSM based on the tangential hybrid magnet rotor structure with the support of the national key research and development project: "Multi-domain optimization design and control of high-efficiency low-noise wheel hub motor"(No: 2018YFB0104801),researching the new structure motor on high-speed magnet eddy current loss,harmonic suppression,intelligent optimization and joint simulation.According to the performance index of the drive motor for EVs,an 12 slots/8poles IPMSM using Nd Fe B is taken as an example to analyze the eddy current loss of the magnet.Furthermore,utilizing the low-cost,high-resistivity,and low-loss characteristics of ferrite,which are reasonably added to the rotor’s D and Q axis magnetic flux paths to form FSCW Tangential Hybrid PMSM(FTHM).The new structure has lower magnet eddy current loss and greater salient pole ratio at high speed,and at the same time greatly reduces the amount of rare earth permanent magnet materials,which significantly improves the cost-effectiveness of PMSM.Secondly,for FTHM,the increase in torque pulsation and local iron loss caused by the decrease in the amount of rare earth permanent magnet materials are used to study the influence of the mixing ratio,magnet size,magnet position and other parameter changes on the performance of the motor.Subsequently,studying the auxiliary slot structure on the outer surface of the rotor of the new structure motor.Research shows that a reasonable auxiliary slot structure can effectively weaken the specific sub-harmonic magnitude of the air gap magnetic density,reduce the cogging torque,and optimize the torque ripple.Furthermore,in order to improve the overall optimization effect of the motor,considering the mutual influence of different structural parameters,the JMAG multi-objective genetic algorithm is selected to perform global optimization on the FTHM,and the FTHM is optimized and the optimal solution is extracted.The 3D finite element loss analysis of the optimized FTHM verifies the effectiveness of the new tangential hybrid structure in suppressing the high-speed eddy current loss of magnets.Due to the poor anti-demagnetization ability of ferrite,taking the permanent magnet demagnetization analysis of FTHM under different temperatures and different working conditions.Finally,build a joint simulation platform based on JMAG-PSPICE-MATLAB.Use this platform to carry out steady-state and dynamic simulation experiments on the all-Nd Fe B structure and the optimized FTHM.The phase current of the motor in the joint simulation experiment is used as the excitation source of the 3D finite element model,and the current time harmonics are taken for the motor.The influence of loss further verifies the performance superiority of the new tangential hybrid structure motor.