| Rare earth permanent magnet synchronous motor(PMSM)is widely used in the field of new energy vehicles due to its high efficiency,high power factor and superior speed performance.However,the use of rare earth permanent magnet materials in this type of motor is relatively high,and the cost of motor permanent magnets has also increased significantly.Therefore,this paper proposes a new type of permanent magnet synchronous motor based on 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),the research focuses on motor cost performance,harmonic content,iron loss parameters and joint simulation.Firstly,a "U" plus "one" type full Nd Fe B PMSM was selected based on the main performance indicators of the drive motor for new energy electric vehicles.The finite element analysis shows that the motor has the problems of high permanent magnet cost,large torque ripple and strong cogging effect.In view of this,the hybrid magnet motor(HM motor)based on Nd Fe B and ferrite is proposed.At the same time,the material mixing method,magnetic pole size and magnetic isolation bridge are optimized to effectively improve the ratio of salient pole and the utilization of reluctance torque,which significantly improves the cost performance of the motor.Secondly,the back-EMF harmonics and torque ripple of the new permanent magnet synchronous motor were effectively reduced by further optimizing the mixing ratio and position placement parameters of the tangential magnet.Subsequently,a comprehensive performance analysis and comparison of Tangential Hybrid Magnet Motor(THM motor)was performed.Compared with HM motors,the harmonics of THM motors were effectively weakened,and torque,air gap magnetic density,and iron loss has improved significantly;Compared with full Nd Fe B motor,the cost of permanent magnet of THM motor was still greatly reduced,cogging torque,torque ripple and no-load iron loss were effectively suppressed,and the average torque,airgap magnetic density and back-EMF were only slightly reduced.At the same time,the suppression effect of segment skew pole on harmonics and torque ripple was analyzed,and the optimal axial segment number and corresponding optimal skew pole angle were obtained.Due to the weak anti-demagnetization ability of ferrite,this paper analyzed the permanent magnet demagnetization of THM motors.Thirdly,the no-load and rated load iron loss of each motor were analyzed and compared in different categories.In order to consider the influence of time harmonic on iron loss,the rated point simulation of hybrid magnet motor under inverter power supply was studied.The fitting of iron loss coefficients for a wide frequency range was performed on the existing frequency B-P curves of silicon steel sheet,and it was applied to the calculation of stator iron loss of THM motors.The regional key point method was used to calculate iron loss,the maximum error between the calculated value of iron loss and the finite element value was 0.65% at the basic frequency and5.3% after taking into account high-frequency,which verified the accuracy and practicability of the iron loss coefficient fitting method and the iron loss calculation method.The 3D finite element simulation was performed on the THM motor to obtain a more accurate loss distribution,the iron loss calculation results of 2D finite element were compared.At the same time,the magnitude and distribution of magnetic steel eddy current loss were analyzed in detail.Finally,a joint simulation platform based on JMAG,PSPICE and MATLAB was built to simulate the steady and dynamic performance of the full Nd Fe B motor and the new motor.The experimental results verified the feasibility and effectiveness of the proposed motor. |
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