Optimization Design Of Torque Ripple Suppression For Surface Mounted Permanent Magnet Synchronous Motor

With the rapid development of national technology in the transportation industry,electrical industry, aerospace field and other main related domains, the increasing use of rare earth permanent magnet materials and the progress of motor manufacturing technology have created a perfect background for the permanent magnet synchronous motor design, manufacturing and application recently. Permanent magnet synchronous motor (PMSM) has been widely used because of its flexibility, high efficiency and high torque density. Although the excellent performance of permanent magnet synchronous motor (PMSM) can meet the needs of the majority of the production field, in some high-performance-required occasion it can not receive the expected effect. For example the high-performance and high-precision servo system where the output magnetic torque of motor needs to be stable. As a common problem of permanent magnet synchronous motor (PMSM), torque ripple will cause the motor vibration and noise.Therefore the suppression of torque ripple has attracted increasing attention among motor designers.Considering the existence of torque ripple in the surface mounted permanent magnet synchronous motor (PMSM), the main research work of this paper is as follows:(1)Conducting a relatively comprehensive overview of the current domestic and foreign torque ripple suppression methods, introducing the basic structure of permanent magnet motor, deducing the cogging torque and torque ripple expression, and elaborating the detailed mechanism of torque ripple.(2)Applying a series of parameters and structure optimization methods to suppress the cogging torque and reduce torque ripple, combined with cogging torque expression the optimized design of motor is conducted. Then the harmonic analysis of air gap flux density in the motor stator and rotor was carried out on MATLAB.(3)A novel permanent magnet shape optimization scheme is proposed. Combined with the simulation analysis of ANSYS Maxwell results, the optimal permanent magnet shape is obtained. The finite element verification proves the effectiveness of the proposed scheme.(4)Double-phase-shifted 30-degree six-phase fault-tolerant permanent magnet synchronous motor is designed and verified with finite element method in this paper.Then, without any control strategy, conducting the output torque simulation analysis of six-phase fault-tolerant permanent magnet synchronous motor under normal and fault occasion. The parameters attained optimal design for the sake of reducing torque ripple in fault occasion and the motor structure optimization. The torque ripple of optimized motor under normal and fault condition is reduced.(5)This paper suggests that the expensive rare earth materials which has the benefits of high remanence, high coercivity, high magnetic energy product is employed as the main pole, and the cheap ferrite materials which is easily manufactured and low remanence is used as the auxiliary pole. Based on the energy method and Fourier expansion, the cogging torque expression is derived under the circumstance that the pole arc to pole pitch ratio of main pole is an arbitrary value and that of auxiliary pole is changed. The way to calculate pole arc to pole pitch ratio of auxiliary pole is given, and the finite element experiment is conducted.The experiment results indicate that the three optimization schemes proposed to suppress motor cogging torque and reduce torque ripple can attain obvious achievements.