Optimization design and torque performance research of interior permanent magnet synchronous motors

The high magnetic saturation at flux isolation bridge of interior permanent magnet synchronous motor (IPMSM) enriches the harmonic content of air gap flux density. When IPMSM operates at low speeds, these harmonics of air gap flux density increase torque ripple. An IPMSM with I2V type is proposed to further improve sine degree of no-load air gap flux density, achieving high torque density and low torque ripple. The V type, IV type and I2V type are selected as the comparative objects for optimization research, the established 2D parameterized finite element analysis (FEA) models are used to optimize and analyze opening angle and pole arc angle of the first layer of permanent magnet, which have the greatest impact on the electromagnetic performance of IPMSMs. Under the constraint of same volume of permanent magnets, the optimization models of three different rotor structures are determined ultimately. The no-load air gap flux density waveforms and harmonic contents of IPMSM with three different optimized rotor topology structures are analyzed and compared, the results show that the no-load air gap flux density of I2V type proposed in this paper have the lowest total harmonic distortion rate (THD).The torque performances are analyzed and compared with the other two, the results show that torque performances of I2V type are superior to the other two as the amount of permanent magnet is slightly reduced. Aiming at problems that the torque ripple of I2V type is greater than the other two under rated operating conditions, this paper proposes a simple and effective method to add a set of circular flux isolation holes under each pole of the rotor, and the position and diameter of flux isolation holes are adjusted to further optimize the magnetic circuit in order to reduce torque ripple. The optimization results showed that reduction ratio of torque ripple with optimized I2V type is 67.3% under rated operating conditions. The I2V prototype is processed and manufactured and a prototype experimental platform is built. Experimental verifications are conducted on the torque, external characteristics. The test results are basically consistent with the FEA results, proving the accuracy of the analysis and modeling, as well as the effectiveness of simulation calculations in this paper.