Studies On Electromagnetic Design And Inductance Parameter Of Six-phase Permanent Magnet Synchronous Motor

With dual advantages of both multi-phase motor and permanent magnet synchronous motor(PMSM), multiphase PMSM has a significant advantage in the field of electric power transmission, and has good prospects. The research on PMSM design and control mainly concentrated on electromagnetic design, torque performance and accurately calculate the inductance parameters. Electromagnetic design and inductance parameter become more complex on account of the increase of multiphase PMSM.This study firstly analyzed and summarized the relationships and characteristics of multi-phase motor’s winding and phase belts; deduced the expressions in time and space of MMF of multi-phase winding, and the rule of harmonic distribution. Especially focused on comparison of MMF harmonic synthesis of the six-phase and three-phase windings. The results of this study show that any symmetric and semi-symmetric windings on the spatial distribution is symmetrical; each phase excitation applied at the time is also symmetrical; with the increase of phase belts, harmonic MMF were significantly reduced, adverse effects on the operation of electrical machines are also reduced.Secondly, this study established a multi-phase PMSM mathematical model in the stationary coordinate system. And deduced coordinate transformation of six-phase permanent magnet synchronous motor. Through the coordinate transformation, this research obtained inductance parameter and mathematical model of six-phase motor in the traditional and cross-coupling dq shaft coordinate system respectively.Thirdly, with the reference of traditional electromagnetic design method of three-phase permanent magnet synchronous motor, the author made the critical steps and design such as size calculation, pole-slot ration winding design, combining the theory and characteristics of multi-phase windings. This study established a six-phase PMSM model by using Ansoft Maxwell. Simulation analysis of the sample PMSM is made at both no-load and load conditions, and the results are compared with those of a three-phase PMSM of the same size. This research also injected different amplitude harmonic voltages into the six-phase motor and analyzed their effects on the electric current, torque and other parameters. The findings of this study suggested that the six-phase winding motor design can improve the utilization rate of the windings, and effectively reduce copper consumption, additional iron consumption, torque ripple; In the case of half- or full-bridge inverters with no isolated neutral point, injecting the specific amplitude 3,5 harmonic voltage into six-phase motor, can effectively improve the torque density and reduce the current peak torque ripple suppression, thereby improving the utilization and reliability of power devices.Finally, this study calculated and analyzed the law of the six-phase motor’s inductance parameter change with the dq axis current, and explored the constituent components of the six-phase motor’s torque and the effects of the six-phase motor inductance on electromagnetic torque by using the mathematical model of in the cross-coupling shaft dq coordinate system. Also, the research compared the similarities and differences of inductance parameter and torque component between six-phase and three-phase motor. The results of this research found that the inductance parameter of the two motors with same magnetic structure changes in the same law with the variation of dq axis electric current, and suggested that on the condition of large torque output, the proportion of the two motors reluctance torque will be reduced due to magnetic saturation, especially cross-coupling reluctance torque can be reduced to a negative value, causing the motor unit current output is decreased, but this time a proportion of reluctance torque of the six-phase motor was slightly higher than that of the three-phase motor.