Analytical Investigation on the Power Factor of a Flux-Modulated Permanent-Magnet Synchronous Machine

Flux-modulated permanent-magnet synchronous machine (FM-PMSM) is characterized as a high-torque direct-drive electrical machine, but may suffer from the low power factor. This paper aims to investigate the issue of the low power factor in theory and explore the possibilities for improvement. An analytical model for the FM-PMSM is developed to obtain the magnetic field distribution, and its accuracy is verified by the finite-element method. On the basis of the developed analytical model, a fast approach is developed to predict the power factor of the FM-PMSM. The analytical results indicate that the low flux density in the inner air gap excited by the PMs is responsible for the low power factor. Finally, the influences of several key design parameters on the power factor are studied, and the FM-PMSM is optimized afterward. The results show that the power factor of the FM-PMSM could be improved by 20% in comparison with the initial design.