Design modifications for improving modulation flux capability of consequent-pole vernier-PM machine in comparison to conventional vernier-PM machines

The Vernier PM (VPM) machine is known as a high-torque and low-speed drive solution suitable for direct-drive applications such as electric vehicles and wind turbines. The Consequent-Pole VPM (CP-VPM) machine is a special structure of VPM that introduces high-torque density as the conventional VPM by incorporating the significantly lower volume of PM materials. Despite the large body of recent research and many experiments concerning the conventional structure, the CP-VPM machine has received attention only by few publications. The paper presented the electromagnetic principles of flux modulation in the CP-VPM machine. The quantities of machine operation were evaluated using analytical equations and the performance of the mentioned machine was compared with that of the conventional machine. It was concluded that the torque density and back EMF of the proposed machine were much larger than those of the conventional machine and the torque pulsation magnitude was lower. However, the power factor was undesirably reduced due to higher spatial harmonic distortion of the CP rotor magnetic field and the presence of magnetic field components, which would not contribute to the flux modulation. Based on the spatial harmonic analysis, design modifications made for enhancing the operational characteristics of the CP-VPM machine were proposed and their effectiveness was verified by comparing the 2D-FE results with those of the conventional VPM machines. (C) 2020 Sharif University of Technology. All rights reserved.