Permanent Magnet Vernier Machines: A Review

Permanent-magnet Vernier machines (PMVMs) gained a lot of interest over the past couple of decades. This is mainly due to their high torque density enabled by magnetic gearing effect. This paper will provide a thorough review of recent advances in PMVMs. This review will cover principle of operation and nature of magnetic gearing in PMVMs, and better understanding of novel PMVMs topologies using different winding configuration as well as different modulation poles and rotor structures. Detailed discussions on choice of gear ratio/slot-pole combinations, design optimization and role of advanced materials in PMVMs will be presented. This will provide an update on the current state of the art as well as future areas of research. Furthermore, design issues, fault tolerance as well as cost reduction will be discussed highlighting the gap between the current state of the art and what is needed in practical applications.