Groove Disk Capacitive Coupler for Wireless Rotor Excitation in Wound Field Synchronous Machines

Permanent magnet motors are widely used in scientific and technological production due to their advantages of high torque density and high transfer efficiency. However, the depletion of natural resources has led to the production of rare-earth materials that are far from meeting the needs of actual production, and the future development prospects of rare-earth materials are limited. As a result, motors that do not rely on rare-earth materials, such as wound field synchronous machines (WFSM), are of interest in scenarios such as high-power generation and traction drives. However, conventional excitation methods require carbon brushes or slip rings for contact power supply, which is less reliable. In recent years, the rapid development of capacitive power transfer has provided a new way for motor excitation, and has the opportunity to become a viable alternative to inductive power transfer technology. In this paper, for WFSM rotor excitation, a new type of coupler for rotating conditions is designed: groove disk type coupler. Using finite element analysis, this coupler is compared with the parallel plate coupler, and it is verified that the groove disk type coupler can form a larger coupling capacitance in air and possesses a stronger anti-offset characteristics.