An Integrated Capacitive Power Transfer System for Field Excitation of Wound Field Synchronous Machine

The development of cost-effective electric vehicles has renewed interest in Wound Field Synchronous Machines (WFSMs) for traction applications. However, low efficiency and frequent maintenance of the brushes prevent a wider adoption of WFSMs. To overcome these challenges, the application of wireless power transfer systems for field excitation has recently been explored. This paper presents an integrated Capacitive Power Transfer (CPT) system for field excitation of WFSMs. The proposed coupling structure for CPT is placed within the air gap of the machine. The CPT coupling plates are made of magnetic material. The novelty of the proposed approach is that the presented design allows power transfer to the rotor without increasing the active volume of the machine. A preliminary feasibility analysis of the system is performed through Finite Element Analysis (FEA) simulations. A prototype with a stator and a Computer Numerical Control (CNC) fabricated replica of a rotor is developed to test the proposed CPT system. Experimental verification of the proposed power transfer system demonstrates an efficiency of 81.3% with a transferred power of 64 W at 2 MHz frequency.