Air Gap-Integrated Capacitive Power Transfer System for Electrically Excited Synchronous Machine

The development of cost-effective electric vehicles has renewed interest in the Wound Field Synchronous Machines (WFSMs) for traction applications. However, efficiency and reliability issues of the brushes for rotor excitation present a bottleneck for adopting WFSMs. To overcome these challenges, the application of wireless power transfer systems for field excitation has recently been explored. This thesis 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 coupling plates, constructed of magnetic material, constitute the coupling structure. 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 and different topologies of matching networks are compared. A prototype with a stator and a Computer Numerical Control (CNC) fabricated fictitious rotor is developed to test the proposed CPT system. Experimental verification of the proposed power transfer system shows an efficiency of 81.3% with a transferred power of 64 W at 2 MHz frequency.