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    Power Electronics for Hybrid and Electric Vehicles

    T08.8 - Rotary Transformer for Wound Rotor Synchronous Motors

    Tuesday, March 24, 2026
    11:20 AM - 11:40 AM CT
    Location: 217D
    In this digest, we present a resonant rotary transformer (RT) with an integrated rectifier for brush-less excitation of wound rotor synchronous motors in electric vehicle applications. The stationary primary employs an LCC resonant tank with litz-wire winding and high-frequency ferrite, while the high-speed rotating secondary integrates the coil and rectifier on a mechanically robust, high-temperature PCB capable of withstanding up to 23,000 rpm. The system is comprehensively analyzed and optimized for electrical, thermal, and mechanical performance. A laboratory prototype was built and tested up to 15,000 rpm and up to 27 A rotor current. The system achieved a maximum efficiency of 96% at 7 kW output power, confirming both high efficiency and mechanical reliability.