A Novel Antiaxial-Misalignment Capacitive Coupler for Rotary Power Transfer

Axial-misalignment in rotary capacitive power transfer (CPT) systems causes variation in the mutual-capacitance C_M, which may result in resonant detuning and output fluctuation. This article proposes an opposite-side disk coupler (ODC) based on a complementary capacitance-path mechanism. In the proposed ODC, axial-misalignment produces opposite variations in the dominant capacitance paths. Under the ideal parallel-plate assumption, these variations theoretically cancel under the designed geometric condition; in the practical coupler, the proposed mechanism substantially suppresses the axial-misalignment induced variation of C_M. In addition, a single ODC unit inherently exhibits a self-capacitance enhancement characteristic. Through multiunit reuse, this characteristic is extended to both ports, enabling the adopted double-sided LC compensation topology to be implemented without external compensation capacitors. A 1-MHz prototype is developed for experimental verification. Under 50% axial-misalignment, the measured output-current variation is 2.8%, while the system delivers 1.06 kW with a DC-DC efficiency of 92.2%. Within the evaluated axial-misalignment range, the variation of C_M is reduced by 91.1% relative to that of the conventional disk coupler. Moreover, the proposed coupler achieves a plate-utilization index r_CM of 1232.3, demonstrating its suitability for compact rotary CPT systems requiring strong axial-misalignment tolerance.