A Sleeve-Type Capacitive Power Transfer System With Different Coupling Arrangements for Rotary Application

This paper presents a sleeve-type capacitive power transfer (CPT) system for contactless rotary applications. Sleeve-type capacitive couplers with different coupling arrangements between primary and secondary metal sleeves are proposed in this research, which lead to different coupling characteristics with positive, zero, and negative coupling coefficients. The effect of coupling coefficient variations caused by both the power transfer distance and the ratio between the overlapping length and the height of outer sleeves is analyzed. Combining the sleeve-type coupler, the CPT system is developed with a double-sided LC-compensated network and half-bridge inverter. For the CPT systems with positive and negative coupling coefficients, parameter design methods are presented to determine system parameters to achieve zero phase angle (ZPA) condition under the same output power. Then overall system performances of the CPT systems with local maximum positive and local minimum negative coupling coefficients are analyzed and compared by simulation in MATLAB/Simulink and Maxwell. Finally, an experimental prototype is constructed, which has demonstrated a power efficiency of 85.3% at 100.8 W. Simulation and experimental results show that the CPT system with local minimum negative coupling coefficient has clear advantages in increasing transfer distance, reducing voltage on sleeves, suppressing fringing electric field, and improving power density.