A Comparative Study of Capacitive Couplers in Wireless Power Transfer

The capacitive power transfer (CPT) technology is mainly used in battery charging systems. The capacitive coupler plays a critical role in a CPT system. The capacitive coupler can be classified into two sections, unipolar and bipolar. The bipolar includes row and column couplers. This paper aims to analyse and compare the capacitive couplers. The plates dimension, plates spacing, and misalignment characteristics were analysed for each coupler. These parameters were considered as criteria to evaluate and compare the capacitive couplers in terms of investigation their effects on the coupling capacitance (C
_m
). All couplers were examined in a CPT system with a dual LCL compensation circuit topology. The voltage stress of the components, power density, electric field emissions, and safety distance were evaluated. The results showed that the most components in a CPT system of a unipolar coupler have the highest voltage stress among other couplers. This indicates that the CPT system with the unipolar coupler requires passive components with high VA ratings, and high insulation requirements are necessary. Likewise, it was found that the highest power density and lowest safety distance among the other couplers were achieved by the unipolar and column couplers, respectively.