Basic Analysis of Coupler Loss in Capacitive Power Transfer Systems

Previous studies on Capacitive Power Transfer (CPT) reported very different levels of coupler loss percentages concerning the total system loss. This paper investigates different types of coupler losses in a CPT system and presents some detailed analyses to find out the actual situation. The coupler loss is categorised into innate loss and region loss, depending on where the loss occurs. The former is about the loss in the coupler structure itself, which includes conduction loss and dielectric loss in between the coupling plates. The latter is about the loss caused by the interactions between CPT couplers and the surrounding environment. Those interactions provide alternative paths for currents to "escape" from the original CPT systems, thus leading to additional power loss. Couplers with different coupling strengths are investigated by experimental studies, and extensive simulations studies are carried out to analyze the percentages of the two types of power losses. It is found that the region loss dominates the total coupler loss of a loosely coupled CPT system, and a higher leakage current can cause a severe performance deterioration in power transfer efficiency.