Rounded-Corner Plate Geometry for Edge Effects Mitigation in Capacitive Wireless Power Transfer Systems

The capacitive wireless power transfer (CPT) systems are limited by the low coupling capacitance and high voltage stress levels constraints. The localized electric field (E/F) intensifications restrict the safe voltage levels and increase the risk of premature breakdown. The geometry of capacitive coupler plates plays an important role in CPT system’s safety. A rounded-corner square plate geometry is proposed in this study as a drop in design alternative to conventional sharp corner square plates to enhance safety and avoid dielectric breakdown due to the intensified electric fringing fields at the sharp corners of plates while preserving compact spatial utilization. A finite element method (FEM) study was conducted using ANSYS Maxwell 3D for four-plate parallel capacitive couplers using square, equivalent-area circular, and rounded-corner square plates. For each geometry, three plate scales were investigated with side lengths of 100, 300, and 610 mm, different transfer distance ranges (1-10, 30-50, and 120-180 mm), and rounding radii from 5% to 50% of the plate side length (L). Results reveal that a small rounding radius of r c =5%L reduces the peak E/F by approximately 20-36% relative to square plates with only 0.3% reduction in mutual capacitance (C m ). The reduction in peak E/F reaches approximately 38-52% at r c =25%L, while the reduction in C m remains about 5%. A net-benefit metric, defined as the difference between peak E/F reduction and C m reduction ratios, identified the optimum r c of 20%L, 15%L and 15%L for the examined small, medium and large-scale plates, respectively. The study findings demonstrate that the rounded-corner geometry offers a practical low-cost design improvement for CPT systems as an alternative to the traditional sharp-corner plates in terms of safety, efficiency, and spatial utilization.