Safety-Oriented Design and Analysis of Dielectric Materials and Plate Geometry in Capacitive Wireless Power Transfer Systems

Abstract

Capacitive wireless power transfer (CPT) technology is emerging as a promising alternative to inductive wireless power transfer (IPT) due to low cost, lightweight and electromagnetic compatibility advantages. CPT, however, has limitations in terms of the power transfer density and operation safety. The use of dielectric materials, both as transfer media and coatings, has an important role to overcome these limitations, making dielectric material selection as an important design approach. This paper presents a detailed safety-oriented design and analysis of CPT systems focusing on how dielectric materials influence the performance and safety of CPT systems. A four-plate coupler configuration was modeled using finite element analysis in ANSYS Maxwell to investigate a wide range of dielectric materials, coating strategies and thicknesses, and plate shapes across application scales ranging from low-power applications such as consumer electronics to high-power applications such as electric vehicles (EV). Particular emphasis is placed on overlooked safety hazards associated with localized electric field intensification caused by geometric discontinuities, fringing fields, dielectric permittivity mismatch, and triple-junction phenomena. In order to quantitatively assess breakdown risks in general CPT systems, two new safety metrics are introduced to CPT research. Simulation results demonstrate that circular plate geometries offer superior field uniformity and reduced risk of premature breakdown, improving the safety margin up to three times relative to square geometries. High-permittivity solid media improve both efficiency and safety in small-gap systems. By contrast, high-permittivity coatings can exacerbate edge-related breakdown risk, especially when they are applied to sharp-cornered plates in either small or large air gaps. However, coatings of moderate permittivity are shown to be effective in reducing field concentrations. In addition, the dangerous triple junction effects can be added or removed depending on the used coating strategy. The study findings provide useful design considerations for use in the different practical applications to realize safer, more reliable and high performance CPT systems.