Fringing Effect Analysis of Parallel Plate Capacitors for Capacitive Power Transfer Application

The classical formula of a parallel plate capacitor (PP-Cap) does not take fringing effects into consideration, which assumes that the side length of a PP-Cap is by far larger than the distance between the two plates. However, for capacitive power transfer applications, especially those designed for electric vehicle charging, this assumption no longer holds since the distance can be as large as 150 mm. Based on conformal mapping, the corrected or improved formula of PP-Cap with the consideration of fringing effect can be obtained; nevertheless, some approximations are introduced for the convenience of calculation. By finite element method (FEM) simulation and experimental measurement, this paper investigates the influencing factors of large distance PP-Cap especially in the capacitive power transfer application and thereby the proposed formula with improved accuracy is verified.