Calculation Method for Distributed Capacitance of Planar Spiral Coils in MHz Wireless Power Transfer System

The presence of high-frequency parameters in the magnetic coupling coil of the MHz class Wireless Power Transfer (WPT) system significantly affects the transmission performance of the system and poses a challenge to the advancement of high-frequency WPT technology. Through the circuit response model of the S/S type WPT system, it finds that the high-frequency capacitance of the coil impacts the constant current output characteristics of the system. Therefore, it is imperative to establish a calculation model for the high-frequency distributed capacitance of the planar coil. This paper presents a novel approach to computing the inter-turn capacitance of a coil based on the electromagnetic field theory. The method is capable of accurately determining the capacitance between non-adjacent turns by applying a charge to the coil, thereby enhancing the precision of the distributed capacitance calculation. The proposed technique's accuracy is validated through the finite element simulation results.