Study of Electric and Magnetic Field Distributions between Two Coupled Plates for Capacitive Power Transfer by Simulation and Practical Measurements

Capacitive power transfer (CPT) has been developed as an alternative technology to Inductive Power Transfer (IPT) for achieving Wireless Power Transfer (WPT). CPT is based on electric field coupling, but it would be useful to analyze the magnetic field distribution too to understand how power is transferred across the coupling plates. This paper presents a fundamental study of electric and magnetic fields between two coupled plates for capacitive power transfer. Methods for measuring the electric and magnetic fields are proposed based on general theoretical analysis, followed by field simulation studies using CST (Computer Simulation Technology) for comparison. Both simulation and practical results show that the electric field magnitude is approximately constant in the middle area of the two coupled plates, but it gets higher near the edges of the coupled plates due to the fringing effect, forming an hourglass shape between the plates. It is also found that the measured magnetic field inside the plates is very low and increases gradually when the test point is placed close to the lead wires of the power supply. The practical measurement results are in a good agreement with CST simulation. The findings regarding the electric and magnetic field distributions from this research are useful for investigating the power transfer mechanism and guiding the practical capacitive coupling design of a CPT system.