Wireless Charging—A Multi Coil System for Different Ground Clearances

Charging electric vehicles wirelessly with inductive energy transfer systems has meanwhile become ready for a widespread practical use. A well known problem is the variation in the magnetic coupling due to the different positions of the vehicle and the ground assembly unit relative to each other. In this work, a method is presented to maintain the input and output current as well as the voltage while changing the ground clearance. For this purpose, a multi-coil system, based on three stacked circular coils, is used. The system has been calculated, simulated and a demonstrator has been built up. Furthermore, a lean system to determine the coupling factor is presented. Measurements, which are showing the satisfactory results, complete the work.