Design and Construction of a 100 W Wireless Charger for an E-Scooter at 6.78 MHz

This paper demonstrates the design and construction of a multi-MHz inductive power transfer (IPT) system with air-core coils, integrated in an electric scooter, whose on-board battery is required to be charged at 100 W. With respect to the magnetics, integration challenges arise due to the proximity of the receive coil to the steel frame of the scooter, which significantly change the coil and link parameters from those calculated and observed in air. The design of the power electronic circuits at both ends of the system are detailed and explained. The battery of the electric scooter was able to be charged with a de-to-battery efficiency of 65.6 % with an air-gap of 17 cm, where most of the losses are found in the battery charger. A losses distribution diagram of the entire system is included. Simulations of human exposure to the electromagnetic fields demonstrate that the designed system is well within the general exposure limits given by ICNIRP.