Hexagonal Geometry Coil for a WPT High-Power Fast Charging Application

Abstract

Magnetic cores for inductive wireless power transfer (WPT) have many applications and regularly use E, U, pot, and planar/circular shape coils. The systems for wireless energy transfer are not conveniently in the power levels required for some applications, as for the electric vehicle (EV), for instance, and there is a necessity to study different coil geometries to improve its efficiency and decrease its volume and weight. In this article, we presented a new hexagonal-geometry coil design placed in the secondary of a WPT, and the tests demonstrate that a Type-II system compliance requirements (SAE J2954) can be accomplished with greater efficiency and lighter weight compared to the circular coil. Finite element analyses accurately allow predicting the mutual inductance and achieving the optimal coil parameters and an experimental setup allows obtaining a rated power output of 7.7 kW operating at 85 kHz. The experimental testbed comprises a series-series resonance compensation circuit, a spiral coil used as primary, the proposed hexagonal pad for the secondary coil, and an ac-output, half-bridge inverter as a source, achieving a lighter, and efficient system in a realist scenario.