Feasibility study on bipolar pads for efficient wireless power chargers

This paper presents the feasibility study of bipolar pads for extremely high efficiency wireless battery chargers used in electric vehicle (EV) and plug-in hybrid electric vehicle (PHEV) applications. Due to the unconventional flux distribution in this system, a 3D finite element method was employed for its design and analysis. The importance of misalignment tolerance in this system is analyzed and discussed. The distinct features of rectangular bipolar topology have been exploited to develop the pads for wireless battery chargers for EV applications. An 8kW wireless charger prototype with 200mm gap and ±300mm horizontal misalignment tolerance has been fabricated and tested. From optimal to critical points of horizontal misalignments, the coupling coefficient of this system can maintain from 18.8% to 31.1%. With a 200mm gap, the charger efficiently transfers energy with an efficiency of 95.66% (overall DC to DC) at the desired position while still maintains at 95.39% efficiency with a ±300mm horizontal misalignment.