Investigation of Multiple Decoupled Coil Primary Pad Topologies in Lumped IPT Systems for Interoperable Electric Vehicle Charging

Today many vehicle manufacturers are interested in an inductive power transfer system design with a secondary side that is simple and low in cost, weight, and size. To achieve this, a more sophisticated primary side design is required to ensure interoperability with various magnetic topologies. Simple secondary pads such as the circular pad and double-D pad (DDP) (similar to the flat solenoid) can only couple either the perpendicular or parallel component of flux entering the surface of the pad respectively. This paper investigates using various known multiple coil pad designs as the primary that can be switched between various excitation modes during operation, without making tuning or other expensive adjustments. The primary pads considered here include; the DDP, the double-D quadrature pad (DDQP) and the bipolar pad (BPP). Results show that the mutually coupled structure of the DDP primary makes it a poor choice for interoperability, whereas the DDQP and BPP are able to achieve good results because of the decoupled coil structures inherent in their design. The DDQP has improved leakage characteristics while the BPP shows better interoperability characteristics with improved material usage efficiency and is easy to drive because of its identical coil structures.