Multi-tap transformer topologies for improved tolerance against misalignment in inductive power transfer systems for electric vehicles

In this contribution the concept of a multi-tap transformer topology for SS-compensated Inductive Power Transfer (IPT) systems is proposed. The objective is an improvement in terms of overall efficiency and maximum tolerable misalignment of the secondary transformer coil that is assumed to be mounted underneath an electric vehicle (EV). In a first step mathematical expressions are derived to describe the fundamental relations in a multi-tap transformer system. It is shown that the resonant current can be significantly reduced with the proposed concept, so that the required power semiconductor rating can be decreased accordingly. In a next step the multi-tap transformer concept is validated in simulation and practice. This is done exemplarily by means of a 6 kW IPT system with an input voltage of 400 VDC that is built in the laboratory. It is demonstrated that the overall efficiency can be increased significantly using a dual-tap transformer with two taps on the primary side compared to a conventional single-tap transformer.