Improving Misalignment Tolerance for IPT System Using a Third-Coil

To improve misalignment tolerance for an inductive power transfer (IPT) system, a third-coil is employed to reversely connect with the primary coil of the loosely coupled transformer (LCT) in series. The LCT with a third-coil (LCT-TC) not only can improve the misalignment performance in x- and y-directions, but also does not affect the inherent output characteristics (such as constant current or voltage output) of original compensation topologies. In addition, the proposed approach can keep the IPT system operating with relatively high efficiency against misalignment. Then, a detailed design method of LCT-TC is presented. Finally, a double-side LCC-compensated IPT system is chosen as an example to verify the feasibility of proposed LCT-TC. A 3.4-kW prototype is constructed, and experimental results show that the proposed method has a good misalignment performance. The LCC-LCC IPT system with LCT-TC can retain 96% of the well-aligned power at 40% misalignment, and the end-to-end (dc-dc) overall system efficiency is at least 92%. Besides, the fluctuation of the output current is [-2%, 5%] while the load varies from 15 to 34 Ω within 40% misalignment.