Due to weak coupling of loosely coupled transformer (LCT) in inductive power transfer (IPT) system, misalignment between primary and secondary coils can reduce the efficiency of IPT system seriously, which inevitably results in preventing application of IPT system in electric vehicle field. To improve the misalignment tolerance of the IPT system, a three-coil LCT with a large intermediate coil and detuned compensation are proposed and analyzed comprehensively. Firstly, analytical model is established and related equations are derived. Then to study the optimal compensation parameters, coil currents are simulated by finite element analysis (FEA) under misalignment condition with different compensation parameters, and the efficiency and output power are also compared. Furthermore, intermediate coil size is determined, and an optimization strategy for IPT system with three-coil LCT is proposed. Finally, it is verified on an IPT prototype that three-coil LCT with a large intermediate coil can improve the misalignment tolerance.
