High-Efficiency Wireless Power Transfer Based on Nonlinear Planar Spiral Coils

While wireless communications are well established, Wireless Power Transfer (WPT), particularly Inductive Power Transfer (IPT), has recently gained renewed interest. This work not only derives the integral functional for the coupling coefficient of generalized spiral coils in the IPT system, but also optimizes it for Nonlinear Planar Spiral Coils (NPSCs), addressing the inefficiencies observed in conventional IPT systems using linear spirals. The optimal NPSCs achieve a coupling coefficient that is 66% higher than that of conventional spiral coils and demonstrate a coupling efficiency of 93% at a transmission distance of coil diameter, significantly improving IPT system performance.