Performance Improvement of Different Resonant Inductive Couplers Used for Wireless Power Transfer

This article experimentally investigates the performance of spiral coil configurations commonly used in magnetic resonant wireless power transfer (WPT) inductive couplers. Three different designs are illustrated, namely, single-core, twin-core “bifilar,” and single-core coaxial cable spiral coils. The major concern is the improvement of both the voltage gain and transmitted power efficiency at different distances between the transmitter and receiver coils. Moreover, the performance analysis of the experimental setup is compared with the results of three-dimensional frequency-domain extensive finite element (FE) simulations of the COMSOL Multiphysics package, through radio frequency modeling of coupled electromagnetic waves and electric circuits. Such FE simulations help in realizing the relative effect of inherent parameters that are hard to be investigated through experimental measurement without disturbing the WPT system. Additionally, PSPICE is used to facilitate the performance investigation of such magnetic resonant WPT couplers. Results reveal that adding the ferrite sheets to single-core spiral coils helps in improving the WPT efficiency. Shorted bifilar wound flat spiral coils show higher WPT efficiency at short coil separation due to their intrinsic self-capacitance and high self-inductance. Self-resonating “capacitorless,” single-core coaxial cable wound flat spiral coils show an enhanced performance improvement when compared with the other two designs.