Coil Orientation Impact on Efficiency in Double-Sided WPT with Magnetic Field Coupling

The coils used in magnetic field-coupled wireless power transfer (WPT) exhibit a higher absolute coupling coefficient when the transmission and reception directions are reversed. In contrast, magnetic field-coupled WPT, which generates a symmetrical magnetic field on both sides of the transmitting coil, enables simultaneous power delivery to coils on both sides. This study investigated the influence of coil orientation in the case of simultaneous power delivery on both sides. Despite that both dual-received coils were coupled each other, the findings indicate that dual-side power delivery case with reversed coil orientation enhances coupling similar to single-side power delivery case. This results in an increase in $kQ$ product and improved wireless power transmission efficiency. We loaded the coil with inductance to resonate at the desired frequency location where the $kQ$ product is maximized. In this case as well, electromagnetic field analysis revealed that reversed-phase orientation leads to higher wireless power efficiency compared to in-phase orientation.