Dual reactive coil application method of wireless power transfer system for leakage magnetic field reduction and efficiency enhancement

Abstract

The wireless power transfer (WPT) system generates high density leakage electromagnetic field (EMF) during the operation. The human exposure to leakage EMF has an adverse effect on human health. In order to reduce the leakage EMF, shielding method can be applied to the WPT system. The shielding methods in previous research reduce leakage EMF, but power transfer efficiency (PTE) of the WPT system has decreased. Therefore, a shielding method providing high shielding effectiveness (SE) without PTE degradation is necessary. This paper proposes a dual loop reactive shield application for the reduction of leakage EMF without PTE degradation. A proposed dual loop reactive shield generates in phase and out of phase magnetic field simultaneously. The out of phase magnetic field depresses leakage EMF, and the in phase magnetic field makes the increases of the PTE. A proposed method is verified for the cases of symmetric and asymmetric WPT systems, including misalignment conditions. The experimental results of the symmetric WPT system were 2.1% PTE increase with 55.5% SE in alignment condition, and 3.9% PTE increase with 53% SE in misalignment condition. In addition, the experimental results of the asymmetric WPT system were 1.6% PTE increase with 61.3% SE in alignment condition, and 2.7% PTE increase with 54.1% SE in misalignment condition.