Dual Loop Reactive Shield Application of Wireless Power Transfer System for Leakage Magnetic Field Reduction and Efficiency Enhancement

The wireless power transfer (WPT) system generates a high density leakage electromagnetic field (EMF) during its operation. Exposure to leakage EMF has adverse effects on human health. In order to reduce the leakage EMF, a shielding method can be applied to the WPT system. The shielding methods in previous studies reduced leakage EMF, but the power transfer efficiency (PTE) of the WPT system was 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 reducing leakage EMF with PTE enhancement. The proposed dual loop reactive shield generates in phase and out of phase magnetic fields simultaneously. The out of phase magnetic field depresses leakage EMF, and the in phase magnetic field increases the PTE. The proposed method is verified for the cases of symmetric and asymmetric WPT systems, including misalignment conditions. The experimental results of the symmetric WPT system showed a 2.1% PTE increase with 55.5% SE in an alignment condition, and a 3.9% PTE increase with 53% SE in a misalignment condition. In addition, the experimental results of the asymmetric WPT system presented a 1.6% PTE increase with 61.3% SE in an alignment condition, and a 2.7% PTE increase with 54.1% SE in a misalignment condition.