An Improved Hybrid Shielding With LC Coil for Wireless Power Transfer System

The leakage electromagnetic field (EMF) from the wireless power transfer system caused by loose coupling is hazardous to the human body and sensitive electronic devices. Studies have shown that the reactive LC coil has good shielding effect in the internal area nearby the coil central axis but poor shielding effect in the external area around the coil boundary. To overcome this, a hybrid shielding structure is proposed, which weakens leakage EMF in the external area by surrounding reactive LC coil with a ring-shaped aluminum plate. Two representative target planes are selected for evaluating the shielding effect. To minimize the average of magnetic flux density on target planes, the position and equivalent inductance of the proposed structure are optimized through ANSYS Maxwell. Experimental results show that, compared with the shielding method using horizontal aluminum plate, the proposed structure has an improvement of 68% shielding effect for target plane at coil alignment, even 88% for individual points, but with a 1.02% drop in efficiency. It also performs well under coil misalignment condition, and the shielding effect is still improved by 50% when the coils are offset by 100 mm.