Novel multi-coil resonator design for wireless power transfer through reinforced concrete structure with rebar array

The wireless power transfer (WPT) has many advantages such as convenience of energy transfer and high reliability of system. Therefore, WPT system is widely applied to IT devices, electric vehicle, and industrial application by using concrete structure. However, when is applied to reinforced concrete structure, there is a severe problem that it has very low efficiency for power transfer, which results in high power loss due to interference of the internal rebar array. In other words, although the conventional WPT system has high efficiency under air condition, it has low transfer efficiency under reinforced concrete structure with rebar array. To overcome this problem, this paper proposes a new multi-coil resonator design. It uses main one coil and intermediate 4 coils. The main coil boosts coupling coefficient and the intermediate 4 coils boost self-inductance and a few coupling coefficients. As a result, high coupling coefficient leads to high WPT efficiency. Moreover, the proposed resonator design enables intermediate 4 coils to avoid interference of the rebar array. Therefore, the proposed new multi-coil resonator design for WPT system has high efficiency under reinforced concrete structure with rebar array. To confirm the operation, features, and validity of the proposed resonator designs, a laboratory WPT system with 3.3V/10W is built and tested.