Maximizing Output Power of Inductive Power Transfer Systems Under Rebar Array Shielding

Sensors in structural health monitoring systems can be wirelessly powered by Inductive power transfer (IPT) technology. However, wireless power transfer to sensors is significantly affected by the shielding effect of magnetic fields due to induced eddy currents in rebar arrays. This article presents a method to lower the equivalent impedance of rebar loops, which thereby transforms the rebar array from a shield to an intermediate relay coil to improve power transmission. The proposed method uses an additional coil mounted on the rebar, which is coupled with two adjacent rebar loops and connected in series with a capacitor. By modifying the capacitance value, the magnitude and phase of the induced current in the rebar array can be modified to increase the induced voltage in the receiver (RX) coil. The equivalent circuit model of the system is analyzed based on the dipole coil as the transmitter and RX coil. Furthermore, a parameter design method for capacitance in series with the additional coil is presented to enable the system to achieve maximum output power capacity. Experimental results showed that the proposed method elevates the output power from 0.15 to 2.67 W.