Effect of Rebar Array on IPT System for Structural Health Monitoring Sensor Supply

Inductive power transfer (IPT) has become a popular supply of sensors in structural health monitoring systems due to its non-contact nature. However, the presence of a rebar array in concrete structures may affect the performance of IPT systems by changing the mutual inductance between the transmitter and receiver coils. Moreover, as a ferromagnetic material, the relative permeability of rebar is a complex function of frequency. In this paper, the approximate relative permeability of rebars at different frequencies is obtained by inductance approximation of finite element simulation and test results. Based on this, we study the influence of the magnetic properties of rebars and eddy current shielding on mutual inductance through simulation and testing. The results indicate that the eddy current shielding effect of rebar loops plays a dominant role in reducing mutual inductance within the frequency range commonly used in IPT systems. An expression for the equivalent mutual inductance of IPT systems with rebars is also derived and validated with experimental results. An expression for the equivalent mutual inductance of IPT systems with rebar array is also derived and validated with experimental results. The findings of this study are expected to assist in designing IPT systems in the presence of rebar obstructions.