Impact of rebar and concrete on power dissipation of wireless power transfer systems

Steel-reinforced concrete has been widely used in the construction of railways because of its robustness and low maintenance cost. This paper focuses on the analysis of unwanted losses in a reinforced concrete track when a high-power online wireless power transfer system is installed on it. Induced dielectric loss in the concrete, and eddy current and hysteresis losses in the reinforcing steel bar are calculated using analytic equations and finite-element analysis. Among the three sources of loss, a dominant one is identified in the first three sections of this paper. It is shown that the dielectric loss in the concrete and the hysteresis loss in the reinforcing bar do not have a critical impact on the efficiency. However, it is found that the eddy current loss of the reinforcing bar is dominant over the other two losses. Furthermore, the eddy current loss of the reinforcing bar overwhelmed the ohmic loss of a transmitter coil if the transmitter coil is not located in a proper position on the concrete track. The theoretical results are evaluated experimentally using a 7-m-long test bed. When the transmitter coil is located 0.14 m above the reinforcing bar, the measured eddy current loss of the steel bar is 3 kW while the Ohmic loss of the transmitter coil is 1.5 kW. As the distance between the transmitter coil and the steel bar increases, the eddy current loss of the bar decreases rapidly. From the simulation and the experimental evaluation of the loss, guidelines for installing a transmitter coil on a reinforcing bar for an in-motion wireless power transfer system are suggested in this paper.