Magnetic Field Energy Harvesting From Current-Carrying Structures: Electromagnetic-Circuit Coupled Model, Validation and Application

Magnetic field energy harvesters (MFEHs) from current-carrying structures/conductors are usually modelled as decoupled electromagnetic and electrical systems. The current-carrying structures may affect the performance of MFEH through the generation of the eddy current and the alteration of the magnetic reluctance. Moreover, the load circuit affects the current generated in the coil and therefore the flux density and eddy current generated. The effects of the current-carrying structure and the load circuit cannot be fully described by the decoupled models. This work develops a finite element model (FEM) that fully couples the electromagnetic and electrical systems by simulating both the magnetic field and eddy current distribution of an MFEH connected to an electrical circuit. The FEM first simulates the coil inductance and resistance of a magnetic field energy harvester (MFEH) placed close to a current-carrying structure exemplified by a rail track. The FEM then simulates the outputs of the MFEH connected to an electrical circuit consisting of a compensating capacitor and optimal load resistor determined by the first step. An MFEH was fabricated and tested under a section of current-carrying rail track. Both experiment and simulation show an increase of both coil resistance and inductance when the MFEH is placed close to the rail track. The good agreement between experimental and simulation results validates that the FEM can predict the full-matrix performances of the MFEH, including the coil parameters, power output and magnetic flux density under the influence of the current-carrying structure and the load circuit. Simulation results reveal that in addition to the permeability of the magnetic core, the electrical conductivity and magnetic permeability of the current-carrying structure considerably affect the performance of the MFEH, which cannot be predicted by decoupled models.