Inductive Energy Harvesting From Current-Carrying Structures

Abstract

This article introduces an inductive method for harvesting energy from current-carrying structures. Numerical simulation of a structural beam shows that the skin effect can lead to significant current concentration at edges, providing a five-fold power benefit at such locations, even at frequencies below 1 kHz. The use of a rectangular ferrite core can provide a ×4 power density improvement. The adoption of funnel-like core shapes allows the reduction of core mass and coil frame size, leading to significant further power density enhancement. Magnetic field simulation and coil analysis demonstrate a power density increase of ×49 by ferrite funnels, in comparison to a coreless coil. Experimental results demonstrate rectified power over 1 mW delivered to a storage capacitor, from a 40 × 20 × 2 mm core-and-coil, in the vicinity of a spatially distributed 20 A current at 800 Hz. Rectification and impedance matching are studied experimentally using a voltage doubler circuit with input capacitor tuning to counteract the coil reactance. Experimental results from a spatially distributed 30 A current at 300 Hz and a 1:7 funnel core demonstrate power density of 36 μ W/g (103 μ W/cm3), opening up the way to noninvasive inductive powering of systems in the vicinity of current-carrying structures.