Resonant Circuits for Split-Core Magnetic Energy Harvesters

Magnetic energy harvesters (MEHs), which extract energy from the magnetic field around current-carrying conductors, enable industrial sensing and computing systems to operate without batteries, cutting costs and environmental wastes associated with battery replacement and maintenance. Split, current-transformer (CT) MEHs enable nonintrusive harvester installation, but exhibit notable power harvest reductions due to core cutting and the presence of surface roughness air gaps. Enhancing the power output of a given MEH magnetic core is critical in the highly volume constrained environments that MEH-powered sensors are installed. This article demonstrates simulation and experimental results of a resonant circuit, which significantly increases the average power output of split, CT MEHs. A repeatable, reliable method of determining MEH core permeability is proposed and experimentally validated. From this permeability estimation, a practically-realizable resonant capacitor is chosen, which increases maximum power harvest by nearly 60%.