Nonlinear, Hybrid, Multicore Magnetic Energy Harvesting

Current transformer magnetic energy harvesters scavenge energy from the magnetic fields around ac transmission lines to power sensor packages. Often, magnetic cores with either extremely high permeability (nanocrystalline alloys) or extremely high saturation flux density (silicon steel) are employed to make these harvesters. Although both high permeability and high saturation flux density are theoretically desirable for a magnetic energy harvester, a practical demonstration of a multi-material harvester core that leverages the benefits of both high permeability and high saturation flux density core materials has yet to be shown. This paper presents analysis and experimental demonstration of a multi-material multi-core magnetic energy harvester that is constructed from concentric toroids of different magnetic materials. Nonlinear flux models for this “hybrid” multi-core energy harvester are presented and validated. The power harvest of the hybrid core is evaluated in comparison to traditional nanocrystalline and silicon steel harvesters and a critical result is shown. While the traditional nanocrystalline and silicon steel harvesters drastically outperform each other depending on the amplitude of the ac transmission line current, the hybrid core exhibits a high average power harvest over the entire range of transmission line current amplitudes, exploiting the high permeability of its nanocrystalline material at low currents and the high saturation flux density of its silicon steel material at high currents.