Shaped coil-core design for inductive energy collectors

Coil design is important for maximizing power density in inductive energy harvesting as well as in inductive power transfer. In this work, we present a study of coil performance, based on simulated flux distributions corresponding to a real aircraft application case. The use of funnel-shaped soft magnetic cores boosts magnetic flux density by flux concentration and allows the use of a smaller diameter coil. This reduces the transducer mass as well as the coil resistance $(R_{COIL})$, thereby increasing the power density. Analysis and simulation shows a fifty-fold power density increase from moderate funneling and another two-fold increase by coil size optimization. Results are compared with experimental measurements presented in [1] which demonstrate a $\mu \mathrm{W} / \mathrm{g}\left(106 \mu \mathrm{W} / \mathrm{cm}^{3}\right)$ power density from alternating environmental magnetic fields in the $10 \mu \mathrm{T} /300$ Hz range.