Design of Passive Magnetic Energy Harvester Clamped on a High-AC Currents-Carrying Conductor for Optimized Rechargeable Battery Interfacing

The article concerns designing a passive (i.e., employing an uncontrolled rectifier) magnetic energy harvester (MEH) clamped on a high-ac-currents-carrying conductor, aimed to power rechargeable batteries under the maximum allowed charging current constraint. Such a system may serve as, e.g., a part of platform residing on a split phase of an overhead power line for uninhabited aerial electrical vehicle battery charging. It has been recently shown that a passive MEH may be optimally matched (in terms of harvested power amount) to a given constant voltage load by appropriate selection of core cross-sectional area and secondary conductor turns number. However, battery terminal voltage does not remain constant but undergoes a significant increase during the charging process. Hence, MEH power averaged over the range of voltage values expected during charging cycle should be maximized in such a case. Corresponding simplified design guidelines are derived and verified by both simulations and experiments. The guidelines are used to design a MEH capable of charging a 44.4 V, 10 Ah Li-Ion battery with a nearly constant power of ∼115 W when clamped on a conductor carrying 200 A current while complying with 3 A maximum charging current constraint. It is revealed that due to the relatively low sensitivity of output passive MEH power–voltage characteristic around the corresponding maximum power point, average charging power remains within the range of 2% of the maximum device yield while battery terminal voltage undergoes 31.25% variation.