Optimal Number of Secondary Winding Turns in Practical Active Magnetic Energy Harvesters

Magnetic energy harvester clamped on high-AC-currents-carrying conductor (e.g. split phase of an overhead power line) may serve as a part of uninhabited aerial electrical vehicle batteries charging platform. The brief reveals analytical expression for the power delivered to a constant voltage type load (e.g. battery or regulated DC bus) by an active magnetic energy harvester (AMEH) operated under transfer-window-alignment control for determining the optimal (in terms of load power maximization) number of secondary winding turns (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i>). It has been recently demonstrated that for a given core, the power harvested by an AMEH from a current-carrying conductor increases monotonically when <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> is reduced. On the other hand, it is discovered that AMEH conversion losses are concurrently increased. As a result, the power supplied by an AMEH to the load is a non-monotonic function of secondary winding turns number, attaining a global maxima for certain unique value of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i>. Analytical expression allowing to obtain the optimal secondary winding turns number is developed in the letter and validated experimentally by application to an AMEH clamped on 200A, 50Hz current carrying conductor while driving a 45V constant voltage load (emulating 12s Li-Ion battery).