Efficiency of Passive Magnetic Energy Harvesters Operating Under High Primary Currents

Magnetic energy harvesters (MEHs) are highly reliable devices employed to supply low-power DC loads from high AC current carrying conductors. Recent literature provided means for estimating the input power of a MEH feeding a constant voltage load (CVL) via an uncontrolled rectifier. The goal of the paper is to quantify the different types of losses and thus the conversion efficiency and output power of clamped-type MEHs. Analytical expressions for losses in the magnetic core, secondary winding, and rectifier diodes are developed, in relation to circuit variables. It is shown that the total losses can be considerable, leading to an efficiency in the order of 83%. The analytical predictions demonstrate close resemblance with corresponding results obtained by a passive MEH harvesting ~218 W from a conductor carrying 200 – 300 A<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RMS</inf>.