On the Maximum Power of Passive Magnetic Energy Harvesters Feeding Constant Voltage Loads Under High Primary Currents

The letter concerns clamped-type magnetic energy harvesters (MEH), supplying power to constant voltage (CV) loads via a diode rectifier. Presented analysis suggests that if primary current magnitude reflected to the secondary side is much higher than core saturation current, then optimal (in terms input MEH power maximization) transfer window length and corresponding load voltage-per-turn ratio become independent of primary current. As a result, certain unique value of load voltage maximizes the power of a given MEH irrespective of primary current magnitude. Moreover, mean magnetic flux path length, B-H curve shape and permeability of the core have no effect on either optimal load voltage-per-turn ratio or maximum harvested power under the above circumstances. Experimental results of MEH capable of harvesting 173 W from a conductor carrying 250 A_rms validate the revealed findings.