Low-Frequency Wireless Power Transfer Via Rotating Permanent Magnets

Abstract

The surging applications of low-power sensors and portable electronic devices require a safe, convenient and low-cost charging method which draws interests of the wireless power transfer research field. Conventional WPT techniques using resonant coupling structures are limited by complexity, safety concerns and hardware costs. Electromechanical wireless power transfer (EWPT) techniques provide a low-cost, easy-to-control and safe wireless charging method via moving magnets; but transmission failures may occur due to the position and orientation misalignments of loads from optimum conditions. This article proposes an EWPT system that is able to charge loads at different tilt angles via a low-frequency rotating magnetic field and a permanent magnet rotor. The magnetic field has a uniform distribution in a space volume over 125 000 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . A custom permanent magnet rotor embedded with six identical cylindrical magnets and an induction coil is employed to capture transmitted power. Theoretical analyses and experimental results are presented to prove the feasibility and output capability of the proposed system. The peak output power achieves 130 mW under a magnetic field strength around 1 mT and the system output maintains stable for loads at different tilt angles. Such EWPT method can be applied as a stable power supply for free-positioned and free-oriented sensors or other low-power devices in an enclosed or semienclosed area.