Leakage Flux of the Trans-Rotary Magnetic Gear

Abstract

This paper investigates the leakage flux of the trans-rotary magnetic gear (TROMAG). TROMAG is a magnetic gear that converts a high-force low-speed linear motion to a low-torque high-speed rotation and vice versa. TROMAG is tailored to force-intensive linear motion applications such as backpack energy harvesting and artificial heart in which the gear is positioned close to the human body and/or electronic devices. In such applications, it is critical to ensure the TROMAG’s magnetic field penetrating the surrounding environment (referred to as the leakage flux hereafter) is below the limits permitted by standards. This paper employs 3-D finite-element analysis (FEA) to study spatial distribution and magnitude of the leakage flux. The FEA calculations of magnetic field are verified by experimental measurements. Both radial and quasi-Halbach configurations are investigated, and it is revealed that the quasi-Halbach configuration exhibits less leakage flux. Moreover, it is shown that the use of a thin iron shield surrounding the TROMAG can effectively reduce the leakage down to permissible values.