Analysis and optimization of Triple-speed Coaxial Magnetic Gears

Besides introducing the triple-speed coaxial magnetic gear, the paper studies the influence of the geometric structure on torque and tangential and radial flux density. As rectangular and trapezoidal structures are more welcomed in most projects thanks to their ease of use, the present paper also introduces triple-speed coaxial magnetic gears with rectangular and trapezoidal structures. Then these gears are compared with crescent-shaped magnetic gear using the finite element method. The comparison shows that rectangular magnetic gears are not much different from crescent-shaped gears in terms of the flux density on the edges and corners. However, flux density distribution is more desirable in the former as the air gap between the middle rotor and modulators is variable, and less oscillation is experienced considering tangent and radial flux density distributions. Nonetheless, the trapezoidal structure presents unsatisfactory performance in comparison to the crescent-shaped structure in terms of flux density distribution and torque. An experimental crescent-shaped magnetic gear was built. The obtained results prove the validity of the use of this structure in triple-speed coaxial magnetic gears and the high performance of it compared to other structures used in magnetic gears.