An Axial Magnetic Gear Design with Changeable Ratios

Abstract

Recent developments in the field of magnetic gear and magnetic gearing machines have opened up innumerable opportunities for engineers and researchers. Conventional mechanical gears require direct mechanical contact between the drive and driven toothed wheels, which gives rise to problems such as wear, breakages and noise. Generally, the wheels are made of case hardened metal alloys and are relatively heavy. In contrast, magnetic gears work on the interaction of magnetic flux between the drive and driven wheels. The difference in the number of magnetic pole pairs on the two wheels generate a torque amplification or reduction effect. Hence, magnetic gears offer lighter weight, reduced maintenance, high reliability, no wear and tear, contact-free operation, inherent overload protection, decreased noise and increased efficiency. In some applications, there is a need for the gear ratios to be varied during operation. A conventional gearbox would have several gear wheels of varying sizes, where one would be engaged in turn as the operating condition requires. Carrying a number of mechanical gears also adds to the weight. In this paper an overview of magnetic gear topologies and their characteristics is first presented. Then, a new design of a compact axial electromagnetic gear with variable gear ratios is proposed. The design makes use of electromagnets to vary the effective number of pole pairs, and hence the flux interaction, between the drive and driven wheels. The steady-state response of the proposed axial magnetic gear is then studied through finite element analysis simulations. The simulation results show that the magnetic gear ratio could effectively be varied through this technique.