Comparison of Modulator Retention Shapes for Radial Flux Coaxial Magnetic Gears

Magnetic gears perform the same function as mechanical gears using magnetic fields instead of interlocking teeth. The radial flux coaxial magnetic gear, the most common topology, requires a set of magnetically permeable modulators, which must be supported against strong magnetic forces. A bridge is often employed to connect the modulators together, but this reduces the slip torque. This paper proposes a new crescent-shaped feature, which allows modulators to be supported solely by nonmagnetic material between the modulators without a bridge. Using 2D finite element analysis, its slip torque performance is compared to bridged modulator designs and two other curved, bridgeless modulator designs. For lower modulator counts, a modulator with curved indents on both sides can slightly increase the slip torque. However, for higher modulator counts, the proposed crescent-shaped modulator outperforms other modulator retention strategies.