Optimal Design of Low-Cost Coaxial Magnetic Gear with Hybrid Permanent Magnets

Abstract

Magnetic gears transfer power similarly to mechanical gears between exclusive speeds and torques; however, magnetic gears’ contactless structures offer inherent performance advantages over mechanical gears. Nevertheless, the cost of fluctuation and the restricted availability of rare-earth permanent magnets have hindered the broader adoption of magnetic gear technology. To minimize the consumption of the rare-earth permanent magnet material, this paper proposes a less-rare-earth magnetic gear layout wherein the inner rotor uses spoke-type magnet slots filled with each rare-earth and ferrite permanent magnets to form a hybrid permanent magnet excitation. This rotor topology employs an additional asymmetric flux barrier in each pole for torque density enhancement and cogging torque suppression. For a more comprehensive study, the permanent magnet’s geometry was modeled using a trapezoidal shape. The influence of permanent magnets and barriers geometry parameters on air gap flux density was analyzed. The torque performance of the less-rare-earth magnetic gear was analyzed through 2-D and 3-D finite element analysis and compared with conventional spoke-type and flat type interior permanent magnet rotors.