Optimal Design of Magnetic Gears With a General Pattern of Permanent Magnet Arrangement

A general pattern of the arrangement of permanent magnets (PMs) in electromagnetic devices is presented. As an example to demonstrate its advantages, it is applied to the optimal design of magnetic gears in this paper. It automatically offers several different choices when deciding the PM arrangement in diverse magnetic gears. By choosing the best arrangement of PMs, one can obtain a higher torque density than the conventional configuration. Five kinds of PM arrangements can be obtained through the proposed general pattern, which are the most commonly used. The first one is the traditional surface-mounted N-pole and S-pole type, the second one is the spoke type, the third one is the simplified Halbach type, the fourth one is the consequent-pole type, and the fifth one is the consequent-pole Halbach arrangement. The magnetic flux distributions of magnetic gears are calculated by finite-element method (FEM), and the magnetic torques are correspondingly derived. Magnetic gears are optimally designed based on a tabu search algorithm. By using the optimization, the proposed general PM pattern can automatically derive two novel topologies of the magnetic gears, which supply higher torque density than the conventional configuration. The two new structures employ an extra part of PM to form magnetic poles both in the outer rotor and the inner rotor, which can improve output torque.