A comparative analysis of power density for single-stage and dual-stage magnetic gear with rare-earth magnets and non rare-earth magnets

The magnetic gear that solves the physical contact problem of the mechanical gear has advantage of no mechanical friction loss, very little noise and vibration, and no need for lubricant. Due to this unique non-contact characteristic, the magnetic gear which is capable of non-contact torque transmission has replaced mechanical gear. However, the magnetic gear with a high gear ratio is disadvantageous to implement the exact gear ratio because the number of rotor poles increases. Therefore, dual-stage type magnetic gear was proposed in order to distributes the gear ratio by using two magnetic gears as to the mechanical gear is used the multi-stage in order to implement the high gear ratio. The dual-stage type magnetic gear can improve the power density and efficiency compared to the single-stage magnetic gear. Also, the dual-stage type magnetic gear can be designed differently permanent magnet type because the use of the two magnetic gear. Therefore, in this paper, permanent magnet material of second magnetic gear was not changed and only permanent magnet material of first magnetic gear was changed to bonded NdFeB magnet or ferrite magnet from sintered NdFeB magnet. Transfer torque and magnetic field analysis method for dual-stage magnetic gear was used 2-D numerical analysis.