Studies on coaxial magnetic gears (CMG) have been actively conducted. CMGs can replace mechanical gears as they can perform noncontact power transfer, thereby minimizing loss and damage from friction.
However, the permanent magnet eddy current loss among the electromagnetic field loss of the magnetic gear is pointed out as the biggest problem in the high speed drive. Among other losses, iron loss can be greatly reduced by stacking electrical steel sheets, while permanent magnets have many technical problems to be stacked like electric steel sheets. The biggest cause of permanent magnet eddy current loss is electrical conductivity of rare earth magnets. In this paper, we applied the ferrite permanent magnet and the NdFeB permanent magnet to the magnetic gears in order to compare the characteristics of the magnetic gear according to the electric conductivity of the permanent magnet. Ferrite and NdFeB were used to design magnetic gears that exhibited the same torque, and then the characteristics of each magnetic gear at the same drive speed were compared. Since the ferrite is not electrically conductive, the ferrite-applied magnetic gear does not exhibit permanent magnet eddy current loss. However, we observed mechanical and electric problems due to its size. Also, the efficiency of the two magnetic gears was reversed on a specific speed.
In this paper, we provide information on mechanical and electromagnetic losses of magnetic gears, and it is possible to examine suitable application fields of magnetic gears according to permanent magnet materials. Each model was compared with the mechanical and electromagnetic characteristics of the two models through FEM design and prototype production. Specific design and experiment contents are disclosed through the full paper.
Acknowledgement: This research was supported by Korea Electric Power Corporation. (Grant number: R19XO01-34)