Experimental Verification of Torque Density Improvement by Magnetic Interaction in 500 N•m IPM-Type Magnetic-Geared Motor

Magnetic-geared motors (MGMs) can achieve high torque density without mechanical contact. A previous article described that an interior permanent magnet (IPM)-type MGM has higher efficiency than a conventional surface permanent magnet (SPM)-type MGM. However, the permanent magnet (PM) motor part and the magnetic gear (MG) part magnetically interact with each other. In a previous article, the magnetic interaction in IPM-type MGM was fully clarified. If the magnetic interaction is effectively used, then the torque density of IPM-type MGM may increase without requiring additional magnets. This article presents an experimental verification of torque density improvement by magnetic interaction. First, the IPM-type MGM with a target torque of 500 N center dot m is designed by using a 3-D finite-element method (3D-FEM), and then, it is prototyped and demonstrated. In the prototype tests, the prototype MGM slips at 456 N center dot m, which is 90% of the target torque. Moreover, the stall torque can be increased to 470 N center dot m due to magnetic interaction, resulting in a torque density of 83 N center dot m/L.