Development of a large torque motor using a polar anisotropic Sm-Fe-N bonded magnet

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In 2012, we examined the optimum configuration of an outer rotor type surface permanent magnet (SPM) motor using a polar anisotropic Sm-Fe-N bonded magnet by using finite element method (FEM). As a result, it was clear that the proposed SPM motor exhibits the same torque as a conventional Nd-Fe-B sintered magnet motor when the number of pole-pairs is increased up to 40 while keeping a ratio of width and length per one magnet 2:1.In 2013, to further increase the torque, we investigated an interior permanent magnet (IPM) structure. As a result, it was clear that the proposed IPM motor demonstrates 1.2 times larger torque than a conventional Nd-Fe-B sintered magnet motor, when the IPM rotor has two-layer flux-barrier structure which has small amount of Nd-Fe-B sintered magnet in the first layer, while the large amount of ferrite magnet (it has less flux density than Sm-Fe-N bonded magnet) in the second layer.