Investigation of Magnetic Interaction of IPM-Type Magnetic-Geared Motor

A magnetic-geared motor (MGM) has attractive features including high torque density, which contributes to reducing the overall size and weight in comparison with conventional motors, especially for low-speed and high-torque applications. The MGM consists of a magnetic gear (MG) and a permanent magnet (PM) motor, and they share one high-speed rotor (HSR). In general, the HSR has a structure of surface PM (SPM) in order to magnetically decouple between the MG and the PM motor by the HSR yoke. However, this structure is the cause of the worse eddy current loss in the HSR magnets. In a previous study, to resolve the issue, a structure of interior PM (IPM) that the HSR magnets are embedded in the HSR yoke was proposed. It was clear that the eddy current loss in the magnets can be reduced and the efficiency is improved. In the IPM structure, however, there is concern that the MG and the PM motor have magnetically interacted and its influence has not been clarified. This article presents the investigation of the magnetic interaction of the IPM-type MGM by using the finite-element method (FEM). The influence of the interaction is described by comparing SPM and IPM types. Moreover, the magnetic interaction is demonstrated by a prototype IPM-type MGM.