VP20-10 Experimental Verification of Eddy Current Loss Reduction in Magnets of Flux-Modulated-type Magnetic Gears
Creators: Emiri Asahina and Kenji Nakamura
Publisher: name: IEEE
Year: 2025

Next-generation mobilities, such as advanced air mobility and electric aircraft, have attracted great attention. Their drive trains require an extremely high power-to-weight ratio of over 20 kW/kg [1]. Although their electric motors need to be driven at 50,000 rpm or more, no mechanical gearboxes are feasible. Magnetic gears can be a candidate for overcoming this problem because they have no mechanical contact. However, eddy current loss in magnets must be addressed under such ultra-high-speed operation [2] [3]. Ref. [3] discusses magnet division in permanent magnet motors to suppress eddy current loss and clarifies that a circumferential division can reduce the eddy current loss more effectively than an axial division. This paper experimentally investigates whether the above results are also effective in flux-modulated-type magnetic gears. Fig. 1(a) shows the specifications of a flux-modulated-type magnetic gear used in this study. Fig. 1(b) compares the calculated eddy current losses in magnets when the number of magnet divisions in the axial and circumferential directions is varied. It is understood that the circumferential division can reduce eddy current losses in magnets more effectively than the axial division. Fig. 2(a) depicts the outer stators with different magnet divisions and the experimental setup for measuring the magnet temperature of the outer stator of the prototype magnetic gear (MG). Fig. 2(b) shows the measured temperature changes in different magnet divisions when the inner rotor rotates at 18,669 rpm. The temperature is the average value measured at four different points using thermocouples, as shown in Fig. 2(a). The figure reveals that the no-division exhibits the most significant temperature rise, while the circumferential division has a smaller temperature rise than the axial division. At the conference, the measured temperature changes at higher speeds and the relationship between the eddy current loss distribution in magnets and the temperature distribution will be discussed.References: [1] J. Z. Bird, IEEE Trans. Magn., vol. 58, no. 2, 8201108, 2022. [2] J. J. Scheidler, V.M. Asnani, and T. F. Tallerico, Proc. AIAA/IEEE Electric Aircr. Technol. Symp., pp. 1–12, 2018 [3] K. Yamazaki and Y. Fukushima, pp. 1-6 2009 International Conference on Electrical Machines and Systems, 2009.
Next-generation mobilities, such as advanced air mobility and electric aircraft, have attracted great attention. Their drive trains require an extremely high power-to-weight ratio of over 20 kW/kg [1]. Although their electric motors need to be driven at 50,000 rpm or more, no mechanical gearboxes are feasible. Magnetic gears can be a candidate for overcoming this problem because they have no mechanical contact. However, eddy current loss in magnets must be addressed under such ultra-high-speed operation [2] [3]. Ref. [3] discusses magnet division in permanent magnet motors to suppress eddy current loss and clarifies that a circumferential division can reduce the eddy current loss more effectively than an axial division. This paper experimentally investigates whether the above results are also effective in flux-modulated-type magnetic gears. Fig. 1(a) shows the specifications of a flux-modulated-type magnetic gear used in this study. Fig. 1(b) compares the calculated eddy current losses in magnets when the number of magnet divisions in the axial and circumferential directions is varied. It is understood that the circumferential division can reduce eddy current losses in magnets more effectively than the axial division. Fig. 2(a) depicts the outer stators with different magnet divisions and the experimental setup for measuring the magnet temperature of the outer stator of the prototype magnetic gear (MG). Fig. 2(b) shows the measured temperature changes in different magnet divisions when the inner rotor rotates at 18,669 rpm. The temperature is the average value measured at four different points using thermocouples, as shown in Fig. 2(a). The figure reveals that the no-division exhibits the most significant temperature rise, while the circumferential division has a smaller temperature rise than the axial division. At the conference, the measured temperature changes at higher speeds and the relationship between the eddy current loss distribution in magnets and the temperature distribution will be discussed.References: [1] J. Z. Bird, IEEE Trans. Magn., vol. 58, no. 2, 8201108, 2022. [2] J. J. Scheidler, V.M. Asnani, and T. F. Tallerico, Proc. AIAA/IEEE Electric Aircr. Technol. Symp., pp. 1–12, 2018 [3] K. Yamazaki and Y. Fukushima, pp. 1-6 2009 International Conference on Electrical Machines and Systems, 2009.