AP3-1

Estimating the rotational loss of the axial-type superconducting magnetic bearing using coupled H and A-V formulation base finite element method

Dec.1 16:00-16:20 (Tokyo Time)

*Yusuke Ishida1, Takemi Onoue1, Doa Ahmad1, Yutaka Terao1, Hiroyuki Ohsaki1, Yuki Sakurai2, Tomotake Matsumura2, Nobuhiko Katayama2

Graduate School of Frontier Sciences, The University of Tokyo, Japan1

Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo, Japan2

A superconducting magnetic bearing (SMB) has been applied to various applications, including the cosmic microwave background polarimeters [1], because of its contactless rotational mechanism and low power dissipation. When the required heat dissipation is stringent and the levitational force is high, it is important to establish a reliable method to simulate them at the time of a design phase. So far, there has been a community-wide effort to model the levitational force in SMB [2], and yet it has been less addressed for the energy loss of SMB due to the large computational load.

SMB can achieve a contactless rotation. Yet, even in vacuum, there is an energy loss due to the inhomogeneous magnetic field generated by the permanent magnets of a rotor, and also by the superconducting currents induced in YBCO bulks. These sources of the magnetic field inhomogeneity can result in the hysteresis loss in the YBCO and also the eddy current loss in the permanent magnets and electrically conducting components of the rotor.

In this presentation, we modeled SMB and computed the prospective levitational height and the energy loss during its rotation due to the magnetic field inhomogeneity. Our SMB consists of permanent magnets arranged in a ring and an array of YBCOs forming a ring. We employ the H-formulation for superconducting components and A-V formulation for normal conducting components because H-formulation is suitable to handle the strong nonlinearity effect of the superconductors. We constructed the model using COMSOL [3] and estimated both the levitational force and the energy loss. We introduced the static mesh by using time dependent Dirichlet boundary conditions to emulate the permanent magnet rotor’s movement instead of rotating the PM rotor in the model. Using static mesh helps to reduce the required computational power. We also addressed the energy loss in the YBCO and the rotor. Finally, we compare the results with the experimental data and discuss the validity and limitation of the proposed approach.

Reference
[1] Sakurai Y, et al. 2017 IEEE Trans. Appl. Supercond. 26 no 4 3601904.
[2] Loïc Quéval et al 2018 Supercond. Sci. Technol. 31 084001.
[3] COMSOL Multiphysics® Version 5.5 www.comsol.com

Keywords: superconducting magnetic bearing, finite element method, H-formulation, rotational loss