AP9-3

Study of rotational loss characteristics of superconducting magnetic bearings by FEM analysis based on H-Φ and A-V formulations
*Takemi Onoue1, Satsuki Okumura1, Yutaka Terao1, Hiroyuki Ohsaki1, Yuki Sakurai2, Tomotake Matsumura2, Nobuhiko Katayama2

Superconducting magnetic bearings (SMBs) have excellent characteristics such as low loss, long life and low maintenance, which come from the contactless support of a rotor. For example, in the development of the cosmic microwave background polarimeters, the SMB system has been studied because it requires an extremely low loss of 4mW [1]. It is important to study the rotational loss characteristics of the SMB systems for the purpose of their optimal design.

The rotational losses of the axial flux type SMB in the cosmic microwave background polarimeters mentioned above are mainly composed of hysteresis loss in superconductors and eddy current loss in electrically conducting components. The inhomogeneous magnetic field generated by the permanent magnets in the rotor causes hysteresis loss in the superconductors in the stator, and the magnetic fluxes trapped in the superconductors causes eddy current loss in the electrically conducting components in the rotor.

We have created FEM analysis models of the SMB and analyzed energy losses caused by the magnetic field inhomogeneity in the SMB. In the SMB models, the stator has an array of YBCOs forming a ring, and the rotor is composed of permanent magnets arranged in a ring shape, steel components for magnetic circuits, and electrically conducting components. In 3D electromagnetic field analysis, it is very important to reduce the computational load. We have used the H formulation to analyze the electromagnetic field in the superconductor, Φ formulation for the magnetic field generated the PMs [2], and the A-V formulation for the magnetic field created by the superconducting current and eddy current loss in the rotor. We used COMSOL Multiphysics [3] to analyze the SMB models and investigate the dependence of their hysteresis and eddy current losses on the model parameters and operational conditions.

References
[1] Y. Sakurai et al., IEEE Trans. Appl. Supercond., Vol. 28, No. 4, 2018, 3601404, doi: 10.1109/TASC.2018.2797302.
[2] Alexandre Arsenault et al, IEEE Trans. Appl. Supercond., Vol. 31, No. 4, 2021, 6800609, doi: 10.1109/TASC.2021.3073274
[3] COMSOL Multiphysics® Version 5.6 www.comsol.com

Keywords: Superconducting magnetic bearing, Finite element method, H-formulation, Rotational loss