High-performance Magnetic Bearings using Field Shaping Function of Bulk Superconductors

在小型实验装置上，研究了利用块状超导体的场整形函数的超导磁轴承的静态和动态特性。然后讨论了它在大型高速旋转机械低损耗轴承中的应用和性能的进一步改进。小型实验装置由用于磁场产生的Bi2223超导线圈、用于磁场成形的YBCO块状超导体和作为转子的铁件组成。超导线圈和块状超导体由GM制冷机直接冷却。利用该装置测量了超导磁悬浮轴承的基本特性：冷却特性、超导线圈的励磁特性、块体超导体的场成形特性、磁场成形材料分割结构的影响、电磁力等，并与数值分析结果进行了比较，结果表明两者具有很好的一致性。由于旋转振动的共振，最大转速低至9000rpm，旋转损失比预期的要大。这是因为用于整形的块体超导体的超导性能在高场中恶化，数值分析几乎证实了这一点。因此，提高块体超导体的临界电流密度，提高每个超导体样品和超导体之间的均匀和均匀的超导性能，对于提高超导磁轴承的性能，使其成为更实用的低损耗轴承具有重要意义。

In this study, static and dynamics characteristics of superconducting magnetic bearings using field shaping function of bulk superconductors have been examined with a small-scale experimental equipment. Then its application as low-loss bearings for large high-speed rotating machines and further improvement of the characteristics have been discussed.The small-scale experimental equipment consists of Bi-2223 superconducting coil for magnetic field generation, YBCO bulk superconductors for field shaping, and an iron component as a rotor. The superconducting coil and the bulk superconductors were directly cooled down by a GM refrigerator. The maximum flux density at the center of the coil was about 0.8 T. Fundamental characteristics were measured using this equipment: Cooling characteristics, excitation of the superconducting coil, field shaping characteristics of the bulk superconductors, influence of division structure of the field shaping material, electromagnetic forces, etc. These characteristics were compared with the results of numerical analysis, which indicates fairy good agreement between them.Characteristics of electromagnetic force and rotational losses of the superconducting magnetic bearing and their dependence on several parameters such as the magnetic flux density were measured. The maximum rotational speed was as low as 9000 rpm due to the resonance of rotational vibration and the rotational losses were larger than expected. This is because superconducting properties of the bulk superconductors for field shaping were deteriorated in a higher field, which was almost confirmed by numerical analysis. Therefore, the increase of critical current density of the bulk superconductors and homogeneous and uniform superconducting properties in each superconductor sample and among superconductors are important to improve the performance of the superconducting magnetic bearings and to develop them as more practical low-losses bearings.