Development of superconducting tape stacks for implementation in contactless magnetic bearings with high rotational speed

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Superconducting magnetic bearings (SMB) based on high-temperature superconductors (HTSC) are a key component for energy-efficient rotating devices as flywheels, superconducting motors or liquid gas pumps as well as for new high-speed friction-free technologies in textile machinery. So far, such bearings use expensive bulk HTSC blocks having a limited availability due to the time-consuming fabrication process. Within the last years, tape stacks prepared from HTSC coated conductors are discussed as a suitable alternative for bulk material in levitation application. Here, state-of-the-art coated conductors are cut into pieces and stacked above each other. The application of such tape stacks promises a high potential for significant advances as a more compact bearing design, a higher design flexibility, improved thermal performance and mechanical strength, higher availability and reduced costs of the superconductor. At the same time, this approach has important challenges, which deserve a thoroughly scientific study. They are particularly related to the geometry of the conductor consisting of a two-dimensional superconducting layer on a significantly thicker substrate resulting in a superconducting multilayer architecture in the stack, which influences the functional properties in view. Therefore, the main focus of our project is to study the implementation of HTSC tape stacks in high-speed rotational superconducting magnetic bearings. A major objective is the efficient preparation of such stacks with different tape arrangements to study their general properties and the interaction of these stacks with a typical magnetic field configuration used in bearings. It will be accompanied with numerical modelling of the stack’s properties and the force interaction between the magnet und the superconductor. This allows to select the most appropriate tape stacks for the bearing and to specify the requirements of bearing-specific conductor materials in the future. The second major objective is to study the properties of HTSC tape stacks in a real SMB to compare them with standard bulk material. Therefore, the stacks will be integrated in an existing SMB setup designed for applications in textile machines. Static and dynamic measurements will be performed to determine the bearing properties, which allows to identify the advantages and challenges of the tape stack in comparison to bulks. Again, the experimental studies will be accompanied by a numeric modelling of the setup, which enables also a future design optimization of the bearing itself. In summary, we expect the proposed project to generate a significant contribution to the application of coated conductor material in SMB systems for energy-efficient technologies, which will extend the application range of this high-quality material. It might also trigger the quest for a specific optimization of the material itself to improve the performance for demanding levitation application.