Affiliations: [a] Laboratory of Applied Superconductivity – LASUP/UFRJ, Rio de Janeiro, RJ, Brazil
Correspondence:
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Corresponding author: Elkin Rodriguez, Laboratory of Applied Superconductivity – LASUP/UFRJ, P.O. Box 68504, 21941-972 Rio de Janeiro, RJ, Brazil. E-mail: elkin@dee.ufrj.br
Abstract: Magnetic bearings offer the best solution to mitigate mechanical friction. A variety of geometries and new materials are being studied. The advantage of using a passive bearing system, like the Superconducting Magnetic Bearing (SMB), is that it offers low friction without the need of feedback control, increasing the reliability and decreasing the energy consumption. SMB devices work at very low temperatures that are often achieved with the use of Liquid Nitrogen inside of cryostats. This paper describes the design and experimental tests of a SMB passive magnetic bearing system. An innovative design of a cryostat that uses YBCO bulks refrigerated by a cryocooler is presented. With this setup, it is possible to perform vibration tests in several temperatures from 45K up to 77 K to find the resonance speeds at each temperature. Pieces of equipment that use SMB can benefit from reducing the working temperature. The mechanical response of the pinning force may vary with the choice of refrigeration used. To perform those tests, units of accelerometers are installed on the rotor body and displacement sensors monitor the behavior as function of the rotor speed. This improved magnetic bearing will be used in energy storage systems to reduce the instability of the rotor used in flywheel applications by changing the refrigeration temperature of the superconductor. This investigation can lead to an improvement of the levitation force, the levitation gap and damping.
Keywords: Superconducting magnetic bearing, cryocooler, YBCO bulks, natural frequency
