Permanent Magnet Enhancement of Fully Superconducting MgB2-YBa2Cu3O7−x Bearing
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This paper reports the experimental verification and improved concept of the previously reported fully superconducting magnetic bearing using bulks on both the rotor and the stator in a cylindrical geometry. Experimental measurements on pulsed magnetisation and levitation force between a magnetised 25.5 mm diameter YBCO bulk inside an MgB2 hollow cylinder are reported proving the concept of a bulk–bulk bearing. The maximum force achieved after field cooling of the MgB2 bulk in the field of a 1.68 T magnetised YBCO bulk was 501 N. The improved concept relies on additional ring shaped permanent magnets placed on the bottom of the MgB2 cylinder. These rings create additional axial force in the bearing system. Permanent magnet rings can boost the force for the existing bearing design by enhancing the field trapped in the MgB2 tube and providing a ‘cushion’ of magnetic field for the bottom YBCO bulk by exploiting zero field cooling. In particular the enhancement of the force is largely due to the favourable distortion of the trapped field in the MgB2 cylinder and is much greater than the direct repulsive force between a magnetised YBCO bulk and permanent magnet only. Various permanent magnet configurations are evaluated by modelling of levitation force using the perfectly trapped flux model. The high force densities of bulk–bulk bearings allow them to support large loads useful for application such as flywheel energy storage.
KeywordsMgB2 YBCO Magnetic levitation Pulsed magnetisation Magnetised bulk Superconducting bearing
We would like to acknowledge the kind support and advice of Professor Emeritus Fritz Herlach of K U Leuven, Belgium when designing and constructing the 10 T pulsed magnetic field coil used in the experiments. This work was supported by the Engineering and Physical Sciences Research Council, UK.
- 5.Patel, A., Palka, R., Glowacki, B.A.: New bulk-bulk superconducting bearing concept using additional permanent magnets. Przegląd Elektrotech. (Electr. Rev.) 88, 108–110 (2012) Google Scholar