Contrary to the interaction between two magnets with opposite magnetizations directions, the interaction between a permanent magnet and a field-cooled superconductor can be stable and result in magnetic levitation (Superconducting Magnetic Levitation or SML). This property can be exploited for the development of high velocity rotating bearings with no mechanical contacts and for the development of levitated trains. Considering a cylindrical magnet levitating above a cylindrical superconductor with the same geometrical axis, the system stability is given by the lateral restoring force, F_Y. This force depends on the distance Z_cp between the field source and the superconductor during field cooling in a way opposite to the levitation force, F_Z : the larger the cooling distance, the lower the restoring force. In this talk, we’ll report measurements of F_Y and F_Z carried out on three possible SML designs comprising either YBCO or MgB₂ discs. In the first design, the magnet diameter D_PM is larger than D_SC, the superconductor one. In the second design, we have D_PM<D_SC. The third one is a new SML concept that was presented at ASC2018 [1], in which two superconductors are interacting with two magnets. We’ll report measurements establishing the domain of stability of the investigated systems and we’ll compare their levitation and restoring forces in this domain. In the case of the first design, we’ll present an analytical model accounting for the measurements and we’ll establish the conditions securing the stability of this type of levitating systems.

[1] P. Bernstein, L. Colson and J. Noudem, "A New Magnetic Levitation System With an Increased Levitation Force," in IEEE Transactions on Applied Superconductivity, vol. 29, no. 5, pp. 1-4, Aug. 2019, Art no. 3602204, doi: 10.1109/TASC.2019.2899950.

Keywords: Superconducting Magnetic Levitation, STABILITY