An effective noncontact torque mechanism and design considerations for an evershed-type superconducting magnetic bearing system

An Evershed type of superconducting magnetic bearing is designed and fabricated. An alternative torque mechanism is proposed to drive the rotor of the designed bearing. The design consideration for the rotor consists of a permanent magnet with 7.5-kg mass and its force interaction with the superconductor defined in terms of a semi-analytical frozen image model. The driving mechanism is based on eddy-current induction on a conducting disk placed on the rotor of the bearing. The driving system is intended not only to sustain stable levitation during the variation of the rotor speed but also to rotate the rotor with a speed higher than that of the torque provider. Levitation, drag, and lift forces are discussed via considering various conditions such as the rotor configuration and conducting material. The thickness of the conductor strongly affects the optimum working conditions of the magnetic bearing. In order to compensate the repulsive force due to lift force on the rotor, the top of the rotor was covered with iron sheet. The results indicate that the designed rotor and driving system have potential solutions for more advanced bearing applications for superconducting flywheel energy storage.