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The bias current in the magnetic is a fatal element in energy storage flywheel system for heat and rotational resistance. A bigger flywheel is used in the energy storage flywheel system for higher energy storage density. This lead to a strong gyroscopic effect. This paper verify a new method of design reduced-order model for mechanical system with strong gyroscopic effect which is proposed in one of our paper. The method used cholesky decomposition to construct the reduced-order model of mechanical system. In order to demonstrate the validity of this method, a 0.5 KWh class magnetic bearing system is designed based on the 10 MWh class energy storage flywheel system which used in this paper. The new zero bias magnetic bearing is used in the system. From the simulation and experiment, it had been verified that the proposed method is useful for control system design taking into account a strong gyroscopic effect.

In order to clarify the rotation loss and levitation force reduction characteristics of two kinds of radial and axial-type superconducting magnetic bearings (SMB) consisting of a ring-shaped YBCO and a permanent magnet composite, we measured rotation losses and levitation forces of each SMB with a new rotation-loss measuring device using active magnetic bearings. The rotation loss of the SMB increased with increased initial load of the SMB. The levitation force o the SMB decreased remarkably just after activating the initial load to the SMB and during acceleration of the rotor suspended by the SMB. The reduction in levitation force was improved by means of applying a pre-load, that means a temporary load, before the initial load against the SMB. But the rotation loss of the SMB was increased as pre-load was increased. When the YBCO was cooled down from 77 to 66K, the rotation loss of the SMB decreased as the temperature of the SC decreased.