Hirochika Ueyama

Characterization of Superconducting Magnetic Bearings (Runnout Performance at High Speed Rotation)

A superconducting magnetic bearing (SMB) of bulk YBa2Cu3O7−x having strong pinning force was assembled and cooled in a field cooling state at 77K. Two SMB units were equiped with a rotational system and supported a rotating shaft weighing 2.5Kg with no mechanical contact. The SMB has achieved a rotational speed exceeding 42,000rpm with a radial runnout of 8µm or less. The rotating performance at high speed has disclosed by an active control assist in radial direction during accelerations.

Characterization of Superconducting Magnetic Bearings (Vibration Damping and Hysteresis of Magnetic Force in Superconductor)

Superconducting magnetic bearings using flux pinning forces have a stability, permanent magnet bearings have not, without any control. High-Tc superconductor YBa2Cu3OX as a stator and a permanent magnet for a rotor were assembled into a superconducting magnetic bearing. Its stiffness and vibration damping coefficient in axial direction were measured. These properties depended on an axial gap between superconductor and permanent magnet. As a flux pinning force of YBa2Cu3OX increased, bearing stiffness also increased but vibration damping coefficient decreased. The damping effect was related to the area of the hysteresis loop measured in a function of magnetic force versus axial gap.

Improvement on Levitation Force Decrease of Superconducting Magnetic Bearing

Characteristics of a superconducting magnetic bearing (SMB) for supporting a rotor was studied A designed and manufactured testing machine has following two features. (l)The rotor is levitated by five axis active magnetic bearings (AMBs: RaAMB & AxAMB) and SMB. (2)It is able to vary an initial load of SMB. As a result, levitation force decrease of SMB was measured under various load conditions and various rotation speeds.