2005 年 40 巻 12 号 p. 578-584
The operation tests of the 10 kWh-class flywheel energy storage system equipped with radial-type superconducting magnetic bearings (SMBs) experimentally manufactured under the NEDO project on “Superconducting bearing technologies for flywheel energy storage" were conducted. In the tests, we successfully achieved energy storage amounting to 5.0 kWh at high-speed rotation as high as 11,250 rpm. The radial-type SMBs are considered promising bearings suitable for high-capacity systems. However, compared to axial-type SMBs, not many radial-type SMBs have been experimentally manufactured; much less the full-scale outer-rotor-type rotating machines that use these bearings. Therefore, there were many unknown problems related to evaluating the practicality of these machines. The major issues in conducting the operation tests were to control the shaft descent of the radial-type SMB, and to control vibrations in the rotating system supported by the SMB with a small damping ratio. We solved these problems; the former using a pre-loading method, and the latter by using nonlinear zero-power control capable of controlling not only the rigid body vibration mode but also the elastic vibration mode of the rotor. The successful operation achieved in the tests proved the practicality of the radial-type SMBs as well as the feasibility of the outer rotor-type high-speed rotation systems using these bearings.