Interaction of bulk superconductors with flywheel rings made of multiple permanent magnets

M. Ikeda, A. Wongsatanawarid, H. Seki, M. Murakami

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


Compared to conventional mechanical bearings, superconducting bearings have the advantage that there is no friction loss. Thus the superconducting bearings are employed for a flywheel energy storage device, and thereby one can construct the system that stores the energy for a long duration. Hence, superconducting flywheel energy storage system has attracted worldwide attention. For practical applications of the superconducting energy storage system, the stored energy must be maximized that can be achieved by either increasing the diameter of the levitated flywheel or the rotational velocity. Since the suspended flywheel in the superconducting flywheel energy storage system is made of permanent magnets, its size is limited by the size of permanent magnets. In addition, when the rotational speed is increased, there is possibility for the magnet ring to fracture due to a large centrifugal force. We therefore proposed the construction of the magnetic flywheel ring by simply arranging small permanent magnets pasted into machined grooves in Al disk 650 mm in diameter. Then we measured the force interaction between superconductor sample and a invented flywheel design. We have found that the field is almost uniform when the distance from the flywheel surface exceeded 15 mm, showing that frictionless rotation is possible at the gap larger than 15 mm. Furthermore, the repulsive force density was 0.48 N/cm2 at 15 mm, which demonstrates that the mass of 161.32 kg can be levitated.

Original languageEnglish
Pages (from-to)1270-1273
Number of pages4
JournalPhysica C: Superconductivity and its applications
Issue number15-20
Publication statusPublished - 2009 Oct 15


  • Flywheel energy storage system
  • Magnetic flywheel
  • Repulsive force
  • Superconducting energy storage system

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering


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