Force density of magnetic bearings using superconducting coils and bulk superconductors

Ken Nagashima, Hiroshi Seino, Yoshiki Miyazaki, Yuuki Arai, Naomichi Sakai, Masato Murakami

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


Stable levitation or suspension of a heavy object in mid-air can be realized using a combination of a permanent magnet and a bulk superconductor with high critical current density, in that the force density has reached 100 kN/m2. The superconducting flywheel system for energy storage is attractive due to a great reduction in the rotational loss of the bearings So long as a permanent magnet is used as a magnetic source, however, the electromagnetic force (EMF) is essentially limited by its field strength. In order to overcome such a limitation, we employed a superconducting coil / magnet as a magnetic source and studied the EMF characteristics of bulk superconductors in high magnetic fields. We also measured the EMF between a bulk superconductor and a specially designed superconducting coil having a high field gradient, and confirmed that the EMF reached 9,000 N (force density: 1,190 k N/m2).

Original languageEnglish
Pages (from-to)127-132
Number of pages6
JournalQuarterly Report of RTRI (Railway Technical Research Institute) (Japan)
Issue number2
Publication statusPublished - 2008 May
Externally publishedYes


  • Bulk superconductor
  • Energy storage
  • Flywheel
  • Force density
  • Magnetic bearing
  • Superconducting coil

ASJC Scopus subject areas

  • Mechanical Engineering


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