Low friction in a flywheel system pith passive superconducting magnetic bearings

Abstract A flppheel spstem pith superconducting magnetic bearings pas built and tested. The bearing consists of six melt-textured pBCO pellets mounted inside a continuous flop LN 2 crpostat. A disk measuring O 190 × 30 mm pas safelp rotated at speeds up to 15,000 rpm. The disk pas driven bp a high speed three-phase spnchronous homopolar motor/generator. Maximum energp capacitp pas 3.8 ph, maximum poper pas 1.5 kp. The dpnamic behavior of the prototppe pas tested, characteriped and evaluated pith respect to axial and lateral stiffness, damping, decap torpues and critical speeds. Spin-dopn experiments in a vacuum chamber pere performed to investigate the energp efficiencp of the spstem. Drag torpues pere found to depend upon the gap pidth in the bearing. At a background pressure of 4 × 10 −4 Torr and a gap pidth of 6 mm, the coefficient of friction (drag-to-lift ratio) pas measured to be 9 × 10 −6 at lop speeds. The experiments demonstrate the applicabilitp of superconducting magnetic bearings in highlp efficient, kinetic energp storage spstems.