Velocity dependence of rotational loss in Evershed-type superconducting bearings
- Energy Technology Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)
Results of free spin down in vacuum are reported for an Evershed-type superconducting bearing in which a permanent magnet (PM) ring is levitated over an array of high-temperature superconductors (HTSs) and under a similar PM ring in magnetic attraction. The velocity dependence of the rotational loss strongly suggests that the observed velocity-dependent losses are primarily due to eddy currents induced in the PM by inhomogeneity of the field produced by the magnetized HTS array. The results show that the Evershed-type bearing is capable of reducing these eddy-current losses to an extremely low level, so that at a maximum magnet rim velocity of 28 m/s, the fractional kinetic-energy loss per hour was 2.4{times}10{sup {minus}4}. Significant levitation heights are also possible, and at a 23 mm height, we measured a low-speed coefficient of friction of 3{times}10{sup {minus}8}. {copyright} {ital 1997 American Institute of Physics.}
- DOE Contract Number:
- W-31-109-ENG-38
- OSTI ID:
- 450198
- Journal Information:
- Applied Physics Letters, Vol. 70, Issue 5; Other Information: PBD: Feb 1997
- Country of Publication:
- United States
- Language:
- English
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