| 摘要 |
An assembly in which a rotating shaft is supported by a magnetic bearing has a back-up bearing to support the shaft in the event of failure of the magnetic bearing, the back-up bearing comprising one or more coaxial bearing parts each including cylindrical rolling elements supported on a single raceway, or each part comprising a ball race with radially inner and outer raceways. If a radially outer raceway is provided it is secured to an anchorage, such as a housing. A layer of dry bearing material is secured to rotate with each raceway to be rotated by the shaft, the dry bearing material having a surface opposite to the shaft. After any failure of the magnetic bearing the shaft is contacted by the layer of dry bearing material, and the rolling elements are brought up to speed at a slower rate than otherwise would be the case, because of slipping of the shaft relative to the dry bearing material. By the time the back-up bearing is rotating at the same speed as the shaft, the back-up bearing is rotating at a speed not significantly greater than the maximum design speed for the rolling elements.
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