| 摘要 |
The invention provides for flux-shields wrapped around the flux-sources at the core-end of large power generators. They prevent overheating of all core-end parts under all abnormal conditions of operation. A first flux-shield is an electrically conductive cylindrical shell concentric with rotating end-windings, held outside the retaining ring. The rotating flux source induces eddy currents in the first flux-shield whose flux repels the source flux. Only a small part of the rotating source flux is hence received by all the core-end parts, thereby greatly reducing their temperatures. A second flux-shield comprises an electrically conductive tape wrapped over the ground-insulation of stator bars protruding from the core. Alternating flux generated by the stator bars induces eddy currents in the second flux-shield whose flux repels the source flux. Only a small fraction of the source flux is hence received by all core-end parts, thereby greatly reducing their temperatures. The present invention replaces multiple devices such as step-iron, flux-shields, flux shunts, short-rotors etc, used in the prior-art with only two devices. As a result, the design of the core-end is simplified and the cost of the generator is reduced. |
