| 摘要 |
977,402. Turbines. GENERAL ELECTRIC CO. Dec. 5, 1961 [Dec. 7, 1960], No. 43479/61. Addition to 899,914. Drawings to Specification. Heading F1T. [Also in Division G3] In the control system for a multi-stage turbine described in the parent Specification, in which speed and extraction conduit pressure are measured and used to control jointly the position of the inlet valve and an interstage extraction valve, a switchover device provides that, should one valve approach a limiting position, the signal controlling that valve is prevented from modifying the signal to the other valve, which signal is instead boosted. The arrangement specifically described is such that, when conditions prevent the regulation of both valves, due to design limitations, the pressure control (extraction valve) is rendered inoperative and the inlet valve alone is controlled in response to speed, but it is stated that, alternatively, the speed control could be cut out and preference given to pressure control. Each valve is adjusted by a position control servo system with position and velocity feedback, and it is this feedback which triggers the switching device. The Specification describes in detail the manner in which signals proportional to speed and extraction pressure are used to effect joint control of the valves, and provision is made to preset desired and maximum permissible speed, desired and maximum extraction pressure, maximum flow in extraction, maximum and desired load and the maximum degree of opening of the valves; these settings also predetermine the maximum modification of one signal by the other. Unlike the parent Specification, the turbine speed is measured by an A.C. tachogenerator whose output is also used, when great enough, to power the control network. An "economy" setting of controls is provided wherein speed only is controlled. |
