초록 ▼

An electrohydraulic control system and method are disclosed for operating valves controlling the admission of steam to a steam turbine. The system includes a mode transfer unit for effecting a transfer between a full arc mode of valve operation to a partial arc mode of operation such that the temper

An electrohydraulic control system and method are disclosed for operating valves controlling the admission of steam to a steam turbine. The system includes a mode transfer unit for effecting a transfer between a full arc mode of valve operation to a partial arc mode of operation such that the temperature of the steam turbine varies in a controlled manner, thus permitting control of turbine stresses. Apparatus is described for generating mode flow signals, combining the signals using time ratio switching such that during a mode transfer the signals vary linearly with an admission reference factor characteristic of each mode, and generating valve lift signals from a combined flow signal using multi-slope, piecewise linear approximations to the flow-lift characteristics of the full arc mode of valve operation. The system permits mode transfers wherein total steam flow is held substantially constant and first stage turbine temperature is caused to vary linearly with admission reference factor.

대표청구항 ▼

In combination with a control system for a steam turbine having a plurality of valves arranged about nozzle arcs for admitting steam in a full arc mode and in a partial arc mode as determined by an admission reference factor AR and wherein said control system includes a flow reference signal indicat

In combination with a control system for a steam turbine having a plurality of valves arranged about nozzle arcs for admitting steam in a full arc mode and in a partial arc mode as determined by an admission reference factor AR and wherein said control system includes a flow reference signal indicative of turbine load, the improvement comprising a controller for transferring between modes so that steam flow remains substantially constant during transfer and temperature of a predetermined portion of the turbine varies substantially linearly with admission reference factor as it is varied between modes, said controller comprising: means for generating said admission reference factor AR and for varying said factor during a mode transfer; time ratio means for generating a multiplier (1-AR) in responsive to said admission reference factor; a plurality of flow signal generators, there being one flow signal generator per valve, each said flow signal generator producing a full arc mode signal FA, a partial arc mode signal PA, and a reversing signal R, each said signal being a preselected function of said flow reference signal; a plurality of signal conditioners for producing a plurality of combined flow signals according to the signal relationship FA+(R+PA) (1-AR), there being one signal conditioner and one combined flow signal per valve; and, a plurality of lift signal generators for producing valve lift signals in response to said combined flow signals, there being one lift signal generator per valve.