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Manual 35018V1
505XT Digital Control System for Steam Turbines
Woodward
108
Figure 3-33. Configured for Full Decoupled mode (No Map)
Inlet Steam Pressure Control
The Inlet Steam Pressure PID controller can be used to control the turbine inlet pressure, which is directly
related to turbine speed/load.
The selection of the Process Variable to use for this control is:
Inlet Steam Pressure
This input is a 4 to 20 mA current signal. The PID control amplifier compares this input signal with the
Inlet Steam Pressure set point to produce a control output. In a single valve application this signal is sent
to the digital Speed LSS (low-signal select) bus. If the application is for an Extraction/Admission type
turbine then the output is sent directly to the ratio limiter controller.
This control works exactly the same as the Auxiliary Control Limiter in a single valve turbine. In
Extraction/Admission units, this PID is always a controller (if used) and is connected directly to the Ratio
Limiter block to allow operational modes where this parameter is either the primary or secondary control
priority of the 505XT.