Gas Turbine Handbook : Principles and Practices

Gas Turbine Control 75
Figure 5-3. Shaft horsepower vs. inlet temperature.
Controls for a typical gas turbine generator or mechanical drive
application in the early 1970s were electric controls and consisted
of Station Control, a Process Control, and a Turbine Control 2 . In
this type of control system all control functions ( Start, Stop, Load,
Unload, Speed, and Temperature) were generated, biased, and computed
electrically. Output amplifiers were used to drive servo valves,
employing high pressure hydraulics, to operate hydraulic actuators.
These actuators were sometimes fitted with position sensors to provide
electronic feedback.
The advent of programmable logic controllers and microprocessors
(Figure 5-5) in the late 1970s eliminated these independent control
loops, and facilitated multi-function control. Regardless of type,
all controls must accomplish the same basic functions.