Article Ref – ART270
This video explains how the hydraulic twin servo system controls the position of the Inlet Guide Vanes (IGV) and Variable Stator Vanes (VSV) in a gas turbine. It begins with the physical layout of the hydraulic pump and twin servo assembly and introduces the closed-loop control concept used to position the blades accurately.
The video then breaks down the operation of the torque motor and shuttle, or spool, valve. You’ll see how the turbine control system uses a 0–200 mA signal, with 110 mA as the null position, to balance or shift control pressures on either side of the spool valve.
Using a practical example, the video shows how small changes in control current create pressure differences that direct hydraulic oil to extend or retract the actuator. Finally, it explains how position feedback returns the system to a neutral, stable condition once the desired blade angle is reached, ensuring precise and repeatable vane control.