Upon a change in speed of the hydraulic turbine runner, the sleeve of centrifugal governor 1 moves up or down, shifting valve spool 2. Hydraulic fluid from the valve is directed to servomotor 3 and moves piston 4, which changes the position of the regulating member. At the same time, when piston 4 is moving in the closing direction, bell-crank lever 5 and rod 6 move piston 7 of the idle-drain cataract downward. Through lever 12, this shifts valve spool 8 upward. Fluid from the valve is directed to servomotor 9, moving its piston downward and opening idle-drain valve member 13. At this, the required amount of water is drained from the inlet volute chamber to prevent water hammer. Feedback levers 10 and 11 return valve spool 2 to its central position. The idle-drain valve member closes slowly due to throttling of the fluid flowing from one end of the cataract housing to the other. When the regulating member is moved in the opening direction, the idle-drain valve member is not opened because a check valve is provided in cataract piston 7.
$4243$CHP,Rg$