Page 169 - Steam Turbines Design, Applications, and Rerating

Governors and Control Systems 149

Figure 8.7 Woodward electronic governor. (Elliott Company, Jeannette, Pa.)

printed circuit boards. The chassis internally carries the terminal
strips for the input/output connections, transformer, diodes, transis-
tors, potentiometers, etc.
The speed-setting potentiometer establishes the reference voltage
at the input to the EGM box and thus establishes the set point. This
speed-setting potentiometer can be motor operated if remote control
manual speed setting is required. A pneumatic speed changer is also
available.
3. The EGM signal feeds the EGR hydraulic actuator of the system. The
hydraulic actuator adjusts turbine speed as dictated by the signal
produced by the EGM control box. The essential element of the EGR
actuator is the electrohydraulic transducer that directs oil to and
from the power piston or servomotor. This servo is remotely mounted
on the turbine similar to PG governors on multistage turbines.