DESCRIPTION AND OPERATION
CONTROL LOOP OPERATION
2 - 2
I-E96-315B
®
feedback. The HSS is self checking and notifies the MFP if a
failure occurs.
The operator can initiate manual control of the turbine throttle
valve if a HSS communication failure with the MFP occurs. The
HSS provides inputs that the user hard wires to a +24 VDC
source. The user directs the HSS to raise or lower the actuator
through external inputs (pushbuttons, contacts, etc.). Also, a
trip bias circuit on the HSS drives the fuel throttle valve to the
closed position in an emergency.
Frequency Counter Slave
The FCS detects turbine speed by counting pulses it receives
from a magnetic pickup on the turbine shaft. Additionally, it
keeps a 24 bit timer value corresponding to the period of the
pulse count. It stores these values in a buffer and sets a data
available status bit to notify the MFP that it has current data.
FCS operation is automatic. It continuously updates the count
and holds it for the MFP.
Figure 2-1. Turbine Speed Control Loop
FCS
HSS
MFP
TURBINE SPEED
MODULE STATUS
ALARMS
MAGNETIC
PICKUP
FUEL
THROTTLE
VALVE
TURBINE
LVDT
PRIMARY
LVDT
SECONDARY
HYDRAULIC
ACTUATOR
SERVO
VALVE
POSITION
FEEDBACK
MODULE STATUS
DATA
REQUEST
CONFIGURE
SYSTEM
ALARMS
TP25013A
OPERATOR
INTERFACE
MONITOR
TURBINE SPEED
MANUAL CONTROL
POSITION
DEMAND
