DESCRIPTION AND OPERATION
CONTROL LOOP OPERATION
2 - 2
I-E96-322A
®
A linear variable differential transformer (LVDT) measures
actuator position. The HSS module supplies a 400 to 15,000
hertz excitation voltage (selected through function code 55) to
the LVDT primary. A zero in the LVDT frequency specification
of function code 55 enables an excitation voltage for a DC
LVDT. A dipswitch on the HSS module selects the excitation
voltage amplitude ranging from 1.08 volts peak to 9.0 volts
peak.
The LVDT secondary develops a differential voltage propor-
tional to the position of the hydraulic actuator. The HSS mod-
ule converts the differential voltage to digital data and sends it
to the MFP module. Using the data the MFP module stores
(during valve calibration) in its configuration specifications
(S18 through S21), it translates the LVDT secondary
Figure 2-1. Turbine Speed Control Loop
FUEL THROTTLE
VALVE
TURBINE
HYDRAULIC
ACTUATOR
SERVO
VALVE
MAGNETIC
PICKUP
FCS
HSS
POSITION
DEMAND
MODULE STATUS
MODULE STATUS
TURBINE SPEED
ALARMS
DATA
REQUEST
MFP
MONITOR TURBINE SPEED
CONFIGURE SYSTEM
MANUAL CONTROL
ALARMS
OPERATOR
INTERFACE
TP25013A
LVDT
PRIMARY
POSITION
FEEDBACK
LVDT
SECONDARY
