THEORY OF OPERATION
FCS MODULE OPERATION
I-E96-314A
2 - 3
external inputs (pushbuttons, contacts, etc.). Also, a trip bias
circuit on the HSS allows the operator to manually drive the
fuel throttle valve to the closed position in an emergency.
Multi-Function Processor
The MFP is the master module of the control loop and controls
turbine speed automatically. The MFP requests data from the
FCS to calculate turbine speed. If the FCS has data available, it
sends it to the MFP. If there is no data available the MFP must
make another request. If the turbine speed goes above or below
the speed limit set in the MFP configuration, the MFP will send
a position demand to the HSS to adjust the fuel throttle valve.
This process repeats continuously at the cycle time of the MFP.
The user sets the turbine speed limits and high/low speed
alarms during configuration of the MFP and slave modules.
Additionally, the user calibrates the hydraulic actuator and
LVDT. The MFP sends data, module status and alarms to the
operator interface during normal operation. The operator can
monitor system operation and initiate automatic or manual
control through the operator interface.
FCS MODULE OPERATION
The FCS interfaces the MFP to a steam or gas turbine, provid-
ing the MFP with turbine speed data. The FCS microcontroller
(MCU) carries the work load. It is able to perform multiple
tasks with the help of the module support circuitry. The MCU
provides the intelligence (firmware) needed to count and time
input pulses, update process data buffers, do self check diag-
nostics and give module status information. The MFP retrieves
data from the FCS without interrupting the counting and
updating process. Therefore the most current values are avail-
able. There are eight functional blocks (see Figure
Microcontroller (MCU)
Input Signal Conditioning
Module Status (MOD STAT)
Watchdog
Storage Areas (Doubled Buffered and Latched Data)
Sequencing Logic
Slave Expander Bus Address (XBUS ADD)
Slave Expander Bus Interface (XBUS I/O)
All the blocks of the support circuitry work together to condi-
tion the input, time the input, write to buffers and communi-
cate with the master module. Power enters the board by way of
the module mounting unit backplane.
