DESCRIPTION AND OPERATION
HSS MODULE OPERATION
I-E96-315B
2 - 3
For the MFP to work with the FCS, it requires function code
145 in its configuration. Function code 145 defines the slave
address, high/low speed alarms and high/low rate of change
alarms. The block output is frequency of input pulses in hertz.
The frequency counter slave continuously checks itself and
notifies the MFP if a failure occurs.
Multi-Function Processor
The MFP is the master module of the control loop and controls
turbine speed according to the users control strategy. 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 tur-
bine speed goes above or below the speed set point in the MFP
configuration, the MFP will send a position demand to the HSS
to adjust the 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.
HSS MODULE OPERATION
The HSS interfaces the MFP to a servo valve, providing the MFP
with position control of a fuel throttle valve or steam governor
valve. The HSS microcontroller carries the workload. It is able
to perform multiple tasks with the help of the module support
circuitry. The microcontroller provides the intelligence (firm-
ware) needed to relay position demands from the MFP, read
position feedback information, set targets for the output,
present module status information to the MFP, direct manual
control and do self check diagnostics. There are seven func-
tional blocks (see Figure
).
Slave Expander Bus Interface (XBUS I/O)
Status and Data Buffers
Microcontroller (MCU)
Position Demand and Output
Position Feedback Input
LVDT Oscillator
Digital I/O
