INTRODUCTION
I-E96-315B
1 - 1
SECTION 1 - INTRODUCTION
INTRODUCTION
The Hydraulic Servo Slave (IMHSS02) is a position control
module. It provides an interface through which a controller or
processor module can control a hydraulic actuator via a servo
valve. By regulating the current to the servo valve, it initiates a
change in actuator position. A linear variable differential trans-
former (LVDT) provides actuator position feedback to the HSS.
Typical uses for the HSS are positioning of steam turbine throt-
tle and control valves, gas turbine fuel valves, inlet guide vanes
and nozzle angle.
INTENDED USER
Anyone who installs, operates and maintains the HSS should
read and understand this manual before placing it into service.
Installation requires a technician or engineer with analog con-
trol tuning experience. Operation requires an individual who
knows turbine start-up and plant operating procedures.
HARDWARE DESCRIPTION
The HSS is an intelligent module, with on-board microproces-
sor, memory and communication circuitry. The module con-
sists of a printed circuit card attached to a faceplate. Two
status LEDs are visible through the faceplate. The HSS occu-
pies one slot in a module mounting unit (MMU).
HARDWARE APPLICATION
The HSS module interfaces a controller or processor module to
a servo valve, providing control (manual or automatic) of a
hydraulic actuator. The hydraulic actuator positions a gas tur-
bine fuel valve or steam governor valve. As the fuel or steam
valve opens or closes, it regulates fuel or steam flow to the tur-
bine thus controlling the turbine speed. Figure
shows an
example of the HSS within the INFI 90
®
hierarchy.
In most applications, the HSS works with the frequency
counter slave (FCS) through a multi-function processor (MFP).
The FCS counts and times pulse inputs from a magnetic sens-
ing device on the turbine shaft. The MFP uses the data from
the FCS to calculate turbine speed. The configuration within
the MFP uses the calculated speed to drive the servo valve out-
puts according to the control strategy of the user.
® INFI 90 is a registered trademark of the Bailey Controls Company.
