12 engine-mounted thermocouples whose outputs are
system functions. For its internal and external
averaged together. The CIT sensor at the compressor
connections, the 301 sequencer uses a motherboard.
inlet provides the ambient temperature and the CIT
ELECTRONIC GOVERNOR. The electronic
signal. The box computes the CTIT for the governor to
control engine temperature.
governor is located in the LOCOP and is powered by an
external dc supply. The function of the electronic
VIBRATION MONITOR. The vibration monitor
governor is to regulate fuel flow to the engine during (1)
determines the vibration value during all SSGTG
light-off, (2) temperature control, (3) acceleration, and
operations from start-up to shutdown. The vibration
(4) power generation. To produce output control signals
levels are presented on the LOCOP panel. When
for these operations, the governor uses the following
vibration design levels are exceeded, an alarm is
input signals:
initiated on the annunciator panel.
1. Generator current
RELAY BOXES. The relay boxes furnish the
2. Generator voltage
discrete output relay contacts for the electronic
3. Engine speed
sequencer and governor circuits. These contacts provide
4. Compressor inlet temperature (CIT)
isolation for the governor's sensitive circuits, thereby
protecting them from any electrical noise developed on
5. Calculated turbine inlet temperature (CTIT)
the wiring to the devices using the outputs.
The governor uses these inputs to provide several
output control functions. First, the generator current and
OPTOISOLATORS. The optoisolators provide
voltage use provides the load sharing and parallel
isolation for the input data wiring to the sequencer and
operation control signals. The engine speed signal
the governor. Optoisolators use alighting device to keep
provides a fuel schedule during start-up and any
electrical noise on the current path from being
transmitted to the sequencer or governs. The lighting
EPCC. The CIT is used to correct the speed and turbine
device breaks the current paths of the wiring and
inlet temperature (TIT) reference circuits. The CTIT is
associated electronic device with alight beam that stops
any electrical noise on the current path from being
used to maintain safe operating temperatures during
start and rated speed.
transmitted to the sequencer or governs.
The governor control output signal causes the
ELECTROMAGNETIC INTERFERENCE
governor actuator mechanical linkage to position the
FILTERS. The EMI filters are also used on the LOCOP
fuel metering valve. The valve's position is then fed
input and output electrical lines. These filters are tuned
back to the control to tighten the servo loop and improve
devices that shunt current in a certain frequency range
the responses to speed demands.
to ground or the current supply return. This action
prevents these bothersome currents from interfering
For testing, a suitcase-type electronic governor test
Set is used. The test set is equipped with hookup cables
with the desired signals and distorting their value or
for power, an interface, and a 28-volt dc power supply
utility.
10 power the governor during test only.
ISOLATED SIGNAL CONVERTERS. The
ISCs provide very stable and accurate current or voltage
SPEED/TEMPERATURE BOX. The speed/
signal outputs. The ISCs receive inputs that have
temperature box monitors the SSGTG for speed and
inherent instability characteristics. They develop these
correct operating temperatures. This box is an electronic
signals into very stable and accurate current or voltage
digital control that provides data for starting, normal
output signals. The inputs are data from the
running, and emergency shutdown. Inputs to the
speed/temperature box and represent TIT and engine
speed/temperature box include the following:
speed. As a GSM, you may also hear ISCs referred to as
1. SSGTG speed
4-20 milliampere conversion modules.
2. Turbine outlet temperature (TOT)
TRANSIENT LOAD SENSOR. The function of
3. CIT
the transient load sensor is to monitor varying loads and
Turbine speed comes from a magnetic pickup positioned
prevent engine stalls. The transient load sensor uses a
0- to 2-volt ac signal from burden resistors placed
at the power takeoff (PTO) shaft. The TOT is taken from
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