control has been achieved, the start/run latch is
The less current supplied to the actuator, the
set to run. The run indicator LED lights up.
greater the fuel supplied to the turbine.
TEMPERATURE CHANNEL MODULE.--
MOTHERBOARD MODULE.--The mother-
The temperature channel prevents turbine
board's primary function is to interconnect the
temperature from exceeding safe operating limits.
eight daughter boards with each other and the J1,
A signal proportional to TIT is compared with
J2, and J3 receptacles. The motherboard also has
the start or run temperature reference. The
the power drive transistor for the actuator. This
amplifier generates a voltage signal output to the
transistor is mounted on a heat sink that is
LSS bus to limit TIT.
connected to the chassis.
The temperature control amplifiers operate
similar to the speed control amplifiers. Separate
s t a r t and run LEDs are provided. They
compensate for the longer thermocouple reaction
ALTERNATING CURRENT
time at low turbine speeds. This lag is due to low
GENERATOR AND VOLTAGE
airflow at low speeds.
REGULATOR
A start fuel schedule supplies enough fuel for
TIT to reach the acceleration temperature range.
As stated earlier in this chapter, two different
When the turbine reaches the acceleration range,
ac generators are powered by the Allison 501-K17
the temperature control requires less fuel than the
engine. The model 104 GTGS is a 2000-kW,
fuel limiter. The LSS bus then selects the
3200-amp unit, while the model 139 GTGS is a
temperature control for the rest of turbine
2500-kW, 4000-amp unit. Each generator outputs
acceleration.
450-volt, 60-Hz, 3-phase ac at a 0.8 power factor
When the turbine reaches isochronous or rated
with an 1800 rpm input. Each unit is a totally
speed (60 Hz), the speed control takes control
enclosed, salient-pole, two-bearing generator.
from TIT control. Then the start/run reference
Each unit has an air cooler mounted above it to
switches to run limit. TIT is a function of load
cool the generator. An independent lube oil
on the turbine. If load is increased until TIT
system using 2190 TEP lube oil provides
equals the TIT reference, the temperature control
lubrication for the generator bearings.
will maintain TIT at that level. In droop mode
or when paralleled with other units, the generator
load will be maintained at a level to produce the
GENERATOR ASSEMBLY
set TIT. When no other source is available to carry
the excess load, the temperature control will
The model 104 and the model 139 generator
reduce speed.
assemblies both have eight major components.
However, only seven of these components are
identical on both generators. The identical
FINAL DRIVER MODULE.--The final
components are as follows:
driver module generates current to position the
actuator as required by the controlling channel.
An oscillator generates an excitation voltage for
The stator assembly of four-pole, four-
the LVDT located on the LFV. As mentioned
circuit delta connection
before, the LVDT is mechanically linked to the
fuel valve metering sleeve, It senses the fuel valve
The rotor assembly with four salient
position. This sleeve is moved through the action
poles
of the actuator. As it moves, the excitation voltage
transmitted to the LVDT output is changed. The
The front and rear end bracket assemblies
output of the LVDT is proportional to the
position of the fuel metering sleeve. A de-
The front and rear bearing assemblies
modulator in the final driver changes the LVDT
feedback signal to a dc voltage. This voltage is
The permanent magnet alternator (PMA)
and lube oil pump assembly
proportional to the sleeve position on the fuel
valve. The final driver amplifier compares the
The air cooler assembly
input from the control circuits with the LVDT
voltage. Then it correctly positions the fuel valve.
The final driver and actuator are reverse acting.
The stator terminal/connection box.
3-39
