enable the ESU to monitor the oil temperature and
power requirements under normal operating
conditions.
shut down the APU when the oil temperature reaches
275
The control components consist of two governor
control units (GCUs), ESUs, current transformers,
APU Fuel System
BITE boxes, an APU start panel, and generator start
boxes. The controls are used to monitor operating
The APU fuel system automatically provides proper
conditions for both the engine and generator. The control
engine acceleration and maintains a nearly constant
components for each gas turbine generator set are
operating speed under all operating conditions. Fuel is
mounted in a control enclosure.
supplied to the GTE at 5 to 40 psig with a minimum flow
capacity of 200 pounds per hour. The main components
Generator Control Unit
of this system are an inlet fuel filter, a fuel pump, an
engine acceleration control assembly, start-fuel,
A GCU is installed for each ac generator. The GCU
main-fuel, and maximum-fuel solenoid valves, a
circuits are functionally divided into the power supply,
start-fuel nozzle, a purge valve, and a manifold
regulator, generator relay controls, contactor relay
assembly.
controls, feeder fault, overvoltage sensing, under-
voltage sensing, underfrequency, and over-frequency
During the APU start, the start-fuel solenoid valve
sensing sections. Each GCU monitors and controls
opens. The resulting fuel pressure forces the piston in
generator output parameters. The GCU provides voltage
the purge valve to one side in the valve chamber to allow
regulation, controls the generator output voltage,
fuel to flow through the start-fuel nozzle. At
approximately 65 percent engine speed, the start-fuel
rent malfunctions. Generator input power
solenoid valve closes to cut off the fuel pressure. A
a p p l i c a t i o n and output power regulation is
return spring transfers the piston in the purge valve to
accomplished by controlling the excitation applied
the purge position. In the purge position, compressor
to the generator by the GCU. The GCU also controls
discharge air flows through the start-fuel nozzle to clear
the excitation to the line contactor that distributes
the nozzle of residual fuel. The residual fuel is then
generator feeder lines to the load. The GCU also
directed to the combustor to be burned.
contains features that are used to establish a test mode
Electronic Sequence Unit
of operation for the generator.
The ESU is a control device that monitors APU
ELECTRICAL DISTRIBUTION
speed, turbine exhaust temperature, low oil pressure,
The electrical distribution system aboard the LCAC
sequence failure, APU temperature, and APU
is composed of a 400-Hz/208-V ac system and a 28-V
underspeed. The ESU shuts down the APU if
malfunctions occur in these circuits. Each 40
dc system. The generators each supply separate 400-Hz
switchboards which serve as central control points for
milliseconds, the ESU checks all functions and confirms
power distribution. We will take a brief look at these two
that input data is greater or lesser than programmed
power systems in the following paragraphs.
values. In the event input data is outside the programmed
values, an indication is provided in the built-in test
400-Hz/208-V AC Distribution System
equipment (BITE) box assembly and, if required, the
engine is shut down.
Primary power (400 Hz/208 V ac) is provided from
either external shore power or the two APU-driven
Generators
generators. Generator power and shore power is
The generators driven by the APUs produce a
distributed through the craft using the same busses.
120/208-V ac, 400-Hz, 60-kW, 3-phase current. The
After the generators are started and power is available,
generator is a salient-pole, brushless, permanent-
the generators can be placed on line by depressing the
magnet type that incorporates a fan and generator air
appropriate switch on the C&C keyboard. The power
inlet adapter for cooling. The ac voltage generated by
control relays are energized and route power to the main
line contractors to energize the aft busses, port and
the permanent magnet rotor and stator is connected to
an external voltage regulator where it is rectified and
starboard. The forward busses are controlled
regulated. When both generators are operating, the load
automatically through relay contacts of the line
is divided, but either generator can supply total craft
contractors. An isolation power supply wired between
