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 TM 55-1905-223-24-18-1
Section III.
PRINCIPLES OF OPERATION
1-10. General.
The following paragraphs provide principles of operation of the LCU
systems.
1-11. Power Generation System. The power generation system provides the LCU with
primary (240 Vac, 3-phase, 60Hz, 250kW) and emergency (240 Vac, 3-phase, 60Hz, 40kW)
electrical power (FIGURE 1-1). Primary power is generated by one of two ship's
service diesel generator (SSDG) sets, which supply the main switchboard and the
emergency switchboard through a bus tie from the main switchboard. Emergency power
is generated by an emergency diesel generator set, which supplies the emergency
switchboard for continued operation of vital systems and equipment during loss of
primary power. In port, the LCU is capable of receiving shore power (480/240 Vac)
through a shore power cable terminating at a two-connection shore power box. I f
available shore power is 480 Vac, the power is selected at the main switchboard
through a circuit breaker and stepped down to 240 Vac by three shore power
transformers, prior to main switchboard entry. Shore power of 240 Vac is selected
at the main switchboard by circuit breaker, and bypasses the 480 Vac transformers.
Automatic bus transfer equipment, located in the emergency switchboard, isolates the
emergency switchboard from the main switchboard upon loss of primary power and
allows emergency power to be supplied through the emergency switchboard.
a. Ship Service Diesel Generator Engine. Two diesel generator set engines power
individual ship service diesel generators, which provide primary electrical power
throughout the LCU. The port ship service diesel generator engine (No. 2) is air
started; the starboard ship service diesel generator engine (No. 1) is electrically
started. Engine control and monitoring are provided from the engine room console
and at the individual engine control panel.
b. Shin's Service Generator. Two 250 kW brushless exciter generators provide
240 Vac, three-phase, 60 Hz primary ship's service power. Each generator is capable
of providing 110 percent of the necessary at sea load for the propulsion and safety
of the ship under normal conditions. The generators may be operated in parallel;
however, normal operation has one generator on line and the other in reserve.
C. Main Switchboard. The main switchboard (FIGURE 1-2), located in the engine
room operating station, provides generator selection, shore power selection, and
power distribution for ship's service 240 Vac and 120 Vac power. D i s t r i b u t i o n of
120 Vac is accomplished by ship's service 120 Vac transformers located in the engine
room operating station. The emergency switchboard bus tie provides 240 Vac to the
emergency switchboard. Power selection is provided by closing circuit breakers on
the switchboard. Power monitoring is provided by ammeters, voltmeters, frequency
meters, and synchronization meters. Controls are provided for manual and automatic
generator voltage regulation and generator engine speed regulation, The switchboard
bus tie also serves as an emergency 240 Vac power feedback source for the main
switchboard from the emergency switchboard, to power selected equipment systems
during emergency power conditions. An interlock system is incorporated into the
switchboard to prevent shore power from being applied to the switchboard while
generator power is applied. The interlock system also prevents the emergency
switchboard emergency generator circuit breaker from being closed.
d. Emergencv Switchboard. The emergency switchboard (FIGURE 1-3), located in
the emergency generator room, normally receives 240 Vac primary power from the main
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