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 TM 55-1905-242-14
OPERATOR, UNIT, DIRECT SUPPORT, AND GENERAL SUPPORT MAINTENANCE
FOR LANDING CRAFT, MECHANIZED (LCM-8) (ALL VESSELS WITH MOD 2 APPLICATION)
THEORY OF OPERATION
ELECTRICAL SYSTEM
GENERAL
The LCM-8 Mod 2 has two alternating current electrical systems (110 Vac and 220 Vac) and two direct current electrical
systems (12 Vdc and 24 Vdc). The electrical systems supply all of the electrical needs of the LCM-8 Mod 2.
The alternating current electrical systems are both single phase systems. The 220 Vac (Volts alternating current) system has
two power sources. Power may be derived from the diesel generator or from an outside power source via the shore power
receptacle and the shore power cable. The 110 Vac system receives its power from the diesel generator and from transform-
ers powered by the 220 Vac system.
The direct current electrical systems are two-wire isolated ground systems. A 24 Vdc (Volts direct current) system supplies
many of the lighting, communication, and accessory systems on board the LCM-8 Mod 2. This power is supplied by
dedicated battery banks, by a battery charger, and by propulsion engine-driven alternators depending upon the operating
conditions. Certain communication systems require 12 Vdc power. These systems are supplied by 24 Vdc to 12 Vdc
transformers. The generator starting system also requires 12 Vdc power. This power is supplied by a dedicated battery that
is recharged by an alternator mounted on the diesel generator.
Foldout sheets FO-1, FO-2, FO-3, and FO-4 contain wiring diagrams for the LCM-8 Mod 2 electrical system.
ALTERNATING CURRENT POWER SUPPLY
Diesel Generator
A Northern Lights M-844L diesel generator supplies power to the 220 Vac and 110 Vac electrical systems when the vessel is
underway or when shore power is otherwise unavailable. Both 220 Vac and 110 Vac outputs are available directly from the
diesel generator. With the diesel generator running, the LCM-8 Mod 2 is completely self-sufficient with respect to electrical
power even with both propulsion engines secured.
Shore Power
The LCM-8 Mod 2 is provided with a shore power receptacle and shore power cable that provide a 220 Vac single-phase
power supply to the vessel from a pierside power supply or from another vessel. When connected to shore power, the LCM-8
Mod 2 is completely self-sufficient with respect to electrical power, even with both propulsion engines and the diesel
generator secured.
Alternating Current Transformers
The LCM-8 Mod 2 is provided with two alternating current transformers that transform 220 Vac to 110 Vac. The first
transformer, located near the communications rack, supplies power to the data terminal, the parallel port printer, and the serial
port printer. A second transformer, located in the engine room, powers the microwave oven and the 110 Vac receptacles
located in the galley area.
DIRECT CURRENT POWER SUPPLY
Battery Charger
When the diesel generator is running, or the vessel is connected to shore power, 24 Vdc power is supplied to the vessel's
systems by the battery charger. The battery charger transforms 220 Vac to 24 Vdc. The battery charger has a maximum
output of 100 amps and can charge the battery bank and power vessel systems simultaneously. When the vessel load is less
than 100 amps, the remaining charger capacity is available for battery charging.
0005 00-1
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