safety shutdown, an on-off control, and local and remote
output of the stator is fed to a rectifier bridge consisting
of six silicon diodes, which are normally located in the
end bell of the alternator. The rotor of the alternator has
The following is a brief description of the
one coil and two 6-finger rotor halves. In effect, it is a
compressor controls and indicators shown on figure 5-8.
12-pole rotor. Direct current (for field excitation) is
supplied to the rotor coil through a pair of brushes and
OIL PRESSURE GAUGE-- Measures oil
pressure at the oil pump discharge.
slip rings. The rectifying diodes will pass current from
the alternator to the battery or load but will not pass
WATER INJECTION PRESSURE GAUGE--
Indicates the freshwater pressure in the water system
The voltage regulator is the only device used with
manifold downstream of the freshwater falter.
the alternator. It can either be built into the case or
AIR DISCHARGE PRESSURE GAUGE--
externally mounted away from the alternator. The
Indicates the air pressure in the compressed air receiver
voltage regulator uses no mechanical contacts. It uses
only a solid-state circuitry, is a sealed unit, and does not
DEW POINT SAMPLING CONNECTION-- A
suitable instrument can be attached to this connection to
The electrical equipment is designed to operate at a
measure the moisture content of the compressed air
specific voltage irrespective of the speed of the prime
DOWN SELECTOR SWITCH-- Gives remote
Small craft are exposed to the most extreme of
emergent y stop control to the auxiliary control console
weather conditions and must, therefore, receive a great
(ACC) when in the normal REMOTE position. The
deal of attention. Using the information given in the
RESET position is used to reset the control circuitry
previous section, you should have no problem taking
after a remote shutdown to permit restarting the
care of the normal maintenance requirements necessary
compressor. The is a spring return from the RESET
to keep the small craft aboard ship operational.
to LOCAL setting. It is mounted on the controller door.
MATIC-120 PSIG SELECTOR SWITCH-- This
operating mode selector switch is located on the
There are many uses for compressd air aboard ship.
Some of these include operating pneumatic tools,
ejecting gas from guns, starting diesel engines, charging
AIR DISCHARGE THERMOMETER--
and firing torpedoes, and operating automatic
Indicates the compressed air temperature in the air
receiver. It is mounted on top of the receiver.
supplied to the various systems by low-pressure
OFF/ON SELECTOR SWITCH-- Provides
(LP--150psi or below), medium-pressure (151 to 1,000
manual start-stop control of the compressor. It is
psi), or high-pressure (HP--1,000 psi and above) air
mounted on the controller door.
ANNUNCIATOR PANEL-- Shows causes of
LP AIR COMPRESSOR
automatic safety shutdowns using shutdown alarm
Most of the air compressors aboard ship operate on
SEAWATER THERMOMETER-- Indicates the
the same principles, electrical requirements, and
controls. Therefore, the model discussed is typical of
compressor cooling system.
most units installed aboard ship.
SAFETY SHUTDOWN RESET PUSH
The air compressor (fig. 5-8) supplies the air for the
BUTTON-- Resets the control circuitry after an
ship's LP air system. The air compressor is
direct-driven by an electric motor through a flexible
automatic shutdown is initiated by any of the
compressor safety devices. If not pressed to reset, the
coupling. It has a manual and two automatic operating
compressor cannot be restarted.
modes (either at the low or high range), an automatic