Practically all Navy ships are equipped with
diesel-driven emergency generators. Diesel engines
are particularly suited for this application because
of their quick starting ability. Emergency
generators furnish power directly to the radio,
radar, gunnery, and vital machinery equipment
through an emergency switchboard and automatic
bus transfer equipment.
The typical shipboard plant consists of two
diesel emergency generators, one forward and one
aft, in spaces outside engine rooms and firerooms.
Each emergency generator has its own switch-
board and switching arrangement. This controls
the generator and distributes power to certain
vital auxiliaries and a minimum number of
lighting fixtures in vital spaces.
The capacity of the emergency units varies
with the size of the ship. Regardless of the size
of the installation, the principle of operation is
You may obtain detailed information con-
cerning the operation of diesel-driven generators
from appropriate manufacturers technical
Aboard Navy ships, certain weapons, interior
communications, and other electronics systems
require closely regulated electrical power for
proper operation. Special, closely regulated motor
generator (MG) sets supply this power (usually 400
Hz). Any given ship has several MGs to provide
power to specific loads. These MGs are often of
different ratings. The rating of an MG set can be
less than 1 kW or as large as 300 kW. MGs can
also be used to provide electrical isolation.
Isolation is required when certain loads cause
distortion of the power and adversely affect the
operation of other equipment.
The MG set (fig. 12-5) is generally a two-
bearing unit. (Older units often consist of a
separate motor and generator connected together
and mounted on a bedplate.) The frame is of one-
piece construction. The stationary component
parts of the motor and generator are press fit
into a welded steel frame. The rotating elements
are mounted on a single one-piece shaft. The
MG is usually deck mounted horizontally on
its own integral feet; however, some specially
designed, vertically mounted units are also
provided. MGs with 100-kW power and larger are
usually cooled by a water-air cooler mounted on
top of the MG.
Solid-state voltage and, often, frequency
regulating systems are provided on MGs. They are
mounted either in a control box, which is directly
mounted on the MG for forced-air cooling, or in
bulkhead-mounted control panels. The voltage
Figure 12-5.Motor generator.