Figure 12-10.—Switchboard indicating meters.
watertight integrity than steam pipes or
MOTOR
mechanical shafts. Another reason is that damage
to a steam line can cause steam to escape,
resulting in personnel injury. If an electric
cable is used and a fault occurs, the circuit
breaker protecting the cable opens automatically.
The ac motor is used extensively by the Navy
because it is smaller and requires less maintenance
than the dc motor.
Most ac motors used aboard ship use three-
phase, 60-Hz, 450-volt power. Although most ac
motors operate at a single speed, some motors,
such as the prime movers for fuel oil pumps, lube
oil pumps, and ventilation fan motors, have two
operating speeds.
CONTROLLERS
Controlling devices are used to start, stop,
speed up, or slow down motors. In general,
these controllers are standard equipment aboard
ship and are operated either manually, semi-
automatically, or automatically. They are drip-
proof and shock resistant. In some installations,
the controllers are operated by remote control,
with the switch at a convenient location.
Motor control devices (controllers, master
switches, and electric brakes) protect the equip-
ment to which they are connected. Controllers
provide protective and governing features for
every type of shipboard auxiliary. Various
types of master switches are used to govern the
12-11
