MOTOR CONTROLLERS
2. Bus feeder: 2S-4P-31
2S--Fed from SS switchgear group No. 2
Motor controllers function to start a motor,
to stop it, or to increase or decrease the speed of
4P--450-volt power cable
a two-speed motor. There are many different
types of controllers. In this chapter we will only
31--Supplying load center SWBD No. 31
discuss the most common types used on gas
turbine ships.
3. Feeder: 31-4P-(3-125-2)
A MANUAL controller is operated directly
31--Fed from load center SWBD No. 31
through a mechanical system. The operator closes
and opens the contacts that normally energize and
4P--450-volt power cable
de-energize the connected load.
In a MAGNETIC controller, the contacts are
(3-125-2)--Supplying power distribution
closed and opened by electromechanical devices.
panel located on third deck, frame 125,
The devices are operated by local or remote master
port side
switches (defined in the next section). Magnetic
controllers may be semiautomatic, automatic,
4. Main: (3-125-2)-4P-C
or a combination of both. Normally, all the
(3-125-2)--Fed from power distribution
functions of a semiautomatic magnetic controller
panel located on third deck, frame 125,
are governed by one or more manual master
port side
switches; those of an automatic controller are
governed by one or more automatic master
4P--450-volt power cable
switches. Automatic controllers must be energized
initially by a manual master switch. A full and
C--Indicates this is the third cable from the
semiautomatic controller can be operated either
panel, fed by breaker C
as an automatic or as a semiautomatic controller.
An ACROSS-THE-LINE controller throws
5. Submain: (3-125-2)-1P-C1
the connected load directly across the main supply
(3-125-2)--Fed from power distribution
line. The motor controller may be either a manual
panel located on third deck, frame 125,
or magnetic type. The type depends on the rated
port side
horsepower of the motor. Most controllers found
on gas turbine ships are magnetic across-the-line
1P--120-volt power cable
controllers.
C1--Indicates first cable fed (through a
transformer) by the main
Types of Master Switches
6. Branch: (3-125-2)-1P-C1B
A master switch is a device that controls the
(3-125-2)--Fed from power distribution
electrical operation of a motor controller. They
panel located on third deck, frame 125,
can be manually or automatically operated.
port side
Drum, selector, and pushbutton switches are
examples of manual master switches. The
1P--120-volt power cable
automatic switch functions through the effect of
a physical force, not an operator. Examples of
C1B--Indicates second cable fed by the
automatic master switches include float, limit, or
submain
pressure switches.
7. Subbranch: (3-125-2)-1P-C1B2
Master switches may start a series of opera-
tions when their contacts are closed or when their
(3-125-2)--Fed from power distribution
contacts are opened. In a momentary contact
panel located on third deck, frame 125,
master switch, the contact is closed (or opened)
port side
momentarily; it then returns to its original
condition. In a maintaining contact master switch,
1P--120-volt power cable
the contact does not return to its original condi-
tion after closing (or opening) until again
C1B2--Indicates second cable fed by the
operated.
branch
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