Figure 3-4.--Front-service switchboard.

The following discussion describes the general

in the rear of the board. This results in a saving of

principles of a forward main IC switchboard, such as

space, which is most important aboard ship.

the one illustrated in figure 3-4. For a detailed

description of the main IC switchboard(s) and

The switchboard is a type 1, deck-mounted, front-

associated equipment installed on your ship, you

serviced, enclosed, box-type structure. The structure

should consult volume 5, part 1, of the Ship

is divided into panels, with each panel having a

Information Book for your ship and any related

hinged door. Lightweight items, such as switches,

technical manuals.

meters, fuse holders of up to 60-ampere capacity, and

other equipment, are mounted on the front of the

hinged doors. The doors are hinged on the left-hand

Power Distribution Section

side and are provided with two "dog-type" latches on

the right-hand side and a door stop assembly.

The power distribution section of the

switchboard (panels 1 through 4) is supplied with

Terminal boards are mounted on the rear of each

power from as many sources as possible. The power

panel. Cables are terminated at the terminal boards

distribution section, in turn, supplies power from

on the inside of the panel. Wiring between the

its various buses to several IC and FC circuits.

terminal boards and the door-mounted equipment is

Power distribution by the switchboard of a

installed to ensure free-swinging of the doors without

particular ship depends on the requirements of the

interference from, or damage to, the wiring harness.

IC and FC systems installed.

The switchboard consists of a power distribution

PANEL 1.-- The 450-volt, 3-phase, 60-Hz bus

section and an ACO section, The power distribution

located in panel 1 is energized from one of three

section may be subdivided into various buses,

power sources (normal, alternate, or emergency).

depending on the individual ship requirements.

Power becomes available through the use of two

Figure 3-4 is an example of a front-service

mechanically interlocked switches and an automatic

switchboard that is currently installed aboard some

bus transfer (ABT) device located in panel 1. An

naval vessels. The distribution section consists of

indication of the power available is provided through

panels 1 through 4, while the ACO section consists of

the use of indicator lights connected via transformers

panels 5 and 6.

to each power source. On some of the newer ships in

27.270

Figure 3-4.--Front-service switchboard.

3-6