Figure 2-10. Double bus arrangement and automatic transfer panel, wiring diagram.

TM 11-5895-1012-10

this provides for losses and the capability to maintain

tages of light weight, quick starting, and acceptance of

constant speed at full load. The engine must also be

load without the usual warmup period. A disadvantage

equipped with a governor to maintain a constant out-

is their high fuel consumption rate.

put when the generator is connected to a varying load.

2-27. Power Distribution

Diesel and gasoline engines are used as prime movers.

a General. As previously indicated, most DCS

Stations have at least two separate power sources, pri-

(1) Diesel Engines. Both low-speed and high-&

mary power and auxiliary power. These two power

diesel engines are used as prime movers. High-speed

sources must be selectable; that is, switching and other

necessary mechanisms must be provided to permit

diesel engines can be installed at less cost than the low-

speed, heavy-duty diesel engine, but not operated or

station personnel to select the desired source. Change-

over must be fast, in fact, it should be possible to

maintained as economically.

(2) Gasoline Engines. Gasoline engines are used as

change power sources without any break in the power

supply to the communications equipment. When pri-

prime movers to drive generators of limited capacity

mary power fails without warning, this may not be

to supply power on an intermittent or purely auxiliary

basis. They should not be used to drive generators to

possible, but activation of the auxiliary power and con-

nection to the communication should comply with the

supply power continuously or over extended periods of

prescribed standards. In addition to the power change-

time, because the useful life of a gasoline engine in

over requirements, normal operation requires that the

continuous service is relatively short. The initial cost

power demands within the station be balanced among

of a gasoline engine is much less than that of a diesel

the phases of *phase primary power supplies.

engine, but maintenance costs are higher.

b. Switchboards and Automatic Transfer Panels.

(3) Gas Turbines. Gas turbines have the advan-

EL3Z0055

Figure 2-10. Double bus arrangement and automatic transfer panel, wiring diagram.