Uninterruptible Power Supply

TM 11-5895-1012-10

Automatic transfer panels provide an automatic

switching arrangement designed to maintain power

with minimum interruption for the operation of DCS

Station equipment. Transfer panels must handle

separate sources of power. In the case of a combination

of generators, or of generators and commercial power

(fig. 2-10). the desired power source can be selected to

permit rotation of the engine-generators. A time-delay

relay will postpone switching the load to any engine-

generator until the engine reaches its recommended

operating temperature. If there is a gradual decrease

in voltage, voltage-controlled relays will switch the

load to an alternate source of power.

c. Station Power Panels. The main power distri-

bution panels are determined by the individual station

requirements. When two or more power sources are

operated in parallel, a master control switchboard pro

vides a means for measuring the output frequency,

voltage, and current. These measurements generally

are made at the main bus bars, and thus indicate the

total load and combined power supplied.

d. Distribution for DCS Stations. DCS Stations re-

ceive power from an external distribution system or

local Class A primary power plant. Distribution within

the DCS Station begins at the main power panel and

extends to the operating equipment. Subpanels, trans-

formers, and circuit breakers may be included in the

distribution circuits. Communication equipment in the

station may he divided into two or more major groups.

Each major group of equipment is connected to the

main power panel. Radio transmitting stations have

the largest and most complex power installation of the

DCS. The output voltage and the configuration of

engine-generators is connected to transformers, or

direct& to the bus bars on the main switchboard.

Distribution lines from the power panel to operating

2-28. Uninterruptible Power Supply

equipment are installed in floor trenches, in ducts, or

(UPS)

on cable racks.

(fig. 2-11, 2-12)

e. Simplified Power Distribution. The following is a

description of the simplified power distribution shown

in figure FO-1. Many different arrangements are

possible at all stages, and each station's requirements

will determine the best arrangement for the particular

installation.

(1) Primary power at 2400 volts is available from

the commercial power source or from either of the two

generators installed at the station. At the main switch-

board, located in the utility building with the gen-

erators, power from any one or more of these sources

can be applied to either or both of the power distri-

bution cables to the operations building. In this

example, all switching is performed at 240 volts, after

reduction by deltadelta transformers. In some cases,

these switching functions may be performed at the

2400-volt level and the transformer located in the

operations building.

2-30