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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
on cable racks.
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
(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.

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