9.
volt load can be fed by connecting it
to the three hot wires.
And finally,
So far, the layout and some of the
any 3 4W 120/208 volt load can be fed
basic fundamentals of electric power
power by connecting it to all four
and distribution systems have been
wires.
discussed.
To operate these systems
properly and efficiently, an adequate
8.
COMPARISON OF SYSTEMS
amount
of
power
must
always
be
produced.
The practical source of
Three-phase four-wire systems require
power
for
the
military
is
the
less wire by weight to transmit a
generator which converts mechanical
specified load over a given distance
energy
into
electrical
energy.
(within the limits set for phase
Hydroelectric and steam-turbine plants
voltage, permissible line drop, and
for developing large amounts of power
wattage lost) than do other types of
are
used
in
commercial
power
systems.
Using the single-phase two-
systems.
The military engineer will
wire system as a basis for comparison
only have to perform minor repairs
(representing 100 percent) a single-
for plants of this type if they happen
phase three-wire system requires only
to fall into friendly hands in a
37.5 percent as much wire by weight;
Theater of Operations.
If possible,
the
three-phase
three-wire
delta
trained
civilian
personnel
should
system, 75 percent; and the three-
be
employed
in
the
repair
and
phase
four-wire
wye
system,
33.3
operation of such plants. Supervisors
percent.
34W 120/208V system Y-connection.
Figure 8.
1-6
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