and
guards
will
be
provided
as
changing the strength of the magnetic
circumstances require, depending on
field.
The generator nameplate gives
the danger of sabotage.
If this is
the characteristics of the machine.
not possible, the operation must be
10.
GENERATOR SELECTION
assigned to the technically best-
qualified
personnel
available
from
friendly forces.
The primary objectives of generator
selection are to determine the size,
a. DC generators. The DC generator
number, and type of generators to be
is
comparatively
simple
in
used in the distribution system.
The
construction,
operation,
and
type of generator to be used is
maintenance,
requiring
little
determined by the type of service that
Generator speed
must be supplied.
If any facility
is not critical, it supplies its own
within the installation requires a 3-
phase 4-wire load, a 3 4W generator
field current, and voltage regulation
can be designed into the machine.
A
must be used since no other generator
basic disadvantage of DC power is the
will supply this type of power. Thus,
limited
distance
it
can
be
even though only one building may
3
transmitted.
Since DC power is used
require
this
service,
a
4W
at
the
voltage
at
which
it
is
generator is needed.
As explained
generated and utilization voltages are
previously, this generator may serve
usually
120
or
240
volts,
large
other loadings in the system, such as
1 2W loads. If only 1 2W and 1 3W
currents are required to produce even
moderate amounts of power.
For this
loads are present in the installation,
a 1 2W generator with a transformer
reason, direct current generators are
used only for special purposes such as
will
suffice.
However,
in
TO
battery charging, communications, and
construction, it is common practice to
use a 3 4W generator to feed 1 3W
searchlights,
and
will
not
be
considered further in this course.
loads.
In such a case, efficiency of
the load is sacrificed when possible
b. AC generators.
For military
to
avoid
the
use
of
costly
However, if the 1 3W
installations
in
the
theater
of
operations (TO), portable generators
load is critical, that is, it requires
precisely 1 3W power for proper motor
will be used for the production of
power.
The
military
generators
torque and/or speed, a transformer
available are driven by either a
will be required.
The capacity of
gasoline
or
a
diesel
engine.
generator required depends upon the
Normally, gasoline engines drive those
size
of
loads
to
be
serviced.
generators
of
10
kilowatt
(KW)
Generator
capacity
should
not
be
capacity and under; diesel or gasoline
confused with generator size since the
engines
drive
those
over
10
KW
required capacity may be supplied by
capacity.
For
electrical
more than one generator of a given
distribution, 60-cycle generators will
size.
be used.
Those producing 400 cycles
are used for radar equipment.
The
a. Load estimation.
In order to
important
characteristics
of
a
estimate the load, a map of the area
generator
are
its
kilowatt
(KW)
to be served should be obtained.
On
rating, the voltage and frequency at
it, the various structures which will
which it generates, and whether it is
be
connected
to
the
distribution
a single- or three-phase generator.
system
should
be
marked.
All
The
KW
rating
determines
the
buildings should be identified (shops,
of
the
prime
mover.
PX, barracks).
Next, the connected
Frequency depends on speed of rotation
load must be determined for each
and the number of poles of the
structure served.
Connected load
generator.
Voltage also depends on
for a given structure is the sum
speed, but is varied within limits by
of
the
wattages
of
all
lights
1-7
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