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GENERAL INFORMATION AND CARE OF THE GENERATOR
Use of Electric Motors
The power
required to start an
electr ic motor
is
considerably more
than is required to keep it running after it is started.
Some motors
require much more current
to
start
than
others.
Split-phase
(AC)
motors require more current
to
start,
under
similar
circumstances,
than other types.
They are commonly used on easy-starting loads, such
as washing machines,
or
where loads are applied after the motor
is
started, such as small power tools.
Because they require 5 to 7 times
as much current
to
start
as
to
run,
their
use
should
be
avoided,
whenever possible,
if the electr ic motor
is to be driven by a small
generator.
Capacitor and repulsion-induction motors require from 2 to
4 times as much current to start as to run. The current required to
s tart any mo tor
var ie s with the load connected to it.
An electr ic
motor connected to an air compressor, for example, will require more
than a motor to which no load is connected.
In general,
the current required to start 11S-Volt motor s connected
to medium starting loads will be approximately as follows:
Motor
Running
Starting
Size
Current
Current
(HP)
(Amperes )
(Amperes)
1/6
3.2
6.4 to 22.4*
1/4
4.6
9.2 to 32.2*
1/3
S.2
10.4 to 72.8*
1/2
7.2
14.4 to 29.2
3/4
10.2
20.4 to 40.8
1
13
26
to S2
*Note that in the above table the maximum starting current is more for
some small motors than for larger ones.
This is because the hardest-
starting types (split-phase) are not made in larger sizes.
Because the
heavy surge of current required
for
starting motors is
required for only an instant, the generator will not be damaged if it
can bring the motor
up to speed in a few seconds of time.
If dif-
ficulty is experienced in starting motors, turn off all other electri-
cal loads and, if possible, reduce the load on the electric motor.
Required Operating Speed
Although individual units may vary slightly,
the normal voltage and
frequency of typical 60-(SO-) Hertz engine-driven generators described
in
this manual are approximately as follows when run first with no
load applied,
then at half
the generator
capacity and finally when
loaded to its full capacity as indicated on the generator data plate.
38
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