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GENERAL INFORMATION AND CARE OF GENERATORS
1.
Use of Electric Motors
The power
~equired
to start
an
electric motor
is considerably
more
than
1S
required
for
keeping it running after
it
is once
started.
Some motors require much more current to start them than
others.
split phase (A.C.) motors require more current to start
them,
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.
Since they require 5 to 7 times as much current to
start as to run, their use should be avoided whenever possible
if
the
electric
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
them
as
to
run
them.
The
current
required to start any motor varies with the load connected to it.
An electr ic motor
connected to an air compressor,
for
example,
will requir_e more than a motor to which no load is connected.
In general,
the current required
to start 115 volt motors con-
nected to medium starting loads will be approximately as follows:
MOTOR
AMPS FOR
AMPS FOR
SIZE
RUNNING
STARTING
1/6
3.2
6.4 to 22.4*
1/4
4.6
9.2 to 32.2*
1/3
5.2
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 52
*Note that in the above table the maximum Namps for starting" 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
difficulty is experienced in starting motors,
turn off all other
electrical loads and, if possible, reduce the load on the electric
motor.
2.
Required Operating Speed
Although individual units and models may vary slightly, the normal
voltage and frequency of typieal 60 cycle engine-driven· generators
described in this book are approximately as follows when run first
20
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