10
OPM-139/E
OPERATING SPEED
The engine-generator must be run at the correct speed
in order to produce the proper electrical voltage and
frequency.
CAUTION: EQUIPMENT DAMAGE
The output voltage should be checked to ensure the
generator is working properly prior to connecting a load
to the generator. Failure to do so could result in damage
to equipment plugged into the unit and possible injury to
the individual.
All engines have a tendency to slow down when a load
is applied. When the electrical load is connected to the
generator, the engine is more heavily loaded, and as a
result, the speed drops slightly. This slight decrease in
speed, together with the voltage drop within the generator
itself, results in a slightly lower voltage when the generator
is loaded to its full capacity than when running no load.
The slight variation in speed also affects the frequency
of the output current. This frequency variation has no
appreciable effect in the operation of motors, lights, and
most appliances. However, electronic equipment and clocks
will be affected if correct RPM is not maintained. See Load
vs. Output chart.
Although individual units and models vary slightly, the
normal voltage and frequency of the engine-generator
described in this manual are approximately as follows,
under varying loads:
LOAD vs. OUTPUT
Generator
Load
Speed
(RPM)
Frequency
(Hz)
Voltage
None
3690
61.5
125V
Half
3600
60.0
120V
Full
3510
58.5
115V
The speed of the engine was carefully adjusted at the
factory so that the generator produces the proper voltage
and frequency. For normal usage, the speed setting should
not be charged. If the generator is being run continuously
on a very light load, it is often advisable to lower the
operating speed slightly.
Reference “D” in the following image is the speed
adjustment for this engine.
D
CAUTION: EQUIPMENT DAMAGE
SPEED ADJUSTMENTS SHOULD ONLY BE MADE BY
A QUALIFIED SERVICE TECH. Whenever making any
speed adjustments, check the unit with a voltmeter and a
frequency meter or a tachometer and be sure the voltage
and speed are correct.
Lower voltage may damage both the generator and any
load connected to it. Running the engine at excessively
high speeds results in high voltage, which may significantly
shorten the life of appliances being used.
Output voltage should be checked periodically to ensure
continued proper operation of the generating plant
and appliances. If the generator is not equipped with a
voltmeter, it can be checked with a portable meter.
