Generator Voltage

 

  I was given an el cheapo generator by a friend. It's intended use for
me was to start and run HVAC equipment for testing. I started a 1/3 hp
fan the other day and the motor ran for a few minutes and then went out
on overload. I checked the voltage (still connected to the motor, motor
thermal limit open) and had 332 volts where I should have had 240 or so.
It's a 3500 watt unit, looks like the Coleman brands but is red.
  What regulates the voltage in these lower price generators? I haven't
had time to re-test it yet but will soon, under a load in case that will
make the voltage drop. Any suggestions? Thanks all!

 

Beachcooler wrote:

The speed of it is the only thing that determines the output voltage
(and frequency). There should be a mechanical adjustment somewhere.
Probably a good idea to get the speed approximately correct with no load
attached first, then tweak as neccessary. There will be some form of
governor.... probably just an adjustable spring.

 

Charles Foot wrote:

Thanks Charles. I think you're right, and you described just what I
have. Why didn't I think of speed?

 



As the other poster said speed is the governor.  But,,, if you want to set a
small genset you need to understand some things.  As the speed climbs so
does the voltage and frequency.  Voltage is not as important as getting 60
cycles here in the USA.

Setting the generator.
Once running place about 50% of rated output as a load.
Check voltage and frequency. Adjust the idle screw or governor until you get
60 cycles. Remove load and then repeat.
Idle and no load voltage will be high, it is the under load voltage you need
to worry about.

Your motor might have tripped on OL because of the way you were running it.
Some motors MUST be installed with air moving over/through them for cooling.
Check the name plate data on the motor and look it up it the manufactures
catalog. You may find that the motor needs some static air pressure all of
the time.
You could have a bad motor.

 

SQLit wrote:

The motor runs fine now.It was in an air handling unit that is now in
service. Checking the genny yesterday after posting showed 363 volts, 79
hz. I will slow it down today and see what happens. Thanks for the input!