Agreed. I'm surprised he hasn't damaged something plugged into it
already. A testament to the power supplies in modern electronics no
doubt.

Jack Goff wrote:
On Thu, 13 Jul 2006 19:32:34 -0400, wrote:

On Thu, 13 Jul 2006 22:13:39 GMT, Jack Goff wrote:

Think of your car idling with the lights
on, the rev it up... the lights get brighter. Conversely, keeping the
same engine speed turn the headlights off, and the voltage will rise.
That is only true until the setting of the voltage regulator is met.
In the case of your car it is not a case of the voltage going too
high, only that at very low RPMs it can't meet the regulated voltage
under load.
With a 120v generator (actually alternator) the engine should maintain
a constant 3600 RPM to keep the 60 cycles constant. The throttle may
have to open or close to maintain the output power but the RPM should
stay the same.
If the RPMs did run away the voltage regulator should be decreasing
the excitation voltage to the rotor.
There are "inverter" style alternators that alter engine speed for the
load but the voltage fluxuating is still a function of the regulator.
I would be as concerned about the wrong frequency as the voltage.
Induction motors run at a multiple of the frequency, or at least they
try till they die.
He should really have this checked by a guy with a frequency counter
and a good meter before something blows up

Of course what you're saying is correct. I was just trying to explain
why the voltage could rise in the case of the throttle not being able
to close after the load is removed. In my car example, even if it
were fully into regulation, there will be some voltage flunctuation.
But it wasn't a very good analogy.

On the genset, if it's outside the regulator's capability to reduce
exitation enough, the described runaway could happen. Unlike the car,
the voltage regulator is designed to operate in an environment where
the motor will be maintaining a constant RPM regardless of load.
Since it's not, the regulator may not be able to compensate. It still
may be just a binding throttle or broken throttle return spring. It
definitely needs to be looked at before things escalate.