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Generator - Large capacitor??

2255 Views 10 Replies 6 Participants Last post by  austinado16
I have an old coleman generator 5000wer with a 10hp tec motor on it
starts up good, runs good have a meter hooked up shows its right where it should be

but its only there cause i have to adjust the carb to get it at a certain speed
under load it varies alot

i checked behind the cover and do not see an avr instead there is a large capacitor

does this hold up extra charge to send out when needed?
so startup load of anything this will cover it?
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That's one problem with a TECUMSEH ON A GENERATOR ,THEIR GOVERNORS were not the smoothest FWIR
I had the same problem with mine. Started great, ran slow, eventually sped itself up and started over revving within about 5 minutes. Never did figure it out. I thought it would be a governor issue. Still had it even after rebuilding the carb (rebuilt because it wouldn't run on anything but starting fluid, if at all).
I rebuilt the carb
it surges slightly
but doesnt over run
but it also doesnt seem like it governs itself when a heavy load is under it

so the capacitor is what i am wondering about
and also im looking into wiring in an aftermarket voltage regulator to even out the voltage some
The brushless type generators use a fairly large capacitor as the voltage regulator. I have the same model generator but mine has brushes and an AVR. It does have a capacitor too but it is only about 3" long by 3/4" round. How big is the capacitor? Can you get a picture of the end bell removed?
The capacitor holds a DC charge which can be used as a power source to 'bridge' from a low load to a higher load condition. The gen set will charge up the capacitor during normal operation, and it will sit in a charged condition until the voltage droops due to a recent load being applied, then it will discharge to 'help' the gen set before the gen set governor can kick in and open the throttle.
It is similar to an accumulator that is air-filled to start, and then is filled with hydraulic fluid under pressure. The fluid compresses the air, and should there be a demand more than the pump can supply INSTANTANEOUSLY, and the pressure had a blip dropping, the fluid will get pushed out at 'normal' pressure and help the pump keep up with demand.
That function is what capacitors do, in addition they can absorb voltage spikes and store that energy rather than passing the spike on to the output.
If the capacitor is dysfunctional, the governor will have a harder time responding to varying loads without stumble and hesitation. In that situation, the engine is expected to provide power right now, and it cannot as the throttle opening from rpm drop will not recover from the added load without some small hesitation.
Actually the capacitor in a brushless-capacitor regulated generator reacts by "shifting " the phasing of exciter windings as a load is applied to the main windings. It does not store power for when a load is applied. This type of generator is simple and has the worst output of any type of generator. It technically isn't REALLY regulated as the output voltage is completely controlled by engine RPM.
the generator is an old brush type just 2 brushes on it
the capacitor is what i consider large, compared to one in a radio, but similar to that for my well pump

like mentioned around 3" x 3/4"

i guess ill have to check the capacitor with my meter and see if it is any good
as when a large load is applied it just falls on its face
markusedma:the capacitor in a brushless-capacitor regulated generator reacts by "shifting " the phasing of exciter windings as a load is applied

Learn something every day.
Some days not what I wanted to learn when I first got up, but something..

Would the exciter windings be the 'field' in a normal DC generator? My understanding of alternators with slip rings is that they produce AC current, while generators with brushes produce DC current. {my understanding is old, dating back half a century} The field in those DC generators was interrupted by points in a regulator opening and closing to limit field strength. Limiting the field limited the output produced.
Yes exciter windings are similar to field windings in operation. And you are also correct on the slip ring vs commutator theories.
To the OP, based on what I'm reading your symptoms are, you simply have a failed carburetor. Sure, it provides enough fuel for the engine to run w/o a other words, a fairly small throttle plate opening.....but once load is applied, the engine won't maintain a governed speed.

Load equals a larger throttle plate opening, requiring more fuel from the carb, and more of the carb's circuits to come into play. If you can't adjust the mixture screw richer to compensate for load, and maintain 3,600rpm, and have confirmed you don't have leaking carburetor intake gaskets, well; you need a new carburetor. Doubtful it can be cleaned completely, due to the damage of ethanol fuel.

Ebay is your friend for the big 10hp Tecumseh generator/rototiller engine carbs with the big choke levers.

In the future, keep fuel out of this thing and run the engine until it dies, after draining the fuel tank. AND, always treat your fuel with Ethanol Shield and Seafoam. Otherwise, you'll be right back in the same boat.
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