generator has no power

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deadonion

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hi. last summer i purchased a returned 3750watt generator from home depot. i got it for half off with no warranty due to the return.
it worked great when the power went out for a few days, tgen suddenly their was no electrical output, though the engine runs great.
i took a look at it and noticed where the wires come out of the alternator, they werent run through a grommet. the vibration cut through both of them.
i put the wires together figuring it would work again.
no dice. it still runs but with no output.
what gives?
 
That's about as far as I can go, post the brand and model, so someone that knows this stuff might help you.
 
Best advice I could provide is to get a wiring schematic and check it all. It is possible that your stator is broken, but check the wiring first.
 
Most likely the stator is open or shorted. When those two wires shorted to the frame the gen would have produced as much amperage as it possibly could have until either the wires burned up and lost contact with the frame or the stator burned up. your best option for troubleshooting, assuming they are stator wires, would be to use a digital multi-meter and ohm out the stator to see if it is open.

to do this you will need the schematic to find out which wires go together. if it is a 240v single phase generator there will be 2 power wires and 2 neutral wires. hopefully they have numbers on them, if so take the corresponding power wire and neutral and ohm them out. if it says infinite or open you might as well buy a new gen.

those portable generators sometimes have a capacitor that helps feed the rotor, if this is the case checking capacitance would be a good idea. If the capacitor top is open or leaking fluid at all that may be the cause of the problem.

The slip rings may have also over heated causing the brushes to crumble losing contact with the slip ring. if this is the case then no field would be produced and no voltage.
 
Hey there, generyac, welcome aboard! Do you think that he should try field flashing before he gets up to his armpits in the diagnosis? I've included it in an attachment and it's appears to be an easy enough process. Maybe it's just spitting into the wind but, at least it's free!

Later,
Chiz

P.S. The attachment tool is only set up for pics and, therefore, won't accept .txt, .rtf, etc. I hope that nobody objects to me copying the instruction text below.


PER Notebook
Field Flashing of Portable Generators
This tip comes from the Briggs & Stratton Customer Education Department. As an alter native to flashing a rotor winding with a battery applied to the brushes, an electric drill may be used. Follow these steps to flash the generator:
· Plug the electric drill into the generator receptacle. (Cordless drills do not work)
· If the drill is reversible, move the direction switch to the forward position.
· Start the generator
· While depressing the trigger on the drill, spin the drill chuck in reverse direction. This will excite the field and the generator will now produce electricity. If spinning the chuck one direction does not work, try spinning the chuck in the other direction as you may have the reverse switch positioned backwards.
Use caution not to get your hand or other materials caught in the chuck. As soon as the field is excited, the generator will produce power and the drill will turn on.

The reason this works is because the electric motor in the drill will act as a small generator when spun backwards. The magnets in the drill's motor induce a voltage into the motor windings, which is fed back through the trigger, cord and into the generators receptacle. From there it goes into the power winding of the stator. The voltage going through the power winding creates a magnetic field, which is intensified due to the iron core of the stator laminations. The rotor intersects this magnetic field as it is spun past the power winding, thus inducing a voltage in the rotor winding. Once current flow is present in the rotor winding the rotor has been flashed.
If flashing the field does not make the generator work, you may have additional problems, besides a lack of magnetism in the rotor. Further testing will be needed. Hopefully, this will give a simple way to field flash your generator if needed - Bruce Perrault



The Precise Engine Repair web site is maintained by Bruce Perrault
The last update to this page was made Sunday, December 07, 2006.
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