Powercraft/Wolf 720 watt generator fault

I'm expecting cries of "bin it" but it's worth a try.
The output from this generator is low to non-existent. If I plug a 500 watt drill in, it might turn sometimes, but only between probably 10rpm and 200rpm, it's very erratic - guessing the speeds of course - then it will stop altogether, and then maybe start up again, slowly.
There doesn't seem to be much that can be done with these other than maybe change the capacitor, but my electrical knowledge is too lacking in such matters to even know if that could be the problem.
Is it a lost cause?
I originally got this from Freecycle knowing the genny side was faulty, in the hope I could make a good one out of two - I have another with a duff engine. Turns out they are sufficiently different that I can't do anything with them, so now I have two non-working genny's :)
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Hi sounds like a great excuse to learn about generators (you can't make it any worse) Basically a generator is a spinning coil (or coils)of wire which spin in a magnetic field usually generated by another coil of wire.( I'm sure you knew this). But did you know the field coil is usually DC whilst the armature is producing AC. Most generator have a rectifier pack or voltage regulator connected to the field and these often go faulty. Another common fault (with long unused sets) is sticking brushes. Yes they DO have brushes these bring the AC output off the armature and can stick in their guides giving symptoms as you describe. Find the brush gear and measure the voltage with the set running also check the field voltage out of the regulator. Oh of course check that the field windings are ok.
Just a few pointers to get you on your way
HTH good luck CJ
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On 24 Jun,

Usually its the other way round, a rotating magnetic field produced by DC in the spinning coil.

See above.

Correct, the fixed coils generate the AC whuch is then rectified.

The brushes are onto slip rings on the armature and take the DC exitation into the winding.

--
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Seems I'm showing my age again. AC field eh! isn't time a b*&"h seems only yesterday watching a pal try and prove that a series genset won't generate if you short the output. Oh well time marches on ... as for brushless systems some Kango sets circa 1970's tried this by using an offset field biased with a capacitor and a squirrel cage type armature IIR. Sorry I can't be of further help as obviously my obsolete training and experience is no longer the "Usual" but one thing that will not change is that a generator makes electricity by moving a conductor across a magnetic field,so good luck in your endeavours.
CJ
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How much work do you want to do on such a low value genset? You could start by multimetering the physical generator while running to see what voltages are where, and resistance testing the same while not running.
I dont suppose its worthwhile to bodge the gen head onto the working motor.
NT
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On Tue, 24 Jun 2008 15:06:19 -0700 (PDT), snipped-for-privacy@care2.com wrote:

It's mostly a matter of having a lot of spare time, combined with a fondness for repairing just about anything if it's possible. Saving money is a bonus of course, even if it's only a few quid.

This is where my knowledge is lacking. I'm happier with spanners in my hands than a multimeter.

That was my original idea, but the crankshaft/armature shaft is a one piece thing, as are the crankcase and one end of the generator case, so it's not feasible.
Still, I can always hack the armature off, stick a pulley on the shaft and use the engine to drive something else. As the old saying goes, "It'll come in handy even if I never use it."
Thanks for all the replies.
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let the fun begin

all you need do is measure everything possible on voltage setting with it going, and on resistance with it stopped. We can interpret from there.
NT
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I don't have a manual or brochure for this, but I'm sure I remember, when they were on sale in Aldi, that the blurb said "brushless self-exciting."

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ALL of todays modern 3000rpm generators, and definately the throw away style 2 strokes use a spinning DC field and the AC power comes off the stationary armature- i.e. NO brushes.
The OP probably has a shorted field or more likely expired diodes (yes, very cheap and nasty) on the field coil. You will need to strip the spinning part out of the generator and replace the diodes, and check the resistance and insulation of the coil.
It's far from unheard of in this league of machine for the windings to move slightly or there be sufficient 'slop' in the bearings for the field coil to contact the case or armature and wear it away / short it.
Tim..
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wrote:

I can't see any diodes unless they are hidden inside the coils. The only thing in sight is a resistor between the two coils.

No signs of anything catching, rubbing, contacting or any other sort of *ing, except it won't *ing work.
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Just in case anyone who replied is remotely interested, a pal took the generator to work and the electrician, who apparently "knows about generators", couldn't get it running any better than it was.
I decided not to bother keeping the engine, so in the interests of recycling, I'm thinking about hiding it in full sight in the allotment, as an appeasement to this months crop of travellers, who will no doubt discover it during one of their nocturnal excursions.
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On Tue, 24 Jun 2008 12:07:59 +0100, curls wrote:

Motors require significantly more power to start than run, in the order of 2 to 3 times. Though as yours does try I'd expect it to spin up eventually. If you give the motor a spin by hand does it run? Can the genset power a simple load like a light bulb? If does 60W without problem cobble together a few more to up the load.
--
Cheers
Dave.




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On Wed, 25 Jun 2008 10:12:54 +0100 (BST), "Dave Liquorice"

I tried it with an 11 watt flourescent handlamp. Depending on how the genny is feeling, it varies from nothing to full brightness.
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On Wed, 25 Jun 2008 12:10:12 +0100, curls wrote:

Flourescent is a "nasty" load again like a motor and 11W isn't a big load. Don't you have a nice tungsten lamp you can plug in? I suspect it might be the regulator that has packed in. Have a dig about on the web, they aren't rocket science maybe just a chunky diode and a capacitor. Probably a single sealed unit but possibly available as a generic spare.
--
Cheers
Dave.




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On Wed, 25 Jun 2008 15:11:46 +0100 (BST), "Dave Liquorice"

Same behaviour with a 40watt table lamp as with the fluorescent and the drill.
It turns out the armature could be separated from the crankshaft so I took the lot apart and took a photo. http://tinyurl.com/5nelwt
There are three pairs of wires from the stator. One pair goes to the 6uF capacitor which you can see in the top middle of the black plastic piece. Another pair goes to the 230v socket, with the live going through a reset switch first. The remaining two wires go to a 12v socket for battery charging. And that's it.
The CBB61 capacitor seems to be only available from China, though there's a similar one on ebay, but that's half the price of a new genny.
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6uF 250vac caps are used in fluorescent lights, motors, etc, and cost 2 or 3 squid max. From any tron component supplier. But thats immaterial until you've found out whats wrong.
NT
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Hi,
Try a google on 'generator field flashing'
There's some info about checking/flashing a brushless self exciting generator here in a manual here.
<http://www.powertechengines.com/NewageData / MarkonPartsServiceInstallation-105-english.pdf>
*If* it needs flashing it looks like you just need to connect a 12V battery across the capacitor for a second.
If using a lead acid battery I'd also connect a fuse inline in case something has shorted.
cheers, Pete.
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Pete C wrote:

if it were that surely it would perform consistently badly. I suspect a bad joint is more likely, which is generally an easy fix.
NT
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snipped-for-privacy@care2.com wrote:

self excited field coils are either all on or all off. once any voltage is genraeted, they build up to a maximum.
However, surely field coils are excited with DC? perhaps there is a rectifier block the far side of that capacitor that has gone partially phut.
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The Natural Philosopher wrote:

If you get desperate, the powercraft uk helpline number is 08707 323023 There are downloadable manuals on the omega wolf website but not one for this generator.
Bob
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