Welder and portable generator problems

I've had a Lincoln SP-100 welder for quite a few years, anymore all I have run in it is .035 Flux core wire and use it outside. The manual calls for a 110 20 amp circuit, but I have been able to run it on a 15 amp with a long extension cord and generally no problems. Finally ended up with some jobs that didn't have a power source so I found a Honda 3500 watt generator at a local pawn shop in great looking shape and a good price.
I figure I should have about 29 amps of power (3500/120).17 amps). Am I doing this right? The generator sometimes will run the welder for 10 minutes straight, other times 30 seconds and its breaker trips. I don't see anything I'm doing that would cause it to trip vs run fine. I don't hearwhat I would think of as the motor straining when it does trip.
Any thoughts on what to do? It was suggested I by pass the breaker and put in a 25 or 30 amp slow blow fuse. That doesn't sound like the best solution, but I am at a loss otherwise. I really don't want to buy another larger generator. With my back this is about all I want to move around. Thank you.

"Wally" wrote: (clip) It was suggested I by pass the breaker and put in a 25 or 30 amp slow blow fuse. That doesn't sound like the best solution, (clip) ^^^^^^^^^^^^^ From the fact that you don't hear the motor start to labor, I conclude that your breaker is reacting much faster than your governor, and tripping due to momentary peaks in the current. If these are very short peaks, they won't damage anything, because don't have time to heat up the generator windings. I think a slow-blow fuse is a practical solution. I would try it, but be prepared to stop welding if you hear the motor start to labor. Maybe have someone standing by to flip the switch if you stick the wire.

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One thought is simply to replace the breaker, sometimes they get a bit crabby with old age. Another is to get yourself a kill-a-watt meter and find out what's actually going on - they seem to be pretty cheap, lots of posters in the homepower group use them, and they show all sorts of interesting and useful things about your power loading/generation (for much less cash than most other meters that might measure all that). IIRC, includes frequency, voltage, watts, amps, and peak values for much of that over a run period. I don't know for sure since I have not yet coughed up my $25-35 to get one. A third thought is that some generators offer you more power on the side of the case than they do in the owner's manual (which you may not have, since it came via the pawn shop).

Consider testing/replacing the breaker on the generator with a factory replacement. It could be that the breaker was used as a switch or that the generator was overloaded by its former owners. The random pattern of failures suggests a weakness in the breaker. How warm/hot is the circuit breaker when it trips open?
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On Sat, 25 Jun 2005 21:41:54 -0500, Thomas Kendrick
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I haven't noticed that it was anything more than ambient temperature when I flipped it back on. Haven't had the box the breaker and outlets are mounted in open when using the machine.
I found the manual on line at the Honda website and it tells me that I have 12.5 amps at 120 volts. Guess I need another generator. Looks like the 5000 watt model would do the trick. I'm surprised this one worked at all.
Thanks everybody. I learned a couple things about generators.

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my buddy went through the motions (so to speak) on running a 110 unit off a portable generator and finally ended up with about a 7KW model that works flawlessly

If you are going to get a larger generator anyway, why not consider the small Miller engine drives. A Blue Star 145 or 185 could be a possibility. Once you consider a 5kw generator, it's wheel kit time anyway.
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I would contact Honda customer service before buying any parts. I suspect that momentary spikes in current may be the problem. I would also try welding with as low a voltage setting as I could get away with.
It's my understanding that most small generators have little or no capacity above the stated maximum output. Even a short spike in current that exceeds the maximum rating may be enough to kill the generating process. For that reason, I suspect that the breaker in this machine may be specially designed to act quickly, possibly even more quickly than the engine can react. Honda customer service should be able to verify if this is so.
Breakers used in a typical home will easily handle current spikes well above the rated values, often for a considerable amount of time; this may be the reason that the machine works fine then powered from your home or shop wiring.
Another possibility is that there may be some compatibility problem between the SP-100 and the generator. The SP-100 with the continuous voltage control, (not the SP-100T), is controlled by SCRs in the transformer primary circuit and needs a reasonably clean sine wave with good clean zero crossings to operate properly, and small generators are notorious for producing output waveforms that are not so perfect. If the SP-100 is having trouble with the input power, the result may be high current spikes that could cause the breaker to trip.
Bob
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Actually your generator is fine the wattage on that unit is based on full winding utilization therefore the manufacturer rated it at 3500/240  amps .Your 120 volt winding is only good for about 15 amps. Your breaker is thermal cycling properly do not heavy it up. If you have tripped it several times under max load it could start operating at a lower amperage and then it will require replacing with OEM. You only have 14 to 15 amps available at 120 volts.
Pete
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