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Welding from a Listeroid/ST generator rig

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I live off grid and I've been using a Listeroid CS1 (6hp) coupled to a ST generator (7.5kw) for the last six years. Generally, I only run workshop tools from the ST generator. All domestic stuff such as lights, music, computers, etc are supplied from a small (1.8kw) inverter off a 24v battery bank. The battery bank is charged from a heavy duty 24v automotive alternator on the listeroid.

So I want to do a bit of welding and I'm interested to know what your collective thoughts are on running an inverter based TIG welder from the ST generator. I'm not too concerned about power - I accept that I'll have to keep the welding current down otherwise I could stall the engine. What concerns me is the quality of the electricity produced - by that I mean the voltage spikes, etc and whether this will damage the nice new welder that I've already ordered? Do any of you out there run a welder off your listeroid based rig? I'd be interested to hear your experiences and thoughts on the subject.


The typical ST head THD is pretty high from waveform distortions (ratcheting from non-skewed rotor windings, harmonic hump from harmonic winding) will have no adverse affect on your welder.  All the new designs are switch mode power supplies, so the first thing they do is create bulk DC from the AC input.  The cheaper welders with bad power factor (direct rectification of the mains to bulk capacitors may do this in a manner that has lousy power factor.  That will affect an electronic regulator, if you use one on your ST-7, and it is a typical cheapy that doesn't do true RMS voltage regulation...causing it to regulate voltage too low.  I've experienced this situation on my ST-3 with electronic regulation.  On your stock harmonic winding, it will regulate fairly well with a rude, low PF load.  i switchover my ST-3 to the backup harmonic for this situation. 

The usual 10 Hz Listerflicker variation in voltage and frequency will normally be handled quite well by a decent electronic welder.

The big issue I see you having is that you will have to limit your welding current pretty seriously.  If it's a small MIG welder, with output at 24VDC at the machine, you should get 85-90 amps of welding current (allowing for losses), but you're at the limits of the 6/1 power (2300W generated power)  If you can live with that, you should be OK.  I have had a smaller amp MIG welder running on 230VAC, on my 6/1-ST-3 with harmonic regulation. It was fine for thinwall square tube welding.

For moderate current stick or other higher power welding, you don't have the power for 1/8 rods of 7018.  You could barely do 5/32 6013 rods. If your duty cycle was low enough, and you had SOM type heavy flywheels, that would probably help.  An 8/1 would be a better match for home/farm welding. 

PS I've got some heavy flywheels I'd sell at cost if you get serious about doing an 8/1 conversion with an aluminum piston and have the typical 6/1 spoke flywheels.  I don't think anyone thinks they should be spun higher than 650rpm. 

Best Wishes,

Thanks for your reply Bruce. Am I understanding you correctly - when you say you use an electronic regulator on your ST-3, do you mean that you have an AVR on it? Is it one of these?

I looked at them a while ago, but something about the low price didn't inspire me with confidence. Not really a sensible way to judge a product, I admit! Do you find it a worthwhile modification? Are you saying that you disable it when you weld?

I called my listeroid a 6/1 because I run it at 650rpm, but in fact I bought it as a 8/1 and it has the solid flywheels. When I first set it up I found the vibration a bit high, so I changed the governor spring and down rated it to a 6/1, running at the lower speed. It would be a simple task for me to up rate it back to an 8/1 if necessary.


I do use an AVR on my ST-3 and so does my neighbor on his.  My neighbor uses one similar to the one you show, his purchased on ebay.  They last about 4 years so he keeps a spare on hand.  His ST-3 setup IS using the harmonic winding; in fact his CGG "brand" ST-3 requires it, the stock harmonic setup is grossly over-voltage. I use an AVR of my own design; a hand soldered prototype. I can flip a switch and revert to the stock harmonic regulation.  My St-3 had a very nasty "harmonic hump" so I use the mains for excitation of my homebrew AVR.  I also offered a schematic and PCB design for a simple AVR here many years ago.  A few members made them. The China AVR's are so cheap that even I recommend them.  As I said, you should stick to harmonic regulation for a welder as these cheap AVRs won't handle a low PF load like some welders well, and will regulate at way too low of an true RMS voltage.  I learned this the hard way, though it was not a welder.

I'm happy to share schematics, etc. with a forum member who needs them.  You can't buy parts for what you can buy the finished China product for these days.

Since you have an ST-7 and what is really an 8/1 already,  you have all the makings of a good welder generator.
Balance issues are easy.  I highly recommend 38AC's method.  I used it on my neighbor's 8/1 and will never go back to the Mr X wheel chalking method.  The latter works, but takes much more time.  38AC first corrects the counterbalance offset angles to match the key location, then adds weight to the lighter of the two wheel's counterbalance weight to make have identical on-axis counterbalance weight as measured by string can and weights..  Then you just add equal weight to each wheel either at or opposite the counterbalance.  Hoppers need more, fore and aft movement or sliders need less. 1 oz per each wheel increments work OK.  It's can be done with only a handful starts/stops.  My hat's off to 38AC for this simple, powerful method.  I used a short, leveled section of hot rolled angle iron on wood blocks and a 12" section of 2" OD axle from Amazon for doing the measuring and matching. Plus a can, string and lead shot.

I would rather not limit myself to 2300 watts continuous for welding if I already had an 8/1 and ST-7!
The faster rpm of the 8/1 does seem a bit "nervous" for a while but it grows on you.

Best Wishe

I did try the chalk method when I installed the engine about 6 years ago, but to be honest, I didn't have much success with it. I deduced, rightly or wrongly, that the flywheel balance was almost insignificant compared to the reciprocating weight of the piston, etc. Perhaps it's time to have another look at it. I'm looking for 38AC's method, but I can't find it. I did come across some posts where other members refer to him leaving the group and taking down his posts. Do you happen to know where I can find a description of his method?



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