Welding -- what to do about HUGE 2" arcs

When I say that it failed, it did not fail as in "died", it shut itself down with a FAULT LED indicator. Which is a good thing. It has a built in detector of phase imbalance, which could happen if power drawn exceeds the capacity of my phase converter.

i

How about some r.f.i. protection which, I suspect caused 'latch-up' in a chip or more.

A couple HV diodes, resistors and capacitors to make a low pass filter (you only want the welding buzz (or DC), not the hash the arc makes) and envelope detector. Toss on a voltage divider (to put it in terms a comp can handle), add a comparator with pot to vary trigger voltage and send the now detected signal to your shutdown thingie.

Oh, and some clamping after a resistor, so you don't blow caps or other stuff. Voltage spikes are fun.

I'm guessing this doesn't have to be very fast at all, as long as 100ms could be considered acceptable? Should be pretty easy then.

But really, you're COMPLAINING about 2" arcs? I've got to see this.

Tim

I think that I understand about LP filter, but what do you mean by envelope detector.

Absolutely. I could as well throw a zener in there.

Sure. Maybe 50 ms, but there is no need to be fester than that.

I played some more with welding tonight. If I withdraw the electrode quickly, there is no problem at all. It is when I pull it away slowly, then I see the unbelievable 2" arcs.

It is unreal, I have never seen anything like that. Not that I can claim great life experience.

i

How about a foot pedal? Like standard tig. Btw..if I set my control on Local rather than remote..when tigging I can get the HV to run at least 1.5-2" when I draw away from the work. I had to turn down my HV a fair amount when doing a weldment that I coulnt use the foot pedal on (no torch mounted controller)

Gunner

"If thy pride is sorely vexed when others disparage your offering, be as lamb's wool is to cold rain and the Gore-tex of Odin's raiment is to gullshit in the gale, for thy angst shall vex them not at all. Yea, they shall scorn thee all the more. Rejoice in sharing what you have to share without expectation of adoration, knowing that sharing your treasure does not diminish your treasure but enriches it."

- Onni 1:33

I think that you have a good point, that with a remote control it will not be as much of an issue (not that it is a show stopper now). I will definitely do remote control soon.

i

Peak detector- think AM demodulation (hence envelope detector). Just a diode into a capacitor, with another resistor and capacitor to add the RC delay, and an RC in front of the diode to slow transients.

Hmm, you have HF start right? A notch filter might not hurt, even with the slow front end of this circuit.

Tim

Oh, I see. Thanks. I had some very educated opinions that what I have (big arcs) is not a bad thing as it could let me weld over dirty spots and such -- and that all that I should do about it is pull electrode away quickly when I am done with a bead.

Yes, I have HF start indeed.

I have not yet wired it up.

i

2" arc at how many amps? When I borrow my friends tig, we usually use HF start and it arcs at about 3 CM out at a maybe 100 mA, then as you get close to the work the arc thickens into the normal welding arc. Maybe you have it close to being right?

Steve Roberts

Not sure how many amps, but if I recall correctly (I did look at dials, but in haste and mostly at the voltage dial), it was at about

100 amps.

Maybe, indeed, it is close to being right.

i

I've seen this with my Lincoln Square Wave TIG 300 also. It means the HF system is really healthy, and maybe you could turn it down a bit, if it is adjustable. This is NOT the main arc, but pure HF.

I think my Lincoln has a circuit that detects excessive OC voltage and shuts it down, too. I had that happen when I was starting out, I haven't seen it at all, since I got comfortable with the machine.

Are you doing TIG or stick welding, here? You don't generally use HF for stick. I don't lift the electrode to stop the weld, I take my foot off the pedal, and keep the torch there for the shielding gas. I can't comment on using a TIG machine in stick mode, I have not done one bit of stick since I got the TIG! Unless some special case comes up, I DON'T INTEND to ever do that horrible, nasty stick process again, either. Yes, I know TIG gets expensive, especially the gas, but the stick flux is SO NASTY, I just don't want to ever small the damn stuff again.

Jon

Jon, that's what is weird, there was no HF. It was just the main arc.

So, at least some designs include something like that. Don says that it is a good thing and that I should just pull the electrode quickly enough, and I think that he is right.

Stick, so far, no HF.

Yes, I like TIG too, but right now TIG is not yet configured properly.

i

take a picture of it :)

Colin =^.^=

Try something small and simple like a Crouzet Millennium II - the programming is done with logic blocks on screen, and downloaded to the device. They have analog inputs (0..10V) and PWM outputs too.

Steve

Sorry, I'm having trouble believing you. Without Argon, it would take thousands of Volts to sustain those 2" arcs. With HF and Argon atmosphere, it is easy. If you were using HF start, and the main arc shut down, the HF will come back on. With lots of gases and a still-hot electrode in the area, these HF arcs are not surprising. But, I just don't believe any welder with an open-circuit voltage of less than 100 V can possibly produce a 2" arc without the HF system on. Now, a totally HUGE welder, delivering several hundred Amps, can make some pretty large arcs as you back the electrode away. But, you can't really SEE them, because the arc energy will be like a little sun!

Was this one tight, totally white-hot arc, with lots of sizzling, and plenty of heat to the workpiece, or a thin, bluish arc or bundle of arcs that danced around on the work? The former is the main arc current, as you say, the latter is characteristic of HF.

Maybe I'm coming around to agree with you because the welder shut down. It would have to, as the lengthening arc requires more voltage, and the current remains at the setpoint. As the product of volts x current increases, it eventually exceeds the power capacity of the welder, and it has to shut down, blow the mains breaker, or self-destruct.

Jon

Jon, I will try to make a pictureof taht arc (through a junk welding helmet that I have)

i

Well, I just went out and held an "arc" of about 1 1/2" at 65 amps,6011,RP, no HF at all. Easy to do if you hold the rod perpendicular to the work, strike the arc, then slowly raise it. It's a soft yellow cloud. I just figured it's some kind of ionization maintaining the path. Even easier on galvanized....

Believe it. Think of the fact that the air is already ionized by the arc. In the right conditions this can be extended. I've had it happen on my unmodified welders on occasion. I admit that it's not a common thing with stick but it has happened (especially in a tight place). It's definitely more common in TIG or MIG with argon flooding the area. I made some pretty big arcs last year while MIGing stainless with the high percentage argon mixture. It was also real good at totally melting the tips on the gun.