Help Stick Welder needed for experiment

[Boron]

Hi Guys
Is there anyone out there who has a dc stick welder that can pull say 100A?

Reason I ask is that I have a postulate on my mind - Given that its easy to draw an extended arc of say 1" or more can this be extinguished by squirting say a plant mister spray of water at it - you need the OH to help here?

Things needed to sustain an arc flash
Current source
Sufficient Volts to start the arc (eg 12Vdc wont work - needs >24V) Sticks oc is ca 50V?
Distance will quench an arc when increased beyond a limit, determined by Voltage (a complex state)
Removal of heat will stop ionisation which gives negative resistance path
Magnets can lengthen the arc path
Compressed air can blow an arc out like a candle
Sand can extinguish an arc

So could a humble plant spritzer be an effective arc quencher?

I dont have such equipment

Please advise?

 

[Korishan]

Why not just get one on Amazon that's inverter style? These use Mosfets to drive the output voltage/current. I have one, and only paid about $100USD for it. Harbor Freight has one that is actually reliable and does the job really well. There's several reviews on YT about its performance.

Granted, some will be against it, of course. But most welders are only as good as the person operating it.


Addendum: Just realized your in Auz land. Might be a little harder to find one that price there. Aliexpress has them, though not sure what the shipping would be.

 

[Boron]

Jeez K you completely missed my point.
I dont want to become a welder

I want a sympathetic soul with some kit to do a quick test for me
Jeez kerriste

 

[Korishan]

Ohhhh, I see, you want someone else to zap their welder, got it! Didn't realize you wanted someone else to do the testing.

you need the OH to help here?

I missed this before. I don't know what "OH" means, sorry. You do quite a bit of short hand that is possibly not recognized by the rest of us

Tbh, it's going to be very difficult to sustain an arc more than a few millimeters with a welder. They aren't quite designed for that. The longer the arc, the more current that needs to be delivered, plus voltage. A welder is a set device, it doesn't change its output as the arc is being move around. This is because the weld needs a specific "heat" to make things fuse together, and this is accomplished by CC/CV output (CC/CV at the same time, not like charging where it switches part way through)

And tbh, I don't think a "mister" sprayer will put out an arc. The water droplets would vaporize before they got to the arc. Not to mention that there are those who actually weld "in the rain" or "underwater". It creates enough heat to make its own bubble shield.

 

[Boron]

Really I'd like to hear from members who know something about the matter and like to share knowledge rather than armchair speculation

 

[Korishan]

rather than armchair speculation

Considering that I "am" a welder, I wouldn't say it's "speculation". No need to be rude to other members, regardless of who they are. If they don't respond with the information you are searching for, just thank them for their time, readdress and clarify the question better with what you are looking for. It's that simple.

I gave you valid information as to how a DC welder works. Easy enough to verify the information by looking it up on other sites. The information you requested is pretty much answered based on the original posting. There's no need to have someone go out and test it for you.

 

[Boron]

Hi Members
Getting back to my OP point
I feel I must share this vid showing the effect of a dc arc flash - says it all IMHO - ignore the product promo.
I suspect BTW that the guy probably put a bridge rectifier in his 220Vac supply when doing his dc supply test ie his supply will be at 220Vdc @ 1kW but instructive nonetheless. Note that a rectified ac output is quasi dc, ie the wave form is 1/2 cycle repeatedly @100hz. Hope thats obvious, means the voltage will drop to zero - unlike a battery source, solar panel source, dc diesel generator (I owned one of those once - Japanese Denyo 180 what a fantastic m/c turned my numpty attempts into something reasonably useful as it made the arc so much easier to control - those were the days down on the farm. Brilliant m/c like the ubiquitous Ford Truck of Diesel Welders 2cyl Kubota and the gen turned into a motor to start the m/c using some old lorry batteries and a decompression valve lifter)

View: https://www.youtube.com/watch?v=YxHCDs03UEg


I proposed the use of a water spritzer to quench the flame, as you dont want to squirt water around you distribution board near inverts etc. Obviously no one would try an put out a mains grid board fire with water, but its not so obvious that this might be a property saving resort for ELV dc systems - hence my question. Obviously CO2 extinguisher should probably work , its very cold and gives a blast of gas, but I havent noticed any sheds with one of those hanging up prominently? Anyone else?
Should a CO2 bottle, 14" cable cutters, sand bucket/tongs for Lion cells, gloves and goggles be mandatory safety equipment hanging on the board - or is this over the top or alarmist?

OBTW 12Vdc is inherently safe as you cant strike an arc flash (24Vdc you can weld) - I am tempted to build that blindingly simple wooden rig in the video and do some tests

 

[Korishan]

As mentioned in the video you posted, he's using approximately 120VAC rectified to about 120VDC. This is why he was able to sustain such a large arc.

My DC welder is rated for 20-26VDC with 160A max output. I tried from 50A - 160A and was not able to sustain an arc for more than 2 seconds, and I was not using a welding rod that's designed with flux and to melt quickly into the pieces. I was using 2 pieces of mild-hardened steel, one of which is a piece of rebar, so it wouldn't melt very fast. Same with the piece of angle iron used.

The arcs were decent, sure. Bright and pretty large. The plasma would drive away from the work pieces pretty quickly, self quenching the arc. There was no to little wind at the time testing (I was doing this test just outside my garage). So if wind is a factor, just blowing on it would be enough to extinguish it**. The works pieces however got very hot after a few tries. So I stand by my statement earlier where a misting spray bottle probably wouldn't do anything much, other than possibly create air flow, which would be more likely to put it out.

I did not record the test as I wanted to verify if I was able to get a sustained arc like in the video mentioned. I spent about 30mins setting up my gear and getting the steel prepped. With such low voltage, compared to the video, I didn't see any reason to spend a lot of time getting the recording gear set up, and then do the video editing. If anyone else wants to have a go at it, by all means go for it.

But my final results are, DC arcs aren't sustainable in open air with low voltage DC. If I had a 48VDC welder, things may be different, but I don't have one of those. My other welder can do AC welding, and that won't work for this test.

** I did notice that in the video the arcs where traveling up. This is due to heat rising, and this is how a Jacobs Ladder works (which, btw, uses 1000's to 10,000's of Volts; AC usually tho). So this is probably why his arcs lasted so much longer at the higher voltage. The plasma was keeping itself energized and the air ionized because it was being blocked by the piece of wood.
Now, had this been done inside a breaker box or switch, I can really see how this would be a major issue. And I've seen plenty of videos where this happens, and the unit goes up in smoke, literally, sometimes taking everything else in the panel with it too.

 

[Boron]

Thnx @Korishan . Thats an valuable contribution to Board knowledge on this subject. As you say , if the arc is constrained as in the original vid showing an MCB self destruct violently then maybe the Water Spritzer might save the day (though I would reach for the cable cutters pdq). I does support the sense in have fire extinguishing means on hand.
I think it also supports the case for the ubiquitous knife switch I showed. These are everywhere in the far east domestic properties by the billions. They also use ceramic bottle fuses (original Siemens design WW2).
I have received two of these Knife Switches (brings back memories) and will subject them to arc tests if I can set up some old LAB batteries with enough juice for a 2s shot say. Interesting thing about these switches is that they contain a master fuse strip on each line inside, I had over looked this - neat. Notice with the design that they should be mounted vertically - handle at the top and it is shrouded against flash. If this can be demonstrated on a current source of 100A - this could make a valuable protective device for solar panels for example. Naturally there will be huge outcry against such heresy as the cartel will be outraged against a simple device costing a small fraction of their very complicated MCB offerings.
Of course this is for manual disconnection in emergency conditions where you normally disconnect downstream load first - but I have a lot more faith in that than the fire cracker MCB - that was in widespread use in OZ before its danger was exposed WOW.

FWIW the units I have are rated for 32Aac and 63Aac. dpst. The poles could be wired in series to give you twice the distance protection - belt and braces?
Also - but this is probably not Kosher - the two sp channels could be wired in parallel to give you a 100A load. This wouldnt work for connection under load - but that not what this switch is is for - but it could function as a circuit breaker but this type of connection is frowned upon as (in theory) one blade could weld and not enable disconnection - out of my comfort zone here.

Still, say a cheap reliable 50 A breaker for panels and batteries - would be a contribution.

I also had the idea of using welding lead connector - big brass tapered plugs from my Denyo days never had any problems with them, just keep them clean, free from corrosion - good for 400Adc IIRC. If in doubt pull 'em out. KISS

Will post back when I get some tests done, this make take a week to set up have -5C in my garage.

What views have you got on fuselinks for Lion battery banks?

 

[Korishan]

Notice with the design that they should be mounted vertically - handle at the top and it is shrouded against flash.

Yeah, with the handle in the up position for it being on. You pull it down to turn it off. This would make the arc self extinguish like the Jacob's Ladder, as the arc would go up away from the handle.

 

[Boron]

You pull it down to turn it off. This would make the arc self extinguish like the Jacob's Ladder, as the arc would go up away from the handle.

Thats your opinion with 24Vdc ? We shall see wackamole.

 

[Korishan]

I figured I'd add this visual experiment as to why the arcs don't last very long:

View: https://youtube.com/shorts/qo64B3Jbi60

Probably has something to do with the O2 floating around causing rapid oxidation during the arcing. Not certain of that, though.

 

[Boron]

Yes K it demonstrates what an arc flash is to noobs (as opposed to a typical spark noobs might have encountered in the auto world)
Thing is you cant make an arc flash at 12v but you can at 24vdc+ So a demo showing this under similar conditions should make the point I have been banging on about. When I get round to setting up my high current rig I hope to demonstrate this.

BTW some Mod advice needed here, I am reluctant to get entangled with YT to make a video so I propose to make a short clip of say 5 secs as a low res mpg file to keep file size down (<1MB) and post a link on (Notdropbox I'll use another as DB is no longer free and costs £100 pa) for members to view if they are sufficiently interested) I dont know if that will work, is it allowed on here?

 

[Korishan]

it demonstrates what an arc flash is to noobs

There's lots of noobs that visit the site and the information in pertinent. The video was to show that it is much harder to make and sustain an arc in normal atmospheric conditions.

I am reluctant to get entangled with YT

Not sure what this means, but ok.

I propose to make a short clip of say 5 secs as a low res mpg file to keep file size down (<1MB) and post a link on

Should be able to be under 5MB, and if you aren't going to add audio to it, just convert to animated gif and post directly here. That way links don't get broken in the future.

https://electricalsafetyworkshop.com/wp-content/uploads/sites/255/ESW-2023-06.pdf

They used a copper rod with flat ends (25 mm in diameter). That's pretty substantial. They used this size partially to make sure the metal doesn't melt during operation.

Analysis of the 150 Vdc test results
The summary results at 150 Vdc can be found in Table I.
At 145 Vdc, it was possible to initiate an electric arc
generating more than 1.2 cal/cm² at 457 mm (18") with the
vertical in-line configuration and an initial inter-electrode
spacing of 6 mm (0.25"). The arc extinguished itself after 300
to 500 ms with a final inter-electrode spacing of about 25 mm
(1"). However, the measured incident energy at 457 mm (18")
never goes above 1.4 cal/cm². The arcing current were
between 30 to 45 % of the bolted fault current.
With a initial gap of 12 mm an arc was able to sustained but
not sufficient long to reach the threshold of 1.2 cal/cm².
After 9 tests, it was not possible to initiate an arc with a
parallel electrode spacing of 8 mm. The arc was blow out
extremely fast and did not sustain enough long (< 17 ms) to
even dissipate an incident energy above 0.1 cal/cm².
These results are in accordance with similar results
obtained in 2018 [1]. With similar inputs parameters, similar
results are obtained. In these previous tests, the maximum
incident energy found at 144 Vdc was 1.7 cal/cm² at 450 mm
for an initial gap of 6 mm with a box.
With the vertical in-line configuration, all tests stopped by
themselves when the electrode gap reached 20 to 25 mm.
The burn back on the electrodes for some of the tests was
significant. The electrode burn back depends on the material
and the size of the electrode (bus bar).

Burn back was quick, even with such a large piece of metal. They couldn't sustain for more than 1-2 seconds. And this is at 150VDC source.


It'll be interesting to see what kind of results you can obtain with 24VDC. I would also like to see it at 58VDC, considering the majority of the diy home power storage systems use 48V systems, not 24.

 

[Boron]

My test vid - This seems to have solved the issue - but I started with a 0.75MB MP4 and now have a 6.5MB Gif? is that how it works , it was a 6s clip but I would aim for 5s - should be enough? No sound needed

 

[Boron]

Burn back was quick, even with such a large piece of metal. They couldn't sustain for more than 1-2 seconds. And this is at 150VDC source.


It'll be interesting to see what kind of results you can obtain with 24VDC. I would also like to see it at 58VDC, considering the majority of the diy home power storage systems use 48V systems, not 24.

Wow I am floored K Thnx^6, thats the best bit of info Ive received so far. I will need some time to digest and get back to you. Clearly this is aimed at what can happen with busbars on dc systems eg large computer UPSs - scary.

Of course a big difference between a horizontal vs vertical gap

I have been advocating staying with 24V systems rather than 48V. I have in the back of my skull a notion that there is a cubic relationship to risk factor eg you double 24-48 = 8x risk and sustains a distance 3x the min 1/4" arc for 24V ie nearly an inch - but I need to justify this hunch (vaguely based on when I did a bit of welding years ago and I could sustain an arc for over 1/2" - messing about).

 

[Boron]

This is another video clip test for a free alternative to Dropbox $$$ to make a short clip to present here

Seems to work ok nothing suspicious AFAIK just click and close after viewing

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[Boron]

Had to post this

View: https://www.youtube.com/shorts/hF9gZvCh70g?feature=share

shows how to disconnect live panels, must be 48v 100A + see how the flame creeps up your arm, always wear gloves and googles. Vertical cables worst case. Horizontal would tend to self extinguish

Pretty scary eh?

 

[Korishan]

Yup, cuz plasma be hot

I didn't know they disconnected them like that. Would be interesting to know why they disconnected that way instead of a junction box. But that's for another topic/thread.

This is a good example of why not to take a large set of cutters and just snip the whole bundle, too. It'd be quite possible that the resulting plasma arc would go down into the conduit burning the cables and igniting the piping. Kinda crazy over all

 

[Boron]

Yup, cuz plasma be hot
HOTTER THAN THE SUN
I didn't know they disconnected them like that. Would be interesting to know why they disconnected that way instead of a junction box. But that's for another topic/thread.

This is a good example of why not to take a large set of cutters and just snip the whole bundle, too. It'd be quite possible that the resulting plasma arc would go down into the conduit burning the cables and igniting the piping. Kinda crazy over all

Yes in fact this is why I have been banging on about dc circuit safety and what a big yawn it gets here from the couch colonels.
I have found that knowledgeable Solarists will keep a proper pair of cable cutters (not those crappy electrician's pair in the vid - see how long it took) on a regular hook, cw gloves and googles. When you get an incident like that, do you think your circuit breakers are going to interrupt that kind of arc flash. Once the arc is struck, it stays on unless quenched or separated by distance (which cools the arc so its resistance shoots up and currents drops ).

Cutting the cable is very quick and fail safe. All Solarists should be taught the procedure.

This is the proper job ca $15 a life saver

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