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Author Topic: Welding on clean DC  (Read 2371 times)

BruceM

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Re: Welding on clean DC
« Reply #75 on: July 04, 2019, 06:08:49 AM »
Lucky break for me, back on Bromelain, which I'd run out of, and once again feeling much less head pain in stores and driving/riding.  Did a big shopping run with my neighbor Jeff and got the new 6V battery and the 3/16 rods. Got a nice collection of scrap steel for $10 from the fence co. for my further welding/cutting education, and was offered more to pick over next week.  When you've been mostly homebound for a few decades, shopping in stores is a treat.

I've been stewing over using my newer linear PV charge regulator PCB as a welding regulator. It is a low side regulator, 7 TO247 or TO3 style large Mosfets in parallel, linear mode, an op amp and current sense resistor for each for current matching.  Very little mods needed though I'm concerned about arc EMI and what I should do to address that.  Found a couple Fairchild Mosfets, 75 and 100V that have good linear capability, while still having low on resistance, around $5 ea. One 75V one can handle 50A at 6V drop, with just one, so 7 would be loafing.  All together about $100 in parts to build one, not counting what I need for arc EMI supression.  Chokes rated 200 amps are NOT standard products.  Surge supressor devices might be helpful with some modest line to line metal film capacitors, and perhaps I can get some large ferrite and powdered iron cores.



 

glort

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Re: Welding on clean DC
« Reply #76 on: July 04, 2019, 10:20:28 AM »
Good to hear you are feeling better Bruce. The longer and more often you can stay on top of the Roller coaster the better.
Definitely at the Bottom of mine right now.


When you've been mostly homebound for a few decades, shopping in stores is a treat.
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Unfair and ironic.  I'm able and capable to go wherever and do what ever I want yet these days I only leave home when necessary.
Mrs is always at me to go somewhere and get out the house but there are very few places I want to go . I went to the tractor place Day before yesterday after some parts for my Kubota engine. Woman on the parts counter was ignorant then rude when I pointed out her mistake. I left before I tore her a new one. That will do me for a while till the mrs forces me to go with her somewhere again.

   Shopping centres Bore the Bejesus out of me. 8 of 10 places are for women. When I have to go to the shops I can be in and out and get what I want in direct reverse proportion to the hours my mrs takes when she goes to get bread and milk. I like the hardware and tool shops but seen all I want and have all I need so bored with those too now.
Pity I can't give you some of my "Freedom " and sit out your restrictions for a while.  Would be a good arrangement for both of us but I think you'd soon get over going to shops.

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One 75V one can handle 50A at 6V drop, with just one, so 7 would be loafing.

The power little Mosfets can handle these days is amazing. Would 4 not do what you want being 120A with plenty of overhead?

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  Chokes rated 200 amps are NOT standard products.


Seems the cores for winding your own Mega Chokes are getting more available. Was just reading about a place the other day that makes them to order. They do some Rippers and charge $11 Per Kg which seems very reasonable to me.  Some of them I saw in pics were huge. They did rings and E cores.
They do them in various materials and one can get some very high amps before they saturate. I think winding the cores to get best efficiency is hard work given how tight they need to be wound.

I can see you developing this far beyond where any battery welding has gone before!

BruceM

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Re: Welding on clean DC
« Reply #77 on: July 04, 2019, 04:51:18 PM »
Sorry you're down, Glort. The statistics on current SSRI/Tricyclics for depression are quite poor. I've read the books of Datis Kharrazian, quite impressive guy. Teaching at Loma Linda now.  https://drknews.com/  I think the future of medicine is in the group now known as functional medicine.

I looked more at the PV board for welding regulator-  it was designed for much lower currents and higher voltages so traces and wires for power are going to be a challenge.  It would need a spider's web of additional large wires added.  I will try the simple resistive method first.  Operating MOSFETs in linear mode, you must stay well away from the safe operating area specification, and a massive heatsink will be needed.  If dropping 4V at 150 amps, you must heatsink 600W (!), sharing that among 7 mosfets still leaves a very hefty 85W of heat dissipation per mosfet.
Because of short welding duty cycle, either a big slab of aluminum or a water filled heatsink might be effective, sort of a hopper cooled welder.   PWM is normally used for this reason.  I hope the 3/16 steel rod method will work and will save me a lot of educational lumps in working with such extreme currents and EMI as welding has. 






glort

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Re: Welding on clean DC
« Reply #78 on: July 05, 2019, 12:40:03 AM »
I think the future of medicine is in the group now known as functional medicine.

Went to bed feeling like I was going to throw up, woke up feeling like my guts are in a knot. Worst day of the year for me. Always will be.
I like the idea of " Functional Medicine". Exactly what I need. Something to make me functional again instead of useless.
I haven't touched the Depression medication for a while because that is as it's name suggests, makes me depressed.  I rather feel the hurt and the pain than feel nothing at all and be like a zombie.  Mrs says I'm much more calm when I'm on the poison but I feel dopey and loose cognitive abilities, as little as I already have now.

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I looked more at the PV board for welding regulator-  it was designed for much lower currents and higher voltages so traces and wires for power are going to be a challenge.

I was thinking about this when you mentioned Chokes.  I had an inverter, several of them actually, apart yesterday. They tend to be a 20A@ up to 600V deal now rather than 120A@ 30V. I find working with high power DC a real pain in the arse. Easy to play tiddly winks with 10A @ up to about 60V but  once you go over that, Choices of components, cost and complexity skyrockets.

I have been trying to come up with a simple enough controller that I can build to Hook some panels to a standard water heater element and will keep the panels on power point. Lots of designs around that will do something useless like 300W but I want something practical AND simple. It is my observation that the electronically Gifted tend to make things a lot more complicated than they could be and want to cover every eventuality no matter how unlikely. Just like with Diesel mechanics that insist an injector pump could never Be ok with just a simple repair and EVERY IP in the world needs a complete and total Rebuild, electronic gurus tend to be incapable of building simple effective circuits without a ton of over complication.

The  bare minimum for what I want would be 1 KW output and 2 would be a lot more practical still.  I want to feed the panels to a bank of caps, Charge them up then Dump the full load to the element to get the max power output from the available input. With a bank of panels outputting near the desired Voltage and amperage the system may Cycle at mains frequency or higher and the power could be almost direct.  As with everything solar power, it's the before 10 and after 2  hours that are where the efficiency comes into play. Here the frequency of the power pulse would be accordingly longe as the caps would take longer to charge but the panels would stay at power point and the element would get a lot more power than just directly hooking up the power and pulling them down to a fraction of their rated output.
Some bits aren't too hard but others to handle that sort of power are very frustrating.  It just needs to be a simple PWM which at 12 V and 10 A would be easy but ramp it up.... If this was AC it would be $5 off the shelf boards from China. Highest Boost boards do about 80V and anything beyond that which goes to mains type outputs is in Ma. 

 
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If dropping 4V at 150 amps, you must heatsink 600W (!),
Because of short welding duty cycle, either a big slab of aluminum or a water filled heatsink might be effective, sort of a hopper cooled welder.

That part is Easy and practical! Get yourself an Aluminium Kettle and mount the mosfets on that. By the time you are finished welding, you will have Hot water ready for a nice cuppa tea and will be content in the knowledge you have not wasted the energy!  Probably have enough to wash up with as well.  :laugh:

Failing that, Heatsinks out of Solar GTI inverters would be great. I have a few up the back that are great heavy lumps with a great C o/w rating.  Put a couple of computer fans on the things in series and you could sink a LOT of heat into them.

Or Just put the Mosfets at either end and when you are finished welding,  you'll have a hotplate to cook your Dinner on!

I saw something the other day that made me think of your welding. An old Forklift battery charger.  Was for a 24V system so would probably do around 28V and was 135A output.  Probably a good starting point for what you want to do and would save the battery aspect as you could go from your normal  power supply.... if your inverter was up to it. Might be some components you could modify at least as a head start.

mikenash

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Re: Welding on clean DC
« Reply #79 on: July 07, 2019, 03:36:47 AM »
Hey Bruce - stupid question perhaps. but are these old-fashioned type of welder somethinh you can tolerate?

No electronics, obviously.  And I wondered if the pull-in-and-out (voltage?) adjustment might serve you in some way to modify your DC

I would guess there are still a few rattling around Old Farts' workshops

Cheers

BruceM

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Re: Welding on clean DC
« Reply #80 on: July 07, 2019, 02:35:29 PM »
The old school AC welders were just big linear, adjustable step down transformers.  No EMI from  power switching electronics but horrendous ELF magnetic fields both at transformer and at the welder where the welding leads are separated. Plus some healthy EMI due to AC arc- starting and stopping of the arc generates broad sprectrum EMI.  Likewise, those old DC units with linear transformers plus rectification for lumpy "DC" generate a great deal of EMI from the diodes- at start and stop of conduction, diodes make a little burst of high frequency EMI proportional in strength to the current.  So old tech doesn't solve the problem, but direct linear use of batteries does get rid of all EMI sources except the actual DC arc start/stop and current variation.

After it stopped drizzling yesterday I did hook up 12 foot of 3/16" diameter mild steel rod along with the extra 6V battery for a total of 30V nominal plus rod resistor.  It worked well in terms of welding with 3/32 7018 with the luxury of stable arc and the ability to "whip it". I checked via meters and camera in video mode, the rod was dropping 3.5 V at a current around 110 amps.  The rod did heat up quite rapidly, which concerns me, but I hope it will work out OK.  Steel electrical resistance increases with temperature.  I also tried the same resistance rod from 24V, to see if 1/16" 6013 would then be OK for thin stock. (It's way too hot on 24V.) That results in about 55 amps and while miserable to start and maintain arc, it does work. I tried it on some very thin stock to small square tube and it did the job. 

I also tried brazing the 3/16 rod to make a bronze coating for electrical connection. That works fine.  My plan is to bronze a spot every couple feet or so, and to use my spring type electrode holder with bronze jaws to clamp to the rod; that will by my simple current adjuster.  I'll paint the rest of the rod with high temp spray enamel to avoid corrosion. The fixed end of the rod will connect via 2 gauge wire and welding connector to either 24 or 30V battery connection (and arc stabilizing choke).  I bought the screw clamping, type electrode holder to try for the electrode as Mikenash had suggested.

So now I'm ready to build a new case for the three batteries and rod resistor. If I'm not happy with the rod resistor regulation, I'll hack one of my PV regulator boards.

I did some cutting on oxy-acetylene and have no problems with that outside with a light wind.  Brazing flux stinks but is doable outside.  I haven't tried gas welding with steel rods yet.  Much practice is needed on all fronts.


mikenash

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Re: Welding on clean DC
« Reply #81 on: July 07, 2019, 03:50:20 PM »
Hey Bruce, I hadn't realised you were dabbling in oxy/acetylene as well . . .

Check out this product "steel brazing rod"

https://www.globalweldingsupplies.co.nz/range-page.php?sku=R_TWNS

See specs?  Especially temp chart?

The general engineer up the road used to use it for things like repairs to truck parts.  Said it was really strong & caused less distortion than arc welding in some of his applications

Possibly a mild steel solution up to maybe 5mm or more

Not necessarily that particular product of course - that's just one vendor's take on things.  Maybe google "steel brazing rods" or something like that?

Cheers

BruceM

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Re: Welding on clean DC
« Reply #82 on: July 07, 2019, 04:45:51 PM »
I've got some copper coated mild steel filler rods for gas welding, just haven't put in the time yet.  That would have the advantage of no flux but more skill is needed since blow out of the base material is possible. 

High strength brazing rods like nickel silver are interesting- keeping temperature below steel deformation is a plus.

Back to woodworking today, I must bang up a new case for 3 batteries.  I have wire and terminals on order for new interconnects and connection to the steel rod resistor/regulator.
There will be 3 welding connector sockets, one negative, plus 24V, plus 30V. The resistor rod will have a whip to connect to any of these, the electrode cable will have an electrode holder on each end, it always connects to the rod on bronzed spots. That gives me reverse polarity, adjustable low current <=24V, and adjustable higher current <=30V. 

Being able to adjust current is a huge help. I hope electronic (linear) regulation isn't needed,
but will see how it works out.


BruceM

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Re: Welding on clean DC
« Reply #83 on: July 07, 2019, 05:27:28 PM »
By my calculations, 26 gauge steel sheet (0.476 mm) in 37.375 mm wide strips will have the have the same cross section as 3/16 steel rod, but has 5 times the surface area for better air cooling.  Hmmm, I should get out the tin snips. 

The zinc plating will increase conductivity...how much is a subject for testing.
« Last Edit: July 07, 2019, 06:04:12 PM by BruceM »

BruceM

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Re: Welding on clean DC
« Reply #84 on: July 07, 2019, 08:55:06 PM »
I made a test welding resistor cut into alternating 1.5" strips as shown in my test setup below.   13 strips total, so roughly 26 feet of 1.5 inch wide 26 gauge galvanized steel sheet.  Full length it is providing about 5 volts drop at 85 amps.   So the zinc plating is nearly halving the resistance, but that's good for radiating surface area.  It doesn't get very hot for a full stick of of welding in one go, so it's a winner.  I'll mount it on the new welder case side via some sort of standoffs to get airflow on both sides. I'm still thinking about standoff materials and moveable cable connection.


mike90045

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Re: Welding on clean DC
« Reply #85 on: July 08, 2019, 12:42:01 AM »
.... 26 gauge galvanized steel sheet..... It doesn't get very hot for a full stick of of welding in one go, ....

Mmmmmm   zinc fumes if it ever heats up too hot.  Be careful.

BruceM

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Re: Welding on clean DC
« Reply #86 on: July 08, 2019, 02:07:18 AM »
Good warning, Mike.  This should stay under 250F. It was under 165F, where you can't hold you finger on it for more than 3 seconds. 393F is the max safe temperature for exposed zinc.  I'll check it out carefully but thanks very much for the reminder. 


« Last Edit: July 08, 2019, 02:16:27 AM by BruceM »

glort

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Re: Welding on clean DC
« Reply #87 on: July 09, 2019, 03:06:15 AM »

Gave my new auto darkening welding helmet a workout this morning fixing my  IBC based Trailer.  I didn't get the new welder out it's box ( yet!) Didn't want to do this job but was forced on me when a wheel hub fell apart and was the right time to mod the thing as I have been going to since 10 Min after I built it and thought " WTF did I do it like that for?"  :embarassed:

VERY happy with the way The helmet works. Makes things so much easier. Just being able to see what you are doing and hit the gun and go is a huge leap in ease and productivity.  Even though this is a $100 helmet, it's not a great deal better in staying on my head or the adjustments for that. Also not great at staying up when you lift it. May be able to tighten that a bit more. Would be ok to leave down but was out in the sun and it gets hot breathing into it. When actually welding, the thing is fantastic.  You can see every bit of the job before,during and after you weld it.
When having to tack or stitch things, would be a boon.

I have always wondered about plasma cutting without a shade as that is throwing a big arc as well but I don't see anyone using a mask. Never really felt my eyes were sore after using it a lot either so never worried. I remember once welding without a shield I forget and thought  being careful to close my eyes would be OK> It wasn't so I know the feeling well of getting a hit from the UV.

 I cutting today with this helmet and it was good. I can see where I am cutting into the molten metal pool even better and found it an advantage. As fate would have it, When Cutting a Piece of axle at a funny angle, I sprayed myself fair in the face with a shower of hot metal. I heard and felt it as well as saw it hit the mask full on. That might have stung had I not had the shield on. Then again, spray myself on the arms all the time and stings a bit but only while it's happening.

With more irony, the old welder ran near perfect. I was welding some thicker material so had it dialled up a bit and the welds were as good this time as they were so poor last time.  Rather than felt despondent, I was actually hoping a mate I am expecting for a visit would show up and I could show off my handy work. I was quite proud of the way the welds were coming out instead of embarrassed even for myself. He'll probably turn up any time now I'm finished!   :embarassed:

I am encouraged to get another torch for the old machine and see if that refurbishes it. Might need a wire feed too.  Was a pleasure to use it today but on the lighter stuff I did last time, was a night mare.

I'm hoping for a lot out of the new machine... when I get it out it's box finally. No rush, I got it for a great price when the sale was on so all good.

For those behind the times like me with these helmets, I strongly recommend them. I'm amazed how much easier, faster and satisfying they make a welding or Plasma cutting job.

Are you sure you couldn't get by with a few layers of foil round the control box or lining the things Bruce?

BruceM

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Re: Welding on clean DC
« Reply #88 on: July 09, 2019, 03:53:07 AM »
Foil won't hack it, all connected wires radiate, which includes LCD panel and PV panel(s). Can't shield those. 

Any sustained electrical arc will generate plenty of UV, so I'm sure plasma cutters do too.

Maybe this winter I'll work on the linear circuitry for the digital one I took apart. I'm doing pretty good with the shade 8 lens, so I'm not in a hurry.

I have the new 3 battery case put together on wheels. Much work left to do, pondering the best way to hook up the "resistor" panel, so I can have either less than 30V, or less than 24V.  I had to hook up the whole thing on the shop floor again to weld the 5/8 axle stubs to some steel angle.  Sure is easier welding with the right power.  I did it with 1/8 6013, almost 3 sticks in fairly rapid order.  The galvanized stayed below 210F and rapidly cools while I'm picking slag and wire brushing. 

I'm not impressed with the performance below 24V, on 1/16 6013.  I tested that yesterday via the resistor on 24V.  The arc is tough to start and stops often. I suspect that a much larger choke (which can have smaller wire due to current down to around 50A) might be needed just for low current operating (below 24V).  I'm not sure it's worth the effort.

Figuring how to best mount the sheet resistor is next.  I want it 2-3 inches out so that there is good upward airflow behind it when it heats up.  Wood isn't going to hold up well in direct contact with the metal so I may use some silicone tubing as an insulator.



« Last Edit: July 09, 2019, 04:00:26 AM by BruceM »

BruceM

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Re: Welding on clean DC
« Reply #89 on: July 12, 2019, 04:18:53 AM »
Almost done with the new battery welder.  The zig zag strip galvanized steel power resistor was enlarged to the whole side of the new larger, 3 battery case, with strips going horizontal so I could use 2.25"x0.75" vertical maple stand offs to attach it. Maple has long history of good heat tolerance.  In testing today, I found that thanks to the much longer strip, at the very top of the strip, it does 1/16 - 6013 rods for very thin stock nicely.

What's left is moving the big wheels axle forward a bit and making some sort of push bar for moving it around.  I'm very happy with the performance; today I tested several different types and sizes of rods, and marked the best power setting for each right on the strips. In all cases, the sheet steel stays well below 210F.

So, no electronics required, beyond the custom gapped toroidal choke used as an arc stabilizer.

I'll post some pictures soon.