AC225 converted to DC with Choke.

[Greg (2N) TX]

It has been a while since last posting circa 2017.
Been preoccupied I guess?
Anyway, thought I should share the DC conversion pics before I close it up.
I am able to use it secured to the trailer with the generator for welding fence H braces.
Very nice arc with 225A Bridge diodes and the lovely choke coil out of an old Ranger 250.
Regards,
Greg

 

[MarkB_MI]

Nice work. That's a MONSTER choke!

 

[Geo-TH,In]

Is it worth making a DC welder?
I have the huge diodes, no choke.
How much power is lost in the choke?
What's the advantage of a DC welder over an AC?

 

[buzz saw]

(quoted from post at 17:01:58 02/25/23) Is it worth making a DC welder?
I have the huge diodes, no choke.
How much power is lost in the choke?
What's the advantage of a DC welder over an AC?

Smoother arc, more versatility with electrode selection, DC will run 7018 like a champ.

This post was edited by buzz saw on 02/25/2023 at 05:32 pm.

 

[gears]

Greg, I was following your post intending to try the conversion too but managed to pickup an MP210 at a pawn shop for a song.

 

[JustIn Case]

(quoted from post at 15:28:15 02/25/23) It has been a while since last posting circa 2017.
Been preoccupied I guess?
Anyway, thought I should share the DC conversion pics before I close it up.
I am able to use it secured to the trailer with the generator for welding fence H braces.
Very nice arc with 225A Bridge diodes and the lovely choke coil out of an old Ranger 250.
Regards,
Greg


So what happens if I install bridge rectifier but nut the choke. I gather that the choke "smooths out" the full wave rectified DC. What else would work for a choke? I have the diode bridge but not the choke. Thanks in advance. Jim
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[Greg (2N) TX]

Jim,
I just happened to find the diodes and choke at a welding repair shop
about 6 years ago, a customer never paid for the repair I guess.
Well the choke is the heart of the system to say the least.
I was floored when I first struck the arc with the 7018 on that
upgrade.
That choke is outrageously priced today for as much as about $800
in some places.
It measures between 3 to 4 millihenries, can handle 250A.
You can see the number of heavy flat solid wire wraps, double
layered, very impressive!
Well, besides smoothing the full-wave pulsating DC, it provides some
serious current regulation once the arc gets started.
So, when you have a fidgety hand that moves the tip away and back
to the work, the arc is sustained very well.
The inductor wants to keep the current flowing so when you move the
tip away, the voltage will rise to sustain the arc, absolutely beautiful!
I estimate the max arc length to be about 3/4 on the 120A setting.

You will have to get quite a few wraps of very heavy wire in a large
gutted transformer lamination assembly to get 3 to 4 mH of
inductance.

I saw that inductor choke available at a lower amount, say about $600
from somewhere on the internet, I found the part #:

Lincoln OEM Choke Coil & Lamination Assembly (9SL9036-1 /
L9036-1)

Take Care,
Greg

 

[MarkB_MI]

> Is it worth making a DC welder?
> I have the huge diodes, no choke.
> How much power is lost in the choke?
> What's the advantage of a DC welder over an AC?

Well, George, I suspect you already know all the answers to your questions, but I'll bite just the same.

Obviously DC is mo' betta than AC. Otherwise Lincoln wouldn't make an AC/DC version of its famous tombstone.

As you well know, inductors and capacitors are energy STORAGE devices, so you don't lose power in the filter circuit of a DC welder. There are always I²R losses in an inductor, but compared to the power delivered to the weld, they should be negligible. Certainly that big hawg of choke that Greg's using shouldn't lose much power.

You can convert your AC welder to DC without adding a filter circuit, but you lose much of the benefit of DC. The current is still going to drop to zero 120 times a second if there's no filter to keep it going.

The main benefit of DC over AC is the smoother arc you get by not shutting off the current 120 times per second. But DC also allows you to use DC-only rods such as 6010. More importantly, it allows you to reverse the weld current, as many rods behave quite different with straight versus reverse polarity. Even an AC-friendly electrode like 6011 becomes quite different when you run it on DC reverse polarity.

As I recall, one advantage of AC over DC is it isn't susceptible to arc blow, a phenomenon where magnetic fields in the work deflect the weld. Also, AC is used exclusively when TIG-welding aluminum, as the current reversal will remove oxidation from the surface of the metal. It's an interesting thing to watch, as the oxidation will literally fly off the aluminum.

 

[Geo-TH,In]

As you well know, inductors and capacitors are energy STORAGE devices.

Mark, I wonder why they don't use capacitors on DC welders and make a Pi filter? I'm not sure if my wire welder uses a choke and or capacitors. I know it uses diodes because I had to replace one.

I don't do that much welding. If my old tombstone dies, I'll buy an AC/DC welder. Good chance I'll be buried under my tombstone before my tombstone dies.

I scrap out any appliance and save switches, wire and anything of value.

I recently scrapped a microwave. I wonder if the transformer would work as a choke. It appears to have healthy windings on the secondary.

I have to talk myself out of trying the transformer. I also have some large run capacitors. 55 uf 440vac

 

[cleddy]

Lots of knowledge about welders here. Would a Wire Welder be DC in most cases. I have a old Hobart Generator Welder (DC & AC outlets) with a Wisconsin Engine and was wondering if it would work with a Miller Wire Feeder/Gas for carbon steel wire. I have had it for 30 plus years and have only used it one time. I thought this welder would be useful as a stand-by Generator but we just have not experenced Outages where I am located. I prefer the buss box and stick welding most of the time?? Cleddy

 

[MarkB_MI]

> Mark, I wonder why they don't use capacitors on DC welders and make a Pi filter? I'm not sure if my wire welder uses a choke and or capacitors. I know it uses diodes because I had to replace one.

Well, George, I think some do use capacitors, either alone or with inductors. But capacitors do have some drawbacks. First, they aren't as reliable as inductors, and it takes a huge capacitor to have much filtering effect on a welder. But the big problem is that as you increase capacitance you also increase the peak current the diodes have to handle. If you add enough capacitance to provide meaningful filtering, it will probably double the peak current through the diodes since the diodes can only conduct when they're forward-biased. Of course if you put diodes downstream of an inductor, that doesn't happen.

 

[MarkB_MI]

> Lots of knowledge about welders here. Would a Wire Welder be DC in most cases. I have a old Hobart Generator Welder (DC & AC outlets) with a Wisconsin Engine and was wondering if it would work with a Miller Wire Feeder/Gas for carbon steel wire.

Wire-feed welders are always DC. The polarity is reversed depending on whether gas or flux-core is used.

Your Hobart welder is constant-current, while wire-feed welders are constant-voltage. That's why you can't normally convert a stick welder to wire-feed. Multi-process welders capable of stick, wire and TIG are capable of running either constant-current or constant-voltage.

 

[cleddy]

Thanks for the answers. So to be specific I have a old Miller Wire Feeder off a Miller CP-200 welder (Probably something wrong with it-was discarded at a weld shop) It seems to run okay but maybe not consistant. Is there ANYTHING at all I can do with it considering I have the Hobart Generator welder and a Lincoln 225 AC/DC Buzz box with a old Lincoln High Frequency unit on it(Set up for dc TIG and AC TIG for aluminum). If it is TOTALY useless than I need to send it down the road with some other trash???Cleddy

 

[UncleTom]

I love how things get modified and hopped up. I bought an old Lincoln welder with the crank dial many years ago at a school auction for $50. I wished it was the ACDC version but it was only AC. I always wondered if i could convert it. What are the diodes out of?

 

[MarkB_MI]

> I have a old Miller Wire Feeder off a Miller CP-200 welder

I believe that's a constant-voltage welder. You can always try running the wire feeder off your tombstone, but I don't think you'll be happy with the results.

 

[Greg (2N) TX]

Tom,
The good diodes were out of old welders capable of at least 250A and the choke was to be a replacement for a welder that was never picked up or paid for.
I remember that not all of the diodes were the same but he said they were all good for at least 250A .
So I got very, very lucky to find such treasures for so cheap!
Goodness, I only paid somewhere around a hundred bucks for all of it at the time.
Greg

 

[cleddy]

About 45 years ago when I thought I could build anything. I wanted to build a DC welder. I went to the Surplus center in Lincoln Ne and bought a big Aircraft Generator and other parts-I suppose a choke and reostat and cables and followed their directions and built a engine driven DC welder with a 9 hp B&S Engine. I used it about two times and welded a transmission & motor mount for a metal lathe I had. Nine horsepower was barely enough to make it work so I concluded it was not worth it. Money wasted and still laying around taking up space?? Then I bought the 250 Amp Hobart engine driven welder for $600.00 dollars and used it once and that wasn't worth keeping up either?? I think I have finally got over that fever to build stuff. After using a few nice Tools that worked good right out of the box I think that is the way to go?? Cleddy

 

[JMOR]

(quoted from post at 08:54:05 02/26/23) As you well know, inductors and capacitors are energy STORAGE devices.

Mark, I wonder why they don't use capacitors on DC welders and make a Pi filter? I'm not sure if my wire welder uses a choke and or capacitors. I know it uses diodes because I had to replace one.

I don't do that much welding. If my old tombstone dies, I'll buy an AC/DC welder. Good chance I'll be buried under my tombstone before my tombstone dies.

I scrap out any appliance and save switches, wire and anything of value.

I recently scrapped a microwave. I wonder if the transformer would work as a choke. It appears to have healthy windings on the secondary.

I have to talk myself out of trying the transformer. I also have some large run capacitors. 55 uf 440vac

incoln SP-130T is a MIG and uses both cap & choke.

 

[Geo-TH,In]

30 years ago I was given these diodes hoping someday I could find a cheap welder that needs new diodes.

So far, no luck finding a welder that needs repaired.

 

[JustIn Case]

(quoted from post at 00:20:50 02/26/23) Jim,
I just happened to find the diodes and choke at a welding repair shop
about 6 years ago, a customer never paid for the repair I guess.
Well the choke is the heart of the system to say the least.
I was floored when I first struck the arc with the 7018 on that
upgrade.
That choke is outrageously priced today for as much as about $800
in some places.
It measures between 3 to 4 millihenries, can handle 250A.
You can see the number of heavy flat solid wire wraps, double
layered, very impressive!
Well, besides smoothing the full-wave pulsating DC, it provides some
serious current regulation once the arc gets started.
So, when you have a fidgety hand that moves the tip away and back
to the work, the arc is sustained very well.
The inductor wants to keep the current flowing so when you move the
tip away, the voltage will rise to sustain the arc, absolutely beautiful!
I estimate the max arc length to be about 3/4 on the 120A setting.

You will have to get quite a few wraps of very heavy wire in a large
gutted transformer lamination assembly to get 3 to 4 mH of
inductance.

I saw that inductor choke available at a lower amount, say about $600
from somewhere on the internet, I found the part #:

Lincoln OEM Choke Coil & Lamination Assembly (9SL9036-1 /
L9036-1)

Take Care,
Greg

Greg,
Thank You very much for the response! I purchased diodes for this online and really, they weren't that much money. I also have and assortment of large capacitors. I was thinking of using them in conjunction with the diodes. I kind of figured the choke was the item that really smoothed out the pulsating DC. Now I will be scrounging around looking for some sort of LARGE inductor that will carry this much current. Sometimes items like that get junked at work so never know I may stumble on to something. I'm not in any hurry, most of the time I use my Hobart 210MVP wire feed. The old Lincoln Tombstone is there when I need more.

For those who've not experienced it moving from a strictly AC "BuzzBox to a good DC source of welding power is a whole LOT smoother. 40+ years ago I worked a summer in a fabrication shop that had some motor driven DC generator welders. Boy, were they smooth running a weld. Then go back to the farm buzz box and find out just how spoiled I was at that Fab shop. Another thing was these were industrial machines that had much better duty cycles and considerably higher max output. It's not like you were crowding the limitations especially when welding with 1/8 6010 rod on a machine that was built to burn 3/16 welding rod or larger. It was pretty fun!

Thanks for your repsonse!
Jim