how to control the output of a transformer stick welder

[robsims]

Hi, i have a small 120 volt AC transformer stick arc welder. Open circuit voltage on secondary side is 42 volts and max amps is 100 amps. The magnetic shunt holder is broken. What are the possible solutions to control the output? Hope someone who did this already can help me

[Andy Chee]

Any controller design you implement will require some method of measuring current.

I believe you have stated in a previous thread discussion that your electrical parts supply is restricted.

What parts do you have available to you? What suppliers are available to you?  This will dictate whether you will be able to obtain the necessary components.

[Zenith]

I don't know what the low-end/second hand market for welders is like in Suriname, but in Europe a welder like that is worth very little even if it works (especially with the low price of introductory inverter welders being sold these days).

I suppose you could supply it from a unit based on a triac, and calibrate it based on its performance with particular sizes of welding electrodes. This is more or less the way they are used anyway, rather than the amp scale being taken as accurate. However, you have the cost and trouble of making the control unit and there may be problems to do with this being designed to work with the magnetic shunt.

I think it makes more sense to find a way to fix the magnetic shunt holder, or look for a used welder of the same sort, rather than mess about trying to find a way to control it without the magnetic shunt.

Mostly people use one size of electrode, for a 100A machine probably 2.5mm, and don't vary the current much. A possibility is to find a position for the shunt which works with the electrodes you normally use, and fix it in position. This is not ideal, but it might do.

[David Hess]

 The magnetic shunt controls the leakage inductance of the transformer which limits the output current.  You could add a really big variable power inductor in series with the output, however it would be easier to repair the variable magnetic shunt.

My transformer powered MIG welder just has a big inductor in series and adjusts the power using transformer taps.

[tautech]

Hi, i have a small 120 volt AC transformer stick arc welder. Open circuit voltage on secondary side is 42 volts and max amps is 100 amps. The magnetic shunt holder is broken. What are the possible solutions to control the output? Hope someone who did this already can help me

Please add detailed pictures of the insides.

There are alternative methods of controlling output by controlling the mains input by various methods using semiconductors. It may require the addition of heatsinks and a cooling fan.

[robsims]

I can only use the welder with 2 mm 6013 rods which is perfect for home use. It performs well but when i weld some slightly thinner material it burns holes in the material, that's why i want to control the output.  i thought the same as tautech. I want to control the output by controlling the mains input. Which method can i use to control the mains input? What can i buy at amazon or other stores as digikey?

[tautech]

Not a $2 fix.
Look up Alternistor < a type of Triac commonly used in welders.
Then you need a controller IC for it also.

Come back with some datasheets of what you find for further guidance.

[robsims]

Can i use this to control mains voltage of the stick welder

https://www.amazon.com/HiLetgo-Control-Regulator-50-220V-Adjustable/dp/B00LODGP2E/ref=sr_1_5?dib=eyJ2IjoiMSJ9.kxIjuDV_j2GuDGKE6t3BngUm4U0MAGsSfow33ZzNlQ9ZvdzzQa08fEbLdnaFjz6n7elKSmD16puCOpZ7jZBLX83MjeXDIS6V5s1ZMlDPFw1Xh3OUTNAdJEIjQMftTY1mJHHs0_hixpLoAYWsYYejvydqoKopJ8-bJIaVjPWHPleIiQ-oy2GjTRGZf8vPRwVKYQiKxjTI3rzmrx5yD37u40OIC2X43DykZBFgOcbDqgEfknrx2n6dDP6LmF1VUMw_uTLElEfQYF_5IDazJ8-7vZmws7zOtezrihpRHs3fODw.DwDP4SJVURZyfORLbPealCqzEoLSi6ccah7sULTjFRY&dib_tag=se&keywords=ac+voltage+regulator&qid=1717205686&sr=8-5#customerReviews

Or this controller

https://www.amazon.com/HARMNEE-Controller-100V-120V-Electronic-Protection/dp/B0BQCDFYXP/ref=sr_1_7?dib=eyJ2IjoiMSJ9.kxIjuDV_j2GuDGKE6t3BngUm4U0MAGsSfow33ZzNlQ9ZvdzzQa08fEbLdnaFjz6n7elKSmD16puCOpZ7jZBLX83MjeXDIS6V5s1ZMlDPFw1Xh3OUTNAdJEIjQMftTY1mJHHs0_hixpLoAYWsYYejvydqoKopJ8-bJIaVjPWHPleIiQ-oy2GjTRGZf8vPRwVKYQiKxjTI3rzmrx5yD37u40OIC2X43DykZBFgOcbDqgEfknrx2n6dDP6LmF1VUMw_uTLElEfQYF_5IDazJ8-7vZmws7zOtezrihpRHs3fODw.DwDP4SJVURZyfORLbPealCqzEoLSi6ccah7sULTjFRY&dib_tag=se&keywords=ac%2Bvoltage%2Bregulator&qid=1717205686&sr=8-7&th=1

[Andy Chee]

Can i use this to control mains voltage of the stick welder

Or this controller

Both those devices are woefully undersized and will blow up if used with a welder.

That said, you could borrow the basic schematic design and upgrade it with a suitably rated triac and snubber.

Incidentally, it might be cheaper to have a replacement shunt holder fabricated, than to design a mains controller circuit.

[Zenith]

In view of the cost of a 120V 100A small transformer welder (buzz-box) these days, and the cost of an electronic control device to replace the magnetic shunt, this strikes me as a dubious project altogether, especially as it's quite likely to end in disappointment. Furthermore this might affect the welding properties of the machine so as to make it difficult or unpleasant to use.

[CaptDon]

Burning 6011 / 6013 rods is like going back to the age of dinosaurs. Also, as someone who didn't understand why you don't rectify the A.C. mains and supply the output of a full wave bridge directly to a transformer it would appear you lack the basic understanding of electronic control circuits. That wouldn't stop you from building a copy of a working circuit however I doubt you also understand proper circuit layout and electrical noise shielding of high power mains switching circuits. All of which could be a good learning experience but far more costly than buying a good used inverter welder featuring A.C. / D.C. / Polarity selections. The advantages are enormous and will give better welds and allow moving into the 7014 / 7018 world. It would be possible to triac control the transformer input but it requires a lot of specialized parts to avoid the creation of static flux build-up in the transformer core which is why your other attempts blew up!

[robsims]

CaptDon you're right. Bought me an inverter welder today and it runs smooth. Thanks

[coppercone2]

The magnetic shunt controls the leakage inductance of the transformer which limits the output current.  You could add a really big variable power inductor in series with the output, however it would be easier to repair the variable magnetic shunt.

My transformer powered MIG welder just has a big inductor in series and adjusts the power using transformer taps.

Do you have a example of what this big variable inductor would look like?

I am way past the days of being interested in doing this, because I have a modern good welder,  but I am curious about this. Like that has got to be a interesting looking component.


Is it like a RF variable inductor with a core? or like a variac? and do you have any idea about the history of manufacturers of variable inductors like this?

[tautech]

The magnetic shunt controls the leakage inductance of the transformer which limits the output current.  You could add a really big variable power inductor in series with the output, however it would be easier to repair the variable magnetic shunt.

My transformer powered MIG welder just has a big inductor in series and adjusts the power using transformer taps.

Do you have a example of what this big variable inductor would look like?

I am way past the days of being interested in doing this, because I have a modern good welder,  but I am curious about this. Like that has got to be a interesting looking component.


Is it like a RF variable inductor with a core? or like a variac? and do you have any idea about the history of manufacturers of variable inductors like this?

The Youngs B/C were good examples.
They used a sliding laminated steel choke core into a winding heavy enough to conduct max output. When the choke was fully inserted output was at minimum. They used a threaded clamp to fix the choke in the required position.
Laminated chokes were known to delaminate over time and spread open resulting in the full range of adjustment becoming unusable.
Some preferred multi-tapped welding transformers because of this at the loss of fine adjustment a sliding choke can offer.

[coppercone2]

with todays technology I imagine you could just dunk it into a tank of high temp retaining compound, pull a vacuum and put it in a press to retain the shape

[CaptDon]

I had a small 'buzz box' style military welder. it was something like 25 to 100 amps at the typical 40vac open circuit. It had a very unusual feature.
It had some additional small transformers, a small mercury vapor thyratron (looked like an 866A with a grid) and a saturable core reactor to control the welding current. The reactor made low current welding a breeze since the reactor (inductor) stabilized the arc at high inductance / low current. The mercury thyratron was not made by Tungar but I think the welder had Tungar's name on it. Just some of the cool stuff left behind by U.S. Armed forces sold as metal scrap, thrown on burn piles or buried.

[coppercone2]

burning mercury 

[tautech]

with todays technology I imagine you could just dunk it into a tank of high temp retaining compound, pull a vacuum and put it in a press to retain the shape

Not when rust has formed between the choke laminations.

While they were covered in transformer varnish it didn't protect all in the long term especially those that were used for outdoor maintenance.

[David Hess]

I am way past the days of being interested in doing this, because I have a modern good welder,  but I am curious about this. Like that has got to be a interesting looking component.

I dusted off my NOS Clarke Turbo 100EN a couple months ago and have been learning to MIG weld with it.  My first project was to add a shelf to my portable welding table to hold the gas cylinder.  The shelf was made from 1/4" steel cutoffs from the local metal supply place that I bought to practice on.

I added a couple fans powered by an LM3578A boost converter to my welding helmet to stop it from fogging up.

Now I am welding together a front bumper kit for my pickup.

It had some additional small transformers, a small mercury vapor thyratron (looked like an 866A with a grid) and a saturable core reactor to control the welding current. The reactor made low current welding a breeze since the reactor (inductor) stabilized the arc at high inductance / low current.

That is clever.

I imagine that an inverter welder is easier to use than my transformer/inductor welder.

[Zenith]

CaptDon you're right. Bought me an inverter welder today and it runs smooth. Thanks

Not just that the DC arc is smoother than a buzz box. They burn a wider variety of electrodes and you can try electrode negative if you need to. You can't use DC rods with a buzz box, they are pretty much intended for 6013. They usually have an easy start feature. They have a much better duty cycle. With a buzz box, if you have any amount of work to do, you spend most of the time waiting for it to cool down after the thermal trip has thrown.

I'm sure you've made a sensible choice.

[Zenith]

The magnetic shunt controls the leakage inductance of the transformer which limits the output current.  You could add a really big variable power inductor in series with the output, however it would be easier to repair the variable magnetic shunt.

My transformer powered MIG welder just has a big inductor in series and adjusts the power using transformer taps.

Do you have a example of what this big variable inductor would look like?

I am way past the days of being interested in doing this, because I have a modern good welder,  but I am curious about this. Like that has got to be a interesting looking component.


Is it like a RF variable inductor with a core? or like a variac? and do you have any idea about the history of manufacturers of variable inductors like this?

Here's a video on those adjustable transformers, where he investigates in some detail. It lasts about half an hour.



I've no idea when this method of controlling a welder came about, but I'd guess it was at least in the 1930s when MMA started to be developed.

[tautech]

I've no idea when this method of controlling a welder came about, but I'd guess it was at least in the 1930s when MMA started to be developed.

Sliding chokes and tapped secondary's have been around forever. Single phase and 3 phase.

Their disadvantages were lack of fine control in most designs and considerable weight if they were required to be transportable.

I learnt to stick weld 50+ years back with a single phase Youngs model B and when purchasing my own selected something that was easier to shift around, a 180A dual SCR controlled welder that could just be lifted with one hand ~1982.
It was novel at that time for comparative lightness and potentiometer control and while it was good to use with 6013 rods as it had a relatively high OC voltage for a better striking arc it didn't much like low Hydrogen rods that prefer a lower working voltage.

Like much from those days semiconductors were unreliable and we had to uprate the SCR's to ensure reliability.
This design required careful adjustment of a 100k trimmer to ensure both SCR's developed precisely the same amount of phase control. < Where I first learnt how to float a scope ! < Never again !
Attached is the RE schematic.