Welding

[Catweazle]

Would simultaneously winding three, identical, single-core, 30-amp wires exactly the same number of turns on the secondary side and then connecting their respective ends as they came out of the secondary, thus presumably combining their output, produce the same voltage/amperage output (combined) as using one single core 90 amp wire? .

That would be fine, there is no need to use single cored wire in the transformer, you could use heavy stranded wire if you like.

Ah yes, I know about using stranded wire as opposed to using solid core Cat. What I am referring to is taking 3 independent, insulated, 30-amp wires of identical resistance and winding them simultaneously and then joining their respective ends (positive to positive and negative to negative) when they came out of the secondary. Assuming that they were wound to produce 40 volts and (given the total wattage) the total amperage available was, say, 90 then I am assuming that each of the 3 individual wires would pick up 30 amps each on the winding, which would then be recombined when they came out of the secondary to produce a combined amperage reading of 90 amps.

That would be fine, electrically no different to using stranded wire.

[Little John]

That would be fine, there is no need to use single cored wire in the transformer, you could use heavy stranded wire if you like.

Ah yes, I know about using stranded wire as opposed to using solid core Cat. What I am referring to is taking 3 independent, insulated, 30-amp wires of identical resistance and winding them simultaneously and then joining their respective ends (positive to positive and negative to negative) when they came out of the secondary. Assuming that they were wound to produce 40 volts and (given the total wattage) the total amperage available was, say, 90 then I am assuming that each of the 3 individual wires would pick up 30 amps each on the winding, which would then be recombined when they came out of the secondary to produce a combined amperage reading of 90 amps.

That would be fine, electrically no different to using stranded wire.

Excellent, that's what I thought. It would save the significant expense of a single, heavy-gauge wire for the transformer secondaries.

I should reiterate, this is just as mental exercise really. I already have a 180 amp ac oil welder and Aldi and the like sell 160 amp ac welders brand new for about 40 quid!

Just one final thought though. A single one of those site-transformers would make a cracking spot welder!

[JavaScriptDonkey]

Ah yes, I know about using stranded wire as opposed to using solid core Cat. What I am referring to is taking 3 independent, insulated, 30-amp wires of identical resistance and winding them simultaneously and then joining their respective ends (positive to positive and negative to negative) when they came out of the secondary. Assuming that they were wound to produce 40 volts and (given the total wattage) the total amperage available was, say, 90 then I am assuming that each of the 3 individual wires would pick up 30 amps each on the winding, which would then be recombined when they came out of the secondary to produce a combined amperage reading of 90 amps.

I'm not sure I followed you there.

If you take 3 independent transformers and try to combine the outputs things will probably end badly. You'd need to also join all 3 return paths otherwise there'd be no circuit but that might allow 90A to flow through your entire circuit, overheating the coils and melting the insulation between windings and core.

As we're talking AC then there's also the question of phasing to consider - will the sine wave outputs of the coils match?

[adam2]

3 wires each designed for 30 amps cant carry a total of 90 amps if twisted together or otherwise in close proximity.
They will overheat since the heat can not escape as readily as from a single wire.

High current transformer windings sometimes consist of more than one wire, but that is because it is easier to handle say 3 wires each of 25mm rather than one of 75mm.

[Little John]

3 wires each designed for 30 amps cant carry a total of 90 amps if twisted together or otherwise in close proximity.
They will overheat since the heat can not escape as readily as from a single wire.

High current transformer windings sometimes consist of more than one wire, but that is because it is easier to handle say 3 wires each of 25mm rather than one of 75mm.

OK that makes some sense to me. I guess the only way to test that out is on a single transformer with a variety of thicknesses of wire. In other words, if all of the 3 wires were individually well in excess of the rating needed for a third of the total amperage (but each still significantly short of the total rating of 90 amps) , then that might sufficiently mitigate the effect you are talking about. Then, again, maybe it wouldn't.

[Little John]

Ah yes, I know about using stranded wire as opposed to using solid core Cat. What I am referring to is taking 3 independent, insulated, 30-amp wires of identical resistance and winding them simultaneously and then joining their respective ends (positive to positive and negative to negative) when they came out of the secondary. Assuming that they were wound to produce 40 volts and (given the total wattage) the total amperage available was, say, 90 then I am assuming that each of the 3 individual wires would pick up 30 amps each on the winding, which would then be recombined when they came out of the secondary to produce a combined amperage reading of 90 amps.

I'm not sure I followed you there.

If you take 3 independent transformers and try to combine the outputs things will probably end badly. You'd need to also join all 3 return paths otherwise there'd be no circuit but that might allow 90A to flow through your entire circuit, overheating the coils and melting the insulation between windings and core.

As we're talking AC then there's also the question of phasing to consider - will the sine wave outputs of the coils match?

You’ve misunderstood what I was saying JSD

[Catweazle]

The three wires will have a greater surface area than one wire, so should run cooler. Also, the greater surface area of the conductors will increase the skin effect, enabling the same sized copper to carry more current.

[adam2]

My basic welding skills have been called on today. To repair the frame of a mobile home that came apart whilst it was being moved.

Used a piece of angle iron from an old metal bed frame, welded in place across the broken part.

I would not trust such a basic repair for future road movement, but the intention is to scrap the mobile home after short term static use. It only cost £800.

[Mark]

HSE - Change in Enforcement Expectations for Mild Steel Welding Fume:
https://www.hse.gov.uk/safetybulletins/ ... g-fume.htm

Just a word of caution - welding fume is now classified as carcinogenic
Make sure you all use the correct RPE/PPE....

[vtsnowedin]

Reminds me of Larskin's 'Far side' cartoon where a group of sad looking scientist are gather around a table stacked with reports.
Caption" The final results are in. Everything causes cancer."

[Catweazle]

Reminds me of Larskin's 'Far side' cartoon where a group of sad looking scientist are gather around a table stacked with reports.
Caption" The final results are in. Everything causes cancer."

Back in the late 70's / early 80's, when tobacco companies were getting hammered by evidence of cancers, there was a huge amount of newspaper space given over to reports of things that cause cancer.

I clearly remember my smoker friends saying "everything gives you cancer...."

Some of them died from it.

[vtsnowedin]

I have lost more then enough family and friends to tobacco caused disease.
The companies should at least be on the hook for all the final hospital bills.
But now it has become a race to see how small an exposure to some chemical compound might be to blame for your cancer or other disease?
Smoke for thirty years? Yah the cigarettes are probably to blame. Wore asbestos gloves a few times at work to not burn your hands maybe not so much.
Left unchecked this trend will keep us from using anything not "totally natural" and deprive us of the net benefits of many things because they carry a small chance of negative effects.
Note that straight tobacco is a natural product before they start adding chemicals to it.

[PS_RalphW]

The most dangerous aspect of tobacco is the inhalation of the smoke. Breathing burning leaves is generally a bad idea. Tobacco does contain specific chemicals that makes it worse, but enough of ordinary wood smoke will eventually kill you.

That said, the last century has seen hundreds of thousands of new chemicals never seen in nature before introduced to the environment. Only a very tiny proportion of these have been thoroughly tested for toxicity.

Humans will never live for ever, but longevity gains from medicine, diet and sanitation are now butting up against increased deaths from novel environmental toxins, and even without the problems of impending economic and social collapse, we have been slowly poisening our homes with a soup of ever more subtle toxins. We are at peak life expectancy.

[vtsnowedin]

Sixteenth century writers noted that Native Americans often developed "irritations of the lungs" in their old age. Apparently a lifetime of sitting around campfires and smoking peace pipes was just as bad for them as two packs a day is for a smoker today.
At any rate I do all my welding outside for good reason.

[Mark]

At any rate I do all my welding outside for good reason.

It's actually quite unusual for the HSE to issue Safety Alerts of this nature.
The change is based on a solid scientific evidence, gathered over many years.

They're not saying 'don't do welding'.
They're saying that people should take sensible precautions when welding.
The majority of welding is done inside, but if you're doing it outside, make sure the wind is in the right direction....