What is the highest amount of amps I can get on a single phase welder?

[hotponyshoes]

I understand they can have higher amperage but a welder at 400 amp single phase vs 400 amp 3 phase. What difference does that make? Iv heard it’s more cost effective on 3 phase

3 phase is (usually) higher voltage than 1 phase.

You use power in Watts.
Watts = VoltsxAmps
So say you are running the mig at 20v and 400a that's 8000 watts

Ignoring the losses in the welder itself,
3 phase at 415v (8000/415) needs a 19a supply

1 phase at 230v (8000/230) needs a 35a supply.

Depends on what tariff you are on for electricity as to the cost difference.
If you are running a few machines you might have to pay a higher standing charge for a 100a 1ph supply than a 32a 3ph supply for example. If you are paying for the Watts you use a 3ph supply can work out a lot cheaper as you effectively get higher voltage for the same price.
I've not seen any electricity companies publish prices for 3ph rates online but they are probably out there somewhere if you look hard enough

 

[voipio]

Single phase stick welding machines can be AC or DC output. Three phase machines have to be DC, as there's no easy way of combining three phases into a single AC output.

 

[arther dailey]

if you have three phase , use it , as above it will give smoother performance , if not get a good electrician in to check and set up suitable supply to maximise whats available , or at least tell you what your max supply can cope with. full stop.

 

[Jelly_Sheffield]

Single phase stick welding machines can be AC or DC output. Three phase machines have to be DC, as there's no easy way of combining three phases into a single AC output.

The archetypal Oxford/Cytrigan/Olympic Oil-Filled AC stick welders were offered with 415V connection intended to be connected across two of the three phases.

If they're 240/415 then there's three connections where the flex goes in: U/L, N, V

240 connects across U/L & N, 415 connects Phase 1 to U/L, and Phase 2 (or 3 if you like) to V, leaving N unconnected.

The result is that it is a bit smoother than on single phase, but still in no way comparable to a DC machine.

You can also get a box that bolts onto the welding terminals of one of those Oil-Filled welders with a whack off great capacitor and rectifier in it to give a DC output, ostensibly for scratch start TIG!

 

[Erie Fred]

Single phase stick welding machines can be AC or DC output. Three phase machines have to be DC, as there's no easy way of combining three phases into a single AC output.

IIRC I did an install long ago for an ESAB 1500 amp AC sub arc machine that ran on 3-phase.

Maybe Brad would know.

 

[hotponyshoes]

You can also get a box that bolts onto the welding terminals of one of those Oil-Filled welders with a whack off great capacitor and rectifier in it to give a DC output, ostensibly for scratch start TIG!

You can also get those boxes to do ac/dc with hf start (plus various other features)
If you want to tig aluminium it's a cheap way to get a high power machine with a very good duty cycle.

 

[premmington]

The archetypal Oxford/Cytrigan/Olympic Oil-Filled AC stick welders were offered with 415V connection intended to be connected across two of the three phases.

If they're 240/415 then there's three connections where the flex goes in: U/L, N, V

240 connects across U/L & N, 415 connects Phase 1 to U/L, and Phase 2 (or 3 if you like) to V, leaving N unconnected.

The result is that it is a bit smoother than on single phase, but still in no way comparable to a DC machine.

You can also get a box that bolts onto the welding terminals of one of those Oil-Filled welders with a whack off great capacitor and rectifier in it to give a DC output, ostensibly for scratch start TIG!

Most big buzz boxes were the same.

I got Clarke one that will do 240v and 415v

 

[Jelly_Sheffield]

You can also get those boxes to do ac/dc with hf start (plus various other features)
If you want to tig aluminium it's a cheap way to get a high power machine with a very good duty cycle.

The more you know!

 

[premmington]

You can also get those boxes to do ac/dc with hf start (plus various other features)
If you want to tig aluminium it's a cheap way to get a high power machine with a very good duty cycle.

You can TIG aluminium in DC - you'll need to get the right gas into the mix, and helium-argon is a good place to start.

It fierce and hot.

I had a go once and got big drop out puddle on the floor.

 

[hotponyshoes]

You can TIG aluminium in DC - you'll need to get the right gas into the mix, and helium-argon is a good place to start.

It fierce and hot.

I had a go once and got big drop out puddle on the floor.

Cheaper to buy an ac/dc tig than buy the helium I expect!

 

[Ed.]

What’s the difference between 400 amp on single phase vs 3 phase?

Plenty, a big welder on a single phase you would have to have quite thick cables to connect it to all the way to the main board, plus the associated heavy duty circuit breakers, sockets and plugs etc. I have a large 3 Phase inverter type and I can get 600A on 6mm 4C+E connected to a 32A MCB, having said that I have never used more than 350A and most of my welding is between 170-270A and the machine doesn't even get warm.

I am currently building a steel shed on my 1/2 acre block and the sparky used 4mm 3phs cable to a socket as a temporary measure till the shed gets built, it is only about 1.2m away from the main circuit box, and I use a 16m of 3phs 6mm2 extension cable from the socket to the welder, however the circuit box has 25mm2 cable connected to the street, once it is finished I am putting in 10mm2 to all the 3 phase circuits sockets so that way I will not have to worry about getting a large lathe or some other machinery should I choose to. With single phase I think that you will be pushing it unless you have the correct sized wiring system.

My running costs for the inverter MIG are negligible, I used 2/3 of a 15kg roll for under $4 in electricity, and now that I have solar that isn't even an issue, single phase transformer type welders will cost a lot more in electricity.

I prefer to get 3 phase welders/machinery where possible as you can pick up used ones for a fraction of new price as most people don't have 3 phase so much less demand for them and new businesses generally buy new ones.