High Current AC Source

[tautech]

Hmm, my 400A AC 2 phase stick welder cost me just $200.

Duty cycle at full tit is another consideration fan cooled or not.

You can always parallel two welding machines, AC or DC. I have a couple of Millers that I've done that with a few times when using jet rods.

It's a lot easier on the machines when they are sharing the load.

WoD

Quote fixed.

Fine if you have 2 similarly capable welders however I never have.
For a while I had a 180A, 300A and a 250A DC TIG however they all had different control circuitry of which I would never dare to run them in parallel. 

Now with just the big 400A on castors and a 180A MIG, 140A caddy and gas set there's not much I can't handle. TIG I don't really need.
The big 400A was needed for the occasional heavy fab job however most of its work is just maintenance and repair.

[T3sl4co1l]

Mind that welders aren't likely very clean (stability or output ripple), nor very well calibrated.  At low frequencies they should be fairly stable/consistent at least (since that would affect usability if not!).  Output V(I) characteristics likely not well controlled either, other than being somewhere resistive to CC for TIG/stick types, and lower resistance for MIG.

Kind of a similar thing with electrophoresis supplies, AFAIK they're quite noisy/nasty because it doesn't matter for just pulling charge through a solution.

Tim

[tautech]

There's a pool of designs Tim ranging from tapped primaries, choked outputs, phase control and what could best described as SMPS.
Every dog of these designs has their advantages, power vs weight, fanless and just the plain efficiency latest designs offer.

Pick your poison !

[Stray Electron]

Ever used a 400A welder running at full tit ?
If not you are in for an experience.......300A is as hard as I've used and that ate 6g rods for breakfast ! 

Yes! Both jet rods and arc gouging! 

Most people would never believe the heat generated by either of these at those current levels. A white pipe-liner hood is noticeably cooler than a grey or black one.

WoD

   I have a Miller SynchroWave 350 and if I remember correctly it requires 130 Amps at 240 VAC at full tit.  That's a LOT of power!

   I don't know what voltage the OP requires but he will need something close to the size of the 350 to get 400 Amps.  I don't recall the exact weight of the 350 but IIRC it's between 650 and 800 pounds.

[Wrenches of Death]

Fine if you have 2 similarly capable welders however I never have.
For a while I had a 180A, 300A and a 250A DC TIG however they all had different control circuitry of which I would never dare to run them in parallel. 

Now with just the big 400A on castors and a 180A MIG, 140A caddy and gas set there's not much I can't handle. TIG I don't really need.
The big 400A was needed for the occasional heavy fab job however most of its work is just maintenance and repair.

No control circuitry in either of these. One is straight AC and one is and AC/DC machine. Easy to parallel when running AC.

Lincoln engine driven SA-200 and 300 DC machines even easier to parallel. None of that phase stuff to have to pay attention to.

I've paralleled a pair of gasoline driven 5000 watt AC generators before, too.

You got me to thinking about all that heat. Somewhere around here I still have a pair of thick gauntlet style asbestos gloves. Most people today wouldn't even recognize them for what they are. I doubt you could even buy a pair if your life depended on it.

WoD

[tautech]

I've paralleled a pair of gasoline driven 5000 watt AC generators before, too.

With no regard to phasing ? 

[SoundTech-LG]

Fine if you have 2 similarly capable welders however I never have.
For a while I had a 180A, 300A and a 250A DC TIG however they all had different control circuitry of which I would never dare to run them in parallel. 

Now with just the big 400A on castors and a 180A MIG, 140A caddy and gas set there's not much I can't handle. TIG I don't really need.
The big 400A was needed for the occasional heavy fab job however most of its work is just maintenance and repair.

No control circuitry in either of these. One is straight AC and one is and AC/DC machine. Easy to parallel when running AC.

Lincoln engine driven SA-200 and 300 DC machines even easier to parallel. None of that phase stuff to have to pay attention to.

I've paralleled a pair of gasoline driven 5000 watt AC generators before, too.

You got me to thinking about all that heat. Somewhere around here I still have a pair of thick gauntlet style asbestos gloves. Most people today wouldn't even recognize them for what they are. I doubt you could even buy a pair if your life depended on it.

WoD

https://www.ebay.com/itm/126008474979?hash=item1d56b0bd63:g:df0AAOSwAzNkn3it&amdata=enc%3AAQAIAAAAwNh26bYIlfCyMPcpMMkmEpvJXZLVaDauFN9up%2F1MntbTuEPzevnf3v7BV%2BfJ%2FidgNH8Zc04wvtOZDd%2Bi5ZMs61JJPNEeZ6TKFJB0GMWCsYyeB1mU8awthADWNqCNicAOIwuSNwC%2BslsJaSCGVbQ7jRk1tFXnJ5dNT16H5moTJVgevXvTIc4gyRz3En0P3EfJSyIsLxyxSTs97helb0JTt4rx9NAsQXVKUtiVfX%2BkRA50ZiIQpXp2DQJ6EjSphNqUxQ%3D%3D%7Ctkp%3ABk9SR7qYl-CnYg

[Wrenches of Death]

I've paralleled a pair of gasoline driven 5000 watt AC generators before, too.

With no regard to phasing ? 

No, you have to pay attention to phasing with AC.

WoD

[tautech]

I've paralleled a pair of gasoline driven 5000 watt AC generators before, too.

With no regard to phasing ? 

No, you have to pay attention to phasing with AC.

WoD

And rev matching too for them to properly share the load.

[Wrenches of Death]

And rev matching too for them to properly share the load.

Both need to be turning the same speed to match the frequency. Once they have synced, they will tend to stay that way. Same frequency, same speed, same rpm.

Rotor current/voltage could be tinkered with to tweak the actual output voltage, but not speed. I did that some years back on my PTO driven genset. I changed the value of a couple of capacitors  to lower the output voltage by five volts or so.

I just had a thought. Since 60Hz is the standard here, most generators run at either 1800 or 3600 rpm. You guys have a 50Hz standard. I'm guessing that gensets there run at 1500 or 3000 rpm. It'll take a more engine to product the same number of watts at a lower speed.

WoD

[adam4521]

If the impedance of the thing you are testing is low enough, you could use a current transformer (eg 1000/5A secondary), connected in reverse. Years ago, I saw a switchgear manufacturer do primary current injection tests on busbar this way, although I don’t remember the details.

[CosteC]

I use toroidal transformer with 2 turns of 250 mm2 secondary.
600 A for long time, up to 1600 A for short time.
Limit is in secondary thickness, but it is scalable. Output voltage is less than 5 V. Very simplistic yet not super stable as mains dependant.