Thread: 2 phase welder

Been offered a 2 phase welder which I would need to run off a gen set. Its needs more grunt than I could get from a VFD on my residential single phase setup.

wiring the welder itself shouldnt be an issue, recon one active to a respective phase and of course neutral to neutral.

Leaving one phase without a load. My theory here is to run a resistive load between remaining active and neutral (heater perhaps?) to help balance the phases.

The one thing I'm wondering about is whether I would need to rig up some setup where I switch in more loads on the spare phase to compensate as I crank up the dial? As in amps.

Thoughts?

Sorry I've never run a welder from a genny myself, but I am intrigued by this 2 phase welder. I've never seen or heard of one - what make/model is it?

Are you sure its phase to neutral?
I THINK you'll find its phase to phase i.e. a 415V primary winding.

As for needing to balance the load on between phases....... I don't know. But if you do it would seem to be tricky.

Hopefully someone that knows what they are talking about will be along soon.

Stuart

Originally Posted by Vernonv

I am intrigued by this 2 phase welder. I've never seen or heard of one - what make/model is it?

You do hear of them, but they don't actually exist.
To clarify, it is a common misconception that using two wires from a three phase supply is "two phase", when in actual fact it is single phase 415 volt. Some common "two phase" welders would be the old EMF Pie Heaters, Lincoln Tombstone welders, 415 volt Tig welders such as the CIG Transtig 250 and 275, Hobart Tigwave 250 and multi voltage stick welders.
The easiest way is to think or the 3 wires as a triangle, 2 wires equal one side (phase), but add in the third wire and automatically you create another two sides.

Yes, hence my question.
I have (and use often) an old TransTig 250 which uses "single phase" (415V). The other possibility I thought of is that it could be an old 480V machine.

Anyway, I'd love more info.

When I get this unit into shop will post up some fotos. Certainaly got me thinking some more about wiring up, which is good. Hopefully it will be simpler than I am thinking.

Its an RF welder. Used for PVC fabrics.

Wouldnt be too surprised if its 480V. Current owner by own omission is a bit vague on wiring details, apart from the fact that it was initially a valve unit.

From what the current owner says it weighs quite a bit, so my first challenge will be moving it.

Offered me a demo before removal, so good to see it in action before taking it. Some measurements with the meter will also be in order.

UM YEH there is no such thing as a two phase welder.
What you will have is a singe phase 415volt machine, that runs between two phases.

There are some very rare cases of double singe phase machines, where there are two singe phase sections inside the machine....or machines that use two phases an neutral to select voltages......neutral to phase gives 240v and phase to phase gives 415v...vith corresponding output.

if you want to run off a genny you need to know what is going on inside.

there are some machines that can be run off a 240v or a 415 volt supply.....selected by terminals on the transformer.

cheers

Many older welding machines had a series of bridges under the back cover, (e.g. EMF Transarc 200) this allowed them to be set up for 240 V, 415 V or 480V - very common on many farms years ago, still only single phase though - now sure we you would get on with a generator though??

Had a squiz at the plug wiring.

Put up a foto of the unit as well. Probably not what most folk have come across.

Originally Posted by piney

Many older welding machines had a series of bridges under the back cover, (e.g. EMF Transarc 200) this allowed them to be set up for 240 V, 415 V or 480V - very common on many farms years ago, still only single phase though - now sure we you would get on with a generator though??

I have a Transarc 200, and would like to try it on 415. So if input voltage goes up, output voltage also rises, right? What effect would I be likely to notice from that? I recall Dad saying he liked it better on 415 but not why exactly. Is there a downside?

Originally Posted by Bryan

I have a Transarc 200, and would like to try it on 415. So if input voltage goes up, output voltage also rises, right? What effect would I be likely to notice from that? I recall Dad saying he liked it better on 415 but not why exactly. Is there a downside?

No there will be little change in the output voltage, as you need to connect the input voltage to different taps on the transformer.
I'm not sure you will see significant "improvement" running at 415. The big difference will be in the mains current draw i.e. the higher the input voltage, the lower the current draw for the same welding current.

Originally Posted by Vernonv

No there will be little change in the output voltage, as you need to connect the input voltage to different taps on the transformer.
I'm not sure you will see significant "improvement" running at 415. The big difference will be in the mains current draw i.e. the higher the input voltage, the lower the current draw for the same welding current.

Dead right. I have been down this road with a Peerless welder and while it did perform slightly better on 415 than 240 the difference was minimal and in all probability attributable to the lesser current draw at 415V leading to less fluctuation of output when in a short circuit condition such as when striking an arc.
If the OP runs 415V on the 240V tap, that could give an OCV of 160 odd volts, which will be deadly.

Thank you Vernon and Karl. Of course I would follow the instructions on the plate carefully.

Originally Posted by jatt

Had a squiz at the plug wiring.

Put up a foto of the unit as well. Probably not what most folk have come across.

Looking at your wiring diagram, it appears to be exactly as Soundman said, a 415V single phase unit.

Connecting between either L1 or L3 and N from the supply would provide 240V nominal, connecting between L1 and L3 from the supply will provide 415V. Our normal supply system is 240V between any line and neutral, and 415V between any pair of lines.