Running a 3 phase welder on single phase?

I have a Hobart CyberTig 200 DC-S welder. It is 3 phase, however, the fan motor in it is single phase. (110V). I verified that the welder
powers up on 3 phase 240V. (after I rewired it).
My question is, is it safe to run it on single phase 240V (provided that I select the right wires to power signal transformer and fan). If so, what would be a safe reduced output amperage for welding. For 3 phase, it is rated 200 A continuous, I believe.
It would be great if that was possible, at least for small projects. I could use some 8/3 cable that I have, not worry about the phase converter etc.
i
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Forgot to say, its transformer diagram seems to be triangular, IIRC. It is a "three transformers and a rectifier" kind of welder. I will double check this, I have all schematics.
i
On Thu, 22 Sep 2005 16:57:48 GMT, Ignoramus26924

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get a surplus 3 phase motor. You can run these off single phase AC, and get 3 phase off the other terminals. You can find these motors for cheap or free
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Thanks. I already have a phase converter with a surplus motor, it runs fine etc. Still, it would be nice to run the cybertig without a phase converter.
i
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On Thu, 22 Sep 2005 17:16:41 GMT, Ignoramus26924

No can do with this welder, Ive been told by a welding machine repair tech.
Gunner
"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner
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Thanks Gunner...
i
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On Fri, 23 Sep 2005 10:16:50 GMT, Ignoramus19652

http://www.arcowelder.com /
Give Dennis a call. He is one of the sharpest welding machine guys Ive ever met, and has docs for just about anything you will ever stumble across.
Be sure to tell him Gunner refered you. That way he will know how much to jack up the price <G>
Gunner
"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner
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On Thu, 22 Sep 2005 17:04:48 GMT, Ignoramus26924

Actually there's more to it than that. I bet if you open it you'll find that the three transformers are all in one core. Then there's the reactor which is used to control current. The reactor itself is controlled with SCR's. After all of that then there's the diodes.
Wayne Cook Shamrock, TX http://members.dslextreme.com/users/waynecook/index.htm
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I doubt that they have the same core, otherwise they would be basically all on one phase, transforming one another.
I think that your words in another post make sense, it would be counterintuitive to expect to be able to easily rewire this machine for single phase without substantial loss in either output or weld quality, if it is possible at all.
My 10 HP phase converter, possibly with addition of another 7.5 HP idler (I have both already), should easily take care of making 200A welding current.
By the way, I called the seller of welding cables and changed my order to 1 gauge cable.
Thanks for all your suggestions.
i
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    You haven't seen many three-phase transformers, then. Picture the usual 'E' laminations, except a bit more widely spaced. One winding goes around the normal center pole, and the other two go around the top and bottom bars of the 'E'. The phasing is such that the fields merge cleanly.
    Take a look at what is physically inside your machine, and then come back and say that it can't be done. :-)
    Enjoy,         DoN.
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Sounds like it might be wired in a Delta. Likely - as a missing phase won't knock you out - you have a 2/3 power ability.
Now - think of your 3 phase gen - you put in 220 - a phase at zero (0) another phase at 180 . You generate the missing phase at 90. So 0,90,180 are the 'zero' marks for the positive alternations.
If you put all three phases to the transformer - 3 phase. If you knock out the wild one - 90 - the ends are there - if you really have a delta wired transformer(s) then an Open V , inverted D (several tag names ) condition occurs. 2/3 power is the max.
Security places from Police to ... all of them use Delta x Delta transformers. If an input line/winding is 'lost' then the system survives. What they do is beef up the VA rating so in this lost mode they run 100% other modes they have more than planned for.
Martin Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH, NRA Life NRA Second Amendment Task Force Charter Founder
Ignoramus26924 wrote:

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On Thu, 22 Sep 2005 21:10:13 -0500, Martin H. Eastburn

That's where you confuse me. Is it 2/3 ability or 1/3 ability? If only one side of the three sided "delta" is in operation, that should logically put out only 1/3 of power.

The angles are actually 0, 120, and 240. (or, for all zero crossings, 0 60 120 180 240 300 360=0)

Maybe... What I am thinking about is this. This is a delta wound transformer. Think about a triangle with points A, B, C.
C / \ A---B
Let's say that A and B represent utility power legs, and C is the wild leg. There is nominal 240V between A-B, A-C, and B-C. Each line in this diagram represents one transformer core, one 240V primary and one low voltage secondary. Volts from secondaries are rectified and "united" together, care being taken with diodes to avoid shorts.
What I would like, if possible, is to change this to:
B B / \ A A
A------B
that is, there will not be any longer contact between sides of cores, instead each core/transformer would step down the same phase. Then, the same rectifiers will convert it to DC.
The power that is output by this setup should logically be not too far from the power from 3 phase .
What may suffer is the quality of the DC waveform. Instead of being like this:
_______~~~~~~~___________
(underscores represent the zero level)
it will be more like this:
_____/\/\/\/\________
In both cases the graph of voltage is all above zero, but the top one is more stable.
This waveworm issue may possibly interfere with arc stability.
Also, the control system may expect certain phase differences between legs to run properly.
That's my ignorant take on this issue.

That's very interesting to know. Thank you for your comment Martin.
i
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Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH, NRA Life NRA Second Amendment Task Force Charter Founder
Ignoramus26924 wrote:

Read again. You have a 2/3's power ability when one is not functional.

I'm going to have to look at my books now - not my mind - If those are the angles - looks like 30 HZ to me. How do you shift one phase in by 60 or out by a bunch and then generate a third ? Only the wild is generated the other two generate fields and run.
>> I looked it up and it is 120 degrees between phases. Nice power supply concepts in section 12-3 - see version below on zig-zag.

This might only work in a single core since the two generate the third.

If there was 3 phase already (like the power company) then stepping down a voltage and keeping the same phase is ok. But this (the ABC windings) have to be in one core and connected. You have them that way but the connection is in the panel or somewhere else. B = B somewhere.

Like I have said before - if you already have 3 phase it is a step down/step up. Power company does it all of the time. It is far easier to mount three transformers on a pole than one Honker up there. Many sites - Dr. Offices as an example - don't have a pad to mount a transformer the size of a desk.
It is better to do WYE for rectifiers for AC anyway.
An example Zig-zag from another discussion is in paragraph 82 section 13-83 Standard handbook for Electrical Engineers - Tenth Edition.

You should use 6 phase if you want smooth ripple.

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| I have a Hobart CyberTig 200 DC-S welder. It is 3 phase, however, the | fan motor in it is single phase. (110V). I verified that the welder | powers up on 3 phase 240V. (after I rewired it). | | My question is, is it safe to run it on single phase 240V (provided | that I select the right wires to power signal transformer and fan). If | so, what would be a safe reduced output amperage for welding. For 3 | phase, it is rated 200 A continuous, I believe.
Since you have the schematics, does it explain how to hook it up to 240 two phase? I think that if you don't hit the full current capacity of the welder, you ought to be okay. Make sure you have the wall current required to drive it on two phase, though. The manual ought to discuss the derating. If it doesn't show that its possible (I think unlikely) then your RPC ought to drive it with the derating considered.
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You mean single phase, right?
I will check if it says anything to that effect.
I do recall the delta shaped schematic of the transformer/rectifier setup. A delta shaped triangular transformer and rectifiers.
I am kind of hoping that I could, possibly, rewire just the power terminal board in such a way that all three sides of that triangle rectify the same single phase.
That way, I would end up having a single phase welder. The only downside that I could see is that the shape of the resulting waveform could, possibly, be less flat due to lack of smoothing from rectifying 3 phase AC.

I will check the manual. In fact, I want to read most of it.

My RPC does drive it, at least to the point of simply powering it up with no load. I am not sure why the welder would need derating, provided that the RPC is up to needed capacity.
i
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On Thu, 22 Sep 2005 19:19:32 GMT, Ignoramus26924

That's the schematic. You need to look closer inside. I'm betting that delta schematic is all in one transformer. If you go to hooking all of them up to the same single phase I'm afraid they might fight each other in the transformer.

I have my doubts. If it could be done we'd of heard about it by now. There's been more than one electrical brain work with these machines.

That and burning out the transformer.

Unless the input tag on the back of the machine lists single phase as a possible input then it won't be in the manual.

Correct. This is a smaller welder so you should have no problems with the two phase converters you've got running it.
Wayne Cook Shamrock, TX http://members.dslextreme.com/users/waynecook/index.htm
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carl mciver wrote:

I think that is covered in the on/off section. :)
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Carl,
Where have you been all the years and through all the posts on RCM disclaiming 240V 2-PHASE current? There is no such thing available in the ordinary US residence. 240v SINGLE PHASE current is what just about all residences have in the US. It comes in on 3 wires, one of them being the center tap of the transformer. It is center tapped to provide 240 volts across the entire winding and 2 sides of 120V each.
Try not to confuse Iggy by giving him erronious information - he has enough trouble with the real facts.
Bob Swinney

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Yeah, yeah, I know. My bad. I boo-booed. Will you whip me, spank me, and make me write bad checks? Threaten me with a good time? Pretty please?
I still have this thing in my head after all these years of seeing the two legs 180 out of phase, with the neutral in the middle, so it still comes out as two phases in my head, even though I know better.
Better to call me on it than for me to confuse anyone even more, although I give Iggy credit, he asks a lot of questions before he blows something up, rather than afterwards. He's obviously well spoken and intelligent; obviously not a product of American public schools, and for that I enjoy his posts. He rarely asks a question or gives a response that he hasn't given some thought to, unlike me!
| Carl, | | Where have you been all the years and through all the posts on RCM | disclaiming 240V 2-PHASE current? There is no such thing available in the | ordinary US residence. 240v SINGLE PHASE current is what just about all | residences have in the US. It comes in on 3 wires, one of them being the | center tap of the transformer. It is center tapped to provide 240 volts | across the entire winding and 2 sides of 120V each. | | Try not to confuse Iggy by giving him erronious information - he has enough | trouble with the real facts. | | Bob Swinney
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Bob - there is 180 degrees phase between the two lines. It isn't DC And the phase can be -90 and +90. Depends on the reference .
Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH, NRA Life NRA Second Amendment Task Force Charter Founder
Robert Swinney wrote:

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