Using an old three phase DC welder from single phase?

Let's say I have a big old three phase DC welder that was supposed to have three phase input (and has a three phase transformer and three
phase rectifier).
If I use it from just one phase (hook up two terminals to one line input and the third to another line input), would it be able to make satisfactory welds? I understand the electrics of this a little bit, and instead of relatively smooth rectified three phase AC with only 5% 360 Hz ripple, it would be much less smooth rectified single phase AC.
My question is, how good would that be for actual welding, like with 7018 or some such rod.
i
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i got no help, but i have about the same question. We picked up an old monster miller wire feed with a jib crane and spool gun. I haven't wanted to hook it to three phase cause i don't like to weld in the nice shop area. But at least i didn't have to pay as much for mine as you did. <VBG>
Karl
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wrote:

You might have to make some control circuit changes and replace the fan motor if it is 3 phase. Otherwise it should work just the same as any single phase welder.
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It's totally useless, I'll double your money and give you $1.98 for it if you deliver!
:-)
RogerN
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How about, I give it to you for free (with the high frequency attachment and cables) in exchange for a on-site CNC consultation. Let me know soon because if I do not hear from you, I want to get rid of it quickly. I am in Lisle, IL.
i
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wrote:

I've got plenty of welders but haven't welded anything in years. But I'd be glad to help you get your CNC running but through email or newsgroup posts. Do you have anything to go off of as far as manuals, wiring diagrams, a napkin with some marks on it? Have you connected power? Does it do anything? Or how about a picture of the wires coming out of the motor and the wires going to the amplifiers?
For my Lathe conversion, the motors and amplifiers worked, and the encoders worked, so I had to connect 5 wires from each encoder to my breakout board (Common, +5V, A, B, Z). That plus some configuration gets you numbers on the screen, turn the motors by hand and the numbers change. Change the counts per unit in the configuration file until you read inches or MM, whatever you set it for. If the encoder counts backward, number decreases in the direction it should increase, swap A and B or change it in your configuration.
Ok, after I got my encoders working on the screen and found out they had 12,700 counts per inch, it was just a matter of connecting my control signal (2 wires) to my servo amplifiers, the amplifier to motor connection was already there. I set up a switch to turn the power to the amplifiers on and off. I put in some values for proportional gain, turned on the amplifiers and the thing started to work. I adjusted PID gains and feedforward values to get it working better, the EMC pages have info on adjusting the gains, there is even a scope that you use on the screen that plots what you want to look at, in my case it was positioning and following error.
With your math background I don't think you would have much difficulty, you just need to understand the signals and you can figure out what's missing from there.
RogerN
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Roger, Thanks. I cleaned out my garage and it is ready for the machine.
Regarding the welder on single phase question: I just spoke to some great guy from Craigslist. He want to buy it and he told me that to run it on single phase, you just need to wire some capacitors to the third leg. This is kind of an interesting thought.
i

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Ignoramus3512 wrote:

It depends a bit on the welder. First, it has to be a DC only welder to use 3-phase, unless an inverter-type machine. All the old AC/DC welders were single phase.
Assuming an all-electric welder, no SCRs and phase control stuff, it probably would work OK. They usually have such a huge inductor in there for arc stability that the rectifier ripple won't be very big. I'm a little unclear how these things did current control, though. The old buzz-boxes used a variable core plug in a transformer with a lot of intentional leakage inductance. If the thing has electronic current control using phase control of SCRs, it is VERY unlikely it will work.
Obviously, you will lose a lot of the current rating on single phase power. I have heard of people running them very well on a rotary phase converter, though. If that doesn't appeal to you, I'd strongly urge you to find an AC/DC machine that is known to run on single phase. I have a Lincoln square-wave TIG 300, and it is a fantastic machine. I'll never do stick again, due to the fumes. I LOVE TIG!
Jon
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It is a big OLD (key word old) transformer welder. I doubt it has any electronics.

I agree.
i
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Well, given that it cost 99 cents, it will be a great experiment. I will try when I have time.
i
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Iggy I have used those machines for years. They have several names in the Miller system, 330 AB/P, or Miller Goldstar, also sold through Airco is orange paint.
Maybe I shouldn't burst your bubble here, but I really hate those machines. You have make sure to clean out the spark gap and reset the points in the high frequency generator. The high frequency capacitors tend to die so be prepared to replace those.
In these old TIG machines, Miller's capacitors seem to have a shorter life span than Lincoln's.
The 5 we had at South Seattle CC eventually started blowing their foot pedal fuses all the time. The fuse is an old fashioned screw in type on the side of the front panel. Those fuses are getting harder to find. We eventually found some screw-in type circuit breakers.
These things are just very old, and even in not heavily use, they have very old insulation on all the transformer coils. It is not uncommon for the main coil or reactance coil to blow.
Also check inside the machine to see if it has selenium rectifiers. They look like a stack of big square cards on a long rod. If a selenium rectifier blows it will produce a cloud of hydrogen Selenide gas, which is incredibly bad smelling as well as highly toxic.
At the very worst you got about $600 in copper scrap for $1.
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