3 phase welder

I picked up this Miller 3 phase 400 amp DC welder.

The fella I got it from told me that one of his employees said that it simply quit. Nuther fella he took it to for repair quoted him $950, had a bad circuit board. On the scrap pile it went.

I got it for a song and when he asked me what I was going to do with it, I told him that I was going to fix the circuit board.

I took it home and found that it had no cirruit board in it. It was built in 1958, long before circuit boards were even invented.

I have checked all the rectifiers in it - seleniums. They all have good front to back ratios. The control rectifier bridge also seems to be good. The choke has continuity, the power switch is good and the circuit breaker (heat ativated) is good also.

I can't believe that the transfromers are bad but since I don't have 3 phase here, I can't hook it up and run it. I do have a 5 HP rotary but am not willing to hook it up to the welder.

What would happen if I hook up a single winding to 220 just to test it at low current ?

Oh, and does anybody have any ideas on what might be wrong with this thing ?

JW

Reply to
John
Loading thread data ...

Reply to
Jerry Martes

While I'm not taking responsibility for what might happen, the thing only draws 400 amps DC when you have the knobs set to max and are using a great big rod. So, why not hook it to your phase converter, turn it on, and, if no smoke, see what happens, when you run it at the lowest amperage setting with a 1/8" rod. I guess you could put 3 15 amp fuses in series with the power leads between the phase converter and the welder. You didn't say if you had ohmed out the transformer wiindings. I have a 250 amp mig that had a tempermental current selection switch once. It only gave me trouble in one range; the range I wanted to use most. Maybe it's something that simple, and that "employee" just wanted it "outa there".

Remonds me of the time I took my 1992 Nissan Sentra in and they told me it needed a new timing belt, which they put in and charged me a hundred dollars or so for "while they were working in that area". When I questioned that entry, the service advisor at the dealership got all embarrassed. Seems that model doesn't have a timing belt, but a timing CHAIIN that "never goes bad" (and still hasn't at 292,000 miles).

Pete Stanaitis

--------------------------

John wrote:

Reply to
spaco

Could be high idle current (out of phase). I would, still, try, esp./ if the output of the phase converter is protected by a breaker.

Agreed.

I agree. It is worthwhile to mess wityh that stuff, if only for one's own education.

i
Reply to
Ignoramus10353

What does "out of phase" mean??

Reply to
Jerry Martes

Some welders draw substantial current while idle. That current is out of phase with voltage, which means that current peaks out when voltage is low, so the power consumption is low.

i
Reply to
Ignoramus10353

Reply to
Jerry Foster

John,

I'm running a 400 amp 3 phase DC welder on single phase. Got it for nothing and the only thing wrong was the fuse to the contactor coil. It welds pretty much like my AC buzz box. The arc frequently stops, doesn't like 7018, runs something like 2/3 the amperage setting on the dial. My father in law runs his identical machine off a 10HP rotary phase converter and it welds so much nicer. You can easily stretch the arc over an inch long on his. I'm keeping my eye out for a 10 HP motor to make another phase converter with.

Wayne Sippola Moose Jaw, SK

Reply to
Wayne S

Call your local scrap dealers (check yellow pages), they will be hapy to sell you all sorts of 3 phase motors.

i
Reply to
Ignoramus10353

Corect me if I am wrong but the welder probably does not draw 400 amps on the input side. Depending on the AC voltage required it is probably less than 30 amps per phase. The 400 amps is the maximun current on the output.

Bob AZ

Reply to
Bob AZ

It's also worth checking with an isolation-tester. The ohm-meter doesn't show all. They often use only 1.5V for measuring, the isolation-tester uses

500V. If there is no isolation-tester at hand, ask an electrician or someone repairing electrical motors.

Nick

Reply to
Nick Mueller

snip -

Anybody have details (schematic - capacitor values? - relative power requirements & output?) on running a 3 phase welder from a single phase supply?

I may have an opportunity to buy a 3 phase welder cheaply, but don't expect to have a phase converter for quite a while yet, and would like to have an idea of how useful I can make it in the meantime.

TIA

Mickey

Reply to
Mickey Feldman

You can build a phase converter in one weekend.

i
Reply to
Ignoramus799

OK, here's an update.

I haven't checked coil resistances, nor have I done an isolation test. I don't have a hi-pot tester. However, Nick mentioned 500 volts for hi-pot leakage. I do have a power supply and I can put a high value resistor in series with a milli(micro)ammeter to check for intra-winding and to-ground leakage.

I hadn't thought of any of this and don't have time to do it right now but will when I have a chance. I'll post my results.

JW

Reply to
John

This may be true is you have all the parts (old, large enough, cheaply obtained 3-phase motor) on hand.

If you live in an industrialized, urban area, acquiring parts may be trivial.

If you live on a somewhat remote island, have to take a minimum of two ferries for a couple of hours and drive for several more to get to a seriously industrial area, and of course do this only occasionally, it's another story.

Mickey on Texada

Reply to
Mickey Feldman

Mickey

You're citing the worst case situation for acquiring hardware. I'm not sure if you are describing your situation but if you are, I'm sure there is some very good reason for living there. I wish you well.

Now back to my situation - the thread of this 3 phase welder

While I haven't hooked that 400 amp 3 phase welder up to any electricity YET, I have measured from windings to ground. All measured infinity. I then performed a hi-pot test on all the windings AND the seleniums to ground. I only used 350 volts DC but got absolutely no indicated leakage on my 10 microamp meter.

My next step will be to hook up my 5 HP RPC and try to light the thing up. But that won't be until this weekend. I'll post....

I really have to wonder if the fella who told the boss that it didn't work any more is still with the company.

JW

Reply to
John

Well, here's the final chapter for the 400 Amp Miller welder. I took another close look and it's actually a 600 amp welder.

After cleaning it and doing a reverse ratio check on the seleniums,

And then doing a hi-pot breakdown test on all the windings and the seleniums

I hooked it up to my 220 volt rotary. Then I got to thinking that maybe I ought to check the connections to see if it was 220 or 440. (I had bought a (MONDO) table grinder last summer that was also 3 phase (which is why I got it for a song) and when I hooked it up, it only hummed. I checked and the motor was wired 440. The welder turned out to be wired 220.

So I dug out my welding cables. The welder has bolt-on cable connections and my cables are plug-in. darn

I mean DAMN.

So I jury rigged the connections with VICE GRIPS ! the best invention EVER

I then dug out some rod. First I tired with 1/8 6012 rod with the welder set to 50 amps so as not to strain the RPC. Got some spark and LOTS of arc-blow. So I turned the heat up to about 100 and was able to get some semblence of a bead but the rod wanted to stick more than it wanted to burn. So I turned it up to 120 amps and it smoothed out.

Then I went to 3/16 6012. Had to crank it up to 160 amps to get anything that looked like a weld. By this time I was starting to regain my hand in stick welding, since I hadn't touched a stick for 20 years. MIG tends to spoil you.

So anyway, I now have this working 600 amp Miller that was built in '58 (copper) and I can take it back to the fella I bought it from. Paid him ten bucks and after I told him what I was gonna do, he said that he would buy it back for a hundo if I could get it running. He's got this engine driven Hobart that I want and he said that we could trade for this Miller.

Sure is nice to run into people who are willing to trade when they don't know how to fix electrical things and you do.

JW

Reply to
John

What a great story. Now, what was wrong with it? It sounds as though it was in a good shape. Perhaps I missed something.

i
Reply to
Ignoramus18738

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.