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Is there any reason a 3 phase welder wouldn't run fine on RPC power?

400 amp or smaller machine and I have a 50HP RPC.

Should do.

Pure guess, but the main reason Haas-Kamp conversions have caught-on so well might be that very, very few folks with welders had anything close to a 50 HP RPC as the other choice. You do have.

Might welding's electrical noise affect other consumers, same RPC?

You can count on it being "there". No idea how YOUR gear will handle it.
 
when does a 3 phase welder only use 2 of the windings?

anyway, an 50HP rotary should be rated @ around 65A for welding. something like
a miller CP-302 is rated @ 34A/ph/220v @ 300A output. at 350 amps it would be a bit higher- but it should work in theory....
 
when does a 3 phase welder only use 2 of the windings?

anyway, an 50HP rotary should be rated @ around 65A for welding. something like
a miller CP-302 is rated @ 34A/ph/220v @ 300A output. at 350 amps it would be a bit higher- but it should work in theory....

Before solid state power supplies, 3 phase AC/DC TIG machines only used two of the 3 phases. Some dual voltage AC stick welders only used 2 of the 3 phases. There are probably more example as well. It cost nothing to check first. My warning is based on first hand experience. I've seen this issue 3 times.
 
Before solid state power supplies, 3 phase AC/DC TIG machines only used two of the 3 phases. Some dual voltage AC stick welders only used 2 of the 3 phases. There are probably more example as well. It cost nothing to check first. My warning is based on first hand experience. I've seen this issue 3 times.

Could it be those are single phase ?
Please post a model number or better yet, a schematic.
 
Before solid state power supplies, 3 phase AC/DC TIG machines only used two of the 3 phases. Some dual voltage AC stick welders only used 2 of the 3 phases. There are probably more example as well. It cost nothing to check first. My warning is based on first hand experience. I've seen this issue 3 times.

You can use all three phases using two primary windings. I forget the specifics but I think they are less efficient (more resistive losses) for the same amount of copper but are easier and cheaper to make, which is pretty much the goal for a welder. The balancing may not be perfect but it should be decent.

If it is in fact only pulling two phases, then you will have two low current legs and one leg pulling much higher current. Put the lowest current leg on the generated leg of the RPC. Then wire the remaining two to the pass through legs.
Now you have to determine whether you wired it so that the leading or lagging phase of the RPC is used. One will benefit from your balancing capacitors, and the other will be fighting your capacitors. The easist way to do this is just to swap the two pass through legs where they connect at the welder and see which gives you better balancing.

So long as you keep the lightest load on the generated leg, the RPC should be plenty happy with an unbalanced load. In a delta idler that means only two windings will be passing the load current, so be aware that it drops the FLA of the motor in this case. I don't think you need to derate a star wound idler.

At any rate your RPC is large enough to run the welder fine in any configuration.
 
Before solid state power supplies, 3 phase AC/DC TIG machines only used two of the 3 phases. Some dual voltage AC stick welders only used 2 of the 3 phases. There are probably more example as well. It cost nothing to check first. My warning is based on first hand experience. I've seen this issue 3 times.

that's good to know. my louvered lincoln tig is single phase.

my miller CP is absolutely 3 phase. almost picky that it is balanced, or it
won't run at all.
 
Could it be those are single phase ?
Please post a model number or better yet, a schematic.

Doug, I can't. I sold those problem welders years ago. I now only own solid state power supply welders. One was German and the other two were both Italian. In my experience, this issue does not appear with solid state machines.
 
that's good to know. my louvered lincoln tig is single phase.

my miller CP is absolutely 3 phase. almost picky that it is balanced, or it
won't run at all.

My CPs all run wonderfully on single... and they're not picky at all. CPs, however, do occasionally suffer from cracks around the solder lugs on the back side of the terminal strip. If you're running yours from an RPC and they seem finicky, check the lug rings where windings come off the coil, and land on back of the red terminal strip. When the copper cracks, the wires will heat a bit, and somewhat 'weld' themselves back together for a while, then shrink and break apart.

3-phase welders WILL run on RPCs, but they'll run best if they're on really oversized RPCs. Welding isn't necessarily a 'smooth' electrical operation, and in C_C welding, the stability of the welding machine's output determines performance. A supply that's stretched to it's limits does not a good welding result make.

But if you're talking 400A or less, I think your RPC will be strong enough.
 
I'm in the process of the conversion on my Miller CP-200...Ser.# HD711560 Year = 1973 the face plate is pretty beat up but the Voltage Spec. looks like 230/460 Freq.= 60Hz 3 Phase .
I'm new to this type of work ,and a few of the steps in your conversion are unclear to me .
First...Step 1 &2 everything looks the same as yours but my jumper wire runs directly down the middle of the terminal strip from 1-5 & 5-9 Second...Step #5 My Wire # 8 is located on the Left side of the #12 terminal Strip,The Wire on the right side of Terinal 12 Goes Directly to a Coil ,also Step #6 My Wire # 9 at terminal #8 is also located on the Left side of the terminal strip..I followed wire # 8 on the Left side of the terminal and it leads to the Control switch ,so I'm pretty sure I have the Right Wire there..Everthing else is the Same as shown in the Conversion...My Main Concern is do any wire Leading Directly From the rear of the terminal Strip to the Coils get Cut Coils Get Cut ? I'm Sorry for this Long Message But I'm Really Gun Shy .
Any Help would be Greatly Appreciated . Best regards ,Carl Campbell
 
OK I didn't realize that every wire has a number stamped on it until this morning when I blew out the 40 years of dirt that had accumulated inside the machine . I have know completed the wire removal portion of the conversion and moving on to adding the new wiring. I guess I had a case of Brain Lock... CCampbell
 
OK I didn't realize that every wire has a number stamped on it until this morning when I blew out the 40 years of dirt that had accumulated inside the machine . I have know completed the wire removal portion of the conversion and moving on to adding the new wiring. I guess I had a case of Brain Lock... CCampbell

Hi Carl-

Yes that happens. Sorry, I didn't see your note, as it's not in any of the CP conversion threads. If you've read the Step-By-Step's introductory section, it identifies both HOW and WHY the conversion works, and also shows the 'generic' concept of wiring. When one does this conversion, it's very important that you have the proper wiring diagram for YOUR SPECIFIC machine... by looking up the proper manual for your serial number range, and compare that diagram to the diagram inside the right side cover... if you see ANYTHING that doesn't match, go looking for some other diagram... there were variations.

Follow the concept, and if you see anything that doesn't make sense, PM your email or phone number to me, and I'll help you sort it out.
 
In response to the OP's original question:

Yes, you can run a 3ph welder off an RPC. Gotta be big enough to handle the load, and if you load the welder heavily, you'll certainly put a hurt on the 'generated' leg (voltage will sag). having an RPC capable of substantially more than the welder's rated pull is a good thing.

Conversion to single-phase is always an alternative, and it's a very worthwhile one for many brands and models- The CP-series Millers certainly do well on single phase.

As for TIG supplies... if the're older, and designed for aluminum, they'll most certainly be single-phase transformers... because that's how they got AC TIG capability.

There are many 3-phase welders that are actually only two transformers connected in open-delta configuration... there's no 3rd transformer winding. On these machines, you can usually wire up the two legs in parallel and the machine will know no different.
 








 
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