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27th February 2015, 10:35 AM #1
Converting a 3 phase welder to single phase ....
This is a topic I have been researching for a little while and thought it might be of interest to others.
There is a method out there, dubbed the "Haas-Kamp" conversion method, that allows a 3 phase welder to be used on a single phase supply, to almost it's full potential. It involves rewiring the transformer primary and adding a couple of capacitors to try and emulate the phase shift seen with 3 phase.
So recently I got hold of an old 3 phase Uni-Mig 350 (an Australia made welder, fancy that ) and have done a "proof of concept" conversion. Low and behold it works.
The basis of the conversion is as follows:
- Convert the 415V star configured primary to 240V delta. NOTE: For this conversion to work in Australia, you will need to have a welder that is configured 415V star. If is is configured as 415V delta you are out of luck
- Wire the first transformer primary straight, the third in reverse (180º out of phase) and connect the middle one to the other two via two capacitors (which will give you something approaching 90º phase shift).
- Ensure any accessories (fans, contactors, etc) are running off 240V. This was the case with the Uni-Mig, so nothing to do here.
- As the secondary OCV was a little depressed, I also changed the transformer secondard from a delta configuration to star configuration.
Here are the before and after circuit diagrams (note that the after diagram does not show the change to the secondary).Cheers.
Vernon.
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27th February 2015, 11:02 AM #2
Hey Vern
you are getting into the realm of grass skirt and bone through the nose while dancing in a trance around a sacred fire.
Was the conversion difficult to do?Just do it!
Kind regards Rod
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27th February 2015, 11:26 AM #3
Hey Rod. Nah is was pretty easy.
The hardest thing was figuring out the switching configuration for the welding voltage switch. It switches between taps on the primary side of the transformers to change the output voltage. The circuit diagram did not show any of that information.Cheers.
Vernon.
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27th February 2015, 11:32 AM #4
Your tenacity comes to the again. You won't let anything beat you!!!
You will be pleased to know the drum sander is making forward progress, albeit spasmodic.
Have you got in mind a project for this welder???Just do it!
Kind regards Rod
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27th February 2015, 11:49 AM #5
Yes, good to hear. Let me know if you need a hand with anything.
I actually needed it last week to weld up a cattle grid, however I ended up connecting my old transformer TIG power supply through my small Kemppi MIG (being used as just a wire feeder), but that is a whole different story.
I have been looking for a beefy MIG for a while but couldn't find a single phase one in my price bracket. So no immediate need, but it will get used. Still need to tidy it up a little.Cheers.
Vernon.
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27th February 2015, 08:18 PM #6SENIOR MEMBER
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Interesting conversion - do you still get 28V on the output of the aux transformer?
On a slightly related note, I've always wanted to see how the secondary was wound/wired on a 3 phase AC welder.
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27th February 2015, 08:21 PM #7DISCLAIMER
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27th February 2015, 11:22 PM #8Tool addict
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Interesting!
How's the duty cycle? And does the 240v lead get warm at all?
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28th February 2015, 07:18 AM #9
If you look at the circuit diagrams you will see that the aux transformer has both a 415 and 240 (marked 380 and 220) tap on the primary ... I simply moved one of the wires from the 415 tap to the 240 tap and hey presto we still get 28V on the secondary.
I'll grab some pics today, if I can.Cheers.
Vernon.
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28th February 2015, 07:26 AM #10
The duty cycle shouldn't really change, as I'm still using all transformers in a "3 phase like" configuration.
That would depend on what current you are welding at. In the little bit of welding I have done so far I have not noticed any heating, but I haven't really done much, only testing at this stage. Running off a single phase will mean that more than likely I will be limited by the circuit feeding welder (in my case a standard 15A circuit). Having said that I could always use a 20A or 32A single phase connection, or a hard wired dedicated circuit, but I doubt I will ever want to use this welder at it's full capacity (it is rated at up to 400A ).Cheers.
Vernon.
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28th February 2015, 09:34 AM #11SENIOR MEMBER
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Yup, I was thinking that tap was just an autotransformer output to get a 240 supply, but I guess it would work just as well in reverse.
I'll grab some pics today, if I can.
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28th February 2015, 09:43 AM #12
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1st March 2015, 05:09 PM #13
Here are some photo's of the welder after conversion. You can see the primary side of the transformer (the photo with all the wiring in it) as well as the secondary side (not as much wiring). Still waiting on the right size caps to come in before I can finish it off - I will mount them on the inside back wall of the case.
Cheers.
Vernon.
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17th March 2015, 08:43 AM #14
The new capacitors arrived yesterday, so fitted them last night.
Have done a little welding with it over the past few weeks and I must say that it operates perfectly on single phase. So far I've welded 1.5, 3 and 5mm mild steel and have been very, very happy with the results.
Cheers.
Vernon.
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Bite off more than you can chew and then chew like crazy.
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