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3 phase to single phase

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  • 3 phase to single phase

    I recently bought a older big Miller mig machine with millermatic wirefeeder that came out of a manufacturing plant. Its not been used a whole lot and runs great ...... on three phase power which is where my problem lies. The price I paid made it well worth the purchase, even if I were to just scrap the copper. But I only have single phase power and would much rather use it. I need to know the RIGHT procedure to convert it from 3 phase to single phase.I know this will probably loose some duty cycle but that is ok since I'll only use it for general fabrication. I know there are phase convergers but didn't know if that was the best way. Thanks for the help!

  • #2
    Rotary phase converter

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    • #3
      And what machine did you buy, no esp here. Basically no way to use a 3 phase only machine on single phase for starters. You need a digital phase converter. Rotarys are not the best idea on a welder

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      • #4
        The cheapesy way to make a phase converter is to buy a single phase motor and a 3 phase motor, use the single phase motor to turn the three phase motor and generate the third leg for you mach. Not cheap but any good elec,. not me, can show you or look on the net.

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        • #5
          Originally posted by weldbay View Post
          The cheapesy way to make a phase converter is to buy a single phase motor and a 3 phase motor, use the single phase motor to turn the three phase motor and generate the third leg for you mach. Not cheap but any good elec,. not me, can show you or look on the net.
          Lathes and other non circuit board machines don't mind the rotary converter, Welders do not work well on this system , thus its NOT recommended. The only way to do the conversion is with a Digital phase converter

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          • #6
            Originally posted by cruizer View Post
            Lathes and other non circuit board machines don't mind the rotary converter, Welders do not work well on this system , thus its NOT recommended. The only way to do the conversion is with a Digital phase converter
            Is it me or what. the mach is old so probably not an inverter but a transformer welder. I have used rotary inverters in my welding repair 1-phase shop for years,

            Here is how you do it:
            http://www.metalwebnews.com/howto/ph-conv/ph-conv.html

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            • #7
              model please

              What model is the welder? If the primary on the transformer is "8" wound you can convert it to single phase. I did this to a CP-200 using the info i found here http://www.practicalmachinist.com/vb...-phase-199832/ and it works well no loss of power and no external converter. Cost around $100 to convert.

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              • #8
                Yes, it would have to be an old welder with diodes NOT scrs and NOT using circuit boards. for instance the above, or a SRH stick welder.

                There are ways around things. However, from my point of view. I chuck the old machines like the CP200 and such as they have zero worth to me. I do keep the feeders though

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                • #9
                  Cruizer, you just got me thinking, in 1986 i bought a gold star srh 300 amp 3 phase machine, it sits in my storage trailer, what a great welder, i am 2500 feet from the 3 phase lines, is it cost effective to do what you just suggested, and if so, do you have a ball park cost for this adventure. Thanks kevin

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                  • #10
                    Nope that unit has a circuit board firing scrs, providing its a "Goldstar". The SRH and Goldstar do the same thing (DC stick), but are different animals.

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                    • #11
                      I am still trying to understand, I have used my 3 phase rotary system on every machine I have tested that was not a combo single or three phase power supply. I have run inverters and transformers and "Goldstars", Plasma mach and others. They all worked. Does it damage the mach over time or are you saying that my success was a fluke.

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                      • #12
                        Rotary Converters

                        Not to diss Cruiser as he is one of the best resources on this forum, but from what I have read the rotary phase converter is the way to go. You don't even have to keep the single phase motor powered once you get the three phase up to speed. The only thing is you need to have a big enough 3 phase motor to supply the current required for the welder. A better option than the single phase motor is to use a capacitive starting unit. There are many new units available from Ebay stores that have the necessary relays and starter capacitors to do a proper conversion available for nearly HP of motor. A digital converter as Cruiser calls it (solid state) uses only a capacitor array to generate the third phase and have to be closely matched to the load, which we all know varies with the load on the welder. check out this link. http://www.usphaseconverterstandards...converters.htm
                        I have read of many weld shops that have used rotary phase converters with 100% success.
                        Caddi

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                        • #13
                          LOL...As an unfortunate owner of two 45 HP three phase rotary converters because of the unavailability of a three phase power source at my original shop, you are just going to love your power bill. I bought another property in order to get an adequate three phase power source to build our current facilities and saved money doing so...

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                          • #14
                            The power source is a cp 200

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                            • #15
                              1 of the phases is significantly lower than the other 2, on a rotary, and yes your power bill will be astronomical as you have to size the motor 1/3 higher than what the machine draws. honestly to power a 3 phase welder, not worth the investment. Best buy a single phase unit ment for your exsisting power

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