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Thread: can a 3ph motor be used as a stepdown transformer

  1. #1
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    can a 3ph motor be used as a stepdown transformer

    Recently i acquired a mig welder but it is italian and oddball 3ph. it has voltage taps 220 up through 415v . i have 460 in the shop . --- i was wondering about using a 460 wye motor and while running it from 460 have 3 tap wires leading from it at -T7 , T8 , and T9 to run the welder as there should be roughly 230v at those taps . in effect this should (i think) act as a rotary step down transformer. Im sure as arc load changes there will be voltage fluctuations but i think it may be worth a try. HAS ANYONE ELSE EVER TRIED THIS? Name:  12-25.jpg
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    "The Natural Liberty of Man is to be free from any Superior Power on Earth, and not to be under the Will or Legislative Authority of Man, but to have only the Law of Nature for his Rule."-- John Locke

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    Re: can a 3ph motor be used as a stepdown transformer

    Don't know about the motor but check if the welder is 50hz (for Europe) instead of 60hz for N. America.

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    Re: can a 3ph motor be used as a stepdown transformer

    Interesting question.

    Are the gauge of windings suitable for the current demand of your mig?

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    Re: can a 3ph motor be used as a stepdown transformer

    it is 50 or 60 according to the tag .
    "The Natural Liberty of Man is to be free from any Superior Power on Earth, and not to be under the Will or Legislative Authority of Man, but to have only the Law of Nature for his Rule."-- John Locke

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    Re: can a 3ph motor be used as a stepdown transformer

    Never tried anything like that. Interesting question though.
    I’m thinking that because welder is basically in parallel with one set
    of windings (T7,T8,T9)welder will cause lower impedance at those
    points and low voltage at welder.
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    Re: can a 3ph motor be used as a stepdown transformer

    it was more a -theory question . once i had some input i figured i would try to match up something. the mig is around 11 kw so i was thinking about using an old 15 or 20 hp motor for converter .

    Are the gauge of windings suitable for the current demand of your mig?[/QUOTE]
    "The Natural Liberty of Man is to be free from any Superior Power on Earth, and not to be under the Will or Legislative Authority of Man, but to have only the Law of Nature for his Rule."-- John Locke

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    Re: can a 3ph motor be used as a stepdown transformer

    i was wondering that as well. i have built single to 3 ph rotary converters before so i was also thinking on maybe just running the welder on single ph 220 and add some equalizing capacitors from each outside leg (1 and 2) to power and stabilize the 3rd leg .
    "The Natural Liberty of Man is to be free from any Superior Power on Earth, and not to be under the Will or Legislative Authority of Man, but to have only the Law of Nature for his Rule."-- John Locke

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    Re: can a 3ph motor be used as a stepdown transformer

    Open it up and make sure it is really "3 ph".
    If there are no components(transformer, fan motor, etc) that use all 3 legs then it can be rewired to work on 1 ph.
    We have environmental chambers that are like this. The 230 volt loads are on legs 1 and 2 and all the 115 volt loads
    are on leg 3. For 1 ph you place a jumper between legs 2 and 3. For 3 ph you remove the jumper and hook up all 3 legs.

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    Re: can a 3ph motor be used as a stepdown transformer

    Why don't you just buy a dry pack transformer and set it up for the proper voltage? Usually you can find them for a few hundred bucks used.
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  11. #10
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    Re: can a 3ph motor be used as a stepdown transformer

    Line match auto transformer with multiple taps. should come in single and 3 phase.
    go to a local electrical wholesale retail house and talk to a sales man. Have them look up different transformers you are looking at a 45 to, 64 volt drop depending on if you have 460 or 480 volts. Should be able to come up with either a line match or a buck transformer. a 48 buck transformer should be ok. Also find out what the voltage range the welder will work at. Maybe even the welder manufacture has a line match transformer they sell or recommend.

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