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3 phase equipment on 1 phase supply

  1. Mar 26, 2009 #1
    I was given a 3 phase plasma cutter (no motor in machine only transformers)and my garage is only 1 phase. I have been doing a little research on converting 1 phase to 3 phase but it is just to expensive for my budget!!! I did come across an article that suggested that is can be done without a phase converter. It was talking about a "sub-phase" not really sure how it works. I do know that a normal 3 phase separation is 120º and with 220v a/c the phase separation is 180º it said that with the "sub-phase" has a 90º phase separation. It does however lower the efficiency of the machine. That I can live with. If anyone knows a way I could do this I would be very thankful.
  2. jcsd
  3. Mar 26, 2009 #2


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    Maybe you could have your electric utility bring three phase to you. Very expensive also probably. Other than that you are probably out of luck.
  4. Mar 27, 2009 #3
    What power is the machine?

    What is make and part number? Is there a circuit diagram?

    If it converts to DC and has a transformer you might be able to rewire it for single phase OR rebuild the power supply with a single phase transformer.

    3-phase machines tend to be high power and too much for domestic supplies.
  5. Mar 27, 2009 #4


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    I have been told the reason alot of 3-phase plasma cutters are 3-phase is because when the are full-wave rectified they have a very smooth output with little ripple since all of the phases tend to overlap. Naturally current requirements per phase will also be less than single phase.
  6. Mar 27, 2009 #5
    The Plasma cutter is a Miller Spectrum 701. I do have the operating manual that has the a circuit diagram.
  7. Mar 28, 2009 #6
    If you have an unused three phase induction motor, you can produce an approx three phase system by using of one single phase source.

    For a short discussion you can refer to Machine question No.19 from http://electrical-riddles.com.
  8. Mar 28, 2009 #7


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    You can make or buy a rotary phase converter, which is what msj suggests, but I have been told they don't balance the phases very well. There are also solid state phase converters which, like a VFD, chop the input signal to DC, then rebuild it to what you need. They aren't cheap, though.

    Here's one: http://www.phaseperfect.com/
  9. Mar 29, 2009 #8
    Looks like it does come in a single phase version. A single phase transformer may be available. It is not partucularly high power 6.5 - 7.5 kW so I don't know why they bother with 3 phase.

    If the transfomer is a Y (Delta) input it may be possible to strap all the phases to 'live' and connect the centre point of the transformer to neutral. Maybe try one, two and all three phases. If it does seem to work check that the transfomer does not run too hot.

    If you try it you must have an RCD (earth fault trip breaker) and a suitably low current circuit breaker and/or fuse in circuit. IF ANY DOUBT DONT.
  10. Mar 29, 2009 #9


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    The reason they use 3 phase is as I stated in my previous post. Less regulation and filtering is required after the rectifiers when using 3 phase since the voltage never falls to zero.
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