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3 phase motor - Single phase power

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  • 3 phase motor - Single phase power

    You guys with 3 phase machines and single phase power at home. Have you found it most cost effective to invest in a phase converter, to have the existing motor reworked, or purchase a new single phase motor with the same frame? Thanks

  • #2
    Anther option is to get a VFD which will convert single phase to 3phase but also provide frequency control (RPM).

    3phase motors can't be reworked to operate as single phase.

    Depending on the size of the motor, replacing it with a single phase may be the most economical option.

    [This message has been edited by rotate (edited 07-27-2004).]


    • #3
      I think VFD is the way to go nowadays, even for multiple-motor installations. I have four VFDs and soon will have five. All but one have cost well under $200, and they seem to be getting cheaper all the time. You get speed control, braking, overload protection, and efficient power consumption. You get none of that with a rotary converter. I have even gone so far as to remove a single phase motor and replace it with a three-phase and VFD. Try
      or ebay seller "electriccontrols".
      I've had good service from all three.


      • #4
        If I go with a VFD, I have a change belt pulley type mill currently that is 3 phase. Would I be able to place the belt on one pulley and utlize the VFD for variable speed? That would be great!!


        • #5
          I thought I could just leave my bridgey locked in one speed.

          It actually taxed the inverter to OVerload trip using a 1 1/4" bit at the lower rpm. I now change the transmission into low range and reverse the VFD. Works much better to have a wider range to use the full horsepower of your machine.



          • #6
            On my VFD-powered step-pulley mill I am forced to change belts only occasionally when I need more torque, such as for power tapping.


            • #7
              If you can replace the motor at a reasonable price, that's probably the most straightforward. If you've got something like a grinder, that operates at a constant speed, that may be the way to go.

              On something like a milling machine or lathe though, where speed changes are necessary, I'd look at a VFD, even if it's a slight cost premium. I've got one on my milling machine and leave the belt set in one position nearly all the time.
              Try to make a living, not a killing. -- Utah Phillips
              Don't believe everything you know. -- Bumper sticker
              Everybody is ignorant, only on different subjects. -- Will Rogers
              There are lots of people who mistake their imagination for their memory. - Josh Billings
              Law of Logical Argument - Anything is possible if you don't know what you are talking about.
              Don't own anything you have to feed or paint. - Hood River Blackie


              • #8
                No way would I change a milling machine motor to single phase. The quick stops and reversible at speeds come in too handy that is possible with 3 phase. If you can't budget a VFD right now, then go with a static converter. They are less than $60 new and will get your mill running. They will run more than one machine, sometimes even at the same time.
                David from jax
                A serious accident is one that money can't fix.


                • #9
                  Three phase motors can be reworked to operate on single phase by the addition of capacitors and starting switch.
                  However, they lose 1/3 of the power rating when operating on single phase. Use of a static convertor will also result in 1/3 power reduction.
                  The static convertor is probably the least expensive option. The VFD is probably the best choice.
                  It may be difficult to locate a single phase motor that is a direct replacement as many milling machines have a specific mounting flange or an extended shaft.
                  Jim H.


                  • #10
                    do the vfds cause static in other electronic devises like tv, phone and baby work shop is connected to my house.