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Need advice on 3 phase converter

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  • #16
    Here is a site with "kits" for static phase convertors, which can then be used with a user supplied 3phase motor to make a rotary phase converter. Gives you some idea of how 'simple' these things
    are, but leaves out the box to put stuff in and wiring is up to you. An old computer would do for a box. OTOH no need to experiment with capacitors.... Prices start at $62 and go up.
    Not recommending at all, just for info. They have diagrams. Good deal if you are really sold on the static or RPC idea.
    Last edited by sch; 04-08-2014, 03:14 PM.


    • #17
      To follow up here I ended up with a Hitachi WJ200 VFD and have no regrets. The functionality is impressive, to say the least.


      • #18
        Hitachi is a Cadillac in my opinion. Hard to beat.
        My last VFD purchase was a Teeco/Westinghouse
        and it is super nice. Enjoy your mill.



        • #19
          Forget all the phase converter cheer leading and get your self a quality VFD. Do not use the mechanical variable speed mechanism if you want it to last. The advantages of a VFD are overwhelming compared to any kind of phase converter. You have wide range variable speed, dynamic braking, programmable acceleration, soft starting, instantaneous fault protection, overload protection, a tiny box that doesn't make noise and occupies zero floor space, and digital spindle speed read-out.

          My favorite supplier is They are a full fledged industrial supplier with everything you need for a professional installation. Their house brand VFD's are reasonably priced and their tech support is top notch. I have 3 VFD's in my shop that I purchased from them. The newest one is 10 years old and all have worked perfectly since new. There are other quality brands out there, but you generally get what you pay for in a new unit.



          • #20
            I have been reading the recent threads on VFDs with interest. Target for me is my Kondia mill. I has 3HP main spindle motor but also knee lift motor plus powered X-travel plus coolant motor.

            I do like (feel comforted by) the statements that say if the specs say the VFD is ok for both single and 3-phase input then one can purchase at rated capacity. Certainly 3HP is less expensive than 5HP and I've never felt the mill has been loaded up in a cut.

            Question I still have is, is it as simple as plugging in a VFD to the 3-phase plug of my mill? Will this get everything going in some reliable fashion?

            I think I'd be ok to run the VFD at some solid figure (if figure is the right word; perhaps setting is better) that gave me "normal" 100% speed wise operation of the mill spindle motor (perhaps only changing to slow that motor down when doing some threading or similar) provided it gives me use of the other motors attached.



            • #21
              Get a used 3 phase motor at 2x the motor size at least of the one on your mill. Purchase or build a static convertor or use the suggested heavy push button switch and large Run capacitor to start the above motor and when its running switch in the motor on your mill.

              I built my static convertor years ago from plans published in Home Shop Machinist or the "other" magazine published by Village press. Been working fine for the past 15 years. Run caps can be used in parallel to increase the total capacitance in a circuit.

              Since I was a HVAC tech, I had access to used Run capacitors off broken equipment. Run capacitors are silver or grey covered metal vs the black plastic Start caps which will last about 60 seconds when used instead of the Run caps.
              Retired - Journeyman Refrigeration Pipefitter - Master Electrician


              • #22
                I have used rotary and static converters, I tried a VFD one day......I will never go back to converters, the VFD is so smooth and my machines run much better, I can see it in my parts finishes...
                Here is what you need...