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Transformer recomendation

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  • Transformer recomendation

    I have a machine with 2 motors,One is 7.5 HP the other is 1hp.They are 575 3 phase motors and i am running 220 3 phase.What should i purchase for a transformer?thanks

  • #2
    Your gonna need around a 9 KVA 3 ph stepdown transformer for 575/230, the transformer should step up or down and it may also have taps for 230/115 on it. You might be able to get away with a lil lower than a 9 KVA but I wouldn't go much lower.
    Opportunity knocks once, temptation leans on the doorbell.....


    • #3
      Thanks hardtail ..i`ll have something to go on.


      • #4
        I would compare the cost of the transformer to the cost of replacing the motors with motors from here or another discount place

        Another point - if you get new motors, you could sell the old ones to help defray some of the cost.


        • #5
          Yes Bruce,that is another option worth looking at.I`m another one of those guys that couldn`t pass up on a mint Rockford hydraulic shaper with the universal table and twin screw vise.


          • #6
            Don't know if you looked, but Surplus Center has a Lincoln 7.5hp TEFC motor in your voltage for $249. Don't know if the RPM's are correct, but worth a look.


            • #7
              My horizontal mill has 575V motors and I'm running it on 208V using an "open delta" step up transformer arrangement.

              Note that the ratings of the transformers are much less than you'd expect.


              • #8
                As of a being a licensed electrician.. I can tell you non-electrician-machinists to be wary of buck boost connected transformers.

                They do work, but polarity connections are critical or you lose your investment in smoke and fire. If there is any doubt, hire someone with insurance who can replace the hardware.

                I had fireballs come out of a panel three times in one day doing hookup according to a young electrical engineers drawings. He came out with six connection diagrams that day from the transformer manufacturer, when the first three blowed up I was turning the panel on with a stick after that. I did however get to disassemble the panel repaint, and reassemble after I bondo'ed the holes burned in the back plate.

                the Red dot polarity must be followed. IE winding direction.
                Excuse me, I farted.