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"High leg" three phase

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  • "High leg" three phase

    I have a 240 volt 3-phase 4 wire delta connection supplied to my shop. The "hot leg" to ground is 208v and the other two legs are 120v to ground. I was looking at adding a Miller invision 456P. I do not want to find out that this type of 3-phase will not work after purchasing. I assume whatever components that need 120v in the welder will not be able to run off of the 208v leg without frying a circuit board or something.

    If the welder is wired correctly is this acceptable power for this machine? Do I need to pay special attention to the hot leg in this machine? Will it work?

    I currently have a Miller 180SD single phase running on the 240/120v side.

  • #2
    The manual says 230 volt input, but your miller can advise you better.

    Every machine I have ever bought allows the option of 208 or 230/240 volts.

    Call miller tech services.
    Nothing welded, Nothing gained

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    • #3
      Check the voltage phase to phase.

      I suspect you'll find 240 V. You more than likely have a delta 3 phase setup. I think that's an older version.

      If I remember correctly it was the lack of a dedicated ground that made these systems tricky (especially if ground fault protection was needed). You of course have a neutral. Or maybe that's the other way around. You have a ground, but no real neutral. In either case, depending what you want to hook up, you need to be careful and really want to discuss this with a qualified electrician.

      I believe you can use a transformer to get the more traditional Y setup. The question become, does the transformer in the Miller care or rather act the same way.
      Con Fuse!
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      • #4
        Three Phase

        The power you have is 240 volt three phase (yes, some people call that 230 volt - same thing). That is exactly what you want. The Invision does not care what any leg to ground is. You have exactly the same power most small shops in our area have. Now if you attempt to feed a 120 volt circuit and connect the high leg which happens to be about 208 volts to ground, you are in trouble. Smoke coming from our light fixtures helped me learn this. In general, welders/motors don't know and don't care whether the power comes ftom a delta or a Y configuration. weldersales


        • #5
          Three Phase

          What you do want to be careful about, though, is the model of Invision you get. There is a 230/460 version and a 575 volt only version. The 120 volt supply is generated inside the welder and as long as you feed the machine three 240 volt, line to line, leads, you are good to go in the case of the 230/460 machine, of course. weldersales


          • #6
            The only thing you should do when hooking up the Inv456 or XMT456 to that kind of three phase is to connect that higher leg to the L3 connection at the contactor.

            While connecting this higher leg to either L1 or L2 will not by itself cause a failure that you have to replace a part. It can cause nuissance Help 7 codes. The control board will measure the volatage difference between line 1 and 2 and could set off the help code. Keeping this high leg connected to the line 3 (L3) connection will avoid this.


            • #7

              I have a 456P that I am hooking up to Delta 3 Phase and I could not find any mention of this in the manual , My other machines have Auto Link so it is easy but this machine has a Circuit board and a jumper that need to be moved between 240 and 460 , High leg on L3

              Thanks for the tip

              Once you let the "Magic Black Smoke out it's really hard to get it back in "