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Reverse-feeding this transformer

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    Reverse-feeding this transformer

    Here's the label with diagrams:



    #2
    OK what's the question?

    Welcome to the Forum.
    Rob

    Moderator

    All responses based on the 2017 NEC unless otherwise noted

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      #3
      Originally posted by Cannonmn View Post
      Here's the label with diagrams:


      Sometimes you can use a step up transformer as a step down (or vice versa) and sometimes you can't. Check with the manufacturer.

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        #4
        This is a delta to delta to wye step down.
        If you use it for step up you will end up with either ungrounded or corner grounded delta. Is that OK?

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          #5
          Originally posted by Cannonmn View Post
          Here's the label with diagrams:


          And a nice label it is.

          Roger
          Moderator

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            #6
            Here is a interesting read from GE on the subject:
            http://apps.geindustrial.com/publibr...ormer2|generic
            At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.

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              #7
              Will this transformer work ok when reverse-fed to get 480/3?

              Data in pic below. I need to create 480v.3phase to run machine tools. I have a qualified electrician ready to hook up transformer but he's not a transformer expert so I want to find out about issues in doing this. I know influx current will be momentarily high and we're prepared to deal with that. Big question I tried to get GE customer service to answer was whether this transformer, given where taps are etc., will present any huge problems. The GE instruction cited on the label pictured, only mentions the high influx current issue, but nowhere says you cant reverse-feed it. Then there's the ground issue. The only way I've read that you can create a ground for your loads is to use a corner ground, typically done by grounding the B phase. Comments?

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                #8
                The only simple grounding solution for a delta is the corner ground.
                Motors should have no problems with it, but some VFDs or built-in speed controls will not like it and at a minimum may need modification.

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                  #9
                  Originally posted by Cannonmn View Post
                  Data in pic below. I need to create 480v.3phase to run machine tools. I have a qualified electrician ready to hook up transformer but he's not a transformer expert so I want to find out about issues in doing this. I know influx current will be momentarily high and we're prepared to deal with that. Big question I tried to get GE customer service to answer was whether this transformer, given where taps are etc., will present any huge problems. The GE instruction cited on the label pictured, only mentions the high influx current issue, but nowhere says you cant reverse-feed it. Then there's the ground issue. The only way I've read that you can create a ground for your loads is to use a corner ground, typically done by grounding the B phase. Comments?
                  The short answer is yes, this transformer can be fed from either side. Back in the old days, like before 2011, it was done all the time, backfeed a transformer, corner ground it and your done.

                  Electrons are dumb as a rock and don't care about labels or tech support opinions. Motors are dumb as a rock, they don't care about anything other than having the correct voltage fed to them. Electronics are a different matter, they are still dumb, but they require some special handling.
                  If Billy Idol is on your playlist go reevaluate your life.

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                    #10
                    If you need a wye secondary (277/480V; i.e., a neutral), then that transformer will not work. It is also 480V - 208Y/120V, so if reverse fed, you need 208V on the primary; 240V will be too hot (high a voltage). Yes, it can be fed from either side.
                    Electricians do it until it Hertz!

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                      #11
                      Originally posted by augie47 View Post
                      Here is a interesting read from GE on the subject:
                      http://apps.geindustrial.com/publibr...ormer2|generic
                      What's interestingly relevant in that paper is the fact that it indirectly states that for GE, they are insisting that step-up transformers be custom built to order, which then plays to the NEC requirement* that transformers used to step-up voltage be approved for use by the manufacturer, either on the nameplate of in some other form of documentation. That paper to my reading means you cannot legally use GE transformers for step-up.

                      *Depending on which code cycle you are on.
                      __________________________________________________ ____________________________
                      Many people are shocked when they discover I am not a good electrician...

                      I'm in California, ergo I am still stuck on the 2014 NEC... We'll get around to the 2017 code in around 2021.

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                        #12
                        Originally posted by Jraef View Post
                        ... That paper to my reading means you cannot legally use GE [step-down] transformers for step-up.
                        FIFY


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                          #13
                          Originally posted by GoldDigger View Post
                          FIFY


                          Sent from my XT1585 using Tapatalk
                          Yeah, OK... sheesh

                          Commonnm,
                          By the way this was a duplicate thread. Please refrain from cross posting in the future. I'm merging this thread into the one you started yesterday.
                          __________________________________________________ ____________________________
                          Many people are shocked when they discover I am not a good electrician...

                          I'm in California, ergo I am still stuck on the 2014 NEC... We'll get around to the 2017 code in around 2021.

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