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Thread: 480/480 Xfmr?

  1. #1
    Join Date
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    480/480 Xfmr?

    We're tapping and extending from the secondary from these existing xfmrs so it's not imperative I figure it out, but I want to know why there's a 480/480 transformer. Is it because of distance (of which appears far diagrammatically via several hand holes). It doesn't appear they're using a neutral on the secondary side so not because they needed a wye... thoughts?

    eta for clarity, the question is: under what circumstance would you use a transformer of the same voltage and how would one size and specify?

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    Last edited by follybeacher; 10-26-18 at 03:39 PM.

  2. #2
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    I have seen it used as a means of isolating the upstream and downstream distribution systems from each other. You size the transformer for the calculated load, just like for any other transformer. You specify a 1:1 turns ratio, and include whether the primary and secondary are to be connected WYE or DELTA.
    Charles E. Beck, P.E., Seattle
    Comments based on 2017 NEC unless otherwise noted.

  3. #3
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    Would this be a method to reduce the available fault current?
    Tom
    TBLO

  4. #4
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    Quote Originally Posted by ptonsparky View Post
    Would this be a method to reduce the available fault current?
    Could be. Chokes would be cheaper.
    Si hoc legere scis nimium eruditionis habes.

  5. #5
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    If the xformer has a few taps for minor voltage differences, it could be used to account for voltage drop. It's nominally a 480/480, but might be hooked up to restore a 5% - 10% voltage drop.

    As mentioned, it could also be used as an isolation transformer.

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