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Thread: zig zag transformer

  1. #1
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    zig zag transformer

    What is the purpose of the ziz zag transformer in this drawing?
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    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  2. #2
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    Quote Originally Posted by electrofelon View Post
    What is the purpose of the ziz zag transformer in this drawing?
    Used to create artificial neutral, mitigate harmonics, & more. Check it out on Wikipedia:
    https://en.wikipedia.org/wiki/Zigzag_transformer
    Roger Ramjet NoFixNoPay

  3. #3
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    Looks like it's being fed from a grounded wye secondary, so that's a good question.

  4. #4
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    The customer transformer is a grounded wye-grounded wye transformer, so I do not see any need for a grounding transformer.
    The only thing I can think of is that someone has specified that the inverter output has to remain solidly grounded even when the disconnect is open.

  5. #5
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    I really know nothing, except that I can tell this has something to do with it.
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  6. #6
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    Quote Originally Posted by GoldDigger View Post
    The customer transformer is a grounded wye-grounded wye transformer, so I do not see any need for a grounding transformer.
    The only thing I can think of is that someone has specified that the inverter output has to remain solidly grounded even when the disconnect is open.
    I can't see how an open disconnect would unground the inverter output.

  7. #7
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    Here's a wild and possibly completely boneheaded guess, since I have no understanding of how/why it would work, but...

    Having noticed this (yellow highlight is mine)...

    Click image for larger version. 

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    ...perhaps it is a way of complying with the exception to 705.32, when using a switchboard that was not designed for backfeed.

  8. #8
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    Quote Originally Posted by jaggedben View Post
    I can't see how an open disconnect would unground the inverter output.
    I was thinking (mistakenly) of the disconnect also opening the neutral.
    If there is no neutral connection to the inverters (line to line operation) then opening the three line conductors opens all connections between inverter output and ground.

    Sent from my XT1585 using Tapatalk

  9. #9
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    The customer takes service at, and has mv switchgear. Could that have anything to do with it?
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  10. #10
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    Quote Originally Posted by ramsy View Post
    Used to create artificial neutral, mitigate harmonics, & more. Check it out on Wikipedia:
    https://en.wikipedia.org/wiki/Zigzag_transformer
    There is no neutral conductor running to it on the drawing though, just indicates a ground connection at the midpoint.

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