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Unbalanced power distribution on 208v units only.

Discussion in 'Lighting and Electrics' started by McCready00, Aug 10, 2018 at 12:50 PM.

  1. McCready00

    McCready00 Active Member

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    Hello all,

    Could someone tell me which problems could an unbalanced power distribution produce.

    I understand, and can also calculate, what will return to neutral, and why it could be a big problem when working on fixtures, dimmers or whatever else using 120v.

    Although, if only using fixtures on 208v, where neutral would still be low enough, and phases are really unbalanced... what could be the problems ?

    That question also applies when power is supplied/or not from a generetor.

    Thank you
  2. JD

    JD Well-Known Member

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    North Wales PA
    Although in an ideal world, all phases would balance equally. In the real world it rarely happens. If your source is Wye (120,120,120 with 208 between), then running only 208 loads means you are loading Delta. Not a problem. Any one fixture will load two of the three legs. As long as your source (company switch or generator) can handle the highest current found on any one leg, then you are fine. So, if your source was 100 amps per leg, and your load was 100, 100, 0 you would still be fine. Because you are limited to the current on the highest leg, your ability to use all the power available to you is decreased.
    RonHebbard likes this.
  3. TJCornish

    TJCornish Well-Known Member

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    St. Paul, MN
    208v fixtures do not contribute to neutral current or triplen harmonics. This is indeed a good way to go. Balance phase loading as best you can and you’ll be fine.
    RonHebbard and JD like this.
  4. DavidJones

    DavidJones Active Member

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    Having phases out of balance can be a lot more of an issue on a portable generator. Having unbalanced loads will cause the generator to become physically unbalanced and can actually damage the unit. New generators will shut themselves down before this happens, but you are still going to lose power.
    It's typically very easy to load balance fixtures with portable power since soca outputs are usually wired

    1: x-y
    4: x-y

    Provided you are using the same fixture types or rotating your circuiting so the close to the same number of each fixture types land on each leg, It usually comes out really close.
    RonHebbard likes this.

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