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Voltage at service

  1. Apr 21, 2014 #1
    Hi guys,

    If there was a voltage drop of 20V on a 3ph line of 347/600, is the voltage at the service 327V or 580V, or both? Thanks you for reading.

  2. jcsd
  3. Apr 21, 2014 #2


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    Gold Member

    Is this a homework problem? What do YOU think the answer is, and why?
  4. Apr 21, 2014 #3


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    Science Advisor

    Who observed a voltage drop of 20V ?
    How did they measure it ?
  5. Apr 21, 2014 #4
    Hi guys,

    This isn't school related. That isn't the actual voltage - I'm trying to understand the concept of which would be the operating. With the concept, I can apply it accordingly. I assume it is 580 as it is three phase.
  6. Apr 21, 2014 #5


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    The specified voltage is 347V / 600V.
    The three phases are separated by 120°. 1 / Tan(30°) = √3 = 1.73205
    If you multiply 347V by √3 you get 600V.
    You cannot change one without changing the other.

    When combined with a common neutral you have three single phase supplies of 347V, relative to the neutral. The voltage between the phases is 600V.

    A 20V single phase drop is a 34.6V three phase drop.
    A 20V three phase drop is an 11.5V single phase drop.
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