Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Balanced load at home means no current on the neutral?

  1. May 13, 2012 #1
    I've never read this explicitly, but here is what I've concluded:

    If you could somehow have a perfectly balanced load on the circuits in your home to each of the 2 hot lines coming into your residence from the pole mounted transformer, this would mean:

    The neutral wire connected from your house to the transformer would carry 0 current because the 180 degree phase separation from the 2 hot lines cancel each other out.

    Am I correct?
  2. jcsd
  3. May 13, 2012 #2


    User Avatar
    Science Advisor
    Gold Member

    Correct. BUT remeber that equal current does not necessarily mean those currents are in phase. So the neutral can carry some current when the current in the two hot legs are equal but out of phase due to inductive loads.
  4. May 13, 2012 #3
    Yep, only if the two are absolutely in phase......or opposite phase......you know what I mean!!!! The return current has to be absolute equal and opposite in phase to totally cancel each other so there is no net current on the neutral wire.
  5. May 14, 2012 #4


    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    You get a similar thing with three-phase distribution circuits. The overhead cables consist of three 'beefy looking insulated wires (often there will be two circuits side-by-side) and a tiny uninsulated cable strung between the tops of the towers which may take any unbalanced current but, essentially, the three cables carry the three phases and the instantaneous current in any one of the three is balanced (vector-wise) by the currents in the other two.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook