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Power Factor

  1. May 18, 2009 #1
    Why is it that the utility will penalize a customer for a low power factor.

    I cant imagine why they would penalize you if a purely reactive load puts all its power back into the mains.
     
  2. jcsd
  3. May 18, 2009 #2

    russ_watters

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    Staff: Mentor

    Because it doesn't put all its power back into the grid. Reactive power has no capacity to do work because the voltage and current are out of phase with each other. So essentially, when you take reactive power, you are taking generator capacity (apparent power) that isn't showing up on your meter (real power).
    http://en.wikipedia.org/wiki/Power_factor
     
  4. May 18, 2009 #3
    A purely reactive load still draws current and gives rise to undesirable joule heating losses and voltage drops in the power distribution network conductors and components (such as transformer windings). That loss is not recoverable. Allowing very low power factor conditions to prevail could require the system to have much bigger conductor sizes to reduce the losses and voltage drop - thereby increasing the capital cost.
     
  5. May 18, 2009 #4
    You are correct. A low power factor puts more current in the lines. The utility charges you only for real power, not the reactive part. The extra current in their lines just loads them down with extra I2R losses, which you do not pay for. On the other hand, they may pay YOU for some capacitive power factor. You could put a synchronous capacitor on line (a salient pole synchronous motor w/o load).
     
  6. May 18, 2009 #5

    Averagesupernova

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    Gold Member

    Because power is wasted in the wires carrying current to the load. Do a search on this. It has been covered here on PF numerous times.

    Edit: WOW. Three posts within minutes of each other.
     
  7. May 18, 2009 #6
    had a feeling that, that was the reason, but wasn't sure....thanx
     
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