just some clarification

Discussion in 'Homework Help' started by FullMetalEngineer, Feb 7, 2009.

  1. FullMetalEngineer

    Thread Starter New Member

    Jul 22, 2008
    4
    0
    The power consumers who are suppose to be consuming the true power Pt are paying for the apparent power to the power companies. the power consumers are suppose to be paying less.

    what will you do to your electric fan (inductive load) in order to reduce the apparent power Pa to the true power Pt?

    Here's what my proffessor said.
    we put a capacitor in parallel to the inductor to make it resonate..


    then that could result in an infinite impedance and an open circuit
    then no current

    it is obvious that put it in series resonance is the answer
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Draw the circuit out and I think the correct answer will be quite obvious (and not with a capacitor in series with the load).
     
  3. bvj09

    New Member

    Feb 1, 2009
    3
    0
    Please post your data and calculations. You didn't provide the average size of a household fan (watts), its power factor, the cost of electricity per kwh per year of operation, the cost of a good cap or the savings to be realized.

    I suspect that, unless you are running a really monster fan in your home, you will pay more for the cap than you will save with the "power factor correction" idea.
     
  4. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    When an inductor and capacitor resonate they exchange energy between them and thus current flows between them. If they are ideal then this current exchange will last forever.

    However, in reality the components are ideal and this current exchange reduces gradually with time if a power source is not present.

    In the case of the fan motor, the inductor takes the needed current from the capacitor and the mains voltage provides power only to overcome the resistance in the circuit and keep the current exchange live.
     
  5. Cabwood

    Member

    Feb 8, 2009
    20
    0
    Since the fan motor is doing work (moving air, and working against friction), the load is at least partially resistive, (has a real component). There would not be a zero-current condition.
     
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