power factor

Discussion in 'Homework Help' started by lemon, Apr 25, 2010.

  1. lemon

    Thread Starter Member

    Jan 28, 2010
    125
    2
    Hi:
    If asked to find the power factor - I know the formula to use is cosθ - but sometimes the answer is requires a minus sign in the cos - like cos-θ.
    Is this to do with the direction of the sinusoids and/or whether one leads or lags the other. How do I know when to use the minus sign and when not to?

    many thanks
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Note that the power factor (PF) is cosθ only for sine waves.

    For a general case, PF=real power/apparent power

    θ is the angle of the voltage minus the angle of the current. Apply this and the sign will be obvious.
     
  3. lmartinez

    Active Member

    Mar 8, 2009
    224
    6
  4. alim

    Senior Member

    Dec 27, 2005
    113
    1
Loading...