Power Factor (Leading or Lagging)

Discussion in 'Homework Help' started by xiahbaby, May 21, 2009.

  1. xiahbaby

    xiahbaby Thread Starter New Member

    Joined:
    Feb 4, 2009
    Messages:
    9
    How do you know whether it is leading or lagging in Power Factor?

    [​IMG]

    [​IMG]

    I was told by my lecturer that if the sin θ is positive then it is lagging
    And if it is sin θ is negative then it is leading

    However, in this case, the answers that I got is all positive but it has a variation of leading and lagging.

    I am confused.

    Does he means that if the θ is positive then is is lagging and if it is negative then it is leading ?

    I try to google up on this and this is what I get ...
    But I practically do not understand a thing from the Mnemonics

    From the Mnemonics

    "ELI the ICE man" or "ELI on ICE" – the voltage E leads the current I in an inductor L, the current leads the voltage in a capacitor C.


    CIVIL – in a Capacitor the I (current) leads Voltage, Voltage leads I (current) in an inductor L.

    P/s: I have also upload the solution if you need more detail on the solutions.

    Attached Files:

  2. mik3

    mik3 Senior Member

    Joined:
    Feb 4, 2008
    Messages:
    4,846
    Location:
    Cyprus, but now in UK (GMT+0)
    You calculated cos() and not sin().

    Another way to find it is to look at the angle of the current relative to the angle of the voltage.

    If the currents leads the voltage (greater angle than voltage) then the power factor is leading (capacitive load).

    If the current lags the voltage (less angle than voltage) then the power factor is lagging (inductive load).
  3. t_n_k

    t_n_k Senior Member

    Joined:
    Mar 6, 2009
    Messages:
    4,971
    If the resulting current phase angle is more negative in relation to the driving (source) voltage phase angle, then the power factor is said to be "lagging".

    If the resulting current phase angle is more positive in relation to the driving (source) voltage phase angle, then the power factor is said to be "leading".

    So if the driving voltage phase angle is \theta deg and the resulting current phase angle is \phi deg.

    If \theta > \phi power factor is lagging.

    If \theta < \phi power factor is lagging.

    Then if \theta = \phi power factor is unity and neither leading nor lagging.

    The driving (source) voltage phase is often assumed to be zero (for convenience) and in that situation it is immediately obvious that a lagging power factor condition is indicated by a negative sign for the current phase angle. Similarly a positive sign for the current phase angle indicates a leading power factor.
  4. t_n_k

    t_n_k Senior Member

    Joined:
    Mar 6, 2009
    Messages:
    4,971
    That should read

    If \theta < \phi power factor is leading.
  5. xiahbaby

    xiahbaby Thread Starter New Member

    Joined:
    Feb 4, 2009
    Messages:
    9
    Thanks for the explanation ! I understand it nw XD
  6. hitmen

    hitmen Active Member

    Joined:
    Sep 21, 2008
    Messages:
    156
    Thanks for clarification. Is it safe to say that constant 240V = 240<0 V (phasor)
  7. mik3

    mik3 Senior Member

    Joined:
    Feb 4, 2008
    Messages:
    4,846
    Location:
    Cyprus, but now in UK (GMT+0)
    Yes it is.
Similar Threads: Power Factor
Forum Title Date
Homework Help Distortion Power factor Feb 28, 2014
Homework Help Effective power delivery factor (EPDF) Feb 15, 2014
Homework Help Power Factor Calculation : Need help! Dec 31, 2013
Homework Help leading power factor in capacitors May 26, 2013
Homework Help Power factor May 17, 2013

Share This Page