1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Leading and Lagging voltages

  1. Mar 20, 2012 #1
    This is just an example
    X=-20cos(t)
    y=cos(t-45deg)

    X has to be positive so X=-20cos(t±180deg)
    I know you want the angle ^ to be the smallest magnitude, but for this case both would give you a magnitude of 180 deg.
    So which one would you pick X=20cos(t-180deg) or X=20cos(t+180deg)?
    This would change the answer of whether X or Y was leading.

    Someone told me you should pick the angle that makes a phase difference that is <180deg.
    So in this case it would be X=20cos(t-180deg) since that would give a phase difference of 135 degree compared to the 180+45=225deg phase difference if we picked the positive.

    Is that right?
     
    Last edited: Mar 21, 2012
  2. jcsd
  3. Mar 20, 2012 #2
    X=-20cos(t)
    y=sin(t-45deg)

    Z=Sin(t)
    X=20cos(t)=20Sin(t+90deg)
    Y=Sin(t-45deg)

    X leading normal sine wave Z by 90 degree
    Y lagging normal sine wave Z by 45 degree.

    X leading Y by 135 degree.
    http://img855.imageshack.us/img855/5074/leadlag.jpg [Broken]
     
    Last edited by a moderator: May 5, 2017
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Leading and Lagging voltages
Loading...