LTSpice difference in Phi and time delay for a sine wave

Discussion in 'Programmer's Corner' started by Dookky, Feb 2, 2011.

  1. Dookky

    Thread Starter New Member

    Feb 2, 2011
    5
    0
    While trying to teach myself about zero sequence harmonics and there adverse effects on power systems (particularly with multiple UPS type systems) I had been using this site (which is awesome by the way!) and decided that the best approach would be to build a circuit similar to the poly-phase circuits found in the AC section on harmonics, specifically the Y-Y system with added harmonics as current sources. I didn't follow the netlist to a T though. As I have done for a long time now with LTSpice I put in a phase shift with the very easy to use "phi" parameter. I measured my current across my neutral conductor and... nothing was as expected. Well after several frustrating hours of playing with numbers and finally whittling the graphical interpretation down to a netlist I was unable to produce the neutral harmonics, until I changed my phase angle parameter Phi into what is used in the Spice code given, which is a time delay.

    To sum up, apparently to LTSpice, giving a phase angle is vastly different than giving a time delay to a waveform.

    My question is this, is this a known Spice problem or just an LTSpice problem?

    *Edit: This problem effected both the current source and voltage source
     
    Last edited: Feb 2, 2011
  2. rapidcoder

    Member

    Jan 16, 2011
    37
    3
    Just guessing, I haven't used LTSpice, but is it not the case that the phi parameter is used only in the AC analysis? Some parameters in SPICE work only for some kinds of analyses.
     
  3. Dookky

    Thread Starter New Member

    Feb 2, 2011
    5
    0
    Ahhh, that certainly could be the case, and it sounds like something LTSpice would do. Thanks for the reply, I'll see if I can't do a little research into that.
     
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