Phasor Addition Help

Discussion in 'General Electronics Chat' started by ctishman, Jan 25, 2013.

  1. ctishman

    Thread Starter New Member

    Oct 12, 2011
    So I'm trying to work my way through some of the exercises in my ac course, but I just can't seem to make it make sense. Anyhow, I was hoping someone would be able to help me out with it.

    The example I'm given, and I'm quoting from this (terrible) textbook:

    Anyhow, the entire book reads like it was written from one engineer to another engineer, rather than to a student, but I won't get into that too much. I'm just trying to figure out what the heck they're doing and how it's supposed to work to add phasors together.

    *note that section 14.10 says nothing about adding vectors in polar form, and everything I've seen seems to indicate that it's impossible unless the angles are multiples of 180°.
  2. MrChips


    Oct 2, 2009
    Firstly, know how to convert from polar coordinates to orthogonal coordinates (same as Cartesian or X-Y coordinates) and vice versa.

    For example,

    1V[​IMG]0° + 2V[​IMG]90° = 2.236V[​IMG]63.43°

    work backwards:



    x = r cos(θ), i.e. x = 1

    y = r sin(θ), i.e. y = 2

    Thus, to add two vectors, convert to X-Y coordinates and add the X-values and the Y-values. Then convert to polar coordinates:

    r = √(x^2 + y^2)

    θ = atan(y/x)
    ctishman likes this.
  3. ctishman

    Thread Starter New Member

    Oct 12, 2011
    Okay, NOW it makes sense! I'd been banging my head about it for hours and had lost perspective. I really appreciate the help with that!