Hello,

I am doing some work with the ebook from this forum complex numbers, in the chapter "Vectors and AC waveforms" i get some missunderstanding.

Look at the picture!

In the third waveform where B is ahead of A, I really don't understand why the
vector representaion from A is at -90 degrees. shouldn't it point at +90 degrees and B point at 0 degrees? If A is pointing at -90 (which is +270) degree the waveform should start in the negative direction on the phase at 1/2 pi, right ?

yours faithful
Josef Vukovic

 

You yourself have said "Where B is ahead of A". So if B is at 0 degrees, and should be 90 degrees ahead of A, that means A should be -90 degrees. And just out of curiosity, if you have a question about waveform 3 you should have some doubts about waveform 2 as well. No ?

 

Several conventions are being played with in these drawings, and I can't say that it does justice to explanation.

In the phase diagrams, time typically moves from left to right, so in the third drawing, B lags A. As the A phase is solid, it would be the reference voltage, and is typically referenced to 0 degrees.

 

If we imagine that these diagrams represent wheels rolling it might be easier to see the relationship.

http://www.rkm.com.au/ANIMATIONS/animation-sine-wave.html