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So i'm doing a matlab simulation of delta wye transformer and would need to show the phase shift between voltages. Here is a pictureThree phase voltages of input voltages so how would I show on this graph mathematically or graphically that these voltages are 120 degrees apart?

I tought of doing it like on this picture,picture to find degrees or radians and compare them, but on the graph from simulink above numbers are small so I don't know how.

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  • \$\begingroup\$ Compute the phase angle when blue equals yellow. \$\endgroup\$
    – Andy aka
    Commented Jan 22, 2020 at 18:01
  • \$\begingroup\$ You could do a simple fundamental frequency DFT to calculate the voltage phasors. Then plot all of them on a phasor diagram. \$\endgroup\$
    – relayman357
    Commented Jan 23, 2020 at 1:15

2 Answers 2

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A slightly off-beat approach:

enter image description here

Figure 1. Intersection of the curves.

Because they're sinewaves we can use some trig functions.

  • At (1) the blue phase is at 0. Let's call this 0°.
  • At (2) the blue phase is at 2400. That will be 90°.
  • At (3) and (4), the intersection point with the other phases, the voltage is 1200 which is half the peak. We know that \$ sin\ a = 0.5 \$ has two solutions: 30° and 150° and that these are 120° apart.
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  • \$\begingroup\$ And how would it be then for this one imgur.com/a/Cckv1p9 ? \$\endgroup\$
    – user226621
    Commented Jan 22, 2020 at 23:04
  • \$\begingroup\$ That's a different question. \$\endgroup\$
    – Transistor
    Commented Jan 22, 2020 at 23:10
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The easy way would be to put your vertical grid lines at 60 or 120 degree spacing. Then you'll see that the rising-edge zero-crossings of phase 2 are 120 degrees after phase 1, and the zero-crossing of phase 3 is 120 degrees after that.

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