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In the attached image below, I don't understand the text and phasor diagram that I have highlighted in yellow.

enter image description here

Why does the induced emf on the armature winding lag the magnetic flux of the corresponding rotor pole by 90 degrees? I thought they would have been in phase.

Also how does the power factor affect this?

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In first approximation, a synchronous generator is just a coil.

The behavior of a coil is that current and voltage have 90deg phase angle.

Flux is directly related to current I, because current I generates flux in the coil. So also flux and voltage always have 90deg phase shift.

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I've spent a lot of time recently thinking about flux, current, induced voltages etc. I think a lot of my confusion came from not realising what has come first.

For example, current and magnetic flux are intrinsically linked, one directly creates the other. As current increases, so does flux, in phase. However, if flux creates current, the current will be 90 degrees out (assuming a power factor of 1). This is because only a changing flux will generate voltage, therefore the voltage is 90 degrees out, and therefore also the resultant current from that voltage will be 90 degrees out from the original flux.

I hope this helps. I appreciate the question is old!

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