First and foremost I have a question regarding the MMF distribution in a Motor produced by a single coil. I found a picture here:

Why does the MMF not start at 0 at 0°? When I apply the $$NI=\int{H \mathrm{d}l}$$ with a curve with a small angle opening around the 0 point (horizontal arrow), I’d get 0.

And my second question is the following: What’s the easiest explanation why the fundamental of the permanent magnet flux should be perpendicular to the fundamental MMF to produce the maximum possible torque from a PMSM (without saliency)?

Edit: I’d really prefer a mathematical derivation of the torque equation to understand the behaviour.