I am trying to implement the field oriented control and trying to understand the following video link

In one of the slides he mentions the angle between the current vector and rotor flux using the following diagram
My doubt the angle can be either from 0 to 360 degrees or it should be from -180 to +180? How do we get the notation of -180 to +180, is it a standard? please advise.


Q2. In the video at around 5.58 it says Ia + Ib + Ic the motor currents should add to 0. But in case if did not happen then what should i look for? What will be the torque degradation if Ia+Ib+Ic is not 0?

 

My doubt the angle can be either from 0 to 360 degrees or it should be from -180 to +180? How do we get the notation of -180 to +180, is it a standard? please advise.

I know next to nothing about this realm but I believe the author chose the x-axis range to capture the plotted curve of torque as a conventional looking sine wave. Otherwise it would be negative-going at the origin. The choice of the x-axis labeling is arbitrary, in that 350° can be called -10°.

 

It represents circumference in a linear way.