When the current ia in phase a is interrupted and phase b is energized, the
motor develops a torque that rotates its rotor by 15 in the counterclockwise
direction. Similarly, when the current ib in phase b is interrupted
and phase c is energized, the motor develops a torque that rotates its rotor
by 15 in the counter-clockwise direction.
Finally, when the current ic in phase c is interrupted and phase a is
energized, the motor develops a torque that rotates its rotor by 15 in the
counter-clockwise direction, completing a one-step (i.e., 45 in this case)
rotation in the counter-clockwise direction. Reversing the current-pulse
sequence to acb will reverse the direction of rotation.
For an n-stack motor, the rotor or stator (but not both) on each stack is
displaced by 1/n times the pole-pitch angle.
PMSMs require two phases and current polarity is important.
Hybrid motors differ from a multi-stack VRSM in that the stator pole
structure is continuous along the length of the rotor.