In a three stack 12/8 pole variable reluctance motor, rotor pole pitch is

Concept:

Let N be the number of rotor poles (or teeth) and m is the number of stacks or phases. Then

Pole pitch = 360° / N

Step angle = 360° / (m × N)

Calculation:

In a three-stack 12/8 pole variable reluctance motor,

Number of rotor poles = 8

Pole pitch = 360/8 = 45°

 Mistake Points

Students usually get confused in pole pitch and step angle. Both are different terms with different meanings which are mentioned below.

Pole pitch: The distance measured in terms of armature slots or armature conductors between two adjacent pole centers.

Pole pitch = 360° / N

Step angle: The step angle of a stepper motor is defined as the angle by which the rotor of a stepper motor moves when one input pulse is applied to the stator of the motor.

The step angle for a stepper motor is given by:

\(β = \frac{360°}{m × N_r}\)

where, β = Step angle

m = No. of stator phases

Nr = No. of rotor teeth

Here in our question rotor pole pitch is to be calculated, so the calculations should be done accordingly.