Selection of Poles and Phases (Electric Motors)

5.3.1
The stroke angle is a function of the number of poles, phases, and rotor teeth. It may be calculated in the same fashion as for the step motor.

FIGURE 5.100 Variable-reluctance step-motor lamination stack
Selection of the number of poles and phases should be based on the following considerations:
• One- and two-phase motors have dead zones and need help starting.
• Three-phase motors always generate positive torque but have high torque ripple.
• Four- and five-phase motors have low torque ripple but require more expensive controllers.
• Higher numbers of phases and poles require higher switching frequencies, which increases core losses.