To sustain rotation, the stator field must rotate in advance of the rotor poles, thus constantly "pulling" the rotor along. Some motor variants run on 3-phase AC power (see the synchronous reluctance variant below). Most modern designs are of the switched reluctance type, because electronic commutation gives significant control advantages for motor starting, speed control and smooth operation (low torque ripple).
To maintain rotation, the stator field must lead the rotor poles. This action "pulls" the rotor along continuously. Some motor types use 3-phase AC power (see the synchronous reluctance variant below). Most modern designs are switched reluctance motors because electronic commutation offers significant control advantages for starting, speed adjustment, and smooth operation (low torque ripple).