Rotating Field:

Before discussing how a rotating magnetic field will cause a motor rotor to turn, we must first search out how a rotating magnetic field is produced. Figure describes a three-phase stator to that a three-phase AC current is supplied.

The windings are linked in wye. The two windings in every phase are wound in the similar direction.   At  any  instant  in  time,  the  magnetic  field  produced  through  one  particular  phase  will depend on the current through that phase.  The resulting magnetic field is zero if the current through that phase is zero. If the current is at a maximum value, the concluding field is at a maximum value. Because  the  currents  in  the  three  windings  are  120°  out  of  phase than the  magnetic  fields generated will also be 120° out of phase. The three magnetic fields will merge to generate one field that will act upon the rotor. Within an AC induction motor, a magnetic field is induced within the rotor opposite in polarity of the magnetic field in the stator. Thus, as the magnetic field rotates in the stator and the rotor also rotates to manage its alignment along with the stator's magnetic field.  A notice of this chapter's discussion deals through AC induction motors.

Figure: Three-Phase Stator

From one instant to the further, the magnetic fields of every phase merge to generate a magnetic field whose position shifts by a certain angle.  At last of one cycle of alternating current, the magnetic field will have shifted by 360°, or one revolution.  Because the rotor has an opposing magnetic field induced upon it that will also rotate by one revolution.