AC Motor

AC Synchronous motors do not depend on this induced magnetic flux in rotor and stator to operate. Instead, AC synchronous motors are constructed with magnets in the stator, which produce a rotating magnetic field. In a synchronous motor, current is supplied to the rotor, which also has a magnetic field, typically produced by a permanent magnet. Rotation is caused by interaction of the stator's magnetic field with the rotor's magnetic field.

Unlike an induction motor, the rotor in a synchronous motor will rotate with no lag or time delay. They are called synchronous because at steady state, the rotating speed of the rotor is equal to the speed of the rotating magnetic field in the stator. The rotation of the rotor is synchronized with the supply frequency.

The stator requires three-phase power (typically supplied by a VFD) for all three phases in the stator. Synchronous motors have an advantage over single-phase induction motors – with synchronous motors, the starting direction can be selected.