What is Synchronous Motor?

A synchronous motor is an AC motor, in which the rotor rotates at the same speed as the rotating magnetic field, produced in the stator. As the name implies, it rotates at a constant synchronous speed.

Why Synchronous Motor is Not Self-starting?

In a synchronous motor, due to rapid rotation of the stator magnetic field, the rotor is subjected to a torque that reverses rapidly. Because of the large inertia of the rotor, the rotor will not be able to establish the magnetic locking. Hence it is not self-starting.