A synchronous motor is a type of AC motor that operates at a constant speed, directly proportional to the frequency of the supply current. Unlike induction motors, synchronous motors rotate in synchronism with the line frequency.

A synchronous motor maintains a constant speed by operating in sync with the frequency of the supply current. The speed is determined by the supply frequency and the number of poles in the motor, following the relationship (Speed = \frac{Frequency \times 60}{Number\ of\ Poles}).

Synchronous motors cannot start on their own because they require their rotor to synchronize with the rotating magnetic field of the stator. Various starting methods, such as using a pony motor or damper windings, are employed to bring the rotor up to speed.

The main parts of a synchronous motor are the stator, which contains the motor’s windings and produces a rotating magnetic field; and the rotor, which can be either a salient pole or a non-salient (cylindrical) type, and is supplied with DC current to create a constant magnetic field.

Damper windings consist of short-circuited copper bars placed in the slots of the pole faces of the rotor in salient pole synchronous motors. They help in starting the motor by acting similarly to the squirrel cage in an induction motor and also serve to dampen oscillations or fluctuations in rotor speed.