Synchronous motors. A synchronous motor is one where the rotor normally rotates at the same rate as the revolving field in the machine. The stator is comparable to that of an induction machine consisting of a cylindrical iron frame with windings, generally three-phase, located in slots around the internal periphery.
usually, synchronous motors are used for applications where precise and constant speed is necessary. Low power applications of these motors include positioning devices. These are also applied in robot actuators. Ball mills, clocks, record participant turntables also utilize synchronous motors.
The principle of operation of a synchronous engine can be understood by taking into consideration the stator windings to be linked to a three-phase alternating-current supply. The agricultural Chain effect of the stator current is usually 
to determine a magnetic field rotating at 120 f/p revolutions per minute for a frequency of f hertz and for p poles. A primary current in a p-pole field winding on the rotor will also produce a magnetic field rotating at rotor rate. If the rotor quickness is made add up to that of the stator field and there is absolutely no load torque, both of these magnetic fields will tend to align with each other. As mechanical load is used, the rotor slips back again several degrees with regards to the rotating field of the stator, developing torque and ongoing to become drawn around by this rotating field. The angle between the fields boosts as load torque is usually increased. The maximum available torque is accomplished when the angle where the rotor field lags the stator field is certainly 90°. App of more load torque will stall the electric motor.
One advantage of the synchronous engine is usually that the magnetic field of the machine can be made by the immediate current in the field winding, so that the stator windings have to provide just a power component of current in stage with the applied stator voltage-i.e., the engine can operate at unity power aspect. This condition minimizes the losses and heating in the stator windings.