A synchronous motor is an AC motor in which the frequency of the AC supply is synchronized with the shaft rotation it has electromagnets on the stator of the motor and thus a magnetic field is created and it will oscillate in time of the line current.

There are two types of synchronous motor nonexcited and direct current excited in this direct current excited type we need to do excitation and it doesn’t have any self-starting capability to reach synchronism


These motors are not self-started and they need some external means to bring their speed to synchronous level

Operation speed is synchronized with the supply frequency and thus for constant supply frequency they will operate as a constant speed motor irrespective of the load it has the unique character to operate under any electrical power factor


It is doubly excited, two electrical inputs are used for it. Its stator winding is consist of three phases to three-phase stator winding and DC for the rotor in its three-phase stator it carries three-phase current and it will produce three phases rotating magnetic flux

In certain instant the rotor and stator will be the same polarity which will thus create a repulsive force and at the very next second it will be of different polarity and thus attraction occurs and according to this the rotor is unable to move and thus we need to use some mechanical means for this and thus rotor rotates the same direction as the magnetic field and thus synchronization occurs after this we can remove the mechanical means and it will continue its state


  • It is used in generating stations
  • It can increase power factor when it is connected to bus bar
  • It is used for power factor correction
  • It can be used in places in which it requires constant speed
  • It can be used to operate lagging by varying the excitation
  • Speed is independent of the load
  • By using open loop control we can control speed and position
  • Increased efficiency in low-speed applications