The three-phase synchronous motor is a distinctive and specialized engine. As the name suggests, this motor operates at a constant 
quickness from no load to complete load in synchronism with range frequency. As in squirrel-cage induction motors, the velocity of a synchronous electric motor is determined by the number of pairs of poles and the line frequency.
The operation of the three-phase synchronous motor could be summarized as follows:
Three-stage AC voltage is put on the stator windings and a rotating magnetic field is produced.
DC voltage is applied to the rotor winding another magnetic field is certainly produced.
The rotor then acts such as a magnet and is attracted by the rotating stator field.
This attraction exerts a torque on the rotor and causes it to rotate at the synchronous speed of the rotating stator field.
The rotor does not require the magnetic induction from the stator field Taper Lock Pulley because of its excitation. Consequently, the engine has zero slip when compared to induction engine, which requires slip to be able to produce torque.
Synchronous motors aren’t self-starting and therefore need a method of bringing the rotor up to close to synchro nous speed prior to the rotor DC power can be applied. Synchronous motors typically start as a normal squirrel cage induction electric motor through use of unique rotor amortisseur windings. Also, there are two fundamental methods of providing excitation current to the rotor. One technique is by using an external DC supply with current supplied to the windings through slip rings. The other technique is to really have the exciter installed on the common shaft of the engine. This arrangement will not require the usage of slip bands and brushes.
A power system’s lagging power factor can be corrected by overexciting the rotor of a synchronous electric motor operating within the same system. This will produce a leading power factor, canceling out the lagging power factor of the inductive loads. An underexcited DC field will produce a lagging power aspect and because of this is seldom utilized. When the field is generally excited, the synchronous electric motor will operate at a unity power factor. Three-phase synchronous motors can be used for power factor correction while at the same time executing a major function, such as for example operating a compressor. If mechanical power output is not needed, however, or can be provided in additional cost-effective ways, the synchronous machine remains useful as a “nonmotor” means of con trolling power element. It can the same job as a financial institution of static capacitors. This kind of a machine is called a synchronous condenser or capacitor.