The three-phase synchronous motor is a unique and specialized electric motor. 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 quickness of a synchronous motor is determined by the amount of pairs of poles and the range frequency.
The operation of a typical three-phase synchronous motor can be summarized as follows:
Three-phase AC voltage is applied to the stator windings and a rotating magnetic field is certainly produced.
DC voltage is applied to the rotor winding another magnetic field is usually 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 will not require the magnetic induction from the stator field because of its excitation. Because of this, the engine has zero slip when compared to induction electric motor, which requires slip in order to produce torque.
Synchronous motors aren’t self-starting and therefore require a method of bringing the rotor up to near synchro nous speed before the rotor DC power can be used. Synchronous motors typically start as a normal squirrel cage induction engine through use of Screw Air Compressors particular rotor amortisseur windings. Also, there are two fundamental methods of providing excitation current to the rotor. One method is to use an external DC source with current provided to the windings through slide rings. The other method is to have the exciter installed on the normal shaft of the electric motor. This arrangement does not require the use 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 create a leading power aspect, canceling out the lagging power aspect of the inductive loads. An underexcited DC field will produce a lagging power aspect and for this reason is seldom utilized. When the field is normally excited, the synchronous motor will run at a unity power aspect. Three-phase synchronous motors can be used for power aspect correction while at exactly the same time carrying out a major function, such as operating a compressor. If mechanical power output isn’t needed, however, or could be provided in other cost-effective ways, the synchronous machine continues to be useful as a “nonmotor” method of con trolling power element. It can the same work as a financial institution of static capacitors. Such a machine is called a synchronous condenser or capacitor.