Electromagnetism : How synchronous motor works

Motors are cool!!. It power machines,cars,toys and so on. This is all cause of electromagnetism. Some motors, the stator will provide rotating magnetic field and induce the same electromagnet to the rotor. But there's some motor create separate electromagnet in order to rotate the rotor. So Kind of motor we going to learn about. It called The 'Synchronous Motor'.

SynchroInous motors are used in cranes,lift and so on. The reason why the motor called 'Synchronous' is the motor rotate at synchronous speed. Why it rotate at synchronous speed ? Well dummies lets find out.

If you read previous post about (Electromagnetism : Squirrel Cage Rotor Vs Wound Rotor) You will understand how these rotor works. So this is how the synchronous motor works.

When the stator gives three phase supply through slip ring,the stator winding will energize. The slip ring is add with external resistance because the huge amount of current can cause windings burn.

  While the rotor will energize by external DC power supply Alternatively, a permanent magnet also can done this process in rotor. So both stator and rotor creates it own magnetic field separately as you can see the schematics at the picture shown above.

 When both get magnetic field separately, The stator revolving magnetic field and rotor magnetic field will align according to the opposite pole. This will make the rotor rotate at synchronous speed.

To calculate the synchronous speed, there's number of poles (P), motor's frequency (Hz) and Angle of degree (120) are include in synchronous speed formula.

Although the motor rotate at synchronous speed, but the motor will not self start because it's lock with stator revolving magnetic field with rotor constant magnetic field. This will eventual damaged the motor by applying external load. To overcome this problem the wound rotor is redesign by adding damper windings A.K.A squirrel cage to induce magnetic field into the damper windings to self start.

Synchronous motor is used in huge fan blower,compressor,pumps and so on. The advantage of this synchronous motor can provide power factor correction and have high efficiency than induction motor. Even loads is are apply to this motor, it will remain the same synchronous speed.But the down side of this motor is have high maintenance and high cost

ELECTRIFYING FACT OF THE DAY :

THE OPPOSITE OF SYNCHRONOUS MOTOR IS CALLED ASYNCHRONOUS MOTOR.

A  ASYNCHRONOUS MOTOR IS AN INDUCTION MOTOR RUN BY INDUCE  REVOLVING MAGNETIC FIELD ON ROTOR WHILE SYNCHRONOUS MOTOR DO THE OPPOSITE.