Electrical machines are classified into two..

There are two types of motor.

AC motor.
DC motor.
There are two kinds of three phase motor.

Synchronous motor.
Asynchronous motor.
The essential difference between asynchronous and synchronous electric motor , slip presents in asynchronous engine .At running condition slip of an asynchronous electric motor lies from 0 to at least one 1. . In asynchronous engine both starting and working torque is necessary. Asynchronous engine has moderate beginning torque . Asynchronous motor is usually a 12v Motor single fed motor.In asynchronous electric motor field is stationary armature rotates .

Three phase synchronous machines have got a stationary three phase armature and a wound rotor. They are of two types:

synchronous generator or Alternator: Main workhorse of the energy generation industry; they are rotated mechanically by a prime mover at synchronous swiftness and it generates three phase electricity. Picture of PMA found in cars:
2. Synchronous motor: They are continuous speed three phase machines capable of working at synchronous swiftness. They are mostly used in constant swiftness mechanical drives. They are more efficient compared to induction motors.
A synchronous machine has derived its name from the concept that the rotor will rotate in synchronicity with the rotating magnetic field.

Simply speaking, for a 2 Pole machine (electric motor) the rotating magnetic field rotates at 3000 rpm; the rotor of synchronous machine also rotates at the same acceleration i.electronic. 3000 rpm. This is achieved through special constructional features in manufacturing this types of devices. There is no slip in synchronous devices like normal induction motors.

Normally three phase supply is available commercially and the look is also designed for the same. That is why ‘three phase’ is definitely added with synchronous machine name.