Electrical machines are categorized into two..

There are two types of motor.

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

Synchronous motor.
Asynchronous motor.
The basic 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 motor both 12v Motor starting and working torque is necessary. Asynchronous motor has moderate starting torque . Asynchronous motor is certainly a single fed electric motor.In asynchronous engine field is stationary armature rotates .

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

synchronous generator or Alternator: Primary workhorse of the power generation industry; they are rotated mechanically by a primary mover at synchronous quickness and it creates three phase electricity. Picture of PMA found in cars:
2. Synchronous motor: They are constant speed three phase devices capable of working at synchronous swiftness. They are mostly used in constant speed mechanical drives. They are more efficient in comparison 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 rate i.electronic. 3000 rpm. That is achieved through particular constructional features in manufacturing this types of machines. There is absolutely no slip in synchronous devices like regular induction motors.

Normally three phase supply is available commercially and the design is also designed for the same. This is why ‘three phase’ is usually added with synchronous machine name.