Electrical machines are classified into two..
Motor.
Generator.
There are two kinds of motor.
AC motor.
DC motor.
There are two types of three phase motor.
Synchronous motor.
Asynchronous motor.
The essential difference between asynchronous and synchronous electric motor , slip presents in asynchronous 12v Motor engine .At running condition slide of an asynchronous engine lies from 0 to at 
least one 1. . In asynchronous motor both starting and working torque is required. Asynchronous engine has moderate starting torque . Asynchronous motor can be a single fed engine.In asynchronous electric motor 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 energy generation industry; they are rotated mechanically by a primary mover at synchronous quickness and it generates three phase electricity. Picture of PMA found in cars:
2. Synchronous motor: They are continuous speed three phase machines capable of running at synchronous quickness. They are mostly found in constant acceleration mechanical drives. They are better 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.
In other words, 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.e. 3000 rpm. That is achieved through unique constructional features in production this types of machines. There is no slip in synchronous devices like regular induction motors.
Normally three phase supply is available commercially and the design is also meant for the same. This is why ‘three phase’ is definitely added with synchronous machine name.
