An induction motor which connects with a 3-phase supply called 3-stage induction motor. Example fans,blowers, cranes,traction .It is a ac engine. The main drawback of DC motors may be the presence of commutator and brushes, which require frequent maintenance and we can’t use DC motor in explosive and filthy environment. But induction motors are cheaper,tough,lighter,smaller,require much less maintenance and may use in filthy and explosive environment. Slide s may be the imp factor in this type of motor.
There are 2 types of IM.
Squirrel cage IM
Slip ring IM
There are many starting and braking condition.
Important starting methods 
are
three phase ac induction motor china Star-delta starter
Auto transformer starter
Ac voltage controller starter
Rotor resistance starter
Important braking methods are
Regenerative braking
Plugging or reverse voltage braking
Dynamic braking
But one thing swiftness control technique of induction engine is important
Pole changing
Stator voltage control
V/f control
Slip power recovery
Rotor resistance control
