An induction electric motor which connects with a 3-phase supply called 3-phase induction motor. Example fans,blowers, cranes,traction .It really is a ac engine. The main drawback of DC motors may be the three phase ac induction motor china existence of commutator and brushes, which require frequent maintenance and we can not use DC engine in explosive and dirty environment. But induction motors are cheaper,rugged,lighter,smaller,require less maintenance and may use in dirty and explosive environment. Slip s may be the imp aspect in this type of motor.

There are 2 types of IM.

Squirrel cage IM
Slip ring IM
There are numerous starting and braking condition.

Important starting methods are

Star-delta starter
Auto transformer starter
Ac voltage controller starter
Rotor resistance starter
Important braking methods are

Regenerative braking
Plugging or invert voltage braking
Dynamic braking
But one thing rate control technique of induction electric motor is important

Pole changing
Stator voltage control
V/f control
Slip power recovery
Rotor resistance control