An induction electric motor which connects with a 3-stage supply called 3-stage induction motor. Example followers,blowers, cranes,traction .It is a ac engine. The main drawback of DC motors is the presence of commutator and brushes, which require regular maintenance and we can not use DC electric motor in explosive and filthy environment. But induction motors are cheaper,rugged,lighter,smaller,require less maintenance and can use in filthy and explosive environment. Slide s may be the imp aspect in this kind 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 speed control technique of induction engine is important

Pole three phase ac induction motor changing
Stator voltage control
V/f control
Slip power recovery
Rotor resistance control