Three phase induction motor is one of ac machines family. It converts the ac electrical power input into a mechanical power output. The conversion process takes place through the rotating magnetic field. Its theory of operation is based on the mutual electromagnetic induction between the primary circuit and secondary circuit. Three-phase induction motors are the most widely used electric motors in industry. When fed from constant voltage constant frequency they run at nearly constant speed from no-load to full-load. 3-phase induction motors are simple, rugged, low-priced, easy to maintain and can be manufactured with characteristics to suit most industrial requirements. Nowadays, with the development of power semiconductors, induction motors may be considered as serious rivals to dc motors in many speed control systems.