Steady-State Characteristics of a Torque and Speed Control System of an Induction Motor Utilizing Rotor Slot Harmonics for Slip Frequency Sensing

A method is proposed to detect the slip frequency of a three phase squirrel-cage induction motor from rotor slot harmonics. A method of torque and speed control of the induction motor using the proposed slip frequency detector is presented. The torque and speed control system is realized considering characteristics of the slip frequency detector. Experimental results show that the proposed slip frequency detector realizes precise control of the rotor speed and torque over a wide range of the rotor speed (200-300 to 2500 r/min) except for a low-speed region.