TORQUE

Torque is produced from the rotational motion. Torque is equal to force times the radius through which it moves.
The torque developed T is given-

Initially when the motor starts, the slip is high. The torque produced is proportional to the speed. However when the motor attains stable speed, slip is negligible and the torque is inversely proportional to the speed.

The shaft of a induction motor rotates because of the torque produced by the interaction between the magnetic field of the stator and the magnetic field in the rotor. The amount of torque produced by the motor is determined by how stron the magnetic fields are. The strength of the stator field remains fairley constant altoough the strength of the rotors field changes causing the torque to vary.

The moment the stator is energised the stators magnetic field is produced and begins to rotate, although the rotor remains stationary. At this moment in time the positions of the rotor and stator magnetic fields couldn’t be any more different. Maximum voltage is induced into the rotor and the resultant magnetic field is at its strongest and large amount of torque is created. The large amount of torque is good because a large torque is needed to overcome the stationary weight of the load.

As the rotor comes close to the synchronous speed of the stator field less voltage is induced into the rotor so its magnetic field weakens so less torque is developed.

When the speed of the rotor stabilizes to a