Exam Question

(a) A three-phase induction motor operates on the principle of electromagnetic induction. A rotating magnetic field is created in the stator (stationary part) by supplying three-phase AC power to its windings. This rotating field induces currents in the rotor (rotating part), which in turn creates its own magnetic field. The interaction between the stator's rotating magnetic field and the rotor's magnetic field produces a torque that causes the rotor to rotate. The rotor speed is slightly less than the speed of the rotating magnetic field, a difference known as slip. The slip is necessary to induce the currents in the rotor that produce the torque.
Types of Rotors in Three-Phase Induction Motors:
Squirrel-Cage Rotor:
Consists of laminated steel sheets with parallel slots carrying heavy copper or aluminum bars. The ends of these bars are short-circuited by end rings, forming a closed loop resembling a squirrel cage.