1. Explain the principle of working of a three-phase induction motor. 2. Explain why a three-phase induction motor can not run at synchronous speed. 3. What is meant by slip in an induction motor? What will be the value of slip at starting and at synchronous speed? 4. Is it possible to change the direction of rotation of three phase induction motors? How? 5. Explain the purpose of making two types of rotor construction for three-phase induction motors. 6. Derive an expression for the torque developed in an induction motor. 7. Draw the torque-speed characteristic of a three-phase induction motor and explain its shape. Explain the effect of cogging and crawling on its shape. 8. Show that stator magnetic field and the field produced by the rotor mmf are stationary with respect to each other. 9. Differentiate between slip ring and squirrel cage induction motors 10. Explain why the slots of a double cage induction motors have narrow constriction between the space for placing top and bottom bars. 11. Draw and explain the phasor diagram of a three phase induction motor. 12. Draw the power flow diagram of a three phase induction motor and hence derive the relationship between rotor output, rotor input and slip. 13. With a neat speed characteristics explain the modes of operation of three phase induction motor. 14. List the applications of squirrel cage and slip ring induction motors. 15. List the different methods of speed control of three phase induction motors. Explain them in brief. 16. Show that the maximum torque of a three phase induction motor is independent of rotor resistance but the slip at which the maximum torque occurs is dependent on rotor resistance. 17. Sketch the torque slip characteristics of a three phase induction motor and explain clearly the following: (a) starting torque (b) pull out torque (c) Load torque (d) maximum torque (e) stable and unstable regions of operation. Show the regions on the characteristics. 18. Draw the torque slip characteristics of a three phase induction motor and show three major regions of operation. 19. Draw the torque slip characteristics of single cage, double cage, and deep bar induction motor and comment on the shapes with respect to their rotor construction. 20. With neat circuit diagram explain the no load and blocked rotor test to be conducted on three phase induction motor. Explain how the equivalent circuit parameters can be obtained from the test results. 21. Deduce the parameters of the equivalent circuit of a three phase induction motor considering the rotor to be star connected with N2 turns per phase. Draw the equivalent circuit and insert all the parameters. 22. Explain the need for starters for three phase induction motors. With a neat circuit diagram explain star delta starting of three phase induction motor. 23. Explain the constructional features of a double cage three phase induction motor. 24. Draw the torque speed characteristics of an induction motor when its speed is controlled by (i) voltage control (ii) rotor resistance control (iii) voltage frequency (v/f) control. 25. State the effect of increasing rotor resistance on starting current, maximum torque and full load slip of an induction motor. Page 1 of 2 26. Explain how a three phase induction motor can work as a induction generator. Mention the practical application of this method. Page 2 of 2