THREE PHASE INDUCTION MOTORS MCQs – CHAPTER 4 DAE

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1. An induction motor works with;





2. The stator frame in an induction motor is used to;





3. Regarding skewing of motor bars in a squirrel cage induction motor (SCIM), which statement is false?





4. The principle of operation of a 3-phase induction motor is most similar to that of a;





5. The magnetizing current drawn by transformers and induction motors are the cause of their .........power factor.





6. The effect of increasing the length of air-gap in an induction motor will be to increase the;





7. In a 3-phase induction motor, the relative speed of stator flux with respect to ..........is zero.





8. An eight-pole wound rotor induction motor operating on 60 Hz supply is driven at 1800 r.p.m. by a prime mover in the opposite direction of revolving magnetic field. The frequency of rotor current is;





9. A 3-phase, 4-pole, 50-Hz induction motor runs at a speed of 1440 r.p.m. The rotating field produced by the rotor rotates at a speed of .......r.p.m. with respect to the rotor.





10. In a 3-φ induction motor, the rotor field rotates at synchronous speed with respect to;





11. Irrespective of the supply frequency, the torque developed by a SCIM is the same whenever ........ is the same.





12. The number of stator poles produced in the rotating magnetic field of a 3-φ induction motor having 3 slots per pole per phase is;





13. The power factor of a squirrel-cage induction motor is;





14. Which of the following rotor quantities in a SCIM does NOT depend on its slip?





15. A 6-pole, 50-Hz, 3-φ induction motor is running at 950 rpm and has rotor Cu loss of 5 kW. Its rotor input is ......kW.





16. The efficiency of a 3-phase induction motor is approximately proportional to;





17. A 6-pole, 50-Hz, 3-φ induction motor has a full load speed of 950 rpm. At half-load, its speed would be ......rpm.





18. If rotor input of a SCIM running with a slip of 10% is 100 kW, gross power developed by its rotor is ...... kW.





19. Pull-out torque of a SCIM occurs at that value of slip where rotor power factor equals;





20. When applied rated voltage per phase is reduced by one-half, the starting torque of a SCIM becomes ...... of the starting torque with full voltage.





21. The torque developed by a 3-phase induction motor depends on the following three factors:





22. The efficiency and p.f. of a SCIM increases in proportion to its;





23. A SCIM runs at constant speed only so long as;





24. The number of slip rings on a squirrel cage induction motor is usually;





25. The shaft of an induction motor is;





26. The frame of an induction motor is usually made of;





27. The crawling in an induction motor is caused by;





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