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Electrical Engineering Objective Questions { Induction Motors }

43. 5 H.P., 50-Hz, 3-phase, 440 V, induction motors are available for the following r.p.m. Which motor will be the costliest?
A. 730 r.p.m.
B. 960 r.p.m.
C. 1440 r.p.m.
D. 2880 r.p.m.

44. A 3-phase slip ring motor has
A. double cage rotor
B. would rotor
C. short-circuited rotor
D. any of the above

45. The torque developed in an induction motor is nearly proportional to
A. V ?
B. V
C. V2
D. V2

46. Short-circuit test on an induction motor cannot be used to determine
A. windage losses
B. copper losses
C. transformation ratio
D. power scale of circle diagram

47. In a three-phase induction motor
A. iron losses in stator will be negligible as compared to that in rotor
B. iron losses in motor will be negligible as compared to that in rotor
C. iron losses in stator will be less than that in rotor
D. iron losses in stator will be more than that in rotor

48. In case of 3-phase induction motors, plugging means
A. pulling the motor directly on line without a starter
B. locking of rotor due to harmonics
C. starting the motor on load which is more than the rated load
D. interchanging two supply phases for quick stopping

49.  Which is of the following data is required to draw the circle diagram for an induction motor?
A. Block rotor test only
B. No load test only
C. Block rotor test and no-load test
D. Block rotor test, no-load test and stator resistance test

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