Electrical Drives MCQs

46. In case of speed control by injecting e.m.f. in the rotor circuit is possible.

(a) d.c. shunt motor
(b) dc series motor
(c) synchronous motor
(d) slip ring induction motor

Answer
Answer. d

47. A pony motor is used for the starting which of the following motors?

(a) Squirrel cage induction motor
(b) Schrage motor
(c) Synchronous motor
(d) None of the above

Answer
Answer. c

48. In …………………….. the speed can be varied by changing the position of brushes.

(a) slip ring motor
(b) Schrage motor
(c) induction motor
(d) repulsion motor

Answer
Answer. b

49. In which of the following applications variable speed operation is preferred?

(a) Exhaust fan
(b) Ceiling fan
(c) Refrigerator
(d) Water pump

Answer
Answer. b

50. Heavy duty cranes are used in

(a) ore handling plants
(b) steel plants
(c) heavy engineering workshops
(d) all of the above

Answer
Answer. d

51. The travelling speed of cranes varies from

(a) 20 to 30 m/s
(b) 10 to 15 m/s
(c) 5 to 10 m/s
(d) 1 to 2.5 m/s

Answer
Answer. d

52. Besides a constant speed, a synchronous rotor possesses which of the following advantages?

(a) Lower cost
(b) Better efficiency
(c) High power factor
(d) All of the above

Answer
Answer. c

53. By the use of which of the following D.C. can be obtained from A.C.?

(a) Silicon diodes
(b) Mercury arc rectifier
(c) Motor generator set
(d) Any of the above

Answer
Answer. d

54. Which of the following motors are preferred when quick speed reversal is the main consideration?

(a) Squirrel cage induction motor
(b) Wound rotor induction motor
(c) Synchronous motor
(d) D.C. motor

Answer
Answer. d

55. Which of the following motors are preferred when smooth and precise speed control over a wide range is desired?

(a) D.C. motor
(b) Squirrel cage induction motor
(c) Wound rotor induction motor
(d) Synchronous motor

Answer
Answer. a

56. For crane travel which of the following motors is normally used?

(a) Synchronous motor
(b) D.C. differentially compound motor
(c) Ward-Leonard controlled D.C. shunt motor
(d) A.C. slip ring motor

Answer
Answer. d

57. The capacity of a crane is expressed in terms of

(a) type of drive
(b) span
(c) tonnes
(d) any of the above

Answer
Answer. c

58. The characteristics of a drive for crane hoisting and lowering are which of the following?

(a) Precise control
(b) Smooth movement
(c) Fast speed control
(d) All of the above

Answer
Answer. d

59. Which of the following motors are preferred for boom hoist of a traveling crane?

(a) Single phase motor
(b) Synchronous motor
(c) A.C. slip ring motor
(d) Ward-Leonard controlled D.C. shunt

Answer
Answer. c

60. A wound rotor induction motor is preferred, as compared to squirrel cage induction motor, when major consideration is

(a) slop speed operation
(b) high starting torque
(c) low windage losses
(d) all of the above

Answer
Answer. b

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