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
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
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
49. In which of the following applications variable speed operation is preferred?
(a) Exhaust fan
(b) Ceiling fan
(c) Refrigerator
(d) Water pump
50. Heavy duty cranes are used in
(a) ore handling plants
(b) steel plants
(c) heavy engineering workshops
(d) all of the above
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
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
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
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
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
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
57. The capacity of a crane is expressed in terms of
(a) type of drive
(b) span
(c) tonnes
(d) any of the above
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
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
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