Electric Traction MCQ

61. Specific energy consumption is affected by

(a) acceleration and retardation values.
(b) the crest speed and nature of route.
(c) distance between stops.
(d) all of the above.

62. Specific energy consumption is minimum in……….services.

(a) main line
(b) urban
(c) suburban
(d) equal for all type of

63. Specific energy consumption

(a) increases with the increase in maximum speed.
(b) decreases with the increase in maximum speed.
(c) is independent of maximum speed.
(d) none of the above.

64. If the speed-time curves are similar (not identical), the specific energy consumption of the curve having higher maximum speed is …….. than that of lower maximum speed.

(a) lower
(b) equal
(c) higher
(d) none

65. Specific energy consumption becomes

(a) more when distance between stops is more.
(b) more with the higher values of acceleration (or retardation).
(c) more with high train resistance.
(d) less with the increase in crest speed.

66. The specific energy consumption for suburban services is usually ………. watt-hours per tonne-km.

(a) 20 – 30
(b) 30 – 45
(c) 50 – 75
(d) 100 – 150

67. The specific energy consumption for main line services is around …….. watt hours per tonne-km.

(a) 20 – 30
(b) 30 – 45
(c) 50 – 75
(d) 100 – 150

68. Specific energy consumption is maximum in ………. services.

(a) urban
(b) suburban
(c) main line
(d) equal for all types of

69. The electric motor used for traction work should be mechanically

(a) small in overall dimensions (especially in its overall diameter).
(b) light in weight and robust in construction.
(c) capable to withstand continuous vibrations.
(d) all of the above.

70. The electric motor used for traction work, electrically should be

(a) capable of developing high starting torque and withstanding voltage fluctuations, and temporary supply interruptions.
(b) amenable to simple speed control methods, self protective against excessive overloading and amenable to easy and simple methods of rheostatic and/or regenerative braking.
(c) of such characteristics that when they are operated in parallel and coupled mechanically, they share the load almost equal.
(d) all of the above.

71. In suburban trains, the traction motors are installed on

(a) locomotive only.
(b) locomotive and coaches.
(c) coaches only.

72. The type of dc motor used in electric traction is

(a) series.
(b) shunt.
(c) separately-excited.
(d) none of the above.

73. The dc series motor is most suitable for traction services but more particularly for urban/suburban services because

(a) dc series motors are suitable for regenerative braking.
(b) dc series motors are capable of withstanding rapid fluctuations in supply voltage.
(c) dc series motors are capable of developing high torque at start.
(d) dc series motors are capable of withstanding temporary interruption of supply without undue rush of current.

74. The three-phase induction motors have the advantages of simple and robust in construction, trouble free operation, high voltage operation consequently requiring reduced amount of current and automatic regeneration but are not suitable for traction work. This is because of their

(a) flat speed-torque characteristics, constant speed operation and low starting torque.
(b) complicated sped control system and complicated overhead feeding systems.
(c) higher initial as well maintenance cost.
(d) both (a) and (b).

76. DC shunt motors are not suitable for traction services because of their

(a) hard characteristics.
(b) large time constant.
(c) power varying directly with developed torque.
(d) wide variation in torque and flux due to variation in voltage in electric traction.
(e) all of the above.

77. Two dc shunt motors having identical characteristics are used drive a train car with unequal wheel diameters. The two motors will share load equally if they are connected in

(a) series.
(b) parallel.
(c) the loading will always be unequal.

78. Two locomotives having identical tractive effort-slip characteristics haul a heavy train. The loco with larger diameter shares …….. tractive effort.

(a) larger
(b) smaller
(c) equal

79. For single-phase ac system of track electrification, low frequency is desirable as

(a) it improves commutation properties of ac motors.
(b) it increases efficiency of ac motors.
(c) it improves power factor of ac motors.
(d) all of the above.

80. At low frequency of the order of 1/2 Hz to 10 Hz, the induction motor develops

(a) high starting torque with excessive starting current.
(b) high starting torque without excessive starting current.
(c) low starting torque with excessive starting current.
(d) low starting torque without excessive starting current.