Electrical Power Engineering Multiple Choice Questions and Answers (MCQs) Part 12:
552. The electric motor used for traction work should be mechanically
(a) small in overall dimensions (specially in its overall diameter).
(b) light in weight and robust in construction.
(c) capable to withstand continuous vibrations.
(d) all of the above.
Answer : (d) all of the above.
553. 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.
Answer : (d) all of the above.
554. In suburban trains, the traction motors are installed on
(a) locomotive only.
(b) locomotive and coaches.
(c) coaches only.
Answer : (a) locomotive only.
555. The type of dc motor used in electric traction is
(a) series.
(b) shunt.
(c) separately-excited.
(d) none of the above.
Answer : (a) series.
556. 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.
Answer : (c) dc series motors are capable of developing high torque at start.
557. 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 speed control system and complicated overhead feeding systems.
(c) higher initial as well maintenance cost.
(d) both (a) and (b).
Answer : (d) both (a) and (b).
558. DC shunt motors arc 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.
Answer : (e) all of the above.
559. Two dc shunt motors having identical characteristics are used to drive a train car with unequal wheel diameters. The two motors share load equally if they are connected in
(a) series.
(b) parallel.
(c) the loading will always be unequal.
Answer : (a) series.
560. 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
Answer : (a) larger
561. 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.
Answer : (d) all of the above.
562. 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.
Answer : (b) high starting torque without excessive starting current.
563. A locomotive exerts a tractive effort of 40,000 N in pulling a train at 60 kmph on a level track. If the same train is to be hauled at the same speed but on gradient, the tractive effort required will be 60,000 N. The output delivered by the motor will be more if it is driven by
(a) a 3-phase induction motor.
(b) a dc series motor.
(c) an ac series motor.
(d) equal in all the three cases.
Answer : (a) a 3-phase induction motor.
564. When two or more motors are used for traction service, the method of speed control used will be
(a) rheostatic control.
(b) series-parallel control.
(c) field control.
(d) motor generator control.
Answer : (b) series-parallel control.
565. The advantage(s) of series-parallel starting is/are
(a) small energy loss and higher efficiency.
(b) economical speed control.
(c) higher reliability of operation.
(d) all of the above.
Answer : (d) all of the above.
566. Parallel operation of traction motors is easier with
(a) dc shunt motors.
(b) dc series motors.
(c) induction motors.
(d) none of these.
Answer : (b) dc series motors.
568. In motor-generator locomotive control
(a) rheostatic control is used.
(b) series parallel control is used.
(c) the output voltage of generator is regulated by means of field control from exciter.
(d) any one of the above method is used.
Answer : (c) the output voltage of generator is regulated by means of field control from exciter.
569. In metadyne control,
(a) current throughout the accelerating period remains constant.
(b) tractive effort developed is uniform.
(c) there is no wastage of energy in starting rheostat.
(d) all of the above.
Answer : (d) all of the above.
570. The method of speed control adopted in 25 kV, single-phase, 50 Hz traction is
(a) tap changing control of transformer.
(b) reduced current method.
(c) series-parallel control.
(d) rheostatic control.
Answer : (a) tap changing control of transformer.
571. The preferable method of speed control of linear induction motor is
(a) variable flux control.
(b) PAM control.
(c) variable frequency and constant voltage control.
(d) variable frequency and variable voltage control.
Answer : (c) variable frequency and constant voltage control.
572. Which of the following braking systems on the locomotives is costly ?
(a) Vacuum braking on steam locomotives.
(b) Vacuum braking on diesel locomotives.
(c) Regenerative braking on electric locomotives.
(d) All braking systems are equally costly.
Answer : (c) Regenerative braking on electric locomotives.
573. The braking system employed with steam locomotives is
(a) vacuum system.
(b) pneumatic system.
(c) hyraulic system.
(d) any of the above.
Answer : (a) vacuum system.
574. Braking system employed in diesel electric traction is
(a) hydraulic type.
(b) vacuum type.
(c) regenerative type.
(d) any of these.
Answer : (b) vacuum type.
575. The type of braking used in electric traction is
(a) mechanical braking.
(b) vacuum brake system.
(c) electropneumatic braking.
(d) both (a) and (c).
Answer : (c) electropneumatic braking.
576. Vacuum is created by
(a) vacuum pumps.
(b) ejector.
(c) vacuum pump or ejector.
(d) none of the above.
Answer : (c) vacuum pump or ejector.
577. Bearings employed for supporting axles of rolling stock are
(a) bush bearings.
(b) roller bearings.
(c) ball bearings.
(d) journal bearings.
Answer : (b) roller bearings.
578. The wheels of a train, engine as well as bogies, are slightly tapered so as to
(a) reduce friction.
(b) increase friction.
(c) facilitate in taking turns.
(d) facilitate braking.
Answer : (c) facilitate in taking turns.
579. B0B0 locomotives have two bogies with
(a) two driving axles with individual drive motors.
(b) two driving axles with group drives.
(c) four driving axles with individual drive motors.
(d) four driving axles with group drives.
Answer : (a) two driving axles with individual drive motors.
580. A locomotive for Indian Railways has been designated as WAM. In this W indicates that
(a) the locomotive is to run on metre gauge track.
(b) the locomotive is to operate on broad gauge track.
(c) the locomotive is for goods trains only.
(d) the locomotive is only for shunting duty.
Answer : (b) the locomotive is to operate on broad gauge track.
581. Locomotives with manometer bogies
(a) are suited both for passengers as well as freight service.
(b) have better coefficient of adhesion.
(c) have better riding qualities owing to reduction of lateral forces.
(d) all of the above.
Answer : (d) all of the above.
582. Factor(s) affecting the design of rolling stock is/are
(a) environmental condition.
(b) vibrations and shocks.
(c) unbalanced and fluctuating supply voltages for auxiliaries.
(d) all of the above.
Answer : (d) all of the above.
583. In electric traction if contact voltage exceeds 1,500 V, current collection is invariably by
(a) a contact rail.
(b) a conductor rail.
(c) overhead wire.
(d) third rail.
Answer : (c) overhead wire.
584. Conductor rail system of supply is
(a) cheap and easy to repair and inspection.
(b) suitable for heavy current collection at voltages up to 1,200 V.
(c) universally used for all ac railways.
(d) both (a) and (b).
Answer : (d) both (a) and (b).
585. Overhead lines for power supply to tram cars are at a minimum height of a
(a) 10 m
(b) 8 m
(c) 5 m
(d) 15 m
Answer : (a) 10 m
586. The current collector that can be employed with different speeds under all wind conditions and stiffness of OHE is known as the
(a) messenger collector.
(b) pantograph collector.
(c) trolley collector.
(d) bow collector.
Answer : (b) pantograph collector.
587. DC track circuit consists of
(a) amplitude modulation equipment.
(b) a negative booster, feeding points and signals.
(c) insulated joint and track, track bonding, regulating resistance, track battery to track relay.
(d) all of the above.
Answer : (c) insulated joint and track, track bonding, regulating resistance, track battery to track relay.
588. In case of bow and pantograph current collectors
(a) the pantograph current collector is employed for large currents at higher speeds.
(b) the pantograph current collector is employed for large currents at lower speeds.
(c) the bow current collector is employed for large currents at higher speeds.
(d) the bow current collector is employed for large currents at lower speeds.
Answer : (a) the pantograph current collector is employed for large currents at higher speeds.
589. Contact with wire is maintained by
(a) air pressure in both bow and pantograph current collectors.
(b) springs in both bow and pantograph current collectors.
(c) spring in case of bow and air pressure in case of pantograph.
(d) spring in case of pantograph and air pressure in case of bow collectors.
Answer : (b) springs in both bow and pantograph current collectors.
590. Factors affecting quality of current collection in pantograph is/are
(a) contact pressure.
(b) effective mass of frame and span.
(c) adequate damping in the frame.
(d) all of the above.
Answer : (d) all of the above.
591. Advantages of two-stage pantograph is/are
(a) inertia forces are reduced.
(b) takes care of variation in contact height and displacement of contact wire between supports.
(c) takes care of low amplitude displacement of contact wire between droppers.
(d) all of the above.
Answer : (d) all of the above.
592. Span length between supports in electric traction is determined by
(a) weight of wire per unit length.
(b) maximum wind pressure.
(c) permissible tension in the wire and speed of train.
(d) all of the above.
Answer : (d) all of the above.
593. Electrical circuit breaker is
(a) connected between the current collector and the main wiring.
(b) provided on the electric locomotive to protect the electrical equipment against excessive overloads automatically.
(c) provided with a handle to trip it when it is moved to the OFF position by hand.
(d) all of the above.
Answer : (b) provided on the electric locomotive to protect the electrical equipment against excessive overloads automatically.
594. The characteristics of OHE depend on
(a) loss of contact and its duration.
(b) temperature and wear of contact wire.
(c) quality of current collection and pantograph pressure on contact wire.
(d) height, stagger, push up of an gradient of contact wire.
(e) all of the above.
Answer : (e) all of the above.
595. Insulated overlaps are employed in electric traction to provide
(a) protection of transmission equipment in electric locomotives.
(b) isolating facilities required for the maintenance and operation of OHE.
(c) protection of signals in EMU trains.
(d) gap between adjacent terminal sections of railways.
Answer : (b) isolating facilities required for the maintenance and operation of OHE.
596. Neutral sections are provided in single-phase ac traction as
(a) to protect the system from lightning strokes.
(b) supply cannot be maintained from adjacent substations at reduced voltage drops.
(c) adjacent substations tap different phases of three-phase system to achieve balancing.
(d) to provide return section for the communication purpose.
Answer : (c) adjacent substations tap different phases of three-phase system to achieve balancing.
597. Use of booster transformers is restricted to urban areas because
(a) there are no earth and water currents.
(b) they are subjected to densely populated areas and so need protection.
(c) they complicate the OHE and cause more faults in the system and thus reduce the system reliability.
(d) they increase the impedance and need feeding posts to be located at close intervals.
(e) both (c) and (d).
(f) all of the above.
Answer : (e) both (c) and (d).
598. Negative booster
(a) is a separately-excited generator whose armature is connected to negative busbar and far end of the track through negative feeder.
(b) creates low voltage level in the track to allow all currents to flow through it.
(c) provides protection against earth fault currents.
(d) causes additional voltage drop necessary for smooth operation.
(e) both (a) and (b).
Answer : (e) both (a) and (b).
599. In long distance electric trains power for lighting in passenger coaches is provided
(a) through rails.
(b) through locomotive.
(c) through individual generator of bogie and batteries.
(d) directly from overhead electric lines.
Answer : (c) through individual generator of bogie and batteries.
600. Power requirements of a train lighting and air-conditioning is met by
(a) servogenerators.
(b) chargeable batteries in each compartment.
(c) axle driven generators in conjunction with batteries.
(d) either of (b) or (c).
Answer : (c) axle driven generators in conjunction with batteries.
601. Coach air-conditioning equipment includes
(a) standard refrigeration equipment.
(b) mechanical power generating equipment.
(c) electrical equipment for control with accessories.
(d) an air-conditioner with its standard accessories.
(e) all of the above except (d).
Answer : (e) all of the above except (d).
602. Requirement(s) of a railway coach air-conditioning is/are
(a) to provide heating/cooling.
(b) to supply clean, fresh air at a controlled uniform temperature.
(c) sufficient power requirement.
(d) to account for charging passenger traffic.
(e) all of the above.
Answer : (e) all of the above.