Electrical Drives MCQ Questions

1. 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

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2. Which of the following motors is 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

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3. 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

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

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

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5. The characteristics of 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

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6. Which of the following motor is preferred for boom hoist of a travelling crane ?

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

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7. Which of the following motors has series characteristics ?

(a) Shaded pole motor
(b) Repulsion motor
(c) Capacitor start motor
(d) None of the above

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8. For a D.C. shunt motor which of the following is incorrect?

(a) Unsuitable for heavy duty starting
(b) Torque varies as armature current
(c) Armature current is a straight line
(d) Torque is zero for zero armature current

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9. For which of the following applications motor has to start with high acceleration?

(a) Oil expeller
(b) Floor mill
(c) Lifts and hoists
(d) Centrifugal pump

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10. Which of the following types of motor enclosure is safest ?

(a) Totally enclosed
(b) Totally enclosed fan cooled
(c) Open type
(d) Semi closed

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11. While selecting motor for an air conditioner which of the following characteristics is of great importance?

(a) Type of bearing
(b) Type of enclosure
(c) Noise
(d) Arrangement for power transmission

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12. The diameter of the rotor shaft for an electric motor depends on which of the following?

(a) r.p.m. only
(b) Horse power only
(c) Horse power and r.p.m.
(d) Horse power, r.p.m. and power factor

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13. Which of the following alternatives will be cheaper?

(a) A 100 H.P. A.C. three phase motor
(b) Four motors of 25 H.P. each
(c) Five motors of 20 H.P. each
(d) Ten motors of 10 H.P. each

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14. The cost of an induction motor will increase as

(a) horsepower rating increases but r.p.m. decreases
(b) horsepower rating decreases but r.p.m. increases
(c) horsepower rating and operating speed increases
(d) horsepower rating and operating speed decreases

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15. In series motor which of the following methods can he used for changing the flux per pole ?

(a) Tapped field control
(b) Divertor field control
(c) Series-parallel control
(d) Any of the above

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16. Which of the following drives is suitable for mines where explosive gas exists?

(a) Steam engine
(b) Diesel engine
(c) Battery locomotive
(d) Any of the above

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17. The wheels of a train, engine as well bogies, are slightly tapered to

(a) reduce friction
(b) increase friction
(c) facilitate braking
(d) facilitate in taking turns

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18. Which of the following is the advantage of electric braking ?

(a) It avoids wear of track.
(b) Motor continues to remain loaded during braking.
(c) It is instantaneous.
(d) More heat is generated during breaking.

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19. Which of the following braking systems on the locomotives is costly ?

(a) Regenerative braking on electric locomotives
(b) Vacuum braking on diesel locomotive
(c) Vacuum braking on steam locomotive
(d) All braking systems are equally costly

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20. Tractive effort is required to

(a) overcome the gravity component of train mass
(b) overcome friction, windage and curve resistance
(c) accelerate the train mass
(d) do all of the above

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21. For given maximum axle load, tractive efforts of A.C. locomotive will be

(a) less than that of D.C. locomotive
(b) more than that of D.C. locomotive
(c) equal to that of D.C. locomotive
(d) none of the above

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22. Co-efficient of adhesion reduces due to the presence of which of the following?

(a) Sand on rails
(b) Dew on rails
(c) Oil on the rails
(d) Dew and oil on the rails

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23. Due to which of the following coefficient of adhesion improves ?

(a) Rust on the rails
(b) Dust on the rails
(c) Sand on the rails
(d) All of the above

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24. Quadrilateral speed-time curve pertains to which of the following service?

(a) Main lime service
(b) Urban service
(c) Sub-urban service
(d) Urban and sub-urban service

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25. Which of the following is the disadvantage of electric traction over other systems of traction ?

(a) Corrosion problems in the underground pipe work.
(b) Short time power failure interrupts traffic for hours.
(c) High capital outlay in fixed installations beside route limitation.
(d) Interference with communication lines.
(e) All of the above

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26. Speed-time curve of main line service differs from those of urban and sub-urban services on following account

(a) it has longer free running period
(b) it has longer wresting period
(c) accelerating and braking periods are comparatively smaller
(d) all of the above

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27. The rate of acceleration on suburban or urban services in restricted by the consideration of

(a) engine power
(b) track curve
(c) passenger discomfort
(d) track size

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