Electrical Drives MCQs

16. Which feature, while selecting a motor for centrifugal pump, will be of least significance?

(a) Starting characteristics
(b) Operating speed
(c) Horse power
(d) Speed control

Answer. d

17. ………….. motor is a constant speed motor.

(a) Synchronous motor
(b) Schrage motor
(c) Induction motor
(d) Universal motor

Answer. a

18. The starting torque in case of centrifugal pumps is generally

(a) less than running torque
(b) same as running torque
(c) slightly more than running torque
(d) double the running torque

Answer. a

19. Which of the following motors are best for the rolling mills?

(a) Single phase motors
(b) Squirrel cage induction motors
(c) Slip ring induction motors
(d) D.C. motors

Answer. d

20. ……………… is not a part of ball bearing?

(a) Inner race
(b) Outer race
(c) Cage
(d) Bush

Answer. d

21. The starting torque of a D.C. motor is independent of which of the following?

(a) Flux
(b) Armature current
(c) Flux and armature current
(d) Speed

Answer. d

22. A rotor of a motor is usually supported on bearings.

(a) ball or roller
(b) needle
(c) bush
(d) thrust

Answer. a

23. For which of the following applications D.C. motors are still preferred?

(a) High-efficiency operation
(b) Reversibility
(c) Variable speed drive
(d) High starting torque

Answer. c

24. In a paper mill where constant speed is required

(a) synchronous motors are preferred
(b) A.C. motors are preferred
(c) individual drive is preferred
(d) group drive is preferred

Answer. c

25. A reluctance motor

(a) is provided with slip rings
(b) requires starting gear
(c) has high cost
(d) is compact

Answer. d

26. The size of an excavator is usually expressed in terms of

(a) ‘crowd’ motion
(b) angle of swing
(c) cubic metres
(d) travel in metres

Answer. c

27. For blowers which of the following motor is preferred?

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

Answer. c

28. Belted slip ring induction motor is almost invariably used for

(a) water pumps
(b) jaw crushers
(c) centrifugal blowers
(d) none of the above

Answer. b

29. Which of the following is essentially needed while selecting a motor?

(a) Pulley
(b) Starter
(c) Foundation pedal
(d) Bearings

Answer. b

30. Reluctance motor is a …………………

(a) variable torque motor
(b) low torque variable speed motor
(c) self-starting type synchronous motor
(d) low noise, slow speed motor

Answer. c

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