Electrical Drives MCQs

31. ………………….. method of starting a three phase induction motor needs six terminals.

(a) Star-delta
(b) Resistance starting
(c) Auto-transformer
(d) None of the above

Answer
Answer. a

32. In ………………… method of starting three phase induction motors, the starting voltage is not reduced.

(a) auto-transformer
(b) star-delta
(c) slip ring
(d) any of the above

Answer
Answer. c

33. In jaw crushers, a motor has too often started against ………………. load.

(a) heavy
(b) medium
(c) normal
(d) low

Answer
Answer. a

34. For a motor-generator set which of the following motors will be preferred?

(a) Synchronous motor
(b) Slip ring induction motor
(c) Pole changing induction motor
(d) Squirrel cage induction motor

Answer
Answer. a

35. Which of the following motors are usually preferred for kiln drives?

(a) Cascade controlled A.C. motor
(b) Slip ring induction motor
(c) Three phase shunt wound commutator motor
(d) Any of the above

Answer
Answer. d

36. Heat control switches are used in

(a) Transformers
(b) cooling ranges
(c) three phase induction motors
(d) single phase

Answer
Answer. b

37. ……………………  has a relatively wider range of speed control.

(a) Synchronous motor
(b) Ship ring induction motor
(c) Squirrel cage induction motor
(d) D.C. shunt motor

Answer
Answer. d

38. In squirrel cage induction motors which of the following methods of starting cannot be used?

(a) Resistance in rotor circuit
(b) Resistance in stator circuit
(c) Auto-transformer starting
(d) Star-delta starting

Answer
Answer. a

39. In which of the following applications the load on motor changes in cyclic order?

(a) Electric shovels
(b) Cranes
(c) Rolling mills
(d) All of the above

Answer
Answer. d

40. Flame proof motors are used in

(a) paper mills
(b) steel mills
(c) moist atmospheres
(d) explosive atmospheres

Answer
Answer. d

41. Which of the following machines has a heavy fluctuation of load?

(a) Printing machine
(b) Punching machine
(c) Planer
(d) Lathe

Answer
Answer. b

42. For derries and winches which of the following drives can be used?

(a) Pole changing squirrel cage motors
(b) D.C. motors with Ward-Leonard control
(c) A.C. slip ring motors with variable resistance
(d) Any of the above

Answer
Answer. d

43. Battery operated scooter for braking uses

(a) plugging
(b) mechanical braking
(c) regenerative braking
(d) rheostatic braking

Answer
Answer. b

44. ………………… has least range of speed control.

(a) Slip ring induction motor
(b) Synchronous motor
(c) D.C. shunt motor
(d) Schrage motor

Answer
Answer. b

45. …………………… has the least value of starting torque to full load torque ratio.

(a) D.C. shunt motor
(b) D.C. series motor
(c) Squirrel cage induction motor
(d) Slip ring induction motor

Answer
Answer. c

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