130 TOP DC MOTORS Interview Questions Answers pdf free Download

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41. Which D.C. motor will be suitable along with flywheel for intermittent light and heavy loads?
(a) Series motor
(b) Shunt motor
(c) Cumulatively compounded motor
(d) Differentially compounded motor
Ans: c

42. If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens
(a) nothing will happen to the motor
(b) this will make armature to take heavy current, possibly burning it
(c) this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses (d) motor will run at very slow speed
Ans: c

43. D.C. series motors are used
(a) where load is constant
(b) where load changes frequently
(c) where constant operating speed is needed
(d) in none of the above situations.
Ans: d

44. For the same H.P. rating and full load speed, following motor has poor starting torque
(a) shunt
(b) series
(c) differentially compounded
(d) cumulativelyc’ompounded
Ans: c

45. In case of conductively compensated D.C. series motors, the compensating winding is provided
(a) as separately wound unit
(6) in parallel with armature winding
(c) in series with armature winding
(d) in parallel with field winding
Ans: c

46. Sparking at the commutator of a D.C. motor may result in
(a) damage to commutator segments
(b) damage to commutator insulation
(c) increased power consumption
(d) all of the above
Ans: d

47. Which of the following motor is preferred for operation in highly explosive atmosphere ?
(a) Series motor
(b) Shunt motor
(c) Air motor
(d) Battery operated motor
Ans: c

48. If the supply voltage for a D.C. motor is increased, which of the following will decrease ?
(a) Starting torque
(b) Operating speed
(c) Full-load current
(d) All of the above
Ans: c

49. Which one of the following is not the function of pole shoes in a D.C. machine ?
(a) To reduce eddy current loss
(b) To support the field coils
(c) To spread out flux for better uniformity
(d) To reduce the reluctance of the magnetic path
Ans: a

50. The mechanical power developed by a shunt motor will be maximum when the ratio of back e.m.f. to applied voltage is
(a) 4.0
(b) 2.0
(c) 1.0
(d) 0.5
Ans: d

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