DC Generator MCQ Questions

1. In a DC generator, the ripples in the generated DC are reduced by employing

(a) commutator with large number of segments.
(b) equalizer rings.
(c) carbon brushes.
(d) graphite brushes.

SHOW ANSWER

2. In order to ascertain whether a DC machine is lap wound or wave wound on the basis of visual observations of the armature, one should observe the

(a) connections to the brushes
(b) connections to the commutator.
(c) connections to the field winding
(d) direction of end connections.

SHOW ANSWER

3. The coil span

(a) must be exactly equal to pole pitch.
(b) can never be equal to pole pitch.
(c) may or may not be equal to pole pitch.
(d) none of the above.

SHOW ANSWER

4. The commutator pitch for simplex lap winding is

(a) +1
(b) -1
(c) +1 or -1
(d) average pitch

SHOW ANSWER

5. The commutator pitch for simplex wave winding is

(a) +1 or -1
(b) twice average pitch.
(c) average pitch.
(d) half average pitch.

SHOW ANSWER

6. In a DC machine armature winding, the number of commutator segments is equal to the number of armature

(a) coils.
(b) coil sides.
(c) conductors.
(d) turns.

SHOW ANSWER

7. In a drum type DC armature winding the back pitch and front pitch in terms of the coil-sides must be

(a) even and odd respectively.
(b) odd and even respectively.
(c) both even.
(d) both odd.

SHOW ANSWER

8. In a DC machine, fractional pitch is employed to

(a) increase generated voltage.
(b) reduce sparking.
(c) save copper.
(d) improve cooling.
(e) both (b) and (c).

SHOW ANSWER

9. In a DC machine, the armature winding is made up of number of coils distributed in large number of armature slots instead of placing all the coils into two slots to

(a) have maximum EMF at the output terminals.
(b) have maximum EMF generated in the armature.
(c) have minimum heat dissipation from the armature.
(d) make the armature dynamically balanced.

SHOW ANSWER

10. Aluminum is not used as winding wire in DC machine armature as it

(a) is costlier.
(b) is of low resistivity.
(c) is of lower thermal conductivity.
(d) requires large winding space.

SHOW ANSWER

11. Short circuiting is caused in the armature winding due to

(a) failure of insulation between two turns of a coil.
(b) failure of insulation between two commutator bars.
(c) grounding of two or more turns of the same coil.
(d) any of the above.

SHOW ANSWER

12. In a lap wound generator, the equalizer rings are provided to

(a) neutralize the armature reaction effect.
(b) avoid short circuiting.
(c) avoid unequal distribution of currents at brushes.
(d) avoid harmonics generated in the EMF.

SHOW ANSWER

13. In a lap wound DC generator having P poles and Z conductors the maximum number of equalizer rings will be

(a) Z/P
(b) 2Z/P
(c) Z/2P
(d) Z/4P

SHOW ANSWER

14. A frog-leg winding is used in a DC machine to eliminate

(a) the use of equalizers in lap winding.
(b) the use of compensating winding.
(c) the use of compensating winding.
(d) reactance voltage produced due to commutation.

SHOW ANSWER

15. A 250 V DC generator is run at rated speed with no excitation. The open-circuit voltage will be

(a) zero
(b) very small, say about 2 or 3 V.
(c) about 100 V.
(d) 250 V.

SHOW ANSWER

16. At a certain speed and flux, the voltage generated by a DC generator is 230 volts. If the speed in increased by 20% and the flux is simultaneously reduced by 10%, the voltage will be

(a) increased by 10%.
(b) reduced by 20%.
(c) increased by 8%.
(d) decreased by 8%.

SHOW ANSWER

17. In DC machines, the air gap flux distribution in space at no load is

(a) sinusoidal.
(b) triangular.
(c) flat topped.
(d) pulsating.

SHOW ANSWER

18. The armature MMF waveform of a DC machine is

(a) pulsating.
(b) rectangular.
(c) triangular.
(d) sinusoidal.

SHOW ANSWER

19. The armature MMF of a DC machine has

(a) triangular space distribution and rotates at the speed of armature.
(b) trapezoidal space distribution and is stationary in space.
(c) stepped space distribution and rotates at the speed of armature.
(d) triangular space distribution and is stationary in space.

SHOW ANSWER

20. In a DC machine, the actual flux distribution depends upon

(a) size of air gap.
(b) shape of pole shoes.
(c) clearance between tips of the adjacent pole shoes.
(d) all of the above.

SHOW ANSWER

21. In a DC machine, the space wave form of the air-gap flux distribution affects

(a) torque only.
(b) voltage only.
(c) both the torque and voltage.
(d) neither the torque nor the voltage.

SHOW ANSWER

22. In a DC machine, the armature MMF is

(a) stationary with respect to the poles but rotating with respect to the armature.
(b) rotating with respect to field poles as well as armature.
(c) rotating with respect to field poles.
(d) stationary with respect to armature.

SHOW ANSWER

23. Armature reaction in a DC shunt generator, running at full load with the brushes not shifted from the geometrical neutral plane and saturation neglected is

(a) absent.
(b) cross-magnetizing.
(c) demagnetizing.
(d) magnetizing.

SHOW ANSWER

24. In a DC machine without any brush shift, the shift of magnetic neutral axis owing to armature reaction is

(a) in the direction of rotation for both the generator and the motor.
(b) against the direction of rotation for both the generator and the motor.
(c) in the direction of rotation for the generator and against the direction of rotation for the motor.
(d) against the direction of rotation for the generator and in the direction of rotation for the motor.

SHOW ANSWER

25. In a DC machine, on no load the magnetic neutral axis

(a) moves from geometric neutral axis in the direction of rotation.
(b) moves from geometric neutral axis in the opposite direction of rotation.
(c) coincides with the geometrical neutral axis.
(d) none of the above.

SHOW ANSWER

26. Due to magnetic saturation, the flux per pole in a DC machine without brush shift

(a) increases in both the generators and the motors with load.
(b) decreases in both the generators and the motors with load.
(c)[/expander_maker] increases in generators but decreases in motors with load.
(d)[/expander_maker] decreases in generators but increases in motors with load.

SHOW ANSWER

27. If the brushes are given a small amount of forward shift in case of DC generator, the armature reaction effect will be

(a) totally demagnetizing.
(b) totally cross-magnetizing.
(c) partly demagnetizing and partly cross-magnetizing.
(d) totally magnetizing.

SHOW ANSWER

28. In a DC machine, the number of mechanical and electrical degrees will be the same when the number of poles on the machine is

(a) 4
(b) 2
(c) 8
(d) 1

SHOW ANSWER

29. Commutation in a DC machine may be explained as a process

(a) in which magnetic field is set up.
(b) by virtue of which EMF is induced in the armature conductors.
(c) by which current in a coil is reversed during the period it is short circuited by the brush.
(d) how armature flux affects the main field flux.

SHOW ANSWER

30. In a DC shunt generator working on load, the brushes are moved forward in the direction of rotation, as a result of this, commutation will

(a) improve but terminal voltage will fall.
(b) worsen and terminal voltage will fall.
(c) improve and terminal voltage will rise.
(d) worsen and terminal voltage will rise.

SHOW ANSWER

31. In a DC machine, the sparking between brushes and commutator surface may be due to

(a) under commutation.
(b) over commutation.
(c) too rapid reversal of current.
(d) any of the above.

SHOW ANSWER

32. The self induced EMF in the coil undergoing commutation is called the

(a) reactance voltage.
(b) statically induced voltage.
(c) dynamically induced voltage.
(d) none of the above.

SHOW ANSWER

33. The sparking at the brushes, in a DC machine, is due to

(a) armature reaction.
(b) reactance voltage.
(c) presence of commutator.
(d) high resistance of carbon brushes.

SHOW ANSWER

34. The reactance voltage is

(a) directly proportional to armature current and commutation period.
(b) directly proportional to commutation period and inversely proportional to armature current.
(c) directly proportional to armature current and inversely proportional to commutation period.
(d) none of the above.

SHOW ANSWER

35. Sparkless commutation can be achieved by employing

(a) interpoles.
(b) compensating winding.
(c) high resistance carbon brushes.
(d) any one or more of the above methods.

SHOW ANSWER

36. To have sparkless commutation, the armature reaction effect in a DC a machine is neutralized by

(a) compensating winding and commutating poles.
(b) shifting the brush axis from geometrical neutral axis to magnetic neutral axis.
(c) fixing the brush axis in line with the pole axis.
(d) increasing the field excitation.

SHOW ANSWER

DC Generator MCQ Questions

 

  1. DC Motor Quiz MCQ
  2. DC Motor Questions and Answers
  3. Electrical Machines Quiz MCQ Questions
  4. DC Motor Question Bank
  5. DC Generator MCQ Questions
  6. DC Generator Question and Answer with Solution
  7. DC Machines Questions and Answers
  8. DC Motor Questions and Answers
  9. DC Motor Objective Questions Answers
  10. DC Motor MCQ Question Answer
  11. DC Motor MCQ Questions
  12. DC Motor Multiple Choice Questions and Answers
  13. DC Motor MCQ Question and Answer
  14. DC Motor Objective Type Question Answer

© www.yourelectricalguide.com/ dc generator mcq questions.

Leave a Comment

Your email address will not be published. Required fields are marked *