ELECTRICIAN 2nd YEAR MODULE – DC Generator

Question 1 of 56

1. 43. What is the purpose of the slot marked 'X' in a DC generator?

Easy shaft removal

Enable air circulation

Fix the keyway

Lubrication

Question 1 of 56

Question 2 of 56

2. 12. Which rule is used to find the direction of a magnetic field?

Fleming’s left hand rule

Fleming’s right hand rule

Right hand palm rule

Cork screw rule

Question 2 of 56

Question 3 of 56

3. 7. What is the name of the DC generator that requires separate excitation?

Compound generator

Series generator

Separately excited generator

Shunt generator

Question 3 of 56

Question 4 of 56

4. 26. What is the name of the generator if its field is connected in parallel with the armature?

Self-excited generator

Compound generator

Series generator

Shunt generator

Question 4 of 56

Question 5 of 56

5. 39. Why are solid pole shoes used in DC generators?

Reduce copper loss

Increase residual magnetism

Decrease residual magnetism

Reduce magnetic path reluctance

Question 5 of 56

Question 6 of 56

6. 23. Why should a DC generator run only in the clockwise direction?

Avoid generator overloading

Protect brushes from damage

Protect residual magnetism

Avoid short circuit in armature

Question 6 of 56

Question 7 of 56

7. 11. What is the formula for dynamically induced emf?

BLV volts

BLV cosθ volts

BL sinθ volts

BLV sinθ volts

Question 7 of 56

Question 8 of 56

8. 42. Which voltage is induced dynamically in a DC generator?

Alternating voltage

Direct current voltage

Oscillating voltage

Pulsating voltage

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Question 9 of 56

9. 40. Which metal is used for large-capacity DC generator yokes?

Aluminium

Soft iron

Rolled steel

Cast iron

Question 9 of 56

Question 10 of 56

10. 54. Calculate the induced EMF of a 4-pole, lap-wound dynamo at 1000 rpm with 600 conductors and 0.064 Wb flux/pole.

320 V

640 V

480 V

160 V

Question 10 of 56

Question 11 of 56

11. 49. What happens if shunt field resistance exceeds critical value in a DC generator?

Pulsating output voltage

Normal voltage buildup

Voltage buildup failure

Above-normal output voltage

Question 11 of 56

Question 12 of 56

12. 56. What causes heavy sparking in DC generator brushes?

Excessive brush spring tension

Short circuit in field winding

Shift in MNA and GNA positions

Short circuit in armature winding

Question 12 of 56

Question 13 of 56

13. 48. What is the purpose of compensating winding in DC generators?

Decrease field coil excitation current

Minimize rough commutation

Maintain constant output voltage

Neutralize demagnetizing effect

Question 13 of 56

Question 14 of 56

14. 14. How many parallel paths are there in a duplex lap winding of a 4-pole DC generator?

6

12

8

4

Question 14 of 56

Question 15 of 56

15. 29. Which material is used to make brushes in generators?

Steel and graphite

Aluminium and graphite

Carbon and graphite

Cast iron and graphite

Question 15 of 56

Question 16 of 56

16. 35. Which DC generator works without residual magnetism?

Compound generator

Separately excited generator

Series generator

Shunt generator

Question 16 of 56

Question 17 of 56

17. 8. Which type of energy is converted into electrical energy by a generator?

Heat energy

Chemical energy

Mechanical energy

Kinetic energy

Question 17 of 56

Question 18 of 56

18. 36. Which DC generator is used for arc welding?

Series generator

Cumulative compound generator

Differential compound generator

Shunt generator

Question 18 of 56

Question 19 of 56

19. 1. What is the name of the part marked as 'X' in a DC generator?

Armature core

Commutator riser

Commutator segment

Brush

Question 19 of 56

Question 20 of 56

20. 17. What is the necessity of residual magnetism in a self-excited DC generator?

To maintain constant output voltage

To reduce the field current

To build up the voltage

To reduce armature current

Question 20 of 56

Question 21 of 56

21. 9. What is the name of the DC generator's field where the series field opposes the shunt field?

Long shunt compound generator

Short shunt compound generator

Differential compound generator

Cumulative compound generator

Question 21 of 56

Question 22 of 56

22. 51. Calculate the EMF generated in a 4-pole, simplex wave-wound DC generator with 1020 conductors at 1500 rpm and 0.007 Wb flux/pole.

178 V

357 V

428 V

243 V

Question 22 of 56

Question 23 of 56

23. 4. Which formula is used to calculate the generated emf in a DC generator?

B

C

A

D

Question 23 of 56

Question 24 of 56

24. 55. What happens to induced EMF if main field flux distorts in a DC generator?

No change in EMF

EMF becomes zero

EMF increases

EMF decreases

Question 24 of 56

Question 25 of 56

25. 3. Which rule is used to find the direction of induced emf in a DC generator?

Cork screw rule

Right hand palm rule

Fleming's left hand rule

Fleming's right hand rule

Question 25 of 56

Question 26 of 56

26. 33. Which DC generator is used for long-distance distribution lines?

Shunt generator

Differential compound generator

Series generator

Cumulative compound generator

Question 26 of 56

Question 27 of 56

27. 50. What is the effect of armature reaction in DC generators?

Decreased output voltage

Zero output voltage

Pulsating output voltage

Increased output voltage

Question 27 of 56

Question 28 of 56

28. 38. What is the purpose of resistance wire in commutator connections?

Increase statically induced EMF

Maintain constant voltage

Smooth current direction reversal

Nullify statically induced EMF

Question 28 of 56

Question 29 of 56

29. 24. Why is compensating winding provided in large DC generators?

Neutralize armature reaction effect

Connect more loads

Increase generator efficiency

Reduce commutation effect

Question 29 of 56

Question 30 of 56

30. 21. Why is the armature core of a DC generator laminated?

Reduce copper loss

Reduce eddy current loss

Reduce friction loss

Reduce hysteresis loss

Question 30 of 56

Question 31 of 56

31. 31. How does the magnetic circuit complete through the yoke and poles in a generator?

Laminated pole core

Armature winding conductors

Field coils

Armature core

Question 31 of 56

Question 32 of 56

32. 28. What is the function of split rings in a DC generator?

Collect current unidirectionally

Maintain constant voltage

Increase terminal voltage beyond rated

Reduce voltage drop at brushes

Question 32 of 56

Question 33 of 56

33. 41. What is the function of split rings in a DC generator?

Opposite direction output

Continuous output supply

Unidirectional output

Collect output from alternate conductors

Question 33 of 56

Question 34 of 56

34. 52. How is armature reaction neutralized in large DC generators?

Additional interpoles

Increased brush contact resistance

Resistance wires in windings

Compensating winding

Question 34 of 56

Question 35 of 56

35. 53. What happens if a DC generator is idle for a long time?

Increased armature reaction

Loss of residual magnetism

Armature resistance increases

Field coil resistance increases

Question 35 of 56

Question 36 of 56

36. 18. Which two points measure the brush contact resistance in DC machines?

Resistance between brush and armature conductors

Resistance between the opposite brushes

Resistance between brush and commutator riser

Resistance between brush and commutator

Question 36 of 56

Question 37 of 56

37. 5. What is the formula to calculate back emf of a DC motor?

D

B

C

A

Question 37 of 56

Question 38 of 56

38. 37. What is the property of wave winding in DC generators?

High current, low voltage

High current, high voltage

Low current, high voltage

Low current, low voltage

Question 38 of 56

Question 39 of 56

39. 16. How are interpoles connected in a DC generator?

In series with the armature

In parallel with the armature

In series with the shunt field

In parallel with the shunt field

Question 39 of 56

Question 40 of 56

40. 22. Why is the armature resistance of a DC generator kept very low?

Run armature with less weight

Reduce armature voltage drop

Reduce armature current

Reduce temperature of armature

Question 40 of 56

Question 41 of 56

41. 34. Which method improves insulation resistance in DC generators?

Blowing hot air during maintenance

Periodic machine heating

Frequent brush replacement

Regular commutator cleaning

Question 41 of 56

Question 42 of 56

42. 15. Name the part of a DC generator that consists of thin laminated sheets to reduce eddy currents.

Armature core lamination

Commutator segment

Side end plates

Pole shoe lamination

Question 42 of 56

Question 43 of 56

43. 27. What is the purpose of pole shoes in a DC generator?

Reduce air gap

Increase field strength

Spread flux uniformly in the air gap

Minimize magnetic losses

Question 43 of 56

Question 44 of 56

44. 32. Why does terminal voltage decrease with increased load in a DC shunt generator?

Increased shunt field inductance

Reduced brush voltage drop

Armature reaction effect

Increased armature resistance

Question 44 of 56

Question 45 of 56

45. 44. What is the purpose of field coils in a DC generator?

Magnetize poles to produce flux

Increase magnetic path reluctance

Reduce magnetizing current

Increase air gap flux

Question 45 of 56

Question 46 of 56

46. 10. What is the principle of a DC generator?

Fleming’s left hand rule

Faraday’s laws of electromagnetic induction

Fleming’s right hand rule

Cork screw rule

Question 46 of 56

Question 47 of 56

47. 20. What is the name of the compound generator if the shunt field is connected in parallel with the armature?

Short shunt compound

Cumulative compound

Differential compound

Long shunt compound

Question 47 of 56

Question 48 of 56

48. 45. Which metal is used for pole cores in large DC generators?

Cast steel

Soft iron

Stainless steel

Cast iron

Question 48 of 56

Question 49 of 56

49. 30. Why do DC generators lose residual magnetism?

Heavy short circuit in load

Frequent direction changes of rotation

Uninterrupted operation

Continuous no-load running

Question 49 of 56

Question 50 of 56

50. What is the name of the DC generator described as having cumulative short shunt compounding?

Cumulative long shunt compound

Cumulative short shunt compound

Differential short shunt compound

Differential long shunt compound

Question 50 of 56

Question 51 of 56

51. 25. What is the reason a DC generator fails to build up voltage?

Prime mover running above rated speed

High armature resistance

Loose brush contact

Field resistance above critical value

Question 51 of 56

Question 52 of 56

52. 13. What is the name of the part of a DC generator that provides mechanical support and a path for magnetic flux?

Yoke (or frame)

Pole shoes

Pole core

Stator

Question 52 of 56

Question 53 of 56

53. 46. Why are pole core stampings laminated in DC generators?

Reduce eddy current loss

Reduce friction loss

Reduce windage loss

Reduce hysteresis loss

Question 53 of 56

Question 54 of 56

54. 19. Which voltage drop is indicated in the portion marked as 'X' in a DC generator?

Shunt field voltage drop

Full load voltage drop

Armature voltage drop

Armature reaction drop

Question 54 of 56

Question 55 of 56

55. 6. What is the name of the part marked 'X' in a DC generator (pole assembly)?

Pole shoe

Pole coil

Pole core

Pole tip

Question 55 of 56

Question 56 of 56

56. 47. Which DC generator is used for electroplating?

Cumulative compound generator

Differential compound generator

Shunt generator

Series generator

Question 56 of 56