ELECTRICIAN 2nd YEAR MODULE – DC Motor MCQ

Question 1 of 68

1. 32. Which material is used for starting resistance of DC starters?

Constantine

Manganin

Nichrome

Eureka

Question 1 of 68

Question 2 of 68

2. 66. What is the speed, if field winding of a DC shunt motor is in open circuit?

Motor runs normally

Stop running

Runs in very high speed

Runs at slow speed

Question 2 of 68

Question 3 of 68

3. 17. Which speed control method of D.C series motor is used for electric train?

Supply voltage control method

Field diverter method

Armature diverter method

Field tapping method

Question 3 of 68

Question 4 of 68

4. 45. Where D.C compound motors are preferred?

Constant speed requirements

Constant load requirements

High starting torque requirements

Constant speed under varying load requirements

Question 4 of 68

Question 5 of 68

5. 20. Which speed control methods offers below normal speed in DC shunt motor?

Field control method

Voltage control method

Armature control method

Ward Leonard system of speed control

Question 5 of 68

Question 6 of 68

6. 24. Which type of D.C motor is used for constant speed drives?

DC series motor

DC shunt motor

Differential short shunt compound motor

Differential long shunt compound motor

Question 6 of 68

Question 7 of 68

7. 2. Which instrument is used to test armature winding for short and open circuit?

Tong Tester

Digital multimeter

Internal Growler

External Growler

Question 7 of 68

Question 8 of 68

8. 14. What is the name of the equipment?

Internal growler

Earth resistance tester

External growler

Megger

Question 8 of 68

Question 9 of 68

9. 13. What is the formula to calculate back EMF in a DC motor?

Question 9 of 68

Question 10 of 68

10. 1. Which instrument is used to measure armature winding resistance?

Kelvin bridge

Multimeter

Series type Ohm meter

Megger

Question 10 of 68

Question 11 of 68

11. 18. Why shunt field coil is connected in series with holding coil in D.C three point starter?

Protect the shunt field from over current

Increase the holding coil current

Decrease the holding coil current

Protect the motor in case of open in shunt field

Question 11 of 68

Question 12 of 68

12. 33. Which DC compound motor is operated at constant speed under varying load?

Differential short shunt

Cumulative short shunt

Cumulative long shunt

Differential long shunt

Question 12 of 68

Question 13 of 68

13. 8. What is the name of D.C motor?

D.C series motor

D.C shunt motor

D.C differential compound motor

D.C cumulative compound motor

Question 13 of 68

Question 14 of 68

14. 3. What is the name of the speed control method of DC motor?

Voltage control method

Field diverter method

Armature diverter method

Field tapping method

Question 14 of 68

Question 15 of 68

15. 35. Which type of armature winding is illustrated?

Duplex lap winding

Quadruplex lap winding

Triplex lap winding

Simplex lap winding

Question 15 of 68

Question 16 of 68

16. 42. Why the D.C series motor field winding is wound with thick wire?

To reduce the armature reaction

To regulate field voltage

To carry the load current

To keep maximum inductance

Question 16 of 68

Question 17 of 68

17. 51. Which type of DC motor is used for sudden application of heavy loads?

Series motor

Shunt motor

Differential compound motor

Cumulative compound motor

Question 17 of 68

Question 18 of 68

18. 7. Which rule determines the direction of rotation of armature in D.C motor?

Fleming's left hand rule

Right hand grip rule

Right hand palm rule

Fleming's right hand rule

Question 18 of 68

Question 19 of 68

19. 9. Which rule determines the direction of current in D.C motor?

Fleming's right hand rule

Right hand grip rule

Right hand palm rule

Fleming's left hand rule

Question 19 of 68

Question 20 of 68

20. 12. Name the type of DC motor.

Long shunt compound motor

Short shunt compound motor

Shunt motor

Series motor

Question 20 of 68

Question 21 of 68

21. 23. What is the temperature value of class 'F' insulation?

120°C

155°C

105°C

90°C

Question 21 of 68

Question 22 of 68

22. 15. What is the name of winding, if coil pitch is less than pole pitch?

Half pitch winding

Short chorded winding

Full pitch winding

Long chorded winding

Question 22 of 68

Question 23 of 68

23. 54. What is the purpose of tapes in winding?

Insulate slots

Insulate exposed conductors

Bind the coils

Wrap the conductor

Question 23 of 68

Question 24 of 68

24. 6. How many parallel paths in duplex lap winding in the armature of 4 pole D.C Motor?

6

8

2

4

Question 24 of 68

Question 25 of 68

25. 59. Which insulating material used in winding is a highly non-hygroscopic and possess good electrical strength?

Millinex paper

Leatheroid paper

Triplex paper

Empire cloth

Question 25 of 68

Question 26 of 68

26. 64. How the direction of rotation of a DC compound motor is changed?

By changing the direction of series field current

By changing the direction of both field and armature current

By interchanging the supply terminals

By changing the direction of armature current

Question 26 of 68

Question 27 of 68

27. 55. Which type of DC armature winding the front pitch (YF) is greater than back pitch (YB)?

Progressive winding

Wave winding

Retrogressive winding

Lap winding

Question 27 of 68

Question 28 of 68

28. 48. Why the holding coil of a 3 point starter is connected in series with shunt field?

To protect the motor from high speed

To limit the load current

To run motor at low voltage

To hold the handle plunger firmly

Question 28 of 68

Question 29 of 68

29. 46. What is the necessity of starter for D.C motor?

Limit the armature current

Limit the field voltage

Limit the field current

Control the motor speed

Question 29 of 68

Question 30 of 68

30. 4. Which winding wire is used for DC field coil?

PVC covered copper winding wire

Double silk covered copper wire

Single silk covered copper wire

Super enameled copper wire

Question 30 of 68

Question 31 of 68

31. 43. Which type of speed control of D.C series motor?

Field tapping method

Armature diverter method

Field diverter method

Field parallel method

Question 31 of 68

Question 32 of 68

32. 10. What is the formula to calculate the current taken by D.C shunt motor armature?

Question 32 of 68

Question 33 of 68

33. 26. Which method of speed control gives below the rated speed in DC series motor?

Armature diverter method

Voltage control method

Field diverter method

Tapped field method

Question 33 of 68

Question 34 of 68

34. 19. Why the direction of rotation is changed only by changing the armature current direction in a D.C compound motor?

Maintain rated speed

Maintain motor characteristics

Prevent motor from over loading

Avoid armature reaction effect

Question 34 of 68

Question 35 of 68

35. 60. Which type of armature winding is illustrated?

Retrogressive lap winding

Progressive lap winding

Duplex wave winding

Triplex wave winding

Question 35 of 68

Question 36 of 68

36. 57. How to obtain opposite polarity in adjacent poles of a 4 pole DC motor?

Making parallel connection of coils

Making current flow in different direction

Making series connection of coils

Varying the number of turns in coil

Question 36 of 68

Question 37 of 68

37. 28. Why carbon composition brush requires in the armature circuit to operate the D.C motor?

Reduces the spark in the commutator segment

Protects from armature reaction

Increases the starting torque

Protects armature from over loading

Question 37 of 68

Question 38 of 68

38. 49. What is the best method to change the DOR of a compound motor without change of its characteristics?

Change the current in armature and shunt field together

Change series field current direction

Change shunt field current direction

Change armature current direction

Question 38 of 68

Question 39 of 68

39. 67. What is the reason for reduction in speed of a D.C shunt motor from no load to full load?

Armature voltage drop decreases

Shunt field current decreases

Shunt field current increases

Armature voltage drop increases

Question 39 of 68

Question 40 of 68

40. 65. What is the effect in a D.C shunt motor, if its supply terminals are interchanged?

Runs in slow speed

Runs in high speed

Runs in the reverse direction

Runs in the same direction

Question 40 of 68

Question 41 of 68

41. 27. What is the effect, if a four point starter resistance is cutoff during running?

Motor stopped

Runs at slow speed

Runs at very high speed

Runs at reverse direction

Question 41 of 68

Question 42 of 68

42. 63. Why the newly rewound armature must be preheated before varnishing?

Help for quick drying of varnish

Make easy to penetrate varnish inside

Maintain uniform spreading of varnishing

Drive out the moisture from it

Question 42 of 68

Question 43 of 68

43. 68. Which winding fault is determined by the test?

Grounded core fault

Grounded coil fault

Open coil fault

Short coil fault

Question 43 of 68

Question 44 of 68

44. 53. Which speed control system provides a smooth variation of speed from zero to above normal?

Ward-Leonard system control

Field control

Field diverter control

Armature control

Question 44 of 68

Question 45 of 68

45. 22. Which insulating material belongs to class 'B' insulation?

Fiber glass

Cotton

Leatheroid paper

Bamboo

Question 45 of 68

Question 46 of 68

46. 52. Which speed control method is used in food mixture motors?

Armature diverter method

Series field tapping method

Voltage control method

Field diverter control method

Question 46 of 68

Question 47 of 68

47. 36. Which growler test for armature is illustrated?

Open coil test

Shorted coil test

Grounded coil test

Shorted commutator test

Question 47 of 68

Question 48 of 68

48. 39. What is the action of the induced emf in a running D.C motor?

Opposes the applied voltage

Assists the applied voltage

Decreases the armature current

Increases the armature current

Question 48 of 68

Question 49 of 68

49. 44. Which type of D.C motor is suitable for shearing machines?

Series motor

Shunt motor

Cumulative compound motor

Differential compound motor

Question 49 of 68

Question 50 of 68

50. 61. Calculate the average pitch (Y_A ) for retrogressive wave winding, if No. of armature conductor = 14, No. of slots = 7, No. of poles = 2

4

14

6

8

Question 50 of 68

Question 51 of 68

51. 47. Which type of instrument is used to test the armature winding?

Ohmmeter

Multimeter

Megger

Growler

Question 51 of 68

Question 52 of 68

52. 5. Which formula is used to calculate the speed of DC motor?

Question 52 of 68

Question 53 of 68

53. 34. How No volt coil is connected in a three point starter with DC shunt motor?

Connected in series with armature

Connected in parallel with armature

Directly connected to supply

Connected in series with shunt field

Question 53 of 68

Question 54 of 68

54. 37. Which speed control method is applied to obtain both below normal and above normal speed in DC motor?

Armature control method

Ward Leonard speed control

Tapped field speed control

Field control method

Question 54 of 68

Question 55 of 68

55. 16. What is the purpose of series resistor connected with holding coil in a D.C four point starter?

Increase the current in holding coil

Decrease the voltage in holding coil

Limit the current in holding coil

Increase the voltage in holding coil

Question 55 of 68

Question 56 of 68

56. 50. What is the purpose of NVC connected in series with the field in 3 point starter?

To prevent increase in speed

To decrease the back emf

To improve the torque

Reduce the field current

Question 56 of 68

Question 57 of 68

57. 38. Why commutators are sparking heavily?

Incorrect armature connection

Incorrect brush position

Incorrect direction of rotation

Incorrect field connection

Question 57 of 68

Question 58 of 68

58. 41. What is the purpose of resistor connected with holding coil in 4 point starter?

Limit current in NVC

Protect the armature from short circuit

Protect the coil from short circuit

Protect the motor from overload

Question 58 of 68

Question 59 of 68

59. 56. What reduces the cross sectional area of core material for VA rating?

Normal steel sheet

High alloy sheet

Dynamo sheet

Low alloy sheet

Question 59 of 68

Question 60 of 68

60. 29. Why series motor produce high torque and speed initially without load?

Armature current and field current are same

Absence of back emf

Series field winding wound with thick wire

Load current flows through field winding

Question 60 of 68

Question 61 of 68

61. 11. Which rule is applied to identify the direction of flux in DC motor?

Cork's screw rule

Fleming's left hand rule

Fleming's right hand rule

Right hand grip rule

Question 61 of 68

Question 62 of 68

62. 62. Which type of test is illustrated for the armature after rewound?

Voltage drop test

Shorted coil test

Open coil test

Grounded coil test

Question 62 of 68

Question 63 of 68

63. 30. Why the series field is short circuited at the time of starting in differential compound motor?

To increase the speed of motor

To reduce the starting current

To maintain proper direction of rotation

To decrease the speed of motor

Question 63 of 68

Question 64 of 68

64. 40. Which motor has this characteristics curve?

Series motor

Shunt motor

Cumulative compound motor

Differential compound motor

Question 64 of 68

Question 65 of 68

65. 31. Which is the most effective method of balancing armature?

Plugged with lead weight balancing

Static balancing

Dynamic balancing

Attached with counter balancing

Question 65 of 68

Question 66 of 68

66. 25. Which type of DC motor is used in elevators?

DC series motor

DC shunt motor

DC cumulative compound motor

DC differential compound motor

Question 66 of 68

Question 67 of 68

67. 58. What is the operation in the rewinding process?

Cutting of winding wire

Removing of winding

Removing of wedges

Cleaning of slots

Question 67 of 68

Question 68 of 68

68. 21. Why starters are required to start D.C motors in industries?

Reduce the armature current

Regulate the field voltage

Smooth operation of motors

Control the armature reaction

Question 68 of 68