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S/N 86K35004 PU

PROBLEM: FLASH OVER

Date: 5/17/2013

REBUILDER: RPI

REBUILD DATE: 4/1/2013

UNIT: #135

LOCATION: TM#4

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Table IA

Trouble Indications Appearing at Brushes

Indications Appearing at Brushes Immediate Causes

Sparking Commutator surface conditio

Over-commutation

Under-commutatation

Too rapid reversal of current

Faulty machine adjustment

Mechanical fault in machine

Electrical fault in machine

Bad load condition

Poorly equalized parallel oper

Vibration

Chattering of brushes

Wrong brush grade

Fluctuating contact drop

Etched or Burned Bands on Over-commutation

Brush Face Under-commutation

Too rapid reversal of current

Pitting of Brush Face Glowing

Embedded copper

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Rapid Brush Wear Commutator surface conditio

Severe sparking

Imperfect contact with comm

Wrong brush grade

Glowing at Brush Face Embedded copperFaulty machine adjustment

Severe load condition

Bad service condition

Wrong brush grade

Copper in Brush Face Commutator surface conditio

Bad service condition

Wrong brush grade

Flashover at Brushes Machine condition

Bad load condition

Lack of attention

Chattering or Noisy Brushes Commutator surface conditio

Looseness in machine

Faulty machine adjustment

High friction

Wrong brush grade

Brush Chipping or Breakage Commutator surface conditio

Looseness in machine

Vibration

Chattering

Sluggish brush movement

Table IB

Trouble Indications Appearing at Commutator Surface

Indications Appearing at Commutator Surface Immediate Causes

Rough or Uneven Surface

Dull or Dirty Surface

Eccentric Surface

High Commutator Bar Sparking

Low Commutator Bar Sparking

Streaking or Threading of Surface

Copper or foreign material in

Glowing

Bar Etching or Burning Sparking

Flashover

Bar Marking at Pole Pitch Spacing Sparking

Bar Marking at Slot Pitch Spacing Sparking

Flat Spot Sparking

Flashover

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Lack of attention

Discoloration of Surface High temperature

Atmospheric condition

Wrong brush Grade

Raw Copper Surface Embedded copperBad service condition

Wrong brush grade

Rapid Commutator Wear with Blackened Burning

Surface Severe sparking

Rapid Commutator Wear with Bright Foreign material in brush fac

Surface Wrong brush grade

Copper Dragging Brush vibration

Table IC

Trouble Indications Appearing as HeatingIndications Appearing as Heating Immediate Causes

Heating in Windings Severe load condition

Unbalanced magnetic field

Unbalanced armature current

Poorly equalized parallel oper

Lack of ventilation

Heating at Commutator Severe load condition

Severe sparking

High friction

Poor commutator surfaceHigh contact resistance

Heating at Brushes Severe load condition

Faulty machine adjustment

Severe sparking

Raw streaks on commutator

Embedded copper

Wrong brush grade

Table II

Primary Sources of Unsatisfacory Brush Performance

A. Preparation and Care of Machine1. Poor preparartion of commutator surface

2. High Mica

3. Feather-edge mica

4. Bar edges not chamfered after undercutting

5. Need for periodic cleaning X

6. Clogged ventilating ducts

B. Machine Adjustment

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7. Brushes in wrong position

8. Unequal brush spacing

9. Poor alignment of brush holders

10. Incorrect brush angle

11. Incorrect spring tension X

12. Interpoles improperly adjusted

13. Series field improperly adjusted

C. Mechanical Fault in Machine

14. Brushes tight in holder X X

15. Brushes too loose in holder

16. Brush holders loose at mounting

17. Commutator loose

18. Loose pole pieces or pole face shoes

19. Loose or worn bearings

20. Unequal air gaps

21. Unequal pole spacings

22. Dynamic unbalance

23. Variable angular velocity24. Commutator too small

D. Electrical Fault in Machine

25. Open or high resistance connection at commutator

26. Poor connection at shunt terminal

27. Short circuit in field or armature winding

28. Ground in field or armature winding

29. Reversed polarity on main pole or interpole

E. Machine Characteristics

30. Commutating zone too narow

31. Commutating zone too wide

32. Brushes too thin

33. Brushes too thick

34. Magnetic saturation of interpoles

35. High bar-to-bar voltage X X

36. High ratio of brush contact to surface area

37. Insufficient cross connection of armature coils

F. Load or Service Conditions

38. Overload X

39. Rapid change of load X

40. Reversing operation of non-interpole machine

41. Plugging X

42. Dynamic braking43. Low average current density in brushes X

44. Contaminated atmosphere X X

45. "Contact poisons" X

46. Oil on commutator or oil mist in air X X

47. Abrasive dust in air

48. Humidity too high

49. Humidity too low X

50. Silicone contamination

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G. Disturbing External Conditions

51. Loose or unstable foundation

52. External source of vibration

53. External short circuit or very heavy load surge X

H. Wrong Brush Grade54. "Commutation factor" too high

55. "Commutation factor" too low

56. Contact drop of brushes too high

57. Contact drop of brushes too low

58. Coefficient of friction too high

59. Lack of film forming properties in brush X

60. Lack of polishing action in brush

61. Brushes too abrasive

62. Lack of carrying capacity

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Primary Faults

1-2-3-43-45-46-48-59-60

7-12-31-33

7-12-30-32

7-12-30-32

8-9-11

6-14-15-16-17-18-19-20-21-22

25-27-28-29

38-39-40-41-42

ation 7-13-23-34

51-52

See "Chattering or Noisy Brushes"

55-57-59

50

7-12-31-32

7-12-30-32

7-12-30-32

See "Glowing at Brush Face"

See "Copper in Brush Face"

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See specific surface fault in evidence. Also 50

See "Sparking"

tator 11-14-15-16-51-52

54-58

See "Copper in Brush Face"7-12

38-39-41-42

46-47

57-61-62

2-3

43-46-47-48-49

59-61

14-35

38-39-41-53

5-11

See specific surface fault in evidence.

15-16-17

10-11

6-43-45-49-52-58-59

53-58-59

See specific surface fault in evidence.

15-16-17

52

See "Chattering or Noisy Brushes"

14

Primary Faults

1-2-3-4-17

5-44-60

1-19-22-52

17

2-25

43-44-45-46-49-59

brush face 2-46-47-48-61

See "Glowing at Brush Face"

2-3-7-12-30-31-32-33

5-11-14-35-38-39-41-53

25-37

7-12-30-57-60

19-23-25-41-42-53

5-11-14-35-38-39-41-53

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1-5-11

See "Heating at Commutator"

44-46

60

See "Copper in Brush Face"43-45-47-49

59-61

2-3-11-14

See "Sparking"

43-45-47-49

61

39-52-58-59

Primary Faults

38-41-42-53

18-19-20-21-27-28-29

s 8-19-22-25-27-28-29-37

ation 7-13-23-34

6

38-41-42

7-8-9-12-20-33-45-57

10-11-36-43-45-49-58-59

See specific surface fault in evidence.56

38-41-42

7-10-11-12-26

See "Sparking"

urface See "Streaking or Threading of Surface"

See "Copper in Brush Face"

57-58-59-61-62