A. Sparking at the trailing edge
  Possible Causes Remedies
1 Overload of machine Reduce and limit load
2 Vibration from external causes, i.e. forge hammer Remove causes - mount machine on shock absorbers
3 Vibration from internal causes, i.e. out of balance Balance armature and check for bearing wear
4 Interpole field too weak Increase interpole fields
5 Interpole air gap too large Reduce air gap - increase effective interpole flux
6 Air gaps uneven (worn bearings) Replace bearings and realign machine
7 Mica proud Recess mica or use a more abrasive grade
8 High or low commutator segments Tighten, turn or regrind
9 Commutator too loose Tighten, use new mica and turn
10 Solderings interrupted Resolder tags
11 Commutator or slipring excentric Turning and grinding at near rated speed
12 Flats on commutator or slipring Remove cause while turning or grinding
13 Spring pressure too low Adjust to brush grade
14 Spring pressure unequal Adjust spring pressure uniformly
15 Imperfect brush bedding Rebed brushes carefully and clean
16 Brush flexible too short or too stiff Use brush with flexible of correct length and flexibility
17 Brush arc of contact excessive Reduce effective thickness of brush
18 Brush arc of contact insufficient Try with circumferential stagger or increase brush thickness
19 Sparking Check pressure, grade, holders, brush alignment, remove burns
20 Reaction type holder mounted trailing Reverse holders or direction of rotation
21 Brush sticking Check brush size - remove burns and dust
22 Incorrect position of holder Adjust holder to correct position
23 Unequal alignment of holders Correct spacing and alignment of holders
24 Long periods at low or steady load Change brush grade - ask for our recommendation

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South Africa

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