Slip Rings And Brushes; Brush Wear; Brush Sparking - ABB AMA Series Manual

Manual for Induction Motors and Generators
***Following chapter for rotor type: Slip rings

8.4 Slip rings and brushes

8.4.1 Brush wear

8.4.2 Brush sparking

108 - Trouble Shooting
There are two possible remedies for stator Pt-100 detector damage. If there are operational spare
detectors remaining in the stator core, they can be taken into use. If all the working factory
assembled detectors are in use, a new detector can be retrofitted in the winding end.
In case the brushes are wearing rapidly or unevenly, the following points shall be observed:
• Is the brush pressure within the specified range? See Chapter 7.7.2.1 Brush pressure.
• Are all brush pigtail cables reliably connected?
• Are the sliding surfaces of the slip rings deteriorated?
• Is it probable that carbon brushes have absorbed oil or moisture?
• Is the brush quality as specified for the machine?
Always when feasible:
• Control that the brushes are in good condition and that they can move freely in the brush
holders
• Check that the brush pigtail cables are in order and that they are reliably connected
• Remove coal dust by vacuum cleaning.
Any possible sparking of the brushes can be observed through a window in the slip ring
enclosure. Sparking is often an indication of inadequate operation. Measures to prevent
sparking must be taken immediately. The reasons of sparking shall be cleared up and
undisturbed running restored. Possible causes for sparking:
• Inadequate loading condition
• Brushes sticking in their holders
• Brushes too loose in their holders
• Loose connection of brush terminal
• Imperfect brush bedding
• Incorrect or unequal brush pressure
• The sliding surfaces of the slip-rings are deteriorated
• The type of carbon brushes is not acceptable for the operating conditions
• Misalignment of shaft couplings
• The machine is out of balance
• Worn bearings giving unequal air gaps.
3BFP 000 050 R0101 REV E