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FIGURE 19. COMMUTATOR PROBLEMS
Heavy streaks and fine grooves indicate the beginning
of damage to the commutator.
Possible Causes:
Operation of the motor in dirty and abrasive
conditions
Continuous operation of a motor with a light load.
Brush pressure is too low.
Worn brushes.
6939
Possible causes of threading include:
a Low current–density in the brush ( machine is not
heavily loaded).
b. Abrasive dirt or other foreign material imbedded
in the face of the brush
c. Mica flakes or copper imbedded in the brush
face.
d. Wrong brush grade.
GROOVING ON SURFACE
The grooved condition of a commutator must not be
confused with threading. Grooving is a smooth slotted
wear of the commutator and is generally the result of
abrasive dust in the atmosphere. The abrasive dust
contamination between sliding surfaces promotes wear
of both the brush and commutator. The rate of wear must
be considered to determine if the condition is
detrimental.
FIGURE 20. COMMUTATOR PROBLEMS
Grooves and lines that have followed the heavy streaks
and fine grooves shown in FIGURE 19. The armature
must be removed from the motor so that the
commutator can be repaired. A commutator with this
condition will cause the brushes to wear rapidly.
Possible Causes:
Operation of the motor in dirty and abrasive
conditions
Continuous operation of a motor with a light load.
Brush pressure is too low.
Worn brushes.
6939
