
DC Communicator Bar-to-Bar Test
What does it tell you?
Testing the resistance between commutator bars gives an indication of the comparative value of resistance that exists between all like electrical circuits in an armature.
Why is this important?
The commutator consists of insulated segments assembled into a cylinder and held together by insulated rings. Electric current is transferred to the armature winding by "brushes" made mainly of carbon and graphite. Brush wear creates carbon dust, a conductive contaminant, which penetrates into crevices, cracks and openings of the armature. Copper particles add to the contaminant accumulation when the wrong brushes are installed or the brushes are improperly installed, or when the maintenance is inadequate. If the insulating material on the commutator bars or their risers has cracked, these contaminants can short entire windings.
(Graphic pages remain mostly unaltered)
