Influence of Silicone Contamination on Brush-Commutator Contacts in Small-Size DC Motors

The influence of silicones on the brush-commutator contact in direct current (dc) motors was investigated. The surfaces of silicone-contaminated brushes and commutators were observed by a scanning electron microscope (SEM). The surfaces also were analyzed semiquantitatively by means of Auger electron spectroscopy (AES). The results suggest that frictionally polymerized silicones at the (AgPd catalytic) metal surface form insulative layers on both the commutator and the brush surfaces. Such contamination causes contact phenomena that impede motor startup at low voltages. Small quantities of variously located silicone can also contaminate commutator and brush surfaces even during room temperature storage.