Brush-Wear Reduction in High-Altitude Direct-Current Motors

The factors of increased wear of current-carrying brushes in direct-current motors designed for high-altitude operation are considered. The results of testing six motors with different degrees of airtightness are presented. It is found out that increased airtightness makes the lacquer film less resistive (thinner) and increases the brush wear. A method of decreasing the wear of current-carrying brushes at standard and high altitudes is proposed that consists in installing a DMS-140 molybdenum disulfide lubricating brush. The lubricating brush is installed in an auxiliary brush holder or in a pocket structurally connected with the current-carrying brush holder on the header runway. The effect of the collector profile material (copper, cadmium bronze, chromium bronze) on the wear of current-carrying brushes is studied, as well as the efficiency of installing lubricating brushes for standard and high-altitude operations. The effect of lubricating brushes on the performance of a 5-W motor is considered as well as the results of testing seven 5-W motors equipped with lubricating brushes in conformity with the machine and warranty service specifications. Information is given on the results of long-term storage (for 1 and 1.9 years) of four motors with different capacities equipped with lubricating brushes, as well as in thermal vacuum tests of 10-W motors under p = 10 –5 –10 –6 mm Hg.