This discussion, although by no means a full treatment of this complex and lengthy subject, gives some basic elements of an adequate maintenance program. The literature listed in the bibliography, only a segment of that which has been published, should be available to maintenance personnel on each project. Troubles which cannot be readily corrected should be referred to the Facilities Engineering Branch, Code D-5210, Denver Office, Denver, Colorado. Good Performance of both commutators and collector rings is mainly dependent upon the formation of the correct thickness of surface film which is tough, glossy, and has low friction. Moisture absorbed from the surrounding air is an important component of the film.
Heat increases the formation of oxides, which are also essential to a good low friction film.
The most prevalent problem with exciters has resulted from insufficient heat because of insufficient load which has not allowed adequate film formation. Because the exciters are generously rated, the average load is only about half the nameplate rating. The manufacturer customarily equips the exciter with a good grade of electrographic brush according to the nameplate rating. These brushes may have good characteristics and perform excellently at nameplate rating or medium to heavy load, but perform poorly on light load. Recognizing these conditions characteristic of Reclamation operation, it is not surprising that better performance can usually be obtained by removing half the brushes from the commutator surface.