Most of the time the conduction of an electric current in the alternators and related devices is performed by the contact of a graphite brush and a copper ring. Due to the reduction of production costs, there is a growing tendency to omit the copper components and use the alternative cheaper materials instead. The new design of the electric sliding contact in the form of two slip rings enables the use of graphite-graphite contacts instead of graphite-copper. In this paper, we compare the tribological and electrical properties of various graphite- graphite contacts and compare them with conventional graphite-copper contact. We have shown that a graphite-graphite contact in combination with a proper contact geometry and contact conditions exhibits significantly better electrical and tribological properties than graphite-copper contact. This result represents a major innovation in the field of sliding electrical contacts and represents a major step-change in both science and the economy.
The efficiency and lifetime of alternators and related devices is highly dependent on the efficiency of electrical sliding contacts. In this work, we tested the electrical and tribological efficiency of several different types of graphite materials (electro-graphite, polymer-bonded graphites, hard carbons and metal doped graphite). Measurement of the coefficient of friction, contact resistance, temperature and wear of contact materials have shown extremely stable performance polymer bonded carbon in the most severe operating conditions. On the other hand, the electro-graphite and hard carbons showed outstanding electrical efficiency under normal conditions but unreliable operation under sever contact conditions. The result represents important information in the field of sliding electrical contacts and represents significant progress in the science of electrical sliding contacts.