Browsing by Subject "copper graphite"
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Item High-Energy/High-Rate Consolidation of Copper-Graphite Composite Brushes for High Current Applications(1987-11) Wang, M. J.; Persad, C; Eliezer, Z; Weldon, W. F.This paper reviews some of the important materials structure-property relationships that exist for copper-graphite composites, as they influence this class of materials in high current applications. Commercial composite brushes fail in high-speed/high-current duty by loss of the low-melting-temperature, metallic binder, usually lead-tin, caused by the high flash temperature at the sliding interface combined with the softening due to I2R heating. The virtues of binderless copper-graphite brush materials have driven the development of a novel high-energy/high-rate processing approach employing a homopolar generator as a '1 MJ in 1 s' pulsed power source. The discharge of such an energy pulse through a powder mixture under pressure produces a dense product with improved mechanical and electrical properties compared to conventionally sintered commercial material. The rapid processing minimizes internal oxidation, and the fast postpulse cooling promotes the freezing of the copper matrix and tight micro-encapsulation of the graphite particles due to localized energy deposition at the copper-graphite interface. High and low speed testing have been used in the preliminary tribological evaluation. The behavior of these materials has compared favorably to commercial materials for pulsed high-speed, high-current duty.Item Research and Development of High Performance Current Collectors for Homopolar Generators(1985-10) Gully, J.H.; Walls, W.A.Over the past five years three homopolar generators (HPGs) have been operated in our laboratory under a variety of experimental conditions. Two of the machines were routinely used as pulsed power supplies, the third machine is an experimental facility for the development of HPG components. Because of the Center for Electromechanics at The University of Texas at Austin (CEM-UT) recent move into a new facility, all three of the machines have been disassembled and inspected offering a wealth of information on the performance of high-slip-speed, high current- density current collectors. Wear rates of sintered, copper-graphite brushes running on steel slip rings as a function of current density and slip speed will be presented along with effects of slip-ring surface finish, using the brushes as a switch to close the electrical circuit and direction of current transfer. Funding for this research has been provided by the U. S. Army Research and Development Command (ARDC), Defense Advanced Research Projects Agency (DARPA), National Science Foundation (NSF), and the Texas Atomic Energy Research Foundation (TAERF).Item Test Data on Electrical Contacts at High Surface Velocities and High Current Densities for Homopolar Generators(1977-10) Brennan, M.; Tolk, K.M; Weldon, W.F; Rylander, H.G; Woodson, H.H.Test data is presented for one grade of copper graphite brush material, Morganite CMlS, over a wide range of surface velocities, atmospheres, and current densities that are expected for fast discharge (