Sliding Monolithic Brush Systems for Large Currents

An improved system for collecting and transferring electrical current between relatively moving parts, as in a homopolar machine, is described. The use of solid brushes for collecting or transferring current in systems involving relatively moving parts, such as motors or generators, has been proven reliable and reasonably efficient for many commercial and industrial applications. With recent advances in the design of electrical machinery, particularly involving power-rated homopolar machines, the need has arisen for improved systems capable of more efficiently collecting and transferring machine current. This need is primarily due to the combined much greater electrical currents and speeds required to generate more power or transmit more torque within a given volume than was previously possible. The disadvantages and inadequacies of present current collecting and transfer systems are eliminated by providing a new solid brush type current collection system which selectively uses compatible materials for the moving and stationary contact members. These contact members are operated in an atmospheric environment which utilizes nonoxidizing gases, such as carbon dioxide, having either water or organic additives for the purpose of operating the collector system at higher temperatures, higher current densities, and higher velocities than is possible with conventional systems. The system development of compatible brush and ring materials, ambient environment gas and vapors, and the need for adequate cooling are presented here. Preliminary test results of the developed system in a machine environment reveal a strong feasibility for meeting the current collection goal of 155 A/cm2, a requirement which designers of advanced machines consider viable for a number of high power applications of interest. To transfer current in the most efficient artless manner, the solid brush collector system will require forced cooling to maintain the interface temperature at relatively Iow values thus to achieve Iow friction and Iow wear rates of the sliding contact members.