Behavior of Electrical Contact Elements for High Current Applications during Relative axial Motion

In high-current applications, such as circuit breakers, gas insulated switchgear and lines (GIS and GIL), contact elements often carry the nominal and short-circuit currents during motion. To achieve a high number of switching cycles without maintenance, lubricants are used to reduce the frictional wear of the silver-coated high-current contacts. There are numerous studies that measured or calculated the contact resistance of these connections at rest and after motion under continuous and short-circuit loads. However, the connection resistance during relative axial motion is also relevant for the electric-thermal behavior, especially under short-circuit current load.There are numerous studies on this topic for slip-ring contacts under radial movement, but few for silver-coated contacts during relative axial motion. Thus, a test stand that allows the connection resistance and the coefficient of friction to be measured during motion as a function of the movement speed, contact normal force and temperature, is presented. During motion, the voltage drop across the contact, temperature, contact normal force and sliding force are continuously measured. Parameter studies are presented showing mutual influence of the boundary conditions. The results show that the connection resistance during motion is significantly higher than at rest and strongly depends on the speed of motion and temperature.