Peter Braumann

Development of Contact Material Solutions for Low-Voltage Circuit Breaker Applications (2)

The focus of the experimental studies was in the influence of contact material composition, production parameters and the contact material - breaker interaction, as the performance of the breaker is a function of breaker design, contact material and especially their interaction. Therefore, typical material combinations used for low voltage protection devices were compared by means of their switching behavior and performance. Model-switch tests have been carried out to show this performance under stable and well defined boundary conditions. The chosen test parameters simulate device tests, excluding the influence of switching device kinematics and tolerances. Focus of the tests was to scrutinize the influence of the material composition on the erosion behavior and contact resistance for AgWC materials. Additionally a comparison on the performance of different silver refractory metals like AgW or AgMo at comparable vol.-% refractory metal was made. Furthermore, the impact of different graphite contents, manufacturing parameters and fiber orientation of AgC materials on weld break forces have been worked out. This experimental quantification of influences can be seen as a basis for contact material selection during protection device design.

The influence of manufacturing process, metal oxide content, and additives on the switching behaviour of Ag/SnO/sub 2/ in relays

As an introduction a brief historical summary of the use of Ag/SnO/sub 2/ in general-purpose and automotive relays is given. The process for manufacturing contact materials by using wet-chemical precipitation technology (NCF technology) is explained and the potential of this technology for the production and the application of contact materials is demonstrated. The influence of the additives WO/sub 3/, Bi/sub 2/O/sub 3/ and In/sub 2/O/sub 3/ is investigated with materials that are based on the powder blending technology and the NCF technology.