Some Considerations Concerning the Obtaining of Some Ag-SnO2 Sintered Electrical Contacts for Low Voltage Power Engineering Switching Devices

The paper presents some considerations concerning the obtaining and characterisation of some new electrical contact pieces of Ag-SnO2-MeO type, where the MeO is an additive chose from the series of metallic oxides WO3, Bi2O3 and CuO. These have a SnO2 content of 9.5 wt. %, a MeO content of 0.5 wt. %, the balance being Ag. The electrical contact materials were manufactured by powder metallurgy techniques using a new type of powder mixtures obtained from SnO2 and MeO powders which were wet mixed, simultaneously with “in situ” Ag synthesis. These present a very uniform and fine dispersion, which in turn leads to improved functional characteristics of the final electrical contact pieces in comparison to the dry mechanical powders mixtures. The new products were designed for low voltage power engineering switching devices working in air at In = 40, 125 and 200 A.