Silver Metal Oxide Contact Materials Research Articles

Porównanie obniżenia charakterystyk oraz badanie mechanizmu uszkodzeń materiałów stykowych z kompozytów typu srebro-tlenek metalu stosowanych w przekaźnikach elektromagnetycznych na podstawie danych z symulacji komputerowej

To evaluate the electrical contact behaviors of silver metal oxide contact materials in relays application more accurately, and to guide the selection of contact materials, the test device and testing method for simulating electrical contact performance in relays application were analyzed in this paper. The electrical contact simulation test system was designed and developed, which can easily simulate contact materials. The contact resistance, static force and rebound energy degradation parameters of AgSnO2, AgCdO and AgNi contact materials under the same load conditions were obtained through experimental research, the contact resistance and arcing energy degradation parameters of AgSnO2 under different opening distances were acquired at the same time. The result indicated that accurate data are received by the electrical contact simulation testing method. Finally, based on the test data, the degradation performance of three selected test materials was tested, and the failure mechanism of AgSnO2 materials was analyzed.

Testing results analysis of contact materials’ electrical contact performance

Because of the different ways in which contact materials work, the basic requirements for silver metal oxide contact materials are different. They are anti-welded and anti-erosion when closed, anti-erosion when broken, and arc easily moved and have smaller contact resistance. In this paper, La2O3 is used as a stable oxide in contact material to replace CdO. A new type of Ag/SnO2-La2O3-Bi2O3 contact material is first obtained through using powder metallurgical method. Then electrical contact material parameter tester is used to test the electrical contact performance of the contact material. Through experiments, the arcing voltage and current curves, arcing energy curves, fusion power curves while broken and contact resistance while closed were obtained. Analysis of the results showed that the addition of La2O3 makes the contact material have the following advantages: smaller electrical wear, smaller arc energy, smaller contact resistance and arc is more easily extinguished.

Make arc erosion and welding in the automotive area

A make arc has been investigated using a new testing apparatus. This apparatus which includes a piezo-translator, enables controlled bouncing to be studied at make under mechanical conditions similar to those encountered in automotive relays. Material transfer and welding tendency of silver, silver alloys and silver metal oxide contact materials have been studied under inductive, resistive and lamp loads at 14 V dc and 10-70 A. With all loads, anode to cathode material transfer has been observed. AgCdO, Ag and AgNi under lamp and resistive loads show the highest material transfer, as opposed to non doped and doped AgSnO/sub 2/ under inductive loads. This well known transfer is due to the anodic arc, which occurs during bounces when the gap between the contacts is shorter than /spl sim/5 /spl mu/m, at the beginning and the end of the bounce. We have demonstrated that welding occurs at the beginning of the bounce, i.e. when the contacts begin to separate under arc, and not when the contacts close under arc at the end of the bounce. It was found that welding occurs mainly with Ag, AgCdO, AgZnO, AgFeRe, and AgFeO/sub x/ contact materials, and under high inrush current produced by lamp loads.

Development of cadmium-free silver metal-oxide contact materials

A cadmium-free silver-base alloy has been developed to substitute the standard Ag-12% CdO contact alloy which is widely used in electrical and electronics industries. Substitution of cadmium was attempted through the addition of zinc as the basic and major alloying element and with minor additions of tin and copper. The developed alloy, after internal oxidation, possesses better electrical contact characteristics than the standard alloy.

Silver-Metal Oxide Contact Materials Fabricated by Spray Coprecipitation

This paper describes the development of a highly versatile technique for fabricating improved silver-metal oxide contact materials. The spray coprecipitation method, invented at The Allen Clark Research Centre and patented [1] for Plessey Inc., offers both economic and technical advantages over existing processes for making silvercadmium oxide such as conventional internal oxidation of fabricated alloy, conventional powder metallurgy, and internal oxidation of alloy powder/shot. The main technical advantages are the following: a) controlled microstructural perfection in the uniform fineness and long-range homogeneity of the oxide dispersion; b) unlimited composition with respect to both quantity and type of oxide (not limited to oxides of metals with solid solubility in silver); c) ease of doping with beneficial ternary additons without influencing the microstructure, which is simply controlled by the sintering time and temperature. The method relies on converting, to some extent, the intimate dispersion provided on a molecular scale in mixed aqueous solutions to the solid state by instantaneous coprecipitation from small sprayed droplets of mixed nitrates solutions. This paper concentrates in the main on the application of the process to the fabrication of traditional silver-cadmium oxide, but examples are also given of the production of silver-zinc oxide, silver-tin oxide, and silver-lanthanum oxide materials which demonstrate the versatility and simplicity of the method. IEC AC-4 erosion test results are presented for spray coprecipitated Ag-15 weight percent CdO.