An Erosion-Resistant Lithium Additive Modified Ag-CdO

A new modified heterogeneous alloy composition is presented that has been proved to reduce the consumption of silver per operation in 600 VAC motor control gear. The new modified alloy is a powder-metallurgical heterogeneous type of Ag-CdO that preserves ali the typical properties found in conventional powder-metallurgical Ag-CdO. However, the new modified alloy has shown erosion rates in electrical endurance testing that are one-half that expected from conventional Ag-CdO. The new alloy is a lithium-modified Ag-CdO. The lithium content must be controlled in the range of 40-60 parts per million (ppm) by weight to achieve optimum electrical endurance with this contact material. Data derived from IEC, AC-3 tests for motor control gear are presented to support the above electrical endurance claims. A theoretical discussion of the mechanism of erosion reduction produced with this alloy is included.