Effect of Copper-Based Spring Alloy Selection on Arc Erosion of Electrical Contacts in a Miniature Electrical Switch

A spring beam in a miniature electrical switch enables the two electrical contacts to either close or separate and supplies both current and necessary contact pressure between the contacts. Arc erosion and material transfer between the contacts occur, and those aspects depend on various parameters including the kinematics of the contacts. Therefore, the mechanical properties of the spring beam will affect the arc erosion and material transfer, but this topic has not been well studied. In this study, the material transfer phenomena between two AgCu contacts attached to a spring beam made of three different copper-based strip alloys were investigated after 30,000 switching operations under 12 V and 9 A in a direct-current resistive load circuit. For spring beams made of beryllium copper (BeCu) and titanium copper (TiCu) alloy, the material transfer occurred from the cathode to the anode. However, an opposite material transfer occurred for a spring beam made of Corson-type (CuNiSi) alloy. The make- and break-arc voltage waveforms were analyzed, and the results showed that the changes in arcing behaviors depend on the spring beam material. The properties of the spring beam materials responsible for the changed arcing behaviors are discussed and their relationship with the observed contact arc erosion and material transfer is analyzed.