Contact Material Combinations for High Performance Switching Devices

Latest developments in the fields of regenerative energies, industrial automation and automotive application generate new technical requirements for switching devices and contact materials. Rising energy densities in such devices were simulated by contactor endurance tests under heavy duty load. The results show a strong exponential relationship between arcing energy at break and contact material erosion; this effect has to be considered carefully in device design. Opportunities for precious metal reduction and/or enhanced switching capacity were found for Ag-SnO2 materials with increased total metal oxide content. The dynamic sticking behavior at make operation is a second important characteristic of electrical contacts. Especially the application of asymmetric material combinations for cost saving issues - e.g. replacing one side of a symmetric silver metal oxide combination by silver nickel - can lead to unexpected device failure. Appropriate model switch tests and corresponding metallurgy can demonstrate that behavior.