Physical interpretations concerning nonlinear conductivity phenomena across no-load switching contacts

Data that aid physical interpretations concerning no-load switching contacts under high current density operation are presented. Measurements were performed on industrial switches with the following nominal values: isolation switches 400 V/100 A, isolation switches 20 kV/200 A, and fuse isolators 20 kV/100 A. It is shown that beyond a threshold field intensity (corresponding to smaller currents than the nominal values) nonlinear I-V relationships may develop, leading to bistability and negative differential conductance phenomena. This has been attributed to the dominating tunneling current component between oxidized (or nonideally contacted) metallic surfaces at high electric fields, resulting in an increased effective area of contact. The well-established metal-insulator-metal (MIM) theory, as well as that concerning nonlinear current voltage phenomena developing in insulating solids at high electric fields, provide the required theoretical basis for the interpretation of the obtained curves.<>