Potential measurements on electric contacts: An experimental investigation

In this work, an experimental investigation is attempted, concerning electrical contacts evaluation through analog to digital measurements and physical interpretations of the dominant phenomena are presented. The circuit employed is in agreement with IEC0660 specifications concerning switch overheat tests. The commercial switches used for the measurements, had the following nominal characteristics: isolators 20 kV/200 A, fuse isolators 20 kV/65 A and isolators 500 V/100 A. The measurements were performed through A/D converters with a sampling frequency of 4 MSPS, and waveforms of the voltage drop and current were obtained for the nominal current values of the specimens. Current–voltage plots ( I– V plots) by time elimination, corresponding to a part of the waveforms are also presented. Further analysis of the data obtained is performed and it can easily be concluded that the thickness of the interfacial layer determines the conduction mechanisms. In the case of contacts in advanced degradation the current conduction is mainly attributed to field emission or field ionization processes. The above dominant effects characterize high rates of electronic conduction via stationary metal contacts at a state where linear behavior has ceased and instabilities have developed. The data which resulted lead to an effective test for industrial switching contacts and could aid technoeconomical selections.