Structural Change of Low Voltage Electrical Switches Under the Effect of Electrical Arc Erosion

Abstract

The objective of this work is to study the structural change and the behavior of low voltage electrical switches under the effect of electrical arc erosion phenomena. The problem of erosion is regarded as the essential problem of the contacts, and the design of the latter depends directly on the erosion that they undergo. The combined performance of the material, in electrical conduction and in erosion, is at the basis of the design and the sizing of the contact apparatus. The structural change and the behavior in erosion are determined on the basis of endurance tests. The latter were made, in the factory, on switches whose contacts were made of AgNi and AgSnO2, and this was done, according to the NFC standard. The obtained results showed different erosion characteristics and behavior from those usually observed on isolated contact testing machines. In order to determine the nature of the observed deposits on the contact surfaces of AgNi and AgSnO2, analyses by micro-graphs from the electron microscope were made at the National Institute of Research and Physicochemical Analysis (INRAP) and shown various behaviors in erosion according to the number of operations: oxide formation on the surface, intense vaporization and wrenching of the basic material and contamination by carbonaceous deposits coming from the isolated wall of the apparatus. This last phenomenon was specially observed on high voltage circuit breaker devices.
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