Fabrication and testing of silver based composites for electrical contactors

Abstract

In recent days, contactors find their utilization in nearly all kinds of industries and household applications. Their functions are closing the circuit, carrying the current without any electro-thermo-mechanical distortion at the contacting points, interrupting the circuit at times of necessities and prolonging the switching cycle for maximum number of operations without any deterioration. The most common type of contactors used in power distribution applications is Circuit Breakers (CBs) and electromechanical relays (relays). The actuation of CB and relays is subjected to continuous tripping with the fluctuations in current due to variations in load side. Thus, for a load bearing unit, failure is inevitable. Generally, the failure of CB and relays is not caused by a single Failure Mode (FM), but due to the combination of multiple FMs. A review of available literature has shown that the failure assessment of power distribution units and material selection for contact applications is still a relatively new topic of research. Failure analysis of electrical contactors by incorporating all the FMs using Failure Mode and Effect Analysis (FMEA) based on end-user perspective is rarely found in literature. Further the election of the best suitable material with required properties for electrical contact points poses to be a stiff task in the recent era. Development of composite materials with variations in material properties may improve the life of the contactors. The commercially used contact materials are Silver (Ag) based Metal Oxides (MeOs) and refractory carbides. Reviews show that Powder Metallurgy (PM) method is the predominant method for fabricating the Ag based contact material. Fabrication of Ag based composite contact materials by Stir Casting (SC) process is rarely found in literature. newline