Analysis of surface wear of W-Cu contacts in voltage regulator tap changers

Abstract

This study presents the analysis of moving tap-changing contacts in automatic line voltage regulators, focusing on mechanical characterization and surface wear. Given the need to predict and mitigate operational failures in this equipment, and aiming to narrow the scope, this proposal focuses on the surface wear analysis of a voltage regulator's moving contacts. It is crucial to analyze these moving contacts due to the friction generated during automatic tap-changing maneuvers and the effects resulting from electric arcs during these operations. The contacts were evaluated using scanning electron microscopy (SEM) and tested through a rubber wheel abrasive wear test. This work aims to evaluate the performance of moving contacts regarding their mechanical wear resistance properties using microstructural analysis techniques, abrasive wear testing, roughness measurements, and surface hardness testing. The results allow for the conclusion that the analyzed contacts were manufactured through a W-Cu sintering process and exhibit relatively low wear resistance, given that the average volumetric loss was 189.8 $cm^3$. Furthermore, microscopic analysis identified the adhesion of certain chemical elements on the contact surfaces after the abrasive wear test.