A sliding wear tester for overhead wires and current collectors in light rail systems

This paper presents the dedicated experimental equipment developed for a study of the tribological behaviour of current collectors sliding against overhead contact wires under various conditions. A unique wear tester that replicates the operating conditions of actual pantographs in railway power collection systems was developed. The sliding element moves over the wire in a controlled horizontal motion at homogeneous velocity, and a constant normal load can be applied on the contact materials during this motion. Dynamic friction coefficient data, as well as the dynamic contact resistance between the contact couples were monitored using a signal collection device equipped with data acquisition (DAQ) software. The wear couples were examined in sliding using under the same normal load, in dry and lubricated conditions. The friction coefficient decreases during the test in all cases, but electrical resistance and contact resistance increase. For Cu vs. Cu in dry contact, the dynamic friction coefficient measured after run-in was 0.34 and the electrical contact resistance increased by approximately 5% after 10(6) wear cycles. Application of graphite grease - a commonly used lubricant - increased the contact resistance by about 300%. The dynamic friction coefficient of Cu vs. Cu lubricated with common grease was constant - about 0.24, and the electrical contact resistance was 1.97 mu Omega. For carbon-copper composite materials (CCM) in dry sliding against Cu, the dynamic friction coefficient reduces by 20% (from 0.27 to 0.22) after 40,000 cycles, while the dynamic electrical resistance increased slightly from 5.32 to 5.35. (C) 2000 Elsevier Science S.A. All rights reserved.