Sliding contacts with conduction of electrical current have been investigated many times because of their significant importance in many electrical machines and devices. Custom made tribological testing rig with a capacity up to 17 m/s sliding speed and 20 A electrical current was developed and is described in this study. The testing rig was used to perform tribological study of different material combinations, normal contact pressures, electrical currents and surface polarity on wear, friction, contact resistance and temperature. Long-term tests (240 h) were performed to reduce measurement error effect on wear rate evaluation. Positive effect of electrical current passing on coefficient of friction was noted. At sufficient contact pressures electron donating surface (negative bias) exhibited higher wear rate in comparison to positively biased contact surface. On the other hand, arcing in contact usually appears at low contact pressures, which severely increases wear of the contacting materials. Both, friction and contact resistance contribute to contact temperature rise. Therefore, the contact material pairing is of significant importance for efficient electrical and tribological properties of the sliding electrical contacts.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 14134043Because of even longer lifetime, improved efficiency, and reduced or even no maintenance requirements for some electrical devices is also for sliding electrical contacts, as one of key critical elements of those devise, required to improve their life-time, electrical and tribological properties. To achieve much longer lifetime with reducing contact surfaces wear rate, new innovative slip-ring design with new contact materials is in research. Novelty of sliding contacts mean that their contact conditions are changed and unknown, so for their optimal design and successful application usage, new contacts conditions has to be researched. A custom-made tribological testing rig, which is capable to simulate electrical sliding contact conditions in wide range of electrical and mechanical loads comparable to real application conditions, was developed for this purpose. The testing rig has been used to perform tribological study of different material combinations, normal contact pressures, sliding speeds and electrical currents on wear, friction, contact temperature and electrical contact resistance. In this study, findings of different material combinations behaviour during tribological tests and their electrical, sliding and wear resistance properties are described.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 15105051Based on study results, which pointed out that some graphite/graphite material combinations are able of reliable and efficient functioning in operating conditions of end application, and identifying of optimal contact pressure, we decided to produce a prototype series of new product. Because of optimistic study results, we also made a testing device for testing the product in real end application - automotive alternators. Device would not just enable of testing the key product component - sliding electrical contact, but also design solutions of the product.
F.06 Development of a new product