Research On Sliding Electrical Contact Friction And Wear Behavior Of Pantograph Catenary System

The pantograph catenary system is power source of electric locomotive of high-speed electrified railway. Current-carrying friction and wear are the main features of the sliding electrical contact state between pantograph and catenary wires. They constitute a special frictional pair coupled electro-mechanical wear under complex environmental conditions. Current-carrying friction and wear behavior between pantograph and catenary wire has become increasingly complex with the continuous increasing speed of electric locomotive. And more problems on current collection will occur under high-speed, which restricts the further acceleration of electric locomotive. Therefore, the friction and wear characteristics and the stability of current-carrying of the electric locomotive pantograph and contact wire were studied by relying on the National Natural Science Foundation of China (Research on wear steady-state under high-speed sliding electrical contact, NO. 50677027).A sliding electrical contact friction and wear tester was developed firstly (Patent No. CN200920012471.9). It can simulate actual operating conditions of electric locomotive, achieve uniform wear of pantograph and wire, and the friction coefficient, the contact point temperature, relative sliding speed, sliding back and forth movement frequency, the wear loss between contact wire and pantograph, contact current, contact voltage, contact resistance and other parameters are online measured in real time, and the data are saved, which can be achieved within a certain current, load, speed and other single-factor and multi-factor control. Monitoring interface and data processing system were designed based on LabView software. The data detected by the lower computer can be displayed and recorded real-timely, and waveform curve and the reports variously were generated, which create the conditions for further theoretical analysis.Through conducting lots of experiments on copper based powder metallurgy pantograph, immersed copper carbon pantograph and copper-tin contact wire and studying friction and wear behavior under high current, heavy loads, high sliding speed, the current-carrying friction and wear characteristics, current-carrying stability and contact point temperature rise characteristics of the pantograph were obtained. The wear morphologies of pantograph were analyzed by using SSX-550 scanning electron microscope. The results showed that the contact resistance of copper based powder metallurgy pantograph is less than that of immersed copper carbon pantograph in the same condition of contact pressure and current-carrying, contact resistance change rate of immersed copper carbon pantograph is smaller than that of copper based powder metallurgy pantograph and stability of current-carrying is better in the condition of same contact pressure and different current-carrying, the temperature rise rate of two materials pantograph is different in the same current-carrying, the temperature rise range of immersed copper carbon pantograph larger than that of copper based powder metallurgy pantograph with the increasing current, but the temperature rise range of later decrease gradually, the main factors of temperature rise are frictional heat and Joule heat when the current is smaller, the main factors of temperature rise are Joule heat and arc heat when the current increases to a certain value.Among the three important factors, which respectively is contact pressure, sliding speed and load current, current have the greatest influence to current-carrier friction abrasion characteristic of pantograph slide. Under different carriers,the wear rate of two kinds of slide increase with increasing current. But the wear rate of copper based powder metallurgy pantograph slide changes greatly with increasing current, whereas leaching of copper carbon slide has a small change amplitude of wear rate and a fairly perfect wear-resisting property.Under a constant relative sliding speed, both current-carrying quality of slide and contact stability of friction pair are improved while friction factor increases due to increasing contact pressure of the friction pair. Therefore, wear rate presents "U"-shaped variation which firstly decreases and then increases. Contact pressure threshold increases with increasing contact current corresponding to minimal wear rate. Under a constant contact pressure, the friction factor between the friction pair decreases continuously with increasing sliding speed, contact stability and carrier quality deteriorate continuously, while wear rate decreases with increasing sliding speed and increases with increasing contact current.This paper proposes the concept of steady state, which is a state of lower wear loss and relatively stable wear rate after a period of rubbing with each other between pantograph slide and contact wire under certain condition. In steady state stage, there is a bright film layer on the surface of friction pair. Wear steady state has a great influence to the performance and service life of friction pair. The state before reaching the wear steady-state is called transition state, during which the friction and wear form is mainly macroscopic arc erosion and abrasive wear. The period of transition state will be shortened and reach wear steady state rapidly by increasing relative sliding speed and adjusting contact pressure. In the wear steady state rapidly, the friction and wear form is mainly microscopic arc erosion and adhesive wear.