Experimental Research On The Effect Of Hard Particles And Orgfanic Contaminants On Electric Contact Reliability

Electric contact is a specialized science on system electric transmission reliability. A considerable portion of electric contact failure is caused by environmental factors, of which dust contamination is an important factor on electric contact reliability.The paper summarized the research on the effect of dust particles and organic contaminants on electric contact reliability. The electric contact failure caused by hard dust particles was simulated. Both the static and dynamic contact resistance were tested under laboratory environment. The failure mechanism was analyzed by contact resistance and surface detection equipment such as optical microscope, scanning electron microscopy and X-ray energy spectrometer. Based on the definition of the initial failure cycle and contact life cycle, contact life model was established by using statistical tools and the factors on contact life were also discussed.The experiments confirmed that the presence of quartz particles between contact interfaces is embedded or broken. Under the long-term fretting, quartz particles as a role of abrasive debris damaged the gold-plated layer and lead to fretting corrosion, so that contact resistance increased. Contact load, size of quartz particles and the number of particles embedding contact areas are the main factors on the initial failure cycle and contact life cycle. In order to accelerate the failure, small size of quartz particles and low contact load should be used, and also increase the density of dust particles to ensure that particles can enter the contact zones repeatedly. On the contrary, in order to increase the contact life, it is necessary to avoid the small size of quartz particles entering the contact interface, choose larger contact load and improve the connector sealing structure to reduce the density of dust particles.On the other hand, the paper established the adhesion model for dust particles and organic contaminants and carried out qualitative and quantitative analysis on adhesion force and presumed that there should be a film thickness for sodium lactate which can produce a maximal adhesion force. Simulation of the fretting failure with the coexistence of dust particles and sodium lactate confirmed that the sodium lactate could result in high contact resistance. The adhesion force that the sodium lactate produce on the small size of quartz particles is much stronger, which could cause contact failure more likely. Increase the contact load could avoid the probe crossing over the particle pile and push the particles away from the fretting area, this method is effective for the small size of quartz particles. It should take effective measures to prevent the organic compounds volatizing contact interfaces, which could cause electric contact failure.