The Research For The Phisical Effects Of Soft Particals On The Reliability Of Electrical Contacts

According to statistical analysis for components of failure electric contacts, soft particles play important roles in impacting reliability of electric contacts besides hard particles. Two kinds of soft particles gypsum and mica particles which take relatively major proportion in composition of dust often can be found in failure contact areas.The research work focused on the physical effects of gypsum and mica particles on the reliability of electrical contacts respectively. Based on analyzing physical mechanism and geometry characteristics of these two particles, physical models were built. The analysis and calculation results using physical models were verified by both static and dynamic experiments. The physical effects of soft particles on reliability of electrical contacts were discussed based on experimental results.In this paper, original dimension distribution of gypsum and mica particles samples was measured. Then through lapping experiments the changes of dimension distribution and geometry of these two particles undergoing contact load were concluded. These data gave a preliminary impression of physical mechanism and geometry characteristics of these two particles. Based on these data, the physical effects of these two particles on reliability of electrical contacts were researched under static and dynamic situations. Mica particles had sheet structure, even after being broken. In static situation, failure of electric contacts caused by mica particles was mainly attributed to directly enveloping a-spots. While gypsum particles were easy to break, in static situation, gypsum particles accumulated after breaking and reduced the normal force of a-spots, which caused failure of electric contacts. However, gypsum particles in the environment was too less to accumulate on contact areas. So gypsum particles will have little contribution to failure of electric contacts. In dynamic situation, mica particles were easier to enter electric contact interface than particles with ball structure in the same conditions. The smaller the mica particles were much easier to insert electric contact interfaces. And the embedded mica particles which were stirred up by probe covered a-spots again during the dynamic experiment. At the same time, mica particles abrasively wore the contact noble finishes, which accelerated failure of electric contacts.