Reliability Of Several Typical Compositions Of Dust On Electrical Contact

Dust is one of the reasons that cause electric contact failure. Dust consists of two parts:inorganic material and organic material. Choosing appropriate materials to act as artificial dust particles is of urgent importance. Fibers and calcite particles were chosen as typical materials and were adapted to study the electrical contact behaviors by simulated experiments under static and dynamic conditions. The factors of failure mechanisms (such as the density of particles and the normal force) were also discussed.The normal force is the main factor that affects static contact resistance. Increasing the normal force could reduce the contact resistance. Fiber density also had influence on static contact resistance. The effect of fibers on contacts was depended on the coverage of a-spots. Exponential Function Fit was used to analyze the increase trend of the contact resistance on coupon as the densities of fibers increased. The analysis of variance shows the normal force more markedly influenced the contact resistance for the contacts covered by fibers than fiber density. At dynamic conditions, fibers were more easily pushed away under larger normal force and re-entry difficultly. The fibers have no significant effect on fretting wear between contact surfaces.Calcite is the typical material of soft dust.Under certain normal force, the calcite particles were staved to form a compact pancake structure. Exponential Function Fit was used to analyze the increase trend of the contact resistance as the densities of calcite particles increased. For 45μm calcite particles covered contacts, the contact failure was depended on the thickness of the film formed by the crashed large particles. But for 10μm fine calcite particles covered contacts, the contact failure was depended on the density of the fine calcite particles on the contacts. Under dynamic condition, calcite particles were grounded into finer powders to play a role of the abradant. The increase of contact resistance was caused not only by fretting corrosion of exposed nickel, but also by calcite particles remained in the contact zones.