Mathematical Model to Define Electric Capacity of Transient Region of Electrical Contacts

Low-current electrical contacts are used extensively in electronics. Failures of these contacts are mainly associated with dust covering their surfaces, as well as the formation of films, changing contact pressing force, etc. The development of mathematical models for the operation of electrical contacts shall help identify the key switching component parameters and prepare failure-prevention procedures. This article considers the procedure for the calculation of the electric capacity of the transient region of electrical contact of two rough surfaces. The proposed mathematical model accounts for the potential elastic, elastic-plastic, and plastic deformations of specific rough surface protrusions. The calculation model considers two causes of electric capacity formation in the transient region. The first one is associated with the fact that the actual contact surface area is significantly smaller than the rated one because the rated surface has air pockets that form areas of high local capacities. Another cause of local capacity formation is unbroken surface films with dielectric properties. The electric capacity of the transient region can be determined by summing the local capacities of specific protrusions and air pockets. The authors produced a formula for the surface density of electric capacity in the transient region depending on the rated contact surface pressure.