Digital Model of Switching Element Contact Surface

Real contacts adhere to one another only in separate elements of surface, creating so-called contact microfields. This is caused by a lack of perfectly smooth and planar contact elements. Irregularities of contact surfaces cause, in the initial phase of closing contacts, only small surfaces of contact and, moreover, not in many points. As contacts begin to draw nearer, the next irregularities of surfaces touch. Consequently, the real surface of contact becomes greater, and therefore, the resistance of the considered switching element decreases. The sum of the surfaces of all contact microfields creates the total real contact surface. This surface mainly determines the resistance of contact. The amount of the real contact surface depends on the magnitude of force tightening both contacts, on the state of irregularity of contact surfaces, on the structure and mechanical features of contact materials, and so on. These quantities can be described by analytic and empirical random variables. A mathematical model of contact surfaces of metallic electrical contacts is described. This model is created based on random variable functions, which describe mechanical features of contact materials. A program of computation, which makes calculation of relative contact surfaces of contact elements possible, has been prepared.