Electrical contact phenomena during impact

The events occurring during the impact of electrical contacts are vital to the long-term reliability of switching systems. The theory of impact as it applies to electrical contacts, under influence of current loading is described. The theory uses the coefficient of restitution as a means of modeling the events at impact. Design parameters are considered in terms of their influence upon the dynamics of impact and bounce. Experimental studies are presented which include the measurement of impact forces, impact time, and both current and voltage characteristics. The influence of preimpact arcing is evaluated in the medium current range, and is shown to have an effect on the events occurring during the first impact. A semi-empirical mathematical model is proposed for electrical contact bounce