A Study of the Temperature Modes of the Automatic Switch Contacts in Cutoff of Short-Circuit Currents

Abstract

This paper considers processes of electric arc damping by automatic switches in the short-circuit mode. Certain conditions for facilitating a successful short-circuit arc damping are shown, such as the limitation of the short-circuit current amplitude by its active resistance, the reduction of the phase shift between current and voltage, and the amplitude loss in returning and restoring voltages. The article features oscillograms of currents and voltages in the short-circuit mode. Anode heating processes are also described within the framework of the process of arc burning (heat saturation mode) and after the change of polarity current transition through zero processes at the cathode in the temperature equalization mode. Mathematical models of processes at the cathode took into account the thermal flows of the ionic component and evaporation. The calculations were carried out with the average values of thermal coefficients for copper, as the arc base moves from contacts to contact holders, which are made of copper and its alloys. The results of the calculations proved the validity of the considered mathematical models of thermal processes at both the cathode and the anode.