Definitions and high power breakers

Abstract

We term a contact a switch when we wish to emphasize that its behavior on breaking or making is of special interest. The general problem in Part III is confined to cases where the members move at right angles to the contact surface; very little attention is paid to tangential components of the movement. The treatment is also limited as regards the energy of the circuit; as a rule it will be small enough to be taken up by a condenser of manageable size. The arc will be quenched or at least be of short duration. This condition restricts Part III to the theory of relatively short arcs. Only in § 70 and in the present chapter, which is devoted to a general survey of phenomena encountered in switches, shall we go beyond the restrictions. In high power circuit breakers ¹ it is impossible to avoid an arc; but the arc has to be extinguished some few milliseconds after its appearance.