Arc duration during contact closure with voltages below 200 to 300 V

Abstract

Arcing at contact make takes place because of several reasons. 1. Arcs may be drawn at rebounds. This event shall not be discussed here. 2. The contact members may first meet solid surface asperities. These are heated to vaporization by the current, thus interrupting the contact. In the superheated, highly ionized vapor, an arc ignites. Such a happening is apparent from Fig. (58.01). 3. Germer and collaborators assume (see § 49 B,) that an arc can ignite during closure in the narrow gap at points of enhanced field emission. In this book another idea is represented, namely that a whisker forms and, when hit, shortcircuits the gap, thereby exploding and igniting an arc¹. This means an ignition similar to that of case 2. It is a special question if the arc finally produces floating as decribed in § 59.