The chopping current level of vacuum interrupters influenced by the arc quenching operations

In this paper the chopping current level of several vacuum interrupters which differ from each other by their electrode structure and contact material but share the same outer diameter and the same size of contact are measured comparatively before and after several times of arc quenching operations. The experiment result shows that for all interrupters the chopping current level of each interrupter has changed to a different extent after arc quenching compared with that of the virginal interrupters and the sequence according to the chopping current level is also altered. At the same time the microstructure of the contact is tested and the micrograph shows that the microstructure of the contact become smoother and the particles finer, as the main reason for the changed chopping current level. The chopping current level of vacuum interrupter is not constant but changed with operations, which can make some unexpected phenomena concerning the overvoltage and breakdown explicit.