Investigation of the heat affected volume of CuCr contact material for vacuum interrupters

This work is focused on the microstructural changes during switching of simple geometry, butt-type contacts in a demountable vacuum chamber. The heat affected volume in copper-chromium (CuCr) with different chromium (Cr) content and the particle size in the re-solidified area were investigated. It was found that there is only a negligible difference between copper (Cu) with 25 (CC75) and 43 (CC57) wt% Cr. For CC57 a sudden change in the investigated parameters is observed for transferred charges above 35 As and a peak current (I
_p
) higher than 6 kA. It is assumed that a transition into the arc mode occurs. The results were assessed against published work, in which the switching process was observed using a camera and compared with the development of arc voltage.