Functionally graded copper chromium based vacuum interrupter contact tip and its interruption ability

Copper-Chromium (CuCr) based contact material is widely used for vacuum interrupter (VI) contacts and has found worldwide acceptance in medium-voltage VIs, especially for high-current interruption. Contact material with chromium content between 25 and 50 wt. % is almost exclusively used. Conventionally, copper and chromium are uniformly distributed throughout the body of the contact. In a few cases, contacts with grading of the material along the thickness have been used. This paper presents a new concept of functionally graded electrical contact which consists of CuCr50 in the bulk region and the remaining petal region consists of CuCr25. The aim of this grading is to improve the interruption ability with optimum erosion characteristics. The paper further reports the results of the investigations of switching behavior of VI with these functionally graded contact tips. The results indicate that the higher thermal and electrical conductivity as well as anti-welding properties at the required locations of the developed functionally graded contact material improved the interruption ability of the VI. The results of the switching tests are seconded by the results of the microstructural analysis (SEM/EDS) of the arced and un-arced contact tips.