An improvement of a contact spring pin of a 126 kV vacuum circuit breaker by orthogonal experimental design

The objective of this paper is to improve the fatigue life of a contact spring pin in a 126 kV vacuum circuit breaker (VCB). Firstly, the fatigue life of the contact spring pin during the opening or closing operation of the 126kV VCB is analyzed. Secondly, an orthogonal experimental method is used for the improvement of the fatigue life of the contact spring pin, in which three impact factors are considered, including the pin material, the cross section contour of the pin, as well as the location of the limiting apertures of the pin. The improved pin was with a material of Ni-Cr steel, a racetrack cross-section with the straight line length of 12 mm, and a limiting aperture of level 2, respectively. The mechanical endurance test result shows that the original pin is cracked after 178 operations. However, the mechanical endurance of the improved structure shows that the pin keeps normal function after 2000 operations.