Optimization of Dual Motion Mechanism with Double Grooved Cams for High-voltage Gas Circuit Breaker

Abstract

A novel design of a dual motion mechanism for a high-voltage gas circuit breaker is presented. The contact motion of the circuit breaker due to the operating mechanism increases capacitive current switching (CCS) performance. CCS is one of the interrupting duties of the circuit breaker, where high voltage is applied during the half cycle from contact separation. The dual motion mechanism drives two contacts in opposite directions from each other. Operating energy is reduced because the maximum displacement of the moving parts linked to the operating mechanism is shortened. To increase CCS performance at lower operating energies, the contact on the opposite side of the contact linked to the operating mechanism requires quick motion in the CCS period with a short displacement. The dual motion mechanism reported here is composed of two grooved cams that cross each other (double grooved cams). A pin positioned at the intersection point of the grooved cams rotates a lever linked to both contacts while changing the lever ratio that shortens the path length of the pin movement. To implement an optimized displacement curve with low operating energy and low mechanical stress while keeping the CCS performance high, a shape optimization method was developed that uses a direct search to minimize the local contact forces acting on the contact positions between the grooved cams and the pin. In order to maintain the stability of the pin in motion, a position holding part was designed by considering size of the gaps between the grooved cams and the pin. The measured displacement curve was in good agreement with the ideal one. In addition, a fullscale prototype was fabricated that successfully passed a 10,000-motion test.