Design And Development Of Rack Of Cradle Used In Air Circuit Breaker

Abstract

In air circuit breaker (ACB), rack is used to move breaker IN and OUT from the cradle which in process performs a sliding motion in horizontal direction. In this arrangement, rack which has been made from cast steel is used to rotate the pinion shaft. It has been observed that the rack used in current design of air circuit breaker has high cost and manufacturing defects. Hence a cost effective solution needs to be devised considering value engineering (VE) as a research methodology. Manufacturing process used in the proposed design is sheet metal works. The parameters namely dimensional constraints, formability, bend ability, costs of existing part have been considered for the new design. CAD model of rack has been prepared using pro/e software and subsequently static analysis has been carried out. Material has been selected for modified rack. Torque has been measured for rack in & rack out operations for design improvement of rack. PI cam follower used in ACB has also been modified. Fatigue life of the rack is calculated by analytical method. It has been observed that cost of rack is reduced by 65%.