Improvement in First time yield of Air Circuit Breaker

Abstract

Air Circuit Breaker (ACB) is a device designed to protect a low voltage power supply system. ACB is operated at atmospheric air pressure where air blast acts as an arc quenching medium. The main function of ACB is to protect the power supply system from damage produced by a short circuit or overload current and interrupt current on which could be reset (automatically or manually) to perform its normal functioning. ACB is available for 400A to 6300A current rating. Mechanism is mounted on the breaker to ON and OFF the breaker. Main Spring force is applied to the mechanism, for charging and discharging of mechanism . Due to the frictional loss, the closing force is decreasing. In this project, an investigation has been carried out in Air Circuit Breaker(ACB) to increase the First Time Yield(FTY) from 10 % to 15 % by eliminating non-confirmities like Non Closing Defect, Fault in Door Intelock . Quality control tools like Pareto Chart, Fishbone Diagram are used to analyze the target area and root cause of non-confirmities in the breakers. Modification in design has been done according to the requirement of the non conformities observed in the Pareto chart. Analysis has been carried of various components based on the specific requirements.