Improvement in Overload Tripping and Sustainability of Instantaneous Tripping in a Thermo-Magnetic release based Moulded Case Circuit Breaker

Abstract

Moulded case circuit breaker (MCCB) is a short circuit protective device (SCPD) which provides both Overload and Over-current fault protection and it has a wide industrial application. During normal condition the current owing through the MCCB is within prescribed limits but due to any abnormality (Overload and Short-Circuit) results in higher current values. During overloads the current owing will result in increased temperature at the Bi- metal which results in its defection and will actuate the overload tripping. Similarly for over-current tripping the magnetic forces due to over-current will result in operation of magnetic mechanism and thus actuates the tripping. The main approach of the project is to first analyse the problems related to the inconsistency in overload tripping and then identification of the possible solutions first through theoretical calculations of the heater bi-metal assembly and analysing it through ANSYS-Workbench. Over-current tripping sustainability includes the theoretical methodology which determines the sensitivity of dimensions and parameters responsible to maintain the over-current tripping with reduced failures. Possible outcome of the project is improved overload tripping at variable setting validated through theoretical calculations and test data before and after suggested solutions. By DOE methodology sensitivity of dimensions of the components essential for maintaining high over-current tripping accuracy with justification by statistical analysis.