Thermal Analysis to Prepare Derating Chart of U-Power OMEGA Air Circuit Breaker

Abstract

The air circuit breaker is a switching device used in low-voltage power systems to carry current in normal conditions and break currents under specified abnormal circuit conditions by suitable operation. During normal conditions, the current flowing through the air circuit breaker is associated with the generation of heat and hence the temperature rise occurs. The temperature of the breaker should always be within permissible limits as specified by the standards for the safe operation of the circuit breaker. The main problem that arises during the installation of the circuit breaker is calculating the maximum current that the circuit breaker can carry without damaging itself and untimely aging according to the service temperature. The proposed project aims to prepare the derating chart of the circuit breaker having ratings ranging from 400A-6300A. The heat generated in the circuit breaker depends on the internal structure of the switch board, bus bars, cables, cross-section of the conductors, and the path of current flowing in the switchboard. In order to identify the correct rating of the circuit breaker to be installed, it is necessary to analyze the circuit breaker assembly from a thermodynamic point of view. For thermal analysis, modeling of the breaker will be on the CREO software and the thermal analysis of the same will be done on the ANSYS software. The ANSYS simulation parameters include the degree of protection, the material of the bus bars used, the type of installation, the orientation of the adaptors, and the ambient temperature. The analysis will be done for different current ratings. The verification of the results obtained from the simulation will be compared with the practical values of that current rating. Subsequently, a mathematical model has been prepared in MATLAB to obtain the values for different current ratings ranging from 400A-6300A.