ANALYSIS OF TEMPERATURE ON THE ROTARY BREAKING SYSTEM OF A MOLDED CASE CIRCUIT BREAKER AT NOMINAL CURRENT AND OVERLOAD

摘要

The paper deals with an analysis of temperature of the rotary breaking system of a molded case circuit breaker (MCCB). The MCCB has a modern concept of the breaking mechanism which uses rotary breaking system. The first part of the paper focuses on the calculation of the thermal losses of the electrical current path at nominal current of 125 A, and the contact force of 9 N. Results of laboratory measurements performed for verification of the numerical calculations are included too. The second part of the paper deals with calculation of the thermal losses of the current path during overcurrent (6 - 10 × I_n).