Effect of electromagnetic fields in the process of arc extinction in molded case circuit breakers

Abstract

The new computational tools developed in the last decade are a great contribution to solve complex problems related to the design of circuit breakers. In the past, the experimental research was almost the unique way to improve this kind of technology, a lot of tests were made at laboratories and it was so expensive. Finite Element Analysis made possible to simulate scenarios and develop new technology supporting experimental test and decreasing the number of experimental essays. This thesis proposes the analysis of a module of arc extinction of a Molded Case Circuit Breaker (MCCB) by using Finite Element Method (FEM) software. In this work, the Lorentz force that moves the arc to the arc chutes and lets the elimination of the electric arc is calculated and a model is proposed that determines the contribution of each element of the MCCB to increase or align this magnetic force at the arc. The characteristics of the arc chute are reviewed too, the features analyzed were: the shape of plates, the material used in their fabrication, the influence of the number of plates in the Lorentz forces, and the variation of the distance between plates. The contribution to the Lorentz forces at the arc of the main elements of the module of arc extinction is shown in this work. It is also determined the configurations that allow a better design in the construction of arc chutes. As results, we obtain that the main purpose of the cheeks in the MCCB arc module extinction is to align the magnetic field in the arc. All other steel components increase the Lorentz force in it, accelerating the process of extinction. The best material to increase the magnetic forces is the AFK1 due to its high level of magnetic saturation but this material is so expensive. As a conclusion of this work, we obtain a methodology to design and calculate the effects of the magnetic fields in the arc produced in the chamber extinction of the MCCB.