3D FINITE-ELEMENT ANALYSIS MODELING OF THE ARC CHAMBER OF A CURRENT LIMITING MINIATURE CIRCUIT-BREAKER

This paper presents the initial stage of a 3D finite element (FE) mode l of the electromagnetic field in the are chamber of a current limitin g miniature circuit breaker (MCB). The final objective of the model is to compute the magnetic forces on the are, and predict the position o f the are at a series of discrete time steps. The trajectory of the ar e calculated from the model will then be compared.with experimental da ta recorded by a high speed are imaging system (AIS) on a flexible tes t apparatus (FTA) designed to simulate the operation of a commercial M CB under laboratory conditions. By comparing the FE model of the are b ehaviour with the actual are images generated from the AIS an insight into the factors governing the motion of the are can be gained. In par ticular the relative importance of the average flux density across the are chamber is compared with the local flux density distribution at t he are roots. An understanding of the influence of the magnetic flux d istribution can then be used to improve the magnetic design of the MCB to promote low immobility times and effective current limiting operat ion.