3D finite element analysis modelling of the arc chamber of a current limiting miniature circuit breaker

This paper presents the initial stage of a 3D finite element (FE) model of the electromagnetic field in the are chamber of a current limiting miniature circuit breaker (MCB). The final objective of the model is to compute the magnetic forces on the are, and predict the position of the are at a series of discrete time steps. The trajectory of the are calculated from the model will then be compared.with experimental data recorded by a high speed are imaging system (AIS) on a flexible test apparatus (FTA) designed to simulate the operation of a commercial MCB under laboratory conditions. By comparing the FE model of the are behaviour with the actual are images generated from the AIS an insight into the factors governing the motion of the are can be gained. In particular the relative importance of the average flux density across the are chamber is compared with the local flux density distribution at the are roots. An understanding of the influence of the magnetic flux distribution can then be used to improve the magnetic design of the MCB to promote low immobility times and effective current limiting operation.