MAGNETIC AND GAS-DYNAMIC EFFECTS ON ARC MOTION IN MINIATURE CIRCUIT-BREAKERS

This paper presents new results on the magnetic and atmospheric enviro nment in the arc chamber of a miniature circuit breaker under short ci rcuit conditions. Finite element magnetic field calculations provide d ata on the flux density in the arc chamber and the effects of steel pl ates placed around the arc chamber. The magnetic calculations are used with a one-dimensional flow model to assess the influence of the magn etic environment on the arc dynamics. The results are compared with ne w experimental data on arc dynamics obtained using an an optical fiber imaging system in a production miniature circuit breaker. Additional information on the environment within the arc chamber is supplied by p ressure and conductance measurements. Results show that the presence o f steel in the sides of the arc chamber has a large effect on the magn etic field and the arc dynamics. Plasma jet and pressure wave formatio n have a significant effect on atmospheric conditions in the arc chamb er.