Advances in low-voltage circuit breaker modelling

Abstract

This paper is devoted to the study of electric arc behaviour under the influence of an external magnetic field. This situation is close to that occurring in a low-voltage circuit breaker where an arc, after ignition, is submitted to the magnetic field of the circuit. After a discussion of the literature, we present our contribution. Two different methods are compared to take the magnetic effects into account. Arc displacement in the geometry studied is dealt within a specific development presented in this paper. We show the influence of the nature of the gas on the arc velocity and on possible re-strike using air and an air–PA6 mixture as the plasma gas.

Arc tracking energy balance for copper and aluminum aeronautic cables

“…for λ>200 nm, which does not include the VUV part) for a plasma radius Rp =2mm as a function of temperature. In our case one can assume that the mean temperature in the core of the plasma is close to 15 000 K, by comparison to thermal plasmas in similar conditions such as encountered in low voltage circuit breakers [9]. The results show that for both materials the total NEC is similar (~3.0 9 W.m -3…”

Basic knowledge on radiative and transport properties to begin in thermal plasmas modelling

“…These equations help us to characterize the behaviour of thermal plasmas, the interaction of gases with the electrical arc or the interaction of plasmas with the surrounding materials. Usually, the system is composed of three common conservation equations: mass, momentum and energy coupled to the ad hoc Maxwell's equations [1][2][3][4] (depending on the problem). To these equations, a set of complementary equations is added to take into account other electrical or thermal phenomena depending on the application: 5-7 turbulence effects, 8 deviations from chemical equilibrium or thermal equilibrium, 9 modelling of multiphase flows, role of the shielding gases, 10 interactions arcanode/cathode, 11-13 interaction plasma-walls and/or plasma-particles, [14][15][16] diffusion of the gaseous species or particles in the plasma, 17 formation of fume or nucleation/growth/aggregation of particles 18,19 are some examples.…”

“…), metallurgy (plasma welding, plasma cutting) petrochemistry, medical applications (treatment of tumours), protection of humans and electrical installations, or in the environment (syngas production, applications for waste treatments). Depending on the application, we use various technologies which often imply: non transferred arcs (used in plasma torches for spraying, with Ar, H 2 or He gases, their mixtures Ar/H 2 , Ar/He, Ar/H 2 /He, contaminated or not by iron, copper or aluminium particles); transferred arcs (used in plasma torches for plasma cutting, with Ar, O 2 , N 2 or Air gases, their mixtures Ar/O 2 and Ar/N 2 , with or without metallic vapours Fe, Al, Cu, Ag, or Si for welding); the circuit breakers with SF 6 , CO 2 or Air mixed with organic and/or metallic vapours C 2 F 4 , Cu, W, Ag, Al); the wall-stabilized arcs (Ar, H 2 , He and their mixtures Ar/H 2 , Ar/He); the plasmas created by laser impact (LIBS) used to analyse materials or to detect pollutants in liquids (H 2 O + alkaline salts NaCl, MgCl 2 , CaCl 2 ); the short-circuit arcs (phenomena of arc tracking with mixtures of Air-Al or Air-Fe for example); the arc lamps for which the visible radiation represents the efficiency of the process (the main objective consists in obtaining an effective, pleasant and long life luminosity with a low energy consumption; these lamps can work at low or high pressure); the spectro-analysis, the treatment or the synthesis of materials where radio frequency torches (RF) are mainly used (a gas is excited by RF under a pressure often close to the atmospheric pressure as in the case of the inductive coupling plasma torches (ICP), the corresponding plasmas are often thermal plasmas with high volumes, high purity, but the energy densities are generally weaker than those of some arc plasmas leading to a weaker influence of the radiation); the plasmas reactors to synthesize nanopowders such as fullerenes or carbon nanotubes (but the most important region of the process is not really affected by the radiation of the gas). Whatever the fields of applications, the scientific studies concern the modelling of the energy transfers (inside the plasma or outside considering the surrounding materials) usually dominated by the thermal radiation and the transport phenomena.…”

Magnetic field approaches in dc thermal plasma modelling

“…The self-induced magnetic field is due to current circulation not only in the plasma but also in the electrodes. Nevertheless current circulation in the electrode is never or rarely taken into account except in low-voltage circuit-breaker studies to represent arc displacement [15]. Several methods exist to represent the self-induced magnetic field such as also to obtain a satisfactory method in 2D, the elliptic integrals are used to assume the boundary conditions.…”