Thermal Analysis of the Fuse with Unequal Fuse Links Using Finite Element Method
In this paper a three dimensional thermal model of high breaking capacity fuse with unequal fuse links is proposed for both steady-state or transient conditions. The influence of ambient temperature and electric current on the temperature distribution inside the fuse, has been investigated. A thermal analysis of the unbalanced distribution of the electric current through the fuse elements and their influence on fuse link temperature rise, has been performed. To validate the three dimensional thermal model, some experimental tests have been done. There is a good correlation between experimental and simulation results. Keywords—Electric fuse, fuse links, temperature distribution, thermal analysis.
Numerical method for pre-arcing times: Application in HBC fuses with heavy fault-currents
This works deals with calculations of pre-arcing time prediction for fuse links used in industrial protection circuits in case of heavy faults-currents. An enthalpy method to solve heat-transfer equation included two phase-changes is presented. The mathematical model couples thermal and electrical equations based on the principle of energy conservation and the Ohm's law respectively. In order to determine current density and temperature evolution in the fuses, three typical fuse links have been chosen for the calculations with circular, rectangular and trapezoidal reduced sections at their centre. Silver physical properties, mathematical equations and the numerical method are reported. Calculations results show that for the fuse link with rectangular reduced section a major heat-transfer mechanism took place compared to the other ones.
Simulation numérique des phénomènes thermiques et magnétohydrodynamiques dans une cellule de Hall-Héroult
This work is concerned with a numerical simulation of the thermal behaviour of an electrolysis cell for the production of the aluminium. Aluminium is produced by an electrolytic reduction of alumina dissolved in a bath of molten cryolite. In this reduction process, called Hall-Heroult process, the metal is produced at about 965 °C. A frozen bath layer, called ledge, arises in the boundary region and protects the side walls of the cell from corrosive electrolyte. This ledge may change the magnetohydrodynamical equilibrium of the cell and reduce the heat loss through the walls. The ledge is thus playing a significant role in both the thermal and magnetohydrodynamical behaviour of the cell. A precise knowledge of the ledge is thus an imporant ingredient in the optimization process of the cell. The temperature field and the ledge shape in a whole smelter are obtained by simultaneously solving the system of equations formed by: a non-linear convection-diffusion heat equation, which can be considered as a Stephan problem in enthalpy and temperature in the domain of the cell occupied by fluids and ledge, Navier-Stokes equations with a free interface in the fluid domains and Maxwell equations in the whole space. The source term of the heat equation results from the Joule effect due to the electrical current crossing the cell. A Chernoff scheme is used to numerically solve Stephan problem. Three dimensional numerical calculations showing ledge shape, temperature and velocity fields as well as electrical potential for an operating cell are obtained. The effect of thermal field on the electrical current and the effect of fluid motions on the ledge shape in the aluminium cells are presented.