Peculiarities of current overload in the car electric network

Introduction. The data given in the article show that the problem of fire safety in motor vehicles is highly relevant. The purpose of the article is to develop a scientifically based method of research for the copper conductor exposed to overcurrent to find the reason of its damage when making a fire investigation. Materials and methods. The research was conducted using the JSM-6390LV scanning electron microscope for energy dispersive spectroscopy. The surfaces of the copper conductor rupture were analyzed without any preliminary sample preparation. Results and discussion. The analysis of the experimental evidence demonstrates that the temperature of the copper conductor exposed to current overload varies significantly along its length. It was found through the field studies and experimental results that the rupture of the copper conductor under the action of overcurrent happens in the sections that have prestress due to the plastic deformation. The experiment proved that the formation of ball fusing of the copper conductor exposed to current overload may take place at a substantially lower temperature than that of the copper smelting. The analysis of the theoretical data shows that during the current overload not only thermal and electromagnetic processes but also plastic distortion occur at the copper conductor. It also demonstrates that the strand connection of copper wires results in a fire hazard not in every instance. Conclusion. A method for differentiating fire damages at the copper conductor (current overload, short circuit) was suggested. The current overload has such features as blistering or ball fusing in the bending points and the lack of any signs of mass transfer. It was found that the features of the damaged surfaces of the copper conductor exposed to overcurrent are stable and not subject to changes in the natural storage conditions. The data given in the article can be used by specialists when making an expert examination of copper conductors from the fire locations, identifying a mechanism for their damage and, finally, a cause of fire.