On specific short circuit parameters of 12 vautomobile electric systems

Introduction. The data presented in the article show that the problem of differentiating primary and secondary short circuits is very important. The purpose of the article is to develop a scientifically grounded research method for copper conductors of automobile electric systems showing signs of a short circuit to identify the cause of its damage in a fire investigation.
Materials and methods. The research was conducted with the help of JSM-6390LV scanning electron microscope having an energy dispersive microanalysis unit attached, DuraScan 20 microhardness tester, and Fluke Ti400 infrared thermal imager.
Results and discussion. It is experimentally proven that the microhardness of a copper conductor subjected to a primary short circuit differs from that of a copper conductor subjected to an overcurrent or external high temperature. Images of microhardness measurement areas of a copper conductor subjected to a primary short circuit are provided. The results of an energy dispersive analysis and characteristic diagnostic features allowing to establish the cause of the copper conductor damage in case of fire (primary or secondary short circuit) are provided. The temperature of the copper conductor is measured for short circuits that entail sparking and an arc. The applicability of the computational method for determining the conductor temperature in the event of a short circuit is experimentally proved.
Conclusions. A differentiation method is proposed for telling primary short circuits from secondary ones arising in copper conductors of automobile electrical systems. It is shown that the microhardness testing method can supplement the scanning electron microscopy method. The results provided in the article can be used by specialists to study copper conductors extracted from burned vehicles in order to identify the mechanism of their damage and, eventually, the cause of the car fire.

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