PT102038A - Current limiting device - Google Patents

Abstract

The present invention refers to a current limiting device 1 comprising, at least, two electrodes 3, at least one electrically conductive composite material 5 between said electrodes 3, and at least one interface 7, which utilises the electrically conductive composite material 5 and a nonhomogeneous distribution of the resistance structure. The nonhomogeneous distribution is typically chosen so that at least one thin selected layer of the current limiting device 1 has a resistance much greater than the remainder of the current limiting device. In fact, in the device the pressure is typically exerted in the composite material 5 in a direction normal to the thin selected layer. During a short circuit, it is believed that an adiabatic resistive heating of this thin selected layer is followed by a rapid thermal expansion, which results in a partial or complete physical separation of the current limiting device in the thin selected layer, which produces a higher overall resistance of the device to the passage of electric current. Thus, the current limiting device limits the flow of current through the short-circuited current circuit. When the short circuit disappears, the current limiting device recovers its low resistance state, allowing the electric current to pass normally. The current limiter of the present invention can be reused for many short circuit conditions. The current limiting device is produced by the electrical materials industry. <IMAGE>