Patent ID: 6373372
Filing Date: 2002-04-16
Classification: H01C

Abstract:
A current limiting device comprising:at least two electrodes; a layer of an electrically conducting composite material between said electrodes; interfaces between said electrodes and electrically conducting composite materials; an inhomogeneous distribution of resistance at said interfaces whereby, during a high current event, adiabatic resistive heating at said interfaces causes rapid thermal expansion and vaporization of at least a portion of said composite and at least a partial physical separation at said interfaces, thereby resulting in a decrease in current flow; and means for exerting compressive pressure on said electrically conducting composite material, so that a resistance of the current limiting device changes from a first resistive state prior to the high current event to a second resistive state during the high current event, and returns to the first resistive state after release of the high current event, wherein said electrically conducting composite material comprises only one type of polymer matrix and one conductive filler, the polymer matrix consists essentially of at least one linear thermoplastic polymer resulting from a polymerization of at least one cyclic thermoplastic oligomer in which the conductive filler has been dispersed prior to the polymerization, the at least one cyclic oligomer thermoplastic being selected from the group consisting of bisphenol-A carbonate and butyleneterephthalate ester, and the conductive filler being selected from the group consisting of metals and electrically conducting metallic compounds; and wherein said one conductive filler is uniformly present in an amount equal to at least 50 percent by weight of said electrically conducting composite.