Electrical safety device with conductive polymer sensor

摘要

An electrical safety device comprises a sensor strip disposed in the insulation of an electrical power cord or other electrical apparatus. The sensor strip is made of a conductive polymer with a positive temperature coefficient of resistivity which increases with temperature. The sensor strip forms a series connected loop connected to an impedance measuring circuit. A relay interrupts current to the conductors of the cord when the impedance of the sensor strip increases due to an overtemperature condition. The sensor strip is positioned between the conductors of the cord and the outside surface of the cord. The position of the sensor strip allows the strip to act as a mechanical damage sensor, opening the series connected loop before an energized conductor is exposed.