초록 ▼

Arcing faults are detected by sensing a voltage signal proportional to the rate of change, or di/dt, of the line current when the current steps into an arc fault. A current transformer is used to create the di/dt signal. The transformer has a selected core type, number of windings, and size which sa

Arcing faults are detected by sensing a voltage signal proportional to the rate of change, or di/dt, of the line current when the current steps into an arc fault. A current transformer is used to create the di/dt signal. The transformer has a selected core type, number of windings, and size which saturates at a pre determined level of primary current. The saturation acts to clamp the maximum di/dt voltage signal at the transformer output, and produce a constant output voltage. The constant output voltage eliminates a signal with a high di/dt, which may occur during a lamp burnout, from producing a much larger di/dt signal than that caused by an arc fault at a lower level of step current. The di/dt signal is passed through a high pass filter, which attenuates 60 hz sinusoidal signals, after which the signal is integrated. The integrator acts to delay circuit interruption means until a predetermined number of arcs has occurred. When the integrator voltage reaches a predetermined voltage level, a trigger device activates an electronic switch, which in turn activates circuit interrupting means. One of the novel aspects of this invention is the elimination of the need for a DC power supply.

대표청구항 ▼

[ What is claimed is:] [1.]1. A device for detecting arc faults in an electric power circuit, said device comprising:a sensor coupled to the electric power circuit which sensor generates a pulse each each time an arc is struck;an integrator connected to the sensor for accumulating pulses and generat

[ What is claimed is:] [1.]1. A device for detecting arc faults in an electric power circuit, said device comprising:a sensor coupled to the electric power circuit which sensor generates a pulse each each time an arc is struck;an integrator connected to the sensor for accumulating pulses and generating an output voltage;a threshold detector connected to the integrator for generating an arc detecting signal when the voltage reaches a predetermined level;in which the integrator and threshold detector are powered solely by the pulses.