Arc fault circuit interrupter without DC supply
First Claim
1. An arc fault circuit interrupter comprising:
- a sensor responsive to an arc fault for generating a first signal proportional to the rate of change of current with respect to time, and a second signal proportional to the AC power line frequency current produced by the arc;
a first detector responsive to the first signal for generating a first fault signal when the rate of change of current with respect to time exceeds a predetermined value;
a second detector responsive to the second signal for generating a second fault signal if the peak ac power line frequency current exceeds a predetermined value; and
a switch for triggering a circuit disconnector only when both the first and second fault signals are generated.
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Accused Products
Abstract
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.
74 Citations
15 Claims
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1. An arc fault circuit interrupter comprising:
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a sensor responsive to an arc fault for generating a first signal proportional to the rate of change of current with respect to time, and a second signal proportional to the AC power line frequency current produced by the arc;
a first detector responsive to the first signal for generating a first fault signal when the rate of change of current with respect to time exceeds a predetermined value;
a second detector responsive to the second signal for generating a second fault signal if the peak ac power line frequency current exceeds a predetermined value; and
a switch for triggering a circuit disconnector only when both the first and second fault signals are generated. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A device for detecting arc faults in an electric power circuit, comprising:
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a sensor coupled to said electric power circuit, wherein said sensor generates a pulse each time an arc is struck; and
a detector coupled to said sensor and responsive to said pulse for generating a signal indicating a presence of said arc, wherein said detector is powered solely by a plurality of said pulses. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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Specification