Ground fault detector
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorsYukio Miyazaki, Mitsugu Taketa
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Abstract
A sensed current resulting from the occurrence of a ground fault is amplified by a differential amplifier and applied to a waveform shaper after having been delayed. The waveform shaper includes two complementary transistors interconnected into a thyristor and a transistor for amplifying the delayed current from the thyristor to a constant current under the control of a negative feedback transistor. The constant current is applied to a thyristor to turn it on to activate an associated circuit interrupter.
Claims6
A ground fault detector comprising, in combination, a ground fault sensor for sensing a ground fault occurring in an AC line to produce a sensed current, an amplifier connected to said ground fault sensor to amplify a signal representative of said sensed current, a time delay circuit connected to said amplifier to delay said signal amplified by said amplifier, a waveform shaper circuit connected to said time delay circuit to receive the delayed signal to be put in its ON state, and a switching element responsive to an output from said waveform shaper circuit to be conducting, said waveform shaper circuit being formed of a constant current circuit for decreasing operating currents flowing through both said amplifier and said time delay circuit in said ON state of said waveform shaper circuit and supplying at least one portion of said decreased operating current in the form of a constant current to said switching element as a switching current.
Dependencies are inferred from the claim text.