Electricity: electrical systems and devices – Safety and protection of systems and devices – Ground fault protection
Patent
1994-12-29
1997-02-04
Gaffin, Jeffrey A.
Electricity: electrical systems and devices
Safety and protection of systems and devices
Ground fault protection
361 78, H02H 908
Patent
active
056005237
ABSTRACT:
An earth leakage breaker comprising a zero-phase-sequence current transformer for detecting a current difference on an AC line with respect to both positive (+) and negative (-) directions to sense an electric leakage of the AC line, a comparator for comparing an output voltage from the zero-phase-sequence current transformer with a trigger reference voltage, a delay for delaying the output voltage from the zero-phase-sequence current transformer by a desired period, a subtracter for subtracting an output voltage from the delay from the output voltage from the zero-phase-sequence current transformer, first and second level discriminators for discriminating levels of output signals from the comparator and the subtracter, respectively, first and second duration generators for generating durations in response to output signals from the first and second level discriminators, respectively, a first, pulse width generator for generating a pulse width corresponding to the duration from the first duration generator, a second pulse width generator for generating a pulse width corresponding to the duration from the second duration generator, an AND gate for ANDing the pulse widths from the first and second pulse width generators, and a trigger circuit for breaking the AC line by an output pulse width from the AND gate.
REFERENCES:
patent: 4605982 (1986-08-01), Harner
patent: 4783713 (1988-11-01), Chen
patent: 5003426 (1991-03-01), Yeh et al.
Gaffin Jeffrey A.
Goldstar Electron Co. Ltd.
Medley Sally C.
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