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US 5,136,456 AGranted
Faulted current indicator with protection against temporary overloads and transients
AssigneeSigma Instruments, Inc.
InventorThomas Yeh
Life of this patent
Estimating the term…
Abstract
The disclosed faulted current indicator ignores temporary overloads and transients by inhibiting any trip resulting from an overcurrent signal until a disabling circuit senses that a fuse or circuit breaker has reduced the line current to zero.
Claims7
A faulted current indicator, comprising:
- reset means for producing a reset signal in response to a first current value in a cable;
- trip means for producing a trip signal in response to a second current value higher than the first current value in the cable;
- disabling means coupled to said trip means for producing a signal to enable said trip means to produce the trip signal when the current in the cable drops below the first current value within a given time after reaching the second current value and disable the trip signal otherwise.
A faulted current indicator, comprising:
- reset means for producing a reset signal in response to a first current value in a cable;
- signal producing means for producing a signal in response to the cable exceeding a second current value higher than the first current value in the cable;
- distinguishing means coupled to said indicting means and current in the cable for distinguishing between the indications followed by current in the cable dropping below the first current value within a given time and indications followed by current in the cable failing to drop below the first current value within the given time;
- and trip signal means responsive to said distinguishing means for producing trip signals only in response to indications followed by cable currents dropping below the first current value within the given time, and for disabling the trip signals at all other times.
1 more element
Dependencies are inferred from the claim text.