Circuit breaker
AssigneeQinetiq Limited
InventorTimothy Rupert Charles Jarman
Life of this patent
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Abstract
An electronic circuit breaker including a two stage detection mechanism; an instantaneous trip operating at a first threshold and a delayed trip such operating at a second lower threshold. This is advantageous in maintaining operation during very short transient load peaks, which do not warrant isolation from the supply. The breaker can be line powered, can be reset remotely by controlling the line power, and can be implemented entirely in solid state electronics. As such it requires little or no service or maintenance.
Claims12
An electronic circuit breaker comprising:
- a current sensor for monitoring the current in a line and outputting a signal representative of said current;
- control circuitry for receiving and processing said signal to detect a fault condition if said current signal exceeds a first current threshold for a predetermined time period, or if said current exceeds a second threshold, greater than said first threshold;
- a latch which latches on detection of a fault condition;
- and
- a switching element controlled by said latch for interrupting the current in the line on detection of a fault condition by said control circuitry,
- wherein the latch is reset by removing and reapplying power to said line.
3-4. (canceled)
A method of monitoring a current carrying line comprising
- obtaining a value for the current in the line;
- establishing a first current value threshold, a second, higher, current value threshold and a delay period;
- comparing the obtained value with said thresholds to detect an overload condition, applying said second threshold always and applying said first threshold only for overloads having a duration greater than said delay period;
- and
- if an applied threshold is exceeded, operating a latch to interrupt said current, and resetting said latch by removing and reapplying power to said line.
Dependencies are inferred from the claim text.