Electronic processing unit, and circuit breaker including such a

Details Electronic processing unit, and circuit breaker including such a Electronic processing unit, and circuit breaker including such a

1994-12-28

1997-05-06

Gaffin, Jeffrey A.

Electricity: electrical systems and devices

Safety and protection of systems and devices

With specific current responsive fault sensor

361 97, 361115, H02H 300

Patent

active

056277172

ABSTRACT:
Digital processing of current signals allows close matching of arbitrary time delay curves for a circuit breaker. An analog signal proportional to the current is sampled and digitized. Digital samples, with or without further processing, are used to select increment values from a look-up table for accumulation in a counter. The counter is decremented periodically to simulate cooling of the circuit being protected. The values in the look-up table are determined according to the desired time delay curve. Processing of the digital samples may include squaring samples, accumulating the squared values to form a subtotal which is compared with an instantaneous trip threshold, accumulating the subtotals for a time period equal to half a cycle of AC line voltage, taking the square root of the accumulated subtotals, and using that square root as the address for looking up the increment value.

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C. Sullender, "Magnetic Current Sensors for Space Station Freedom", IEEE, Transactions on Power electronics, vol. 8, No. 1, Jan. 1993, pp. 69-75.

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