The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 04, 1994
Filed:
Mar. 03, 1993
Yoshihiro Hatakeyama, Fukuyama, JP;
Mitsubishi Denki Kabushiki Kaisha, Tokyo, JP;
Abstract
An overcurrent detector circuit for a circuit-breaker includes two systems for overcurrent detection. In the first system, the level of the current detected by the current detectors 41 is converted to a digital signal by the A/D converter 91 at each 500 microseconds. The maximum value detector 92 selects the maximum value among these digital signals over each period of 12.5 milliseconds. When the maximum value is greater than a pick-up level, the square thereof is accumulated in the counter 95. In the second system, the calculation circuit 96 squares the digital signals of the A/D converter 91, and switches its outputs in order to the counters 97-1 through 97-5 at a period of 25 milliseconds. Thus, the four counters other than that currently coupled to the calculation circuit 96 hold together the squares of the digital signals accumulated over 100 milliseconds. When this value held jointly by the four counters exceeds a predetermined pick-up level, a value corresponding to the sum is calculated and accumulated in the counter 100. When the output of the counter 95 or 100 exceeds a threshold level, a trip judgment circuit 101 outputs a tripping signal to the switching device 70 to activate the tripping device 71.