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:
Jul. 17, 1979
Filed:
Sep. 06, 1977
Richard J Moran, Milwaukee, WI (US);
McGraw-Edison Company, Elgin, IL (US);
Abstract
The minimum instantaneous voltage output of a phase resistor connected to receive the rectified phase and neutral currents of three wye-connected current transformers, magnetically coupled to respective phase conductors of a three phase electric power circuit, is proportional to the peak current of the phase conductor carrying the center magnitude phase current. A voltage proportional to this minimum instantaneous voltage is measured and stored by a capacitor each cycle. The peak instantaneous voltage output of a ground resistor connected to receive the full wave rectified output of three, parallel-connected current transformers, also coupled to respective phase conductors of the power circuit, is proportional to the peak ground current of the electric power circuit. A voltage proportional to the voltage output of the ground resistor is applied to the base of a NPN transistor, and the voltage stored by the capacitor is applied to the emitter of this transistor, to turn on this transistor every time the peak ground current exceeds a preselected percentage of the center magnitude phase current. The momentary turnon of this transistor at least once every current cycle activates a timing circuit, which after a predetermined time, initiates tripping of a circuit interrupter.