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:
Mar. 24, 1981
Filed:
May. 31, 1979
Alan B Shimp, Monroeville, PA (US);
Westinghouse Electric Corp., Pittsburgh, PA (US);
Abstract
A ground fault detecting circuit interrupter is taught. A ground fault is sensed by utilizing a summing transformer interconnected with the three-phase current transformers for normal fault detection. The turns ratio between the primary winding and the secondary winding of the summing transformer is kept purposely high so that the excitation current for the current transformers is made relatively small when compared to the normal secondary current of the current transformers. This has the effect of improving the accuracy of the normal fault detecting portion of the circuit breaker. The relatively high turns ratio between the primary and second of the summing transformer usually supplies insufficient current to directly actuate the trip coil of the circuit interrupter on the occurrence of a ground fault. However, this latter current is utilized to charge a capacitive storage element after a ground fault has been sensed. When the capacitive storage element is fully charged, it is switched into a circuit disposition suitable for discharge through the trip coil of the circuit interrupter with sufficient current flow to open the separable main contacts of the circuit interrupter.