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:
Nov. 21, 1978
Filed:
Apr. 15, 1977
Hitachi, Ltd., , JP;
Abstract
A protective circuit for protecting a main d.c. circuit of the kind comprising a d.c. power source, a d.c. load, a contactor and a chopper. In the protective circuit, a resistor is connected in parallel with the series-connected contactor and load to permit continuous application of power supply voltage across the chopper. A circuit is connected to the connection point of the load and chopper to provide a signal synchronous with on-off of the chopper, and the output signal of this circuit and a signal corresponding to a chopper-on signal are applied to a logic circuit which provides the logical sum of these inputs for the detection of commutation failure of the chopper. The output of the logic circuit turns on a thyristor for deenergizing the contactor thereby disconnecting the load from the power source.