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:
Sep. 13, 1977
Filed:
Feb. 02, 1976
Winfred R Lemke, Mequon, WI (US);
Square D Company, Park Ridge, IL (US);
Abstract
A self-powered solid state overload relay having current transformers energized by current to a motor to be protected. The transformer has secondary windings connected through diodes to charge a capacitor in a circuit which senses the magnitude of motor current and capacitors in a trip-reset circuit which causes the circuit to be interrupted when the motor current exceeds a pre-programmed value. The diodes in capacitor charging circuits are poled so that the capacitor in the sensing circuit and the capacitor trip-reset circuit are charged by opposite polarity rectified half wave current pulses. The cores of the transformers are sized and impedances are included in the charging circuits to cause the capacitors in the trip-reset circuit to be fully charged before the capacitor in the sensing circuit is charged to a level which would cause the relay to operate to interrupt the motor circuit and the cores of the transformers to saturate in one direction on their associated hysteresis loops when the capacitors in the trip-reset circuit are being charged and in the opposite direction after the capacitor in the sensing circuit is charged.