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:
Feb. 01, 1994
Filed:
Sep. 23, 1992
Richard W Waltz, Milwaukee, WI (US);
Allen-Bradley Company, Inc., Milwaukee, WI (US);
Abstract
A device protects an electric load, such as a motor, from excessive current levels. The current flows from a source to the load through a switch and a primary winding of a current sensing transformer. The voltage across a secondary winding of the current sensing transformer is rectified to produce a voltage which is measured to determine the level of current through the load. The voltage across the secondary winding also powers components of the device. In a first mode of operation, current from the secondary winding is applied to charge a power supply capacitor. In a second mode of operation the level of the rectified voltage is sensed to produce a sample of the level of the current flowing through the load. From this sample the change in temperature of the load since a previous sample is calculated and used to derive the present load temperature. When the present load temperature exceeds a defined threshold level, the switch is opened to disconnect the load from the electricity source.