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:
Jun. 15, 1993
Filed:
Jan. 31, 1992
John M Leuthen, Claremore, OK (US);
Baker Hughes Incorporated, Houston, TX (US);
Abstract
A method and circuit for detecting rapid increase in line voltages applied to variable speed drives utilizing a phase controlled converter. A three phase alternating current line voltage is applied to a full wave bridge rectifier to generate a direct current signal. A buffer amplifier having a high input impedance is coupled to the output of the rectifier and a diode is utilized to ensure that only positive voltage transients are detected. Positive voltage transients output through the buffer amplifier rapidly charge a capacitor through the low output impedance of the buffer amplifier and that charge is permitted to bleed off slowly through an associated resistor. The rate of change of the capacitor charge level is compared to a preset voltage level and increases beyond that preset level are utilized to trigger an inhibit signal which momentarily resets the delay angle of the switching devices within the phase controlled converter. In this manner, a rapid increase in the average slope of the input line voltage, whether or not preceded by a decrease, may be detected and removed from the input of a variable speed drive.