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:
Apr. 29, 1980
Filed:
Jul. 12, 1978
Walter J Pohl, Anchorage, KY (US);
General Electric Company, Louisville, KY (US);
Abstract
A circuit for protecting single phase induction motors of the type having a start winding connected in series with a start/run capacitor. The circuit contains a resistance bridge wherein the motor start winding forms one leg thereof. A d.c. signal is applied to the input terminals of the bridge. A filter is connected to the output terminals of the bridge so that a relatively ripple free d.c. output signal from the bridge can be applied to the positive input terminal of a d.c. comparator, the negative terminal of which is connected to d.c. reference ground. A reference resistor in a leg of the bridge adjacent the start winding is selected so that the bridge is unbalanced to present a positive d.c. signal to a terminal of the comparator so long as the resistance value of the start winding is less than the value of the reference resistor. An excessive temperature increase of the start winding raises its resistance to equal that of the reference resistor to cause the bridge to balance when the temperature of the start winding reaches a predetermined maximum value, whereupon the comparator switches from a conductive to a non-conductive state. An SCR connected to the comparator output controls the operation of a motor-protecting relay to disengage the motor from its driving source when the bridge becomes balanced and when the comparator switches from one output state to another. A re-start button connected across the SCR permits re-start of the motor after it has been disengaged from its driving source by operation of the comparator.