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. 13, 1984
Filed:
Mar. 07, 1983
Mitsubishi Denki Kabushiki Kaisha, Tokyo, JP;
Abstract
Disclosed is an AC elevator control apparatus, in which AC power supplied from an AC source is rectified by a converter and a smoothing capacitor into DC power, the DC power being in turn converted by an inverter into variable-frequency AC power by which an AC electric motor is driven to operate an elevator cage. The apparatus includes a rectifying circuit connected to the AC source, a resistor connected between the rectifying circuit and the smoothing capacitor, a charging time measuring circuit for measuring the time from turn-on of the AC source until the completion of charging the smoothing capacitor, and a control circuit for producing an abnormality detection signal when it is detected that the output of the charging time measuring circuit is shorter than a predetermined value, whereby the reduction in capacitance of the capacitor, and hence the expiration of the lifetime of the same, can be evaluated in advance.