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:
Aug. 31, 2004
Filed:
May. 16, 2002
Otis Elevator Company, Farmington, CT (US);
Abstract
Process and device for controlling the drive of a conveyor system ( ), specifically in the form of an escalator or passenger conveyor, which can be switched from load to no-load operation, comprising a drive motor ( ) and a variable frequency converter ( ), which is at least controllable with respect to the frequency of its output voltage, wherein, under load, the drive motor ( ) is supplied with a line voltage with an essentially constant line frequency and, at no-load, is supplied the output voltage of the variable frequency converter's ( ), wherein, prior to a changeover from no-load to load operation, the output frequency of the variable frequency converter ( ) is essentially brought with phase accuracy to the line frequency by means of a PLL device ( ), and wherein this changeover is brought about as soon as this phase conformance has been realized.