Process for switching between mains supply and a frequency inverter and vice versa

US6782989B2 · kind B2 · utility

Assignee

• OTIS ELEVATOR COMPANY · US

Inventors

• Stefan Spannhake · Berlin, DE
• Herbert Horbrugger · Berlin, DE
• Reinhard Henkel · Berlin, DE

Key dates

• Filing date: May 16, 2002
• Grant date: Aug 31, 2004
• Expiry date: May 16, 2022

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y02B50/00
• WIPO field: Handling
• WIPO sector: Mechanical engineering

Abstract

Process and device for controlling the drive of a conveyor system (10), specifically in the form of an escalator or passenger conveyor, which can be switched from load to no-load operation, comprising a drive motor (26) and a variable frequency converter (42), which is at least controllable with respect to the frequency of its output voltage, wherein, under load, the drive motor (26) 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 (42), wherein, prior to a changeover from no-load to load operation, the output frequency of the variable frequency converter (42) is essentially brought with phase accuracy to the line frequency by means of a PLL device (30), and wherein this changeover is brought about as soon as this phase conformance has been realized.