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, 2007
Filed:
Nov. 09, 2005
Hannu Saren, Lappeenranta, FI;
Hannu Saren, Lappeenranta, FI;
Vacon Oyj, Vaasa, FI;
Abstract
A method of protecting a frequency converter against overvoltage by controlling an AC motor during braking or during light load and a frequency converter, wherein the frequency converter is a voltage-controlled PWM frequency converter operating in single quadrant (Q) and comprising at least one uncontrolled rectifier bridge () to be connected to a AC supply line (U, U, U), a direct-voltage intermediate circuit and at least one controlled inverter bridge () for feeding an AC motor () with an alternating voltage (U, U, U) of varying magnitude and frequency, in which method: the angle (θ) between the output voltage vector (U) and current vector (I), i.e. the power factor, is measured, the angle (θ) between the output voltage vector (U) and current vector (I), i.e. the power factor, is controlled on the basis of the measurement, and the angle (θ) between the output voltage vector (U) and current vector (I), i.e. the power factor, is controlled so that the angle does not exceed a preset threshold value, preferably approximately π/2.