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:
Sep. 30, 2008
Filed:
Apr. 14, 2006
Risto Komulainen, Klaukkala, FI;
Trygve Björkgren, Kvevlax, FI;
Risto Komulainen, Klaukkala, FI;
Trygve Björkgren, Kvevlax, FI;
Vacon Oyj, Vaasa, FI;
Abstract
An overvoltage protection system for the intermediate circuit of frequency converter, said frequency converter being a voltage-controlled PWM-frequency converter comprising an uncontrolled mains bridge () to be connected to an alternating-current source (U, U, U), a direct-voltage intermediate circuit and a controlled load bridge () for producing a multi-phase alternating voltage (U, U, U) of variable frequency, wherein the direct-voltage circuit of the frequency converter contains a low-capacitance direct-voltage capacitor, the mains bridge () being connected to the load bridge () directly without a high-capacitance direct-voltage capacitor serving as an intermediate energy storage, and which overvoltage protection system contains a varistor (R). The overvoltage protection system consists of a series connection of the varistor (R) and a semiconductor switch (V), said series connection being connected in parallel with the direct-voltage capacitor, which semiconductor switch has a voltage rating lower than the normal operating level of the direct-voltage intermediate circuit.