FREQUENCY CONVERTER WITH DC LINK CAPACITOR AND METHOD FOR PRE-CHARGING THE DC LINK CAPACITOR

摘要

A frequency converter has an AC-DC converter and an inverter interconnected via a DC link having a first and a second circuit branch interconnected by a DC link capacitor and a commutation capacitor. To protect the AC-DC converter from damage caused by an overcurrent, the first circuit branch includes a choke in which a capacitor-side terminal is connected to a terminal of the DC link capacitor and a switch-side terminal is connected via a semiconductor switch to a DC link terminal of the AC-DC converter and also via a freewheeling diode to the second circuit branch. The semiconductor switch is configured to control a magnitude of an electric current flowing from the AC-DC converter into the DC link capacitor in accordance with a control signal.