Patent ID: 7200018

Claim:
A method for charging a filtering capacitor comprising: providing a voltage-control PWM frequency converter, including: a rectifier connected to an alternating current source; a direct voltage intermediate circuit; at least one inverter unit for feeding a multi-phase alternating voltage of variable frequency into at least one load; said rectifier having a bridge of controlled semiconductor switches in one arm and diodes in another arm; said direct voltage intermediate circuit being provided with a filtering capacitor of relatively high capacitance for filtering said multi-phase alternating voltage; charging the filtering capacitor by the semiconductor switches by adjusting a firing angle according to a measured voltage of the filtering capacitor; the firing angle being adjusted by forming a sum of the measured voltage of the filtering capacitor and a predetermined limit voltage, the limit voltage being a function of the voltage of the filtering capacitor so that the limit voltage decreases as the filtering capacitor voltage increases so as to keep charging current pulses under control; and comparing the sum to measured main voltages of a supply network.