Patent ID: 7804288
Filing Date: 2010-09-28
Classification: H02M

Abstract:
1. A method for measuring the output current of a frequency converter including a network bridge connectable to an AC network, a controllable three-phase load bridge connectable to an AC load, and a DC intermediate circuit between the network bridge and the controllable three-phase load bridge, the DC intermediate circuit including a filter capacitor, wherein the controllable three-phase load bridge contains a controllable semiconductor switch for each of the three phases, each controllable semiconductor switch controlled by pulse-width modulation, the method comprising: measuring samples of a current of the filter capacitor of the DC intermediate circuit in conjunction with switchings of the controllable semiconductor switches, including measuring a first sample when a gate control pulse of a first of the controllable semiconductor switches ceases and measuring a second sample after a delay subsequent to the starting of a gate control pulse of a second of the controllable semiconductor switches; and determining the output current of the frequency converter based on the measured samples, wherein the network bridge is one of an inactive network bridge and an active three-phase controllable network bridge having corresponding controllable semiconductor switches.