Patent ID: 8924170

Claim:
A method for detecting a failed rectifier in an AC/DC converter for converting three-phase AC power to DC power and having its AC side connected to an AC source for power supply and its DC side connected to a DC load, the AC/DC converter including a rectifier circuit comprising at least three legs, each of the legs connected to a corresponding AC phase and including at least one rectifier, the method comprises measuring instantaneous AC currents of each of the phases, estimating an instantaneous DC current based on the measured instantaneous AC currents during one period of the power supply frequency, characterized in that the method further comprises calculating a ripple value of the estimated instantaneous DC current, determining if the calculated ripple value exceeds a pre-defined threshold value, initiating an alarm upon the calculated ripple value exceeding the pre-defined threshold value, upon the calculated ripple value exceeding the pre-defined threshold value, for each of the legs, calculating a rectifier status value based on a maximum instantaneous AC phase current and a minimum instantaneous AC phase current during the same one period, and determining, for each of the legs, if the rectifier in the leg has a non-conducting fault based on the calculated rectifier status value.