Open Circuit IGBT Fault Classification using Phase Current in a CHB Converter

Recent field failure reports have showed that power cell faults represent the highest contributor to overall CHB converter failure rates. A big portion of these failures are related to power switches, capacitors, gate driver and control circuit boards. Focusing on power switches faults, they normally fail as short circuit or open circuit. Short circuits are dangerous events, however, there is standard method for fast neutralization. On the other hand, open circuit faults are not as fatal as short circuits. Nonetheless, in some situations, the load could not tolerate current imbalance caused by open circuit faults requiring an effective detection and identification method. In general, IGBT open circuit faults are more difficult to detect, and there is no standard method for detection. As a result, there is an industry need for detection, classification, and identification techniques that can perform effectively under different motor loading conditions. In this paper, a proposed method for classifying cell faults caused by IGBT open circuit is presented. Simulation results are provided in order to evaluate the performance of the proposed method.