Open-Circuit Fault Research on Asymmetric Delta-Polygon 18-Pulse Autotransformer Rectifier Unit for More Electric Aircraft

In aviation aircraft, autotransformer rectifier units (ATRUs) have been widely used as front-end rectifiers. The comprehensive analysis of its operating characteristics under the fault is beneficial to assessing the hazards of the faults and developing a fault diagnosis scheme. This article investigates two types of open-circuit (OC) faults in delta-polygon 18-pulse ATRU, namely, diode OC fault and input OC fault. First, the effects of the diode OC fault on five aspects are quantitatively analyzed: diode conduction angle, output voltage ripple, winding current, input current harmonics, and diode and transformer winding losses. Next, the operating characteristics of ATRU are investigated under input OC fault, and the quantitative effects of the five aspects above are also calculated. Then, based on the affected intervals of dc output voltage, a fault diagnosis idea dealing with two types of OC faults is discussed. Meanwhile, the predictive maintenance objects after the fault location are also summarized. Finally, the simulation and experimental results validate the theoretical analysis and discussion. This work is very significant for guiding the fault detection, fault location, and predictive maintenance of ATRUs.