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Aircraft electrical power consumption has dramatically increased in recent years. Technological advancements have led to the replacement of traditional hydraulic and pneumatic systems with electrically powered devices. In addition, new functions such as deicing and entertainment systems have been added, which further increases the demand for electrical power. As power needs increase, voltage or current, or both, must be increased. Increased current can be the least desirable result as it leads to larger and heavier wires. To mitigate the issue of wire weight and distribution losses, the latest “More Electric Aircraft” have adopted 230 V ac as the main power bus voltage. However, this presents a problem as a significant amount of existing electrical aircraft equipment (actuators, pumps, etc.) have been designed to use 270 V dc power, which is obtained by a direct rectification of 115 V ac power. Two hundred seventy volts dc cannot be as simply produced from a 230 V ac bus.

1 Aircraft electrical power is generated in the form of three-phase alternating current. Most electrical loads require DC power to operate; therefore the conversion from AC to DC power is required. The direct rectification of 3-phase AC power into DC power is simple and straightforward; however, it creates unacceptable levels of current distortion. Multiphase power conversion is one of several technologies capable of AC to DC power conversion with low distortion levels that meet aerospace power quality standards. A typical autotransformer based multiphase converter contains two major functional blocks: a multiphase autotransformer and rectifier. Autotransformer rectifier units (ATRUs) have a low part count, and are highly reliable. There are only a few low frequency switching components with this topology, so EMI emissions are relatively low when compared to high frequency switching techniques.