Advantages of Two-Phase Switched Reluctance Machines for More Electric Aircraft Power Generation

The current development of an electric power generation system for the More Electric Aircraft (MEA) is based on a low-risk extension of existing three-phase, switched reluctance machine (SRM) technology. This research program proposes to study an alternate two-phase SRM and its associated power-conditioning converter. By the nature of the proposed machine, it has 50% of its stator coils active at any point in time compared to 33% for the three-phase SRM. Thus, the two-phase SRM has a potential for increased power (or torque) density compared to the three-phase SRM. (Preliminary calculations indicate at least 22% increase in power density.) Further, the stator coil and the power semiconductors switch count for the converter are each 2/3 of the number for equivalent three-phase machine. Consequently, the proposed two-phase SRM generation system should offer a signficantly smaller package with increased reliability over the three-phase SRM system presently under development. Phase I is a theoretical study to determine the two-phase SRM system configuration and to establish valid weight, volume, fault tolerance, and performance comparisons with the three-phase SRM system. A limited preliminary designs suitable for trade-off study will be produced. Design refinement is planned for Phase II. Costwise, now is the opportune time to evaluate this novel technology for potential incorporation into the MEA development. Although the proposed research program focuses on a product for aircraft application, the end result is development of technology for a simplified, robust, high power density SRM that has ready application in harsh environments (hazardous, elevated temperature), such as automotive engine pumps and cooling fans, nuclear power plant pumps, oil well pumps, and mining ventilation systems, where conventional electric machines exhibit a short MTBF.