Tradespace Exploration of Electrified Propulsion and More-Electric Aircraft Generators

Abstract

The ongoing quest for higher electrical power on board electrified aircraft propulsion systems and more-electric aircraft is placing significant importance and challenges on rightly designed electric machines. As the power growth trend continues, the availability of robust and lightweight megawatt-class generators is critical. The design for these high-power generators provides significant challenges compared to present needs, and therefore a better understanding of the feasible generator design space and potential trade-offs between suitable efficiency, specific power, and performance requirements is necessary. Understanding this tradespace helps to reduce risk in generator development and allows for improved coordination between generator designers and aircraft-system integrators. To help achieve this goal, a Generator Design Tool has been developed by the Air Force Research Laboratory. It is a population-based design tool for wound-field synchronous machines that applies a genetic algorithm in order to perform multi-objective optimization to minimize mass and loss. The optimization relies on a magnetic equivalent circuit model to assess the machine’s performance and ensure that all design requirements are fully satisfied. The tradespace exploration capabilities of the tool are leveraged to investigate trends in the size and performance of generator designs for electrified aircraft and more-electric aircraft. Trade-offs in number of poles, mass versus loss, and in setting various design constraints are investigated. Limitations in high-speed operation and possible options for opening up the design space to higher speeds while potentially adding complexity and risk in the design were explored.