Search

The demand for alternative fueling methods to reduce the need for fossil fuels is not limited to the electrification of ground vehicles. More-electric and all-electric aircraft pose challenges, with extensive requirements in terms of power density, efficiency, safety, and environmental sustainability. This paper focuses on electrical machines and their components, especially for high-power applications like the main propulsion. The electrical machine is evaluated from different aspects, followed by a closer look at the components and materials to determine the suitability of the current standard materials and advanced technologies. Furthermore, the mechanical and thermal aspects are reviewed, including new and innovative concepts for the cooling of windings and for the use of additive manufacturing. Aircraft have special demands regarding weight and installation space. Following recent developments and looking ahead to the future, the need and the possibilities for light and efficient electrical machines are addressed. All of the approaches and developments presented lead to a better understanding of the challenges to be expected and highlight the upcoming opportunities in electrical machine design for the use of electric motors and generators in future aircraft. Several prototypes of electrical machines for smaller aircraft already exist, such as the electric drive of the Siemens powered Extra 330LE. The focus of this paper is to provide an overview of current technical possibilities and technical interrelations of high performance electric drives for aviation. A 1 MW drive is exemplified to present the possibilities for future drives for airplanes carrying a larger number of passengers. All presented techniques can also be applied to other drive power classes. [ABSTRACT FROM AUTHOR]

Through applying an exemplary design study, the dependencies between current density, temperatures, and weight in an electrical drive system for a small range aircraft with conventional electrical fan or propeller drives are evaluated. This study applies a combined numerical (Finite Element Method FEM) and analytical approach to the machine design, calculation of temperatures, and cooling system design (cooler, pumps, piping). A design scenario was defined using start and climb flight in a warm tropical surrounding as the worst load case. The design has to move between two fixed temperature limits: The maximum allowable temperature in the machine insulation and the ambient temperature. The implemented method facilitates a comparatively fast-medium depth design of the drive system. The derived results show, in fact, a minimum of weight at a certain current density, which is one of the key interests for the designers of the electrical machine. The main influences on this minimum are the temperature drops in the machine, the heat transfer to the cooling fluid, the heat transfer to the cooler wall, and the remaining heat rejection to the ambient. Method and results are transferable to other types of airplanes with different ratings. [ABSTRACT FROM AUTHOR]

This paper is aimed at giving an overview of possible cooling technologies for electrical machines and their assessment for aviation applications, e.g., fan or propeller drives. The most important demand for aircraft is the minimization of the drive system weight comprising electrical machine, power electronics, and the cooling system. The potential of aluminum winding an overview about several cooling technologies with the Rankine or Brayton cycle or utilizing the phase change of the cooling fluid is given. As an alternative approach, the cooling structure inside the machine is studied. A very interesting potential was discovered with direct slot cooling (DSC) removing the heat where it is produced and, thus, simplifying the cooling system effort and its weight. Since it is one of the most promising approaches, this cooling method is studied in depth. Furthermore, it can also be combined with one of the cooling technologies discussed above. [ABSTRACT FROM AUTHOR]