To achieve benefits similar to those seen in hybrid-/all-electric ground-based and marine vehicles, electric propulsion has been proposed for large commercial aircraft. Among the main drivers of this are improved fuel economy, reduced harmful emissions, and lower audible noise. In converting to electric propulsion, the added electrical components' masses must be minimised so that the benefits that the components enable-improved turbine efficiency, distributed propulsion and propulsionairframe integration-are not cancelled out by their weight penalty. This puts stringent requirements on the large electric machines used in the system, both those that generate electric power from the turbine shaft and those that drive propellers or ducted fans, because they are among the heaviest of the added electric components. A key machine design metric in this application is the specific power (SP), or the power-to-mass ratio. This study gives a comprehensive overview of large electric machines for aircraft electric propulsion applications, with a focus on methods for mass reduction and SP improvement.

With the recent increase in the availability and widespread use of inverters, exotic rare earth permanent-magnet materials, and low-cost, precision manufacturing, new design tools are needed to aid engineers in designing state-of-the-art electromechanical systems. For this purpose, recent software advances allow a reexamination of previously intractable analytical solutions to the boundary value problems governing these systems. This paper presents an analytical field analysis method for electric machines utilizing the Schwarz-Christoffel transformation and implemented with the SC Toolbox software package. With the method, general 2-D electric machine cross sections with linear magnetic materials are analyzed. The method is then extended using superposition to analyze wound-rotor induction machines in the time domain. With this extension, numerous machine geometries, stator excitations, winding and slot harmonics, and torque ripple can be examined.

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