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In this dissertation, combined star-delta windings and single-layer fractional-slot distributed windings are mainly evaluated, which are incorporated within a cage-induction machine and an electrically excited synchronous machine, respectively. Both electrical machines were de-signed as prototypes for automotive applications. The combined star-polygon windings feature an increased fundamental winding factor and a decreased harmonic leakage factor. These characteristics make them suitable for traction appli-cations to increase the torque density of electrical machines, to widen the field-weakening region and to reduce the noise, vibration, and harshness (NVH). Almost every winding, in-cluding some single-layer fractional-slot distributed windings, can be connected in combined star-polygon. Due to the undesired magnetic coupling between the additional spatial harmonics generated by the winding and the low-resistance rotor circuit, the single-layer fractional-slot distributed windings are only suitable for synchronous machines without electrically conductive solid rotors or damper windings. Besides, they do not need an additional insulation layer inside the slots to isolate different coil sides compared to the double-layer windings. This provides an additional space inside the slots, which can be used to increase the slot-filling factor. Moreo-ver, an increased slot-filling factor and a reduced number of insulation layers improve the ef-fectiveness of the cooling system. Nevertheless, a single-layer compared to a double-layer fractional-slot distributed windings excites additional spatial harmonics, which can affect the performance and the NVH behavior of synchronous machines. Therefore, the performance and the NVH results measured on com-parable electrically excited synchronous machines are studied in detail. In contrast to other winding types, the star of slots is found being insufficient to design some single-layer fractional-slot distributed windings. Thus, part of

For the sizing of an electric motor, the diameter and length of the installation space are important parameters that significantly influence and limit the characteristics of the electric motor. From an aerodynamic point of view, it is not technically advantageous to choose a propeller hub diameter that is larger than mechanically necessary. The hub diameter defines the installation space ans thus the outer diameter for the electric motor driving the propeller. The research question that arises is this: Is there an optimum diameter for the hub and thus the electric motor and how is it limited? The present work should help to establish a better understanding of the system combination of electric motor and propeller, especially the choice of the diameter and further geometrical parameters of the electric motor. A parameter study investigating aeromechanical and electromagnetic aspects has been performed and the results are combined to achieve the best solution in terms of efficiency and power density. The investigations show that an increase in the diameter causes little disadvantage from an aerodynamic point of view, but the improvements to the electric motor are significant only up to the point where the diameter-to-length ratio becomes too high and end-region effects become more significant. The installation space for the electric motor could be determined using a hub-to-tip ratio of 0.16 to 0.20, which is applicable to any propeller. In addition, it could be shown that a co-optimisation of the speed throughout a mission profile with regard to the efficiency is affected by the propeller alone.

To make an all-electric aircraft possible, both high power densities and efficiencies are needed. However, particularly high demands are also placed on the thermal management system. Often, the electric motor and cooling system are considered without co-optimization. Particularly in the case of electric motors with conductors directly cooled by a liquid, there is great potential for optimization, since the temperature-dependent Joule losses determine the largest part of the losses. This publication shows the main influencing parameters for the electric motor and cooling system: coolant speed and winding temperature. In addition, the influence of the cooling system control during a flight mission is demonstrated and its potential in mass reduction is quantified. It could be shown that with a low utilized electric motor the maximum winding temperature of 130 (Formula presented.) C is beneficial, the cooling system should work in almost all operation points in its sized operation and the mass of the heat exchanger and pump is negligible compared to the mass of the electric motor and energy storage.