05 Fakultät Informatik, Elektrotechnik und Informationstechnik

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/6

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Institute: search.filters.UBSInstitut.Institut für Elektrische EnergiewandlungSubject: search.filters.subject.621.3

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    Inductive electrically excited synchronous machine for electrical vehicles : design, optimization and measurement
    (2023) Müller, Samuel; Maier, David; Parspour, Nejila
    The demand for electric machines has been rising steadily for several years-mainly due to the move away from the combustion engine. Synchronous motors with rare earth permanent magnets are widely used due to their high power densities. These magnets are cost-intensive, cost-sensitive and often environmentally harmful. In addition to dispensing with permanent magnets, electrically excited synchronous machines offer the advantage of an adjustable excitation and, thus, a higher efficiency in the partial load range in field weakening operation. Field weakening operation is relevant for the application of vehicle traction drive. The challenge of this machine type is the need for an electrical power transfer system, usually achieved with slip rings. Slip rings wear out, generate dust and are limited in power density and maximum speed due to vibrations. This article addresses an electrically excited synchronous machine with a wireless power transfer onto the rotor. From the outset, the machine is designed with a wireless power transfer system for use in a medium-sized electric vehicle. As an example, the requirements are derived from the BMW’s i3. The wireless power transfer system is integrated into the hollow shaft of the rotor. Unused space is thus utilized. The overall system is optimized for high efficiency, especially for partial load at medium speed, with an operation point-depending optimization method. The results are compared with the reference permanent magnet excited machine. A prototype of the machine is built and measured on the test bench. The measured efficiency of the inductive electrically excited synchronous machine is up to 4% higher than that of the reference machine of the Bayerische Motoren Werke AG (BMW) i3.
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    Accelerated 3D FEA of an axial flux machine by exclusively using the magnetic scalar potential
    (2023) Schäfer, Adrian; Pecha, Urs; Kaiser, Benedikt; Schmid, Martin; Parspour, Nejila
    This article focuses on increasing the computational efficiency of 3D multi-static magnetic finite element analysis (FEA) for electrical machines (EMs), which have a magnetic field evolving in 3D space. Although 3D FEA is crucial for analyzing these machines and their operational behavior, it is computationally expensive. A novel approach is proposed in order to solve the magnetic field equations by exclusively using the magnetic scalar potential. For this purpose, virtual variable permanent magnets (vPMs) are introduced to model the impact of the machine’s coils. The effect on which this approach is based is derived from and explained by Maxwell’s equations. To validate the new approach, an axial flux machine (AFM) is simulated using both 2D and 3D FEA with the magnetic vector potential and current-carrying coils as a reference. The results demonstrate a high level of agreement between the new approach and the reference simulations as well as an acceleration of the computation by a factor of 15 or even more. Additionally, the research provides valuable insights into meshing techniques and torque calculation for EMs in FEA.
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    An easily scalable dynamic wireless power transfer system for electric vehicles
    (2023) Noeren, Jannis; Parspour, Nejila; Elbracht, Lukas
    This article deals with a LCC-LCC compensated dynamic wireless power transfer system for electric vehicle charging applications. The presented prototype system allows for a power transfer of about 10 kW at 20 cm coil copper to copper distance. With just one circular pickup coil and a very straightforward control scheme, a new coil arrangement enables a seamless power transfer. Furthermore, the system’s design power level is easily adjustable by the size of the the pickup coil. The hardware architecture as well as the software functionality are described in detail. A 20 m test track was built up according to the outlined principle. By measuring the transmitted power, the efficiency and the interference between the primary segments and its effect on the inverter currents are examined. The results show an effective DC to DC efficiency in the range of 91 to 92% and a power fluctuation of approximately 25%.
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    A review of electromagnetic simulation and modelling approaches for the research on axial flux synchronous machines
    (2024) Schäfer, Adrian; Pecha, Urs; Parspour, Nejila; Kampker, Achim; Born, Henrik; Hartmann, Sebastian; Franke, Jörg; Baader, Marcel; Hahn, Roman
    Extensive electromagnetic (EMAG) studies are necessary to fully realize the potential of axial flux machines (AFMs). However, the disc-shaped air gap and the complex three-dimensional path of magnetic flux pose challenges in modelling AFMs compared to conventional radial flux machines. This study reviews current research on EMAG modelling and simulation of AFMs, highlighting the need for tools that address AFM-specific effects. Existing approaches are analysed based on the requirements composed by fundamental objectives of EMAG simulations and AFM-specific effects, revealing limitations in flexibility and the ability to capture emerging trends in the field of AFMs. While computationally expensive 3D finite element analysis (FEA) offers comprehensive flexibility in EMAG modelling, it lacks efficiency to carry out extensive studies on such trends. Therefore, there is a need to either further accelerate 3D FEA or to increase the flexibility of existing alternatives to facilitate and thereby promote research in the field of AFM and other 3D flux machines. While the integration of some production-specific effects, such as manufacturing tolerances, already is investigated for EMAG simulations of AFMs the future research on the early estimation of manufacturability based on EMAG simulations is crucial for evaluating designs and anticipating manufacturing influences.