Browsing by Author "Schmid, Martin"

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Open Access
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.
Open Access
Additively manufactured transverse flux machine components with integrated slits for loss reduction
(2022) Kresse, Thomas; Schurr, Julian; Lanz, Maximilian; Kunert, Torsten; Schmid, Martin; Parspour, Nejila; Schneider, Gerhard; Goll, Dagmar
Laser powder bed fusion (L-PBF) was used to produce stator half-shells of a transverse flux machine from pure iron (99.9% Fe). In order to reduce iron losses in the bulk components, radially extending slits with a nominal width of 150 and 300 µm, respectively, were integrated during manufacturing. The components were subjected to a suitable heat treatment. In addition to a microscopic examination of the slit quality, the iron losses were also measured using both a commercial and a self-developed measurement setup. The investigations showed the iron losses can be reduced by up to 49% due to the integrated slits and the heat treatment.
Open Access
Comparison of rotor arrangements of Transverse Flux Machines for a robotic direct drive optimized by genetic algorithm and Regression Tree Method
(2023) Kaiser, Benedikt; Schmid, Martin; Parspour, Nejila
Articulated robotics applications typically have a demand for high torque at low speed. However, conventional electrical machines cannot generate a reasonable amount of torque directly by electro-magnetics. Therefore, gearboxes are used to convert speed and torque, accepting loss of mechanical power due to additional friction. Although geared solutions for robotic drive trains already offer exceedingly high torque densities, they are limited by the drawbacks of high reduction gears, such as non-linearities in friction, complex flexibility effects, and limited service life of mechanics in contrary to direct drive solutions. The Transverse Flux Machine with the high gravimetric torque density may be a solution for reducing or eliminating the need for a gearbox. Using a genetic algorithm, the proposed Transverse Flux Machines are optimized. To enhance the optimization’s speed, the machines’ calculations done by Finite-Element-Analysis of selected generations are replaced by a Regression Tree Model whose results are verified after a defined expired model service life with a subsequent adjustment of the model. The eligibility of different arrangements the Transverse Flux Machines’ rotor are compared regarding the application as low-speed direct drive in robotics, also compared to similar Radial Flux Machines. The optimized Transverse Flux Machines have a higher efficiency due to lower copper loss and a higher active gravimetric torque density. However, the Radial Flux Machines have higher total torques and power factors.
Open Access
Identification of electro-mechanical interactions in wind turbines
(2024) Lüdecke, Fiona Dominique; Schmid, Martin; Cheng, Po Wen
Large direct-drive wind turbines with a multi-megawatt power rating face design challenges, especially concerning tower top mass, due to scaling laws for high-torque generators. This work proposes to extend the design space by moving towards a more system-oriented approach, considering electro-mechanical interactions. This requires an extension of the state-of-the-art wind turbine models with additional degrees of freedom. To limit the computational effort of such models, a profound understanding of possible interaction mechanisms is required. This work aims to identify interactions of an additional degree of freedom in the radial direction of the generator with the wind turbine structure, the aerodynamics, and the wind turbine controller. Therefore, a Simpack model of the IEA 15 MW RWT is implemented and coupled to a quasi-static analytical generator model for electromagnetic forces. The analytical model, sourced from literature, is code-to-code validated against a finite element model of the generator in COMSOL Multiphysics. Electro-mechanical simulation results do not show interactions with the aerodynamics or the controller. However, interactions with the wind turbine structure occur. It is shown that the modelling approach can affect the system's natural frequencies, which can potentially impact the overall system design choices.
Open Access
Numerical aspects of a two-way coupling for electro-mechanical interactions - a wind energy perspective
(2022) Lüdecke, Fiona Dominique; Schmid, Martin; Rehe, Eva; Panneer Selvam, Sangamithra; Parspour, Nejila; Cheng, Po Wen