05 Fakultät Informatik, Elektrotechnik und Informationstechnik
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/6
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Item Open Access Modeling and experimental investigation of the interaction between pressure-dependent aging and pressure development due to the aging of lithium-ion cells(2023) Avdyli, Arber; Fill, Alexander; Birke, Kai PeterIn order to meet the increasing demands of the battery in terms of range, safety and performance, it is necessary to ensure optimal operation conditions of a lithium-ion cell. In this thesis, the influence of mechanical boundary conditions on the cell is investigated theoretically and experimentally. First, fundamental equations are derived that lead to coupled models that can be parameterized based on specific cell measurements and predict the pressure evolution due to capacity aging and vice versa. The model is used to derive optimal operating points of the cell, which can be considered in the module design.Item Open Access Surface charge density and induced currents by self-charging sliding drops(2024) Bista, Pravash; Ratschow, Aaron D.; Stetten, Amy Z.; Butt, Hans-Jürgen; Weber, Stefan A. L.Spontaneous charge separation in drops sliding over a hydrophobized insulator surface is a well-known phenomenon and lots of efforts have been made to utilize this effect for energy harvesting. For maximizing the efficiency of such devices, a comprehensive understanding of the dewetted surface charge would be required to quantitatively predict the electric current signals, in particular for drop sequences. Here, we use a method based on mirror charge detection to locally measure the surface charge density after drops move over a hydrophobic surface. For this purpose, we position a metal electrode beneath the hydrophobic substrate to measure the capacitive current induced by the moving drop. Furthermore, we investigate drop-induced charging on different dielectric surfaces together with the surface neutralization processes. The surface neutralizes over a characteristic time, which is influenced by the substrate and the surrounding environment. We present an analytical model that describes the slide electrification using measurable parameters such as the surface charge density and its neutralization time. Understanding the model parameters and refining them will enable a targeted optimization of the efficiency in solid–liquid charge separation.Item Open Access A comprehensive model and experimental investigation of venting dynamics and mass loss in lithium-ion batteries under a thermal runaway(2025) Chen, Ai; Sahin, Resul; Ströbel, Marco; Kottke, Thomas; Hecker, Stefan; Fill, AlexanderThermal runaway (TR) has become a critical safety concern with the widespread use of lithium-ion batteries (LIBs) as an energy storage solution to meet the growing global energy demand. This issue has become a significant barrier to the expansion of LIB technologies. Addressing the urgent need for safer LIBs, this study developed a comprehensive model to simulate TR in cylindrical 18650 nickel cobalt manganese (NMC) LIBs. By incorporating experiments with LG ® -INR18650-MJ1 cells, the model specifically aimed to accurately predict critical TR parameters, including temperature evolution, internal pressure changes, venting phases, and mass loss dynamics. The simulation closely correlated with experimental outcomes, particularly in replicating double venting mechanisms, gas generation, and the characteristics of mass loss observed during TR events. This study confirmed the feasibility of assuming proportional relationships between gas generation and the cell capacity and between the mass loss from solid particle ejection and the total mass loss, thereby simplifying the modeling of both gas generation and mass loss behaviors in LIBs under TR. Conclusively, the findings advanced the understanding of TR mechanisms in LIBs, providing a solid foundation for future research aimed at mitigating risks and promoting the safe integration of LIBs into sustainable energy solutions.Item Open Access Sharp MIR plasmonic modes in gratings made of heavily doped pulsed laser-melted Ge1-xSnx(2023) Berkmann, Fritz; Steuer, Oliver; Ganss, Fabian; Prucnal, Slawomir; Schwarz, Daniel; Fischer, Inga Anita; Schulze, JörgItem Open Access Load-flow-based calculation of initial short-circuit currents for converter-based power system(2025) Deepak, Deepak; Oetoyo, Anisatur Rizqi; Rudion, Krzysztof; John, Christoph; Abele, HansShort-circuit current is a key characteristic value for synchronous generator-based power systems. It is employed for different applications during the planning and operation phases. The proportion of converter-interfaced units is increasing in order to integrate more renewable energy sources into the system. These units have different fault current characteristics due to their physical properties and operation strategies. Consequently, the network’s short-circuit current profile is changing, both in terms of magnitude and injection time. Therefore, accurately estimating fault currents is crucial for reliable power system planning and operation. Traditionally, two calculation methods are employed: the equivalent voltage source (IEC 60909/VDE 0102) and the superimposition (complete) method. In this work, the assumptions, simplifications, and limitations from both types of methods are addressed. As a result, a new load-flow-based method is presented, improving the static modeling of generating units and the accuracy in the estimation of short-circuit currents. The method is tested for mixed generation types comprising of synchronous generators, and grid-following (current source) and grid-forming (voltage source before and current source after the current limit) converters. All methods are compared against detailed time-domain RMS simulations using a modified IEEE-39 bus system and a real network from ENTSO-E. It is shown that the proposed method provides the best accuracy in the calculation of initial short-circuit currents for converter-based power systems.Item Open Access Multidisciplinary design optimization of a transverse flux machine based on a multi-step loss calculation method(2026) Lefringhausen, Tim Jonathan; Knecht, Simon; Parspour, Nejila; Albers, AlbertA transverse flux machines is a special type of electrical machine that offers advantages in terms of torque and power density. Due to the complex simulation, design and manufacturing, transverse flux machines are rarely used despite their many possible applications. The three-dimensional magnetic flux guidance results in a complex geometry of the stator core. As the conventional design of axially stacked electrical steel sheets is not feasible for this type of motor, new manufacturing methods are being researched. In addition, few procedures for simulation and design have been available to date. This paper presents an approach that enables the optimization of an additively manufactured stator core with respect to both efficiency and thermal behavior. In order to efficiently simulate the various power losses of the motor, the results of a 3D-FEM simulation as well as empirical models were combined in several steps. As there is a strong interaction between the thermal and electromagnetic domain for this type of motor, both were simulated iteratively coupled. The shape of the stator core was optimized for low and high speeds, taking into account the respective heating, which led to an improvement in efficiency of more than 5 %pt. in both cases.Item Open Access Quantitative analysis of the sensitivity of UHF sensor positions on a 420 kV power transformer based on electromagnetic simulation(2019) Beura, Chandra Prakash; Beltle, Michael; Tenbohlen, Stefan; Siegel, MartinWith an increasing interest in ultra-high frequency (UHF) partial discharge (PD) measurements for the continuous monitoring of power transformers, it is necessary to know where to place the UHF sensors on the tank wall. Placing a sensor in an area with many obstructions may lead to a decrease in sensitivity to the UHF signals. In this contribution, a previously validated simulation model of a three-phase 300 MVA, 420 kV power transformer is used to perform a sensitivity analysis to determine the most sensitive sensor positions on the tank wall when PD activity occurs inside the windings. A matrix of UHF sensors located on the transformer tank is used to perform the sensitivity analysis. Some of the windings are designed as layer windings, thus preventing the UHF signals from traveling through them and creating a realistic situation with very indirect propagation from source to sensor. Based on these findings, sensor configurations optimized for UHF signal sensitivity, which is also required for PD source localization, are recommended for localization purposes. Additionally, the propagation and attenuation of the UHF signals inside the windings and the tank are discussed in both oil and air.Item Open Access Dead time-free detection of NMR signals using voltage-controlled oscillators(2023) Kern, Michal; Klotz, Tobias; Spiess, Maximilian; Mavridis, Petros; Blümich, Bernhard; Anders, JensIn this paper, we introduce voltage-controlled oscillators (VCOs) as a new type of nuclear magnetic resonance (NMR) detector, enabling dead time-free detection of NMR signals after an excitation pulse as well as the real-time inductive detection of Rabi oscillations during the pulse. Together with the theory of operation, we present the details of a custom-designed prototype implementation of a VCO-based NMR detector with an operating frequency around 62 MHz. The proof-of-concept measurements obtained with this prototype clearly demonstrate the possibility of performing dead time-free NMR experiments with coherent spin manipulation. Moreover, we also experimentally verified the capability of VCO-based detectors for performing real-time inductive detection of Rabi oscillations during the excitation pulse.Item Open Access High-speed oil-cooled PMSM with novel permanent magnet shape and carbon fiber sleeved rotor for high-performance powertrain(2025) Clauer, Maximilian; Bauer, David; Parspour, NejilaFor high-performance vehicles with a single-speed gearbox, maximizing the gravimetric peak power and peak torque density combined with a high maximum speed is the decisive design goal of the electric machine. A low vehicle mass leads to a high vehicle acceleration, while a high maximum rotational speed leads to a high top speed. Therefore, this work presents the design and optimization of a high-speed, oil-cooled permanent magnet synchronous machine with a novel circular sector-like permanent magnet shape and a carbon fiber sleeved rotor in combination with cobalt iron laminations. The result is a gravimetric peak power density of 50.9 kW/kg, a gravimetric peak torque density of 30.8 Nm/kg, and a maximum rotational speed of 30000 rpm. The use of two of these electric machines on one drive axle leads to a gravimetric peak axle power density of 12.1 kW/kg and a gravimetric peak axle torque density of 72.1 Nm/kg at system level, including electric machines, gearboxes and inverters.Item Open Access Modeling and investigating total ionizing dose impact on FeFET(2023) Sayed, Munazza; Ni, Kai; Amrouch, Hussam