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Yvonne Späck-Leigsnering

Publications and source records attributed to Yvonne Späck-Leigsnering.

11 recordsLinked to original sources
arXiv2025

Magneto-thermally Coupled Field Simulation of Homogenized Foil Winding Models

Foil windings have, due to their layered structure, different properties than conventional wire windings, which make them advantageous for high frequency applications. Both electromagnetic and thermal analyses are relevant for foil windings. These two physical areas are coupled through Joule losses and temperature dependent material properties. For an efficient simulation of foil windings, homogenization techniques are used to avoid resolving the single turns. Therefore, this paper comprises a coupled magneto-thermal simulation that uses a homogenization method in the electromagnetic and thermal part. A weak coupling with different time step sizes for both parts is presented. The method is verified on a simple geometry and showcased for a pot transformer that uses a foil and a wire winding.

cs.CE↗
arXiv2025

Transient Nonlinear Electrothermal Adjoint Sensitivity Analysis for HVDC Cable Joints

Efficient computation of sensitivities is a promising approach for efficiently of designing and optimizing high voltage direct current cable joints. This paper presents the adjoint variable method for coupled nonlinear transient electrothermal problems as an efficient approach to compute sensitivities with respect to a large number of design parameters. The method is used to compute material sensitivities of a 320kV high voltage direct current cable joint specimen. The results are validated against sensitivities obtained via the direct sensitivity method.

cs.CE↗
arXiv2025

Thermal Model Calibration of a Squirrel-Cage Induction Machine

Accurate and efficient thermal simulations of induction machines are indispensable for detecting thermal hot spots and hence avoiding potential material failure in an early design stage. A goal is the better utilization of the machines with reduced safety margins due to a better knowledge of the critical conditions. In this work, the parameters of a two-dimensional induction machine model are calibrated according to evidence from measurements, by solving an inverse field problem. The set of parameters comprise material parameters as well as parameters that model three-dimensional effects. This allows a consideration of physical effects without explicit knowledge of its quantities. First, the accuracy of the approach is studied using an academic example in combination with synthetic data. Afterwards, it is successfully applied to a realistic induction machine model.

cs.CE↗
arXiv2025

Thermal Finite-Element Model of an Electric Machine Cooled by a Spray

The need for higher power density in electrical machines require better cooling strategies. Spray cooling is a very promising and relatively simple technology to apply, but involves extremely complicated physics. In this paper, a quasi-3D thermal finite-element model of a stator winding is created, by extrusion of a 2D cross-sectional finite-element model along the winding direction. The possible effects of spray cooling are simulated as a heat flux using an impedance boundary condition at the surface of the winding overhang. The results confirm the beneficial performance of spray cooling. The model indicates that spray cooling may allow a ten times larger power density than for standard air- or water-cooled machines.

cs.CE↗
arXiv2024

Considering Capacitive Effects in Foil Winding Homogenization

In conventional finite element simulations, foil windings with a thin foil and many turns require many mesh elements. This renders models quickly computationally infeasible. With the use of homogenization approaches, the finite element mesh does not need to resolve the small-scale structure of the foil winding domain. Present homogenization approaches take resistive and inductive effects into account. With an increase of the operation frequency of foil windings, however, capacitive effects between adjacent turns in the foil winding become relevant. This paper presents an extension to the standard foil winding model that covers the capacitive behavior of foil windings.

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arXiv2023

Thermal Finite Element Modeling and Simulation of a Squirrel-Cage Induction Machine

Finite element models of electrical machines allow insights in electrothermal stresses which endanger the insulation system of the machine. This paper presents a thermal finite element model of a 3.7 kW squirrel-cage induction machine. The model resolves the conductors and the surrounding insulation materials in the stator slots. A set of transient thermal scenarios is defined and measured in the machine laboratory. These data are used to assess the finite element model.

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arXiv2023

Homogenization of Foil Windings with Globally Supported Polynomial Shape Functions

In conventional finite element simulations, foil windings with thin foils and with a large number of turns require many mesh elements. This renders models quickly computationally infeasible. This paper uses a homogenized foil winding model and approximates the voltage distribution in the foil winding domain by globally supported polynomials. This way, the small-scale structure in the foil winding domain does not have to be resolved by the finite element mesh. The method is validated successfully for a stand-alone foil winding example and for a pot inductor example. Moreover, a transformer equipped with a foil winding at its primary side is simulated using a field-circuit coupled model.

cs.CE↗
arXiv2023

Pyrit: A Finite Element Based Field Simulation Software Written in Python

Pyrit is a field simulation software based on the finite element method written in Python to solve coupled systems of partial differential equations. It is designed as a modular software that is easily modifiable and extendable. The framework can, therefore, be adapted to various activities, i.e. research, education and industry collaboration.

cs.CE↗
arXiv2023

Adjoint Variable Method for Transient Nonlinear Electroquasistatic Problems

Many optimization problems in electrical engineering consider a large number of design parameters. A sensitivity analysis identifies the design parameters with the strongest influence on the problem of interest. This paper introduces the adjoint variable method as an efficient approach to study sensitivities of nonlinear electroquasistatic problems in time domain. In contrast to the more common direct sensitivity method, the adjoint variable method has a computational cost nearly independent of the number of parameters. The method is applied to study the sensitivity of the field grading material parameters on the performance of a 320 kV cable joint specimen, which is modeled as a Finite Element nonlinear transient electroquasistatic problem. Special attention is paid to the treatment of quantities of interest, which are evaluated at specific points in time or space. It is shown that shown that the method is a valuable tool to study this strongly nonlinear and highly transient technical example.

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arXiv2022

Capacitance calculation of unloaded rolling elements -- Comparison of analytical and numerical methods

Various methods for calculating the capacitance of unloaded rolling elements are compared to improve the electric characterization of rolling element bearings. Semi-analytical approximations and finite element simulations are applied and a closed-form analytical two-dimensional solution is derived for comparison. The results show that the most common semi-analytical approximation, which uses effective radii to express the contact geometry, reproduces the trend from numerical and analytical calculations, but overestimates the results derived from numerical simulations. Another semi-analytical approach is presented that delivers better results for the capacitance of unloaded point contacts.

cs.CE↗