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Author: Lengsfeld, Sebastian ×

Publications Search Results

Now showing 1 - 8 of 8
  • Publication
    Investigation of Innovative Cooling Systems for a Direct Driven Lightweight PMSG for Wind Power Applications
    ( 2022)
    Steffen, Jonas
    ;
    Lengsfeld, Sebastian
    ;
    Seibel, Axel
    ;
    Schleicher, K.
    ;
    Herranz Gracia, M.
    ;
    Spagnolo, A.
    ;
    Kloepzig, M.
    ;
    Kraemer, J.
    In this paper, different cooling solutions for a permanent magnet synchronous generator used in wind turbines are investigated. Cooling solutions are developed and narrowed down with the help of an evaluation matrix for more detailed consideration.The cooling performance of the solutions was then analyzed in a simulation. In addition, functional samples of the promising solutions were manufactured and measured in a laboratory environment. For verification purposes, two solutions were integrated into the segments of a scaled demonstrator. The cooling solutions significantly reduce the winding temperature of the demonstration generator in comparison to a passive cooling system.
  • Publication
    Comparing Armature Windings for a 10 MW Fully Superconducting Synchronous Wind Turbine Generator
    ( 2022)
    Lengsfeld, Sebastian
    ;
    Grundmann, Joern
    ;
    Oomen, Marijn
    ;
    Vargas-Llanos, Carlos
    ;
    Ponick, Bernd
    ;
    Jung, Marco
    Defining the armature winding in a fully superconducting generator means to make a fundamental design decision. Especially when using High Temperature Superconductors (HTS), this decision becomes more challenging, because the design has to comply with the general machine design constraints and the behaivor of the superconductor, which can contradict each other.This paper aims to introduce four different fully superconducting machine designs with different armature windings. Therefore, an integer slot distributed winding, a one and a two layer concentrated winding and an airgap winding, are investigated. For each winding a generator design is presented. By using FEM, the field distribution is calculated, which enables to estimate of the AC losses in order to make the overall performance of the four different machine designs becomes comparable.
  • Publication
    An Approach to the Design and the Interactions of a Fully Superconducting Synchronous Generator and Its Power Converter
    ( 2022)
    Lengsfeld, Sebastian
    ;
    Sprunck, Sebastian
    ;
    Frank, S.R.
    ;
    Jung, Marco
    ;
    Hiller, M.
    ;
    Ponick, B.
    ;
    Mersche, S.
    The design of a fully superconducting wind power generator is influenced by several factors. Among them, a low number of pole pairs is desirable to achieve low AC losses in the superconducting stator winding, which greatly influences the cooling system design and, consecutively, the efficiency of the entire wind power plant. However, it has been identified that a low number of pole pairs in a superconducting generator tends to greatly increase its output voltage, which in turn creates challenging conditions for the necessary power electronic converter. This study highlights the interdependencies between the design of a fully superconducting 10 MW wind power generator and the corresponding design of its power electronic converter.
  • Publication
    Classification of Partial Discharge Patterns in Rotating Electrical Machines Using Machine Learning
    ( 2022)
    Lengsfeld, Sebastian
    ;
    Rehwald, Florian
    ;
    Ast, Hardy
    ;
    Schröder, O.
    This paper presents a machine learning approach for the automated classification of partial discharge images recorded on rotating electrical machines. It introduces a classification of different partial discharge patterns for phase resolved partial discharge plots. A major problem in the use of machine learning is the large amount of training data needed for a powerful classifier. An approach is carried out, comprises a realistic partial discharge patterns mentioning off-line and online measurement with a strong focus on electrical machines. This paper shows how to handle the leak of training data by an augmentation of training data, using a few images extracted from the International Electrotechnical Commission (IEC) standards, and discusses convolutional neural network classifier. The classifier will be trained by augmented data and will be tested for different fault conditions in electrical machines. The error conditions that can be applied to the algorithm are shown, and the limitations of this method are discussed.
  • Publication
    Design of a Medium Voltage Generator with DC-Cascade for High Power Wind Energy Conversion Systems
    ( 2021)
    Steffen, Jonas
    ;
    Lengsfeld, Sebastian
    ;
    Jung, Marco
    ;
    Ponick, Bernd
    ;
    Herranz Gracia, Mercedes
    ;
    Spagnolo, Aristide
    ;
    Klöpzig, Markus
    ;
    Schleicher, Klaus
    ;
    Schäfer, Klaus
    This paper shows a new concept to generate medium voltage (MV) in wind power application to avoid an additional transformer. Therefore, the generator must be redesigned with additional constraints and a new topology for the power rectifier system by using multiple low voltage (LV) power rectifiers connected in series and parallel to increase the DC output voltage. The combination of parallel and series connection of rectifiers is further introduced as DC-cascade. With the resulting DC-cascade, medium output voltage is achieved with low voltage rectifiers and without a bulky transformer. This approach to form a DC-cascade reduces the effort required to achieve medium DC voltage with a simple rectifier system. In this context, a suitable DC-cascade control was presented and verified with a laboratory test setup. A gearless synchronous generator, which is highly segmented so that each segment can be connected to its own power rectifier, is investigated. Due to the mixed AC and DC voltage given by the DC-cascade structure, it becomes more demanding to the design of the generator insulation, which influences the copper fill factor and the design of the cooling system. A design strategy for the overall generator design is carried out considering the new boundary conditions.
  • Publication
    Design of a Medium Voltage Generator and Power Converter for High Power Wind Energy Conversion Systems
    ( 2020)
    Steffen, Jonas
    ;
    Lengsfeld, Sebastian
    ;
    Jung, Marco
    ;
    Ponick, Bernd
    ;
    Herranz Gracia, Mercedes
    ;
    Spagnolo, Aristide
    ;
    Schleicher, Klaus
    ;
    Schäfer, Klaus
    In this paper a new topology of a gearless, segmented synchronous generator and power converter system is presented to address medium output voltage in wind power applications. To fulfill the boundary condition, the generator has a high pole count and a stator divided into several 3-phase segments with their own rectifier. With the resulting DC-cascade (series connection of the rectifiers) it is possible to achieve a medium output voltage with low voltage converters and without a bulky transformer. This new topology of the DC-cascade reduces the effort to achieve medium DC voltage in wind turbines and simplifies the converter system.
  • Publication
    T-A Formulation for the Design and AC Loss Calculation of a Superconducting Generator for a 10 MW Wind Turbine
    ( 2020)
    Vargas-Llanos, C.R.
    ;
    Lengsfeld, Sebastian
    ;
    Grilli, F.
    The current capacity of high-temperature superconductors (HTS) has encouraged several applications of these materials in electric power systems. These applications in electrical machines represent a promising solution for more compact and efficient designs. Despite no measurable resistance in the superconducting state, HTS could experience losses under time changing transport current or magnetic field. Therefore, loss estimation is a key input for the design. Maxwell's equations in the T-A formulation form can be used to model and estimate losses in the superconducting tapes of an electrical machine. This formulation requires the current as a function of time in each superconducting tape as an input. A methodology to calculate this current distribution is presented in this article. The procedure introduces a previous step in the building model process and allows a better connection of the machine design with the estimation of losses in the superconductor in order to get a more efficient machine. The approach is applied to a 10 MW superconducting generator, where over one thousand tapes cross-sections are modelled in 2D. The superconductor's non-linear behaviour and critical current density anisotropy are considered. Losses are estimated for different designs and a sensitivity analysis is presented for different temperatures and frequencies, in addition to other alternatives to reduce losses.