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Effects of Nonlinear Magnetic Forces on the Dynamics of Hydropower Generators with Floating Rotor Rim
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.ORCID iD: 0000-0002-4185-2395
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.ORCID iD: 0000-0001-6016-6342
Vattenfall AB Research and Development, Älvkarlebylaboratoriet, 814 70 Älvkarleby, Sweden.ORCID iD: 0000-0003-2812-2985
2024 (English)In: 16th Chaotic Modeling and Simulation International Conference / [ed] Christos H. Skiadas; Yiannis Dimotikalis, Springer Nature, 2024, p. 541-552Conference paper, Published paper (Refereed)
Abstract [en]

Hydropower generators are normally considered rigid in rotordynamic studies; nevertheless, according to previous studies, they should be regarded as elastic, and this will affect the system's dynamics. The interaction between the magnetic flux of the stator and rotor creates attractive forces between the parts that would balance to zero at the centered position. However, asymmetries in the magnetic flux create an uneven distribution of forces that threaten the machine's life; these forces are non-linearly dependent on the gap between the rotation and stationary part of the generators, although it has been considered linear for simplification. This study focuses on how the dynamics of the rotor are affected by static eccentricity and unbalanced masses while considering nonlinear electromagnetic forces. The rotor has been modeled using curved beams and attached to the rotor-spider by connecting plates, allowing the expansion of the ring due to centrifugal and thermal loads. The electromagnetic forces are modeled as a sum of exponential functions. Bifurcation diagrams and Poincaré maps are employed to analyze the stability of the generator. 

Place, publisher, year, edition, pages
Springer Nature, 2024. p. 541-552
Series
Springer Proceedings in Complexity (SPCOM), ISSN 2213-8684, E-ISSN 2213-8692
Keywords [en]
Hydropower, Nonlinear dynamics, Generator, Rotor-dynamics
National Category
Applied Mechanics
Research subject
Machine Design
Identifiers
URN: urn:nbn:se:ltu:diva-104995DOI: 10.1007/978-3-031-60907-7_38Scopus ID: 2-s2.0-85218024858OAI: oai:DiVA.org:ltu-104995DiVA, id: diva2:1849295
Conference
16th International Conference on Chaotic Modeling and Simulation (CHAOS 2023), Heraklion, Crete, Greece, June 13-16, 2023
Funder
Swedish Energy AgencyEnergy ResearchSwedish National Grid
Note

Funder: Swedish Hydropower Centre (SVC);

ISBN for host publication: 978-3-031-60906-0, 978-3-031-60909-1, 978-3-031-60907-7

Available from: 2024-04-05 Created: 2024-04-05 Last updated: 2025-04-04Bibliographically approved
In thesis
1. Dynamic Models for Mechanical Analysis of Synchronous Hydropower Generators
Open this publication in new window or tab >>Dynamic Models for Mechanical Analysis of Synchronous Hydropower Generators
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Hydropower generators are essential for providing electricity for daily human activities. For that reason, designing and building reliable generators contributes to a sustainable energy supply market. Many studies have sought to model the dynamics of hydropower generators, as providing a reliable model would lead to more cost-effective designs; these models need to consider both operational and faulty conditions. A generator comprises many parts that contribute to its dynamics: tilting-pad bearings, rotor-rim, and stator’s core, which are the ones focused on in this study. Modeling a hydropower generator is a complex endeavor that requires considerable computational resources and is time-consuming. Therefore, this thesis aims to propose models to study and predict the dynamics of hydropower generators, which would be beneficial for manufacturers and operators, reducing the complexity of the design without compromising accuracy. To accomplish this, each mentioned individual part is explored. It starts with characterizing eight-pad tilting-pad bearings on vertical rotors, proposing a model, and comparing the results to experiments. Then it continues by considering the rotor rim in a generator to be flexible and proposing a model for the generator with flexible rotor rims while the stator remains rigid; this is accomplished using Lagrange equations, considering the centrifugal and Coriolis effects, the electromagnetic interaction between rotor and stator, and static and dynamic eccentricities. Reducing the complexity of the rotor rim required assembling 2-D curved beam elements to reproduce its geometry and testing on a generator prototype, discussing the impact of the connecting plates and the magnetic forces on the natural frequencies and the effect of static eccentricity and unbalance. A 3-D Finite Element model of the generator was also proposed, and both simulations focused on the similarities and differences between both approaches.  Furthermore, linear and nonlinear models of the electromagnetic forces acting on the rotor are also considered and applied in the model to study whether the nonlinear behavior in a generator can affect its stability by employing Bifurcation diagrams and Poincaré maps. 

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2024
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords
Rotordynamics, Hydropower, Generator, Curved Beam, Tillting-Pad Bearing
National Category
Applied Mechanics
Research subject
Machine Design
Identifiers
urn:nbn:se:ltu:diva-105169 (URN)978-91-8048-548-7 (ISBN)978-91-8048-549-4 (ISBN)
Public defence
2024-06-14, B192, Luleå University of Technology, Luleå, 09:00 (English)
Opponent
Supervisors
Available from: 2024-04-22 Created: 2024-04-19 Last updated: 2024-05-16Bibliographically approved

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Rondon, DavidAidanpää, Jan-OlovGustavsson, Rolf

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