Material characterization, modeling, and incorporation of the models in the machine simulation of large-diameter synchronous machines

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School of Electrical Engineering | Doctoral thesis (article-based) | Defence date: 2024-01-12
Degree programme
112 + app. 46
Aalto University publication series DOCTORAL THESES, 224/2023
This dissertation presents a comprehensive methodology for the realistic and computationally efficient simulation of large-diameter synchronous machines accounting for the effect of cutting on iron losses and magnetization. To achieve this, magnetic materials used in the machine parts are experimentally characterized, material models based on the characterization are developed, the developed models are incorporated into finite-element (FE) simulation software, and machine simulation is performed with the incorporated models. Non-oriented punched electrical steel sheets used in the stator laminations are studied experimentally under different uniaxial stress conditions using a modified single-sheet tester. It is shown that the effect of stress on the iron losses of the punched samples differs based on the extent of degradation observed in the samples following the cutting procedure. Subsequently, in the material modeling, the focus is given to the modeling of punching. A continuous material modeling approach with an exponential deterioration profile is used for the magnetization, and iron losses are modeled similarly by modifying the coefficients of Jordan's method. Thick laser-cut steel laminations used in the rotor poles are studied experimentally using a ringcore measurement system. The characterization of the material properties and iron losses is then achieved by a 2-D axisymmetric FE modeling of the lamination cross-section with the inclusion of a continuous local material model using a quadratic deterioration profile. It is shown that the inclusion of the edge effects for the thick laminations is needed, which requires a 2-D modeling. In light of this, a simple 2-D analytical model is developed for eddy-current loss computation. To achieve a computationally efficient and accurate implementation of cutting deterioration into electromagnetic FE simulation, a new methodology for numerical integration is proposed. The validity of this approach is confirmed by comparing it to the analytical solution for a 2-D beam geometry. Subsequently, the method is utilized in the 2-D FE simulation of transformers, resulting in an enhanced computational efficiency when compared to existing methods. Time-stepping simulation of the studied large-diameter synchronous machine is achieved with the incorporated models developed for the stator laminations and rotor poles following the proposed methodology. The effect of cutting on the loss components and machine operating points is analyzed. The results demonstrate that accurate incorporation of the cutting effect in the machine simulation increases the machine's losses by 16.4 kW, necessitating improved cooling capabilities.
Supervising professor
Belahcen, Anouar, Prof., Aalto University, Department of Electrical Engineering and Automation, Finland
Thesis advisor
Martin, Floran, Dr., Aalto University, Department of Electrical Engineering and Automation, Finland
Aydin, Ugur, Dr., ABB Oy, Finland
electrical steel sheets, cutting, eddy currents, finite-element modeling
Other note
  • [Publication 1]: Ismet Tuna Gurbuz, Floran Martin, Ugur Aydin, Ahamed Bilal Asaf Ali, Marta Chamosa, Paavo Rasilo, and Anouar Belahcen. Experimental characterization of the effect of uniaxial stress on magnetization and iron losses of electrical steel sheets cut by punching process. Journal of Magnetism and Magnetic Materials, vol. 549, pp. 168983, May 2022.
    DOI: 10.1016/j.jmmm.2021.168983 View at publisher
  • [Publication 2]: Ismet Tuna Gurbuz, Paavo Rasilo, Floran Martin, Ugur Aydin, Osaruyi Osemwinyen, Ahamed Bilal Asaf Ali, Marta Chamosa, and Anouar Belahcen. Finite-Element Modeling and Characterization of Iron Losses in 12 mm Thick Steel Laminations Including the Effect of Cutting. IEEE Access, vol. 9, pp. 115710-115718, August 2021.
    DOI: 10.1109/ACCESS.2021.3105909 View at publisher
  • [Publication 3]: Ismet Tuna Gurbuz, Paavo Rasilo, Floran Martin, Osaruyi Osemwinyen, and Anouar Belahcen. 2-D Analytical Model for Computing Eddy-Current Loss in Nonlinear Thick Steel Laminations. IEEE Transactions on Magnetics, vol. 58, no. 9, pp. 1-4, September 2022.
    DOI: 10.1109/TMAG.2022.3162955 View at publisher
  • [Publication 4]: Ismet Tuna Gurbuz, Floran Martin, Paavo Rasilo, Md Masum Billah, and Anouar Belahcen. A new methodology for incorporating the cutting deterioration of electrical sheets into electromagnetic finite-element simulation. Submitted to Journal of Magnetism and Magnetic Materials, May 2023.