Abstract
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.
Translated title of the contribution | Material characterization, modeling, and incorporation of the models in the machine simulation of large-diameter synchronous machines |
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Original language | English |
Qualification | Doctor's degree |
Awarding Institution |
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Publisher | |
Print ISBNs | 978-952-64-1596-3 |
Electronic ISBNs | 978-952-64-1597-0 |
Publication status | Published - 2023 |
MoE publication type | G5 Doctoral dissertation (article) |
Keywords
- electrical steel sheets
- cutting
- eddy currents
- finite-element modeling