### Browsing by Author "Upadhaya, Brijesh"

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Item Alternating and Rotational Loss Prediction Accuracy of Vector Jiles-Atherton Model(Elsevier Science B.V., 2021-06-01) Upadhaya, Brijesh; Rasilo, Paavo; Perkkiö, Lauri; Handgruber, Paul; Benabou, Abdelkader; Belahcen, Anouar; Arkkio, Antero; Department of Electrical Engineering and Automation; Tampere University; Department of Mathematics and Systems Analysis; Graz University of Technology; University of Lille; Computational ElectromechanicsIn this paper, the vector extension of the Jiles-Atherton hysteresis model is modified to predict both alternating and rotational field strength variations observed in a nonoriented silicon steel sheet. The model parameters are changed to be functions of the magnitude and direction of flux density, and the anhysteretic magnetic characteristics are identified from several unidirectional alternating B(H) measurements. We demonstrate that the modified vector Jiles-Atherton model can predict both alternating and rotational field strength variations with better accuracy than the “basic” approach.Item Comparison of Anisotropic Energy-Based and Jiles–Atherton Models of Ferromagnetic Hysteresis(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2020) Upadhaya, Brijesh; Rasilo, Paavo; Perkkiö, Lauri; Handgruber, Paul; Belahcen, Anouar; Arkkio, Antero; Department of Electrical Engineering and Automation; Department of Mathematics and Systems Analysis; Computational Electromechanics; Graz University of Technology; Tampere UniversityIn this article, we apply an anisotropic extension for the energy-based and the Jiles–Atherton (JA) hysteresis models to simulate both unidirectional alternating and rotational magnetic field excitations. The results show a good agreement with measurements for unidirectional alternating fields. However, the results for rotational fields, especially at high magnitudes, show a significant discrepancy with the measurement data. We demonstrate that the JA model with appropriate parameters can estimate the losses in alternating cases up to 1.5 T, whereas both models give reasonable loss estimation up to 1 T in rotational cases.Item A constraint-based optimization technique for estimating physical parameters of Jiles–Atherton hysteresis model(Emerald, 2020-08-24) Upadhaya, Brijesh; Rasilo, Paavo; Perkkiö, Lauri; Handgruber, Paul; Belahcen, Anouar; Arkkio, Antero; Department of Electrical Engineering and Automation; Tampere University; Department of Mathematics and Systems Analysis; Graz University of Technology; Computational ElectromechanicsPurpose: Improperly fitted parameters for the Jiles–Atherton (JA) hysteresis model can lead to non-physical hysteresis loops when ferromagnetic materials are simulated. This can be remedied by including a proper physical constraint in the parameter-fitting optimization algorithm. This paper aims to implement the constraint in the meta-heuristic simulated annealing (SA) optimization and Nelder–Mead simplex (NMS) algorithms to find JA model parameters that yield a physical hysteresis loop. The quasi-static B(H)-characteristics of a non-oriented (NO) silicon steel sheet are simulated, using existing measurements from a single sheet tester. Hysteresis loops received from the JA model under modified logistic function and piecewise cubic spline fitted to the average M(H) curve are compared against the measured minor and major hysteresis loops. Design/methodology/approach: A physical constraint takes into account the anhysteretic susceptibility at the origin. This helps in the optimization decision-making, whether to accept or reject randomly generated parameters at a given iteration step. A combination of global and local heuristic optimization methods is used to determine the parameters of the JA hysteresis model. First, the SA method is applied and after that the NMS method is used in the process. Findings: The implementation of a physical constraint improves the robustness of the parameter fitting and leads to more physical hysteresis loops. Modeling the anhysteretic magnetization by a spline fitted to the average of a measured major hysteresis loop provides a significantly better fit with the data than using analytical functions for the purpose. The results show that a modified logistic function can be considered a suitable anhysteretic (analytical) function for the NO silicon steel used in this paper. At high magnitude excitations, the average M(H) curve yields the proper fitting with the measured hysteresis loop. However, the parameters valid for the major hysteresis loop do not produce proper fitting for minor hysteresis loops. Originality/value: The physical constraint is added in the SA and NMS optimization algorithms. The optimization algorithms are taken from the GNU Scientific Library, which is available from the GNU project. The methods described in this paper can be applied to estimate the physical parameters of the JA hysteresis model, particularly for the unidirectional alternating B(H) characteristics of NO silicon steel.Item Design of Torque Exciter for Induction Machine(2014-05-05) Upadhaya, Brijesh; Arkkio, Antero; Sähkötekniikan korkeakoulu; Arkkio, AnteroThree phase induction machines are becoming more popular and are also being used as variable speed drives. An induction machine driving a load represents a torsional system. The analysis of any torsional system without active damper is somehow based on conventional method i.e. including shaft stiffness and viscous damping provided by the material. This conventional method might lead to somehow highly compromised results. The involvement of induction machine complicates the approach by contributing to both stiffness and damping in the system. So, in-order to verify the contribution from the electromagnetic system in overall torsion dynamics of the drive train, a thorough study on torque exciter has been carried out in this master's thesis work. A new type of excitation system has been proposed on the basis of studied material. A careful investigation on stability of the proposed excitation system has also been performed followed by laboratory set-up and testing. Finally, measurements were carried out to verify the electromagnetic system's contribution toward both stiffness and damping. A brief comparison between simulation results with measurement result has been presented.Item Effects of Magnetic Anisotropy on the Performance of Electrical Machines(2020-01-20) Bhatti, Hassan; Upadhaya, Brijesh; Sähkötekniikan korkeakoulu; Belahcen, AnouarElectrical steel sheets used in the magnetic cores of electrical machines have non-grain oriented material and their magnetic properties are anisotropic in nature. This anisotropic behaviour plays an important part in the performance characteristic of the machines. It is vital to understand this behaviour and develop magnetic anisotropic models to include the effects of anisotropy in the design phase of the electrical machines. In this Master's thesis, four anisotropy models are presented. The models are developed by utilizing unidirectional measurements data for different directions with respect to the rolling direction of the electrical sheet. The implementation of the models developed are performed by using the 2D finite element method. A simple ring core model is used to show the effects of magnetic anisotropy at different points. The results show that the magnetic flux density has different values with respect to the position of the points in the ring core. The conclusions of this work provides a better understanding of the different ways to model magnetic anisotropy.Item Finite element level validation of an anisotropic hysteresis model for non-oriented electrical steel sheets(Elsevier Science B.V., 2022-12-15) Upadhaya, Brijesh; Rasilo, Paavo; Handgruber, Paul; Belahcen, Anouar; Arkkio, Antero; Department of Electrical Engineering and Automation; Tampere University; Graz University of TechnologyThis paper presents the finite element level validation of the anisotropic Jiles–Atherton hysteresis model. Numerical analysis of a round rotational single sheet tester is performed using the 2D finite element method. Anisotropic extension of the Jiles–Atherton hysteresis model is coupled with the 2D finite element method. The finite element simulations are performed for the cases when the magnetic field alternates and rotates in the lamination plane. The simulated results for alternating and rotational flux density excitations agree with the measured data. The measured data used in this paper corresponds to the M400-50A nonoriented silicon steel.Item Modelling anisotropy in non-oriented electrical steel sheet using vector Jiles-Atherton model(2017) Upadhaya, Brijesh; Martin, Floran; Rasilo, Paavo; Handgruber, Paul; Belahcen, Anouar; Arkkio, Antero; Department of Electrical Engineering and Automation; Computational Electromechanics; Graz University of TechnologyPurpose: Non-oriented electrical steel presents anisotropic behaviour. Modelling such anisotropic behaviour has become a necessity for accurate design of electrical machines. The main aim of this study is to model the magnetic anisotropy in the non-oriented electrical steel sheet of grade M400-50A using a phenomenological hysteresis model. Design/methodology/approach: The well-known phenomenological vector Jiles-Atherton hysteresis model is modified to correctly model the typical anisotropic behaviour of the non-oriented electrical steel sheet, which is not described correctly by the original vector Jiles-Atherton model. The modification to the vector model is implemented through the anhysteretic magnetization. Instead of the commonly used classical Langevin function, the authors introduced 2D bi-cubic spline to represent the anhysteretic magnetization for modelling the magnetic anisotropy. Findings: The proposed model is found to yield good agreement with the measurement data. Comparisons are done between the original vector model and the proposed model. Another comparison is also made between the results obtained considering two different modifications to the anhysteretic magnetization. Originality/value: The paper presents an original method to model the anhysteretic magnetization based on projections of the anhysteretic magnetization in the principal axis, and apply such modification to the vector Jiles-Atherton model to account for the magnetic anisotropy. The replacement of the classical Langevin function with the spline resulted in better fitting. The proposed model could be used in the numerical analysis of magnetic field in an electrical application.Item Models of Magnetic Anisotropy for Nonoriented Silicon Steel Laminations of Electrical Machines(Aalto University, 2022) Upadhaya, Brijesh; Rasilo, Paavo, Assoc. Prof., Tampere University, Finland; Sähkötekniikan ja automaation laitos; Department of Electrical Engineering and Automation; Electromechanics; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Belahcen, Anouar, Prof., Aalto University, Department of Electrical Engineering and Automation, FinlandThis dissertation deals with magnetic anisotropy and its impact on the flux density and loss distribution for non-oriented silicon steel laminations. Magnetic material models, such as anhysteretic reluctivity, Bergqvist’s vector Jiles-Atherton and energy-based hysteresis models, are considered in this work. The vector hysteresis models mentioned above are extended: first, to account for magnetic anisotropy observed in non-oriented silicon steel, and second, to predict hysteresis losses for the input excitation rotating in the plane of the sheet, as well as alternating in different directions. Non-oriented silicon steel lamination, commonly used in a rotating electrical machine’s magnetic core, shows a significant level of magnetic anisotropy. Numerical analysis tools often assume the laminated core is isotropic. Preliminary investigations reveal that the anisotropy alters the distribution of magnetic flux density in the core. Thus, some core parts get saturated, which may adversely affect the core losses. Hence, determining how the losses predicted by the anisotropic models differ from their isotropic counterparts is paramount. Firstly, an extension of the isotropic anhysteretic reluctivity model is proposed to account for magnetic anisotropy. After preliminary investigations, the ideas from the anisotropic reluctivity model are then incorporated into the advanced hysteresis models. Hysteresis models, such as Bergqvist's vector Jiles-Atherton and energy-based models, rely upon the anhysteretic properties for quantitatively describing the intrinsic anisotropy. Anhysteretic magnetic characteristics are identified from unidirectional alternating measurements in several directions to include intrinsic anisotropy in the models. Moreover, to reasonably predict the hysteresis losses, the model parameters are allowed to depend on the magnitude and polar direction of the flux density vector. Secondly, the anisotropic models are coupled with the finite element method. This coupling is then applied to simulate magnetic fields and associated losses in the commonly used measurement setups such as a toroidal inductor, round rotational single sheet tester, and a transformer-like device. The results of the finite element simulations are briefly compared and discussed. Furthermore, the material level validation of the proposed hysteresis models is in the peer-reviewed articles at the end of this thesis.Item Representation of anisotropic magnetic characteristic observed in a non-oriented silicon steel sheet(AMER INST PHYSICS, 2020-06-15) Upadhaya, Brijesh; Perkkiö, Lauri; Rasilo, Paavo; Belahcen, Anouar; Handgruber, Paul; Arkkio, Antero; Department of Electrical Engineering and Automation; Department of Mathematics and Systems Analysis; Tampere University; Computational Electromechanics; Graz University of TechnologyThis article presents a modified Jiles–Atherton hysteresis model for a weakly anisotropic non-oriented silicon steel sheet. In a toroidal inductor, the magnetic flux density can point toward any direction compared to the sheet orientation, and the hysteresis model should take this into account. We identify the model parameters independently for unidirectional alternating B(H)-characteristics in seven different directions. Then, we construct an anisotropic hysteresis model, where the model parameters can depend on the magnitude and direction of the applied magnetic flux density. We demonstrate that the parameters identified in the rolling and transverse directions of the silicon steel sheet (M400-50A) are sufficient to describe the hysteresis losses in other directions.