Browsing by Author "Belahcen, Anouar"

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2D Analytical Model for Computing Eddy-Current Loss in Nonlinear Thick Steel Laminations
(2022-09) Gurbuz, Ismet; Rasilo, Paavo; Martin, Floran; Osemwinyen, Osaruyi; Belahcen, Anouar
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
In this article, we propose an analytical method to compute the eddy-current loss in nonlinear thick steel laminations (3-12 mm) by considering the return path of the eddy currents. Initially, a 2-D finite-element (FE) model is applied to segregate losses measured from toroidal material samples into hysteresis and eddy-current loss components to use them as reference. Afterward, a 2-D analytical time-domain model is proposed for the eddy currents based on the solution of the 2-D field problem. The time-domain model is then used to derive a simple frequency-domain eddy-current loss formulation for the sinusoidal flux density case with the inclusion of a skin-effect correction factor, which accounts for the nonlinearity of the material. Highly accurate results are obtained from the proposed model compared to FE reference results with a mean relative error of 5.1% in the nonlinear region.
3 Dimensional Electromagnetic Analysis of an Axial Active Magnetic Bearing
(2016-08-24) Panchal, Jay
Sähkötekniikan korkeakoulu | Master's thesis
In the rotating electrical machines, active magnetic bearing are basically performing the same role like mechanical bearings to support rotor. The function is based on the principle of magnetic levitation. The idea behind this involves creation of a magnetic field by supplying controlled currents in the bearing coil through amplifiers and complex power electronics. The accurate design of a magnetic bearing system incorporates many parameters before its implementation. The current work of the thesis encircles only the three dimensional (3D) modeling of axial active magnetic bearing (AMB). The static and dynamic models are analyzed for the bearing with a consideration of nonlinear material. In the study, the major emphasis is on the magnetic field, eddy current behavior and exerted magnetic forces in the magnetic bearing. The required input parameters for simulation are considered from the available two dimensional (2D) analysis for the same axial actuator. Elmer open source finite element tool is used in the entire work for making 3D simulations. Finally, the computed results are compared with the 2D case. As a part of the thesis work, a modified geometry is simulated to analyze eddy currents. The hypothesis in later task is the reduction of eddy current losses by providing a radial cut in the bearing ferromagnetic path. The radial cut brings asymmetry in the bearing and the three dimensional analysis provides the possibility to analyze the complete model. The results obtained in the above work provide a good understanding of 3D fields in axial AMB and the computed magnetic forces are in good agreement with the 2D results.
3-D Eddy Current Modelling of Steel Laminations to Analyze Edge Effects
(2016-07-01) Sundaria, Ravi; Rasilo, Paavo; Belahcen, Anouar; Arkkio, Antero
A4 Artikkeli konferenssijulkaisussa
The correct estimation of iron losses is still a challenging task in the numerical analysis of electrical machines. For estimation of eddy current losses, various formulations based on 1-D and 2-D models are mentioned in literature which neglect effect of current density at the edges of steel laminations. This paper compares such simplified 1-D/2-D eddy current loss model with a 3-D model to analyze the effect of edges on eddy current loss calculation. Thickness of the lamination along with frequency of field excitation were determined where considerable deviation in eddy current losses among loss models is observed due to edge assumption.
3D Multibody Simulation of Realistic Rolling Bearing Defects for Fault Classifier Development
(2024) Vehvilainen, Milla; Tahkola, Mikko; Keranen, Janne; El Bouharrouti, Nada; Rahkola, Pekka; Halme, Jari; Pippuri-Makelainen, Jenni; Belahcen, Anouar
A4 Artikkeli konferenssijulkaisussa
Rolling bearing faults stand out as the most prevalent type of fault in electrical machines. In this study, we leveraged geometry-based 3D multibody simulation to facilitate data-driven fault diagnosis. A comprehensive dataset was generated, encompassing data from both healthy and faulty bearings with realistic outer ring and inner ring faults of different types and sizes, operating at varying rotational speeds. Spectral analyses of the simulated bearing shaft displacement data proved that the bearing faults consistently appear at expected characteristic fault frequencies, with peak amplitudes correlating to the given fault size and rotation speed. Using the simulated data, we evaluated numerous feature engineering methods for machine learning-based fault classification. The classification results demonstrated a successful differentiation of simulated faults, whether on the outer ring or inner ring, from the healthy counterparts.
AC Loss Analysis Approaches for Hairpin Winding Configuration: Analytical, Hybrid Model, and FEA
(2023) Ghahfarokhi, Payam Shams; Kallaste, Ants; Podgornovs, Andrejs; Cardoso, Antonio J.Marques; Belahcen, Anouar; Vaimann, Toomas
A4 Artikkeli konferenssijulkaisussa
One of the effective options to achieve higher power density and lower-weight electric motors for electric vehicle (EV) applications is to replace the conventional winding with a hairpin configuration. This novel concept has several advantages, but the biggest drawback is high AC loss. Therefore, as this type of winding utilizes in EV motors for high-speed application, the correct estimations of this loss are essential during the design procedure. This paper presents three primary approaches to model and calculate the AC loss of hairpin windings: analytical, hybrid model, and FEA methods. In addition, the FEA method is used to validate and evaluate the accuracy of two other methods. Accordingly, both analytical and hybrid model results agree with FEA results. However, the hybrid model has higher accuracy rather than the analytical method.
AC Losses in Windings: Review and Comparison of Models with Application in Electric Machines
(2023-12-19) El Hajji, Taha; Hlioui, Sami; Louf, François; Gabsi, Mohamed; Belahcen, Anouar; Mermaz-Rollet, Guillaume; Belhadi, M'Hamed
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Industry is increasingly adopting high-speed electric machines due to their high-power density and low cost. However, increasing the speed leads to many challenges that are worth to study since they have relevant impact on the design of the machine. One of these challenges is the losses in stator winding assembly. At low frequency, losses in windings are usually assumed equal to DC losses. However, at high frequency some phenomena become noticeable and worth evaluating since they lead to noticeable losses. AC losses in windings are due to skin effect, proximity effect, and circulating currents. The main models of AC losses in windings in the literature are presented for both circular and rectangular wires. These models are compared using both interior and surface-mounted permanent magnet synchronous machines. Results show that for proximity effect, analytical model is convenient when considering armature reaction only, however, when considering on load case, hybrid model with simple FEA is suitable thanks to its interesting trade-off between accuracy and computation time, which makes it suitable for large-scale optimization. For circulating currents effect, finite element model is unavoidable. Moreover, two important properties concerning circulating currents are stated as well as their mathematical proofs.
AC Magnetic Loss Reduction of SLM Processed Fe-Si for Additive Manufacturing of Electrical Machines
(2021-02-24) Tiismus, Hans; Kallaste, Ants; Belahcen, Anouar; Tarraste, Marek; Vaimann, Toomas; Rassõlkin, Anton; Asad, Bilal; Ghahfarokhi, Payam Shams
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Additively manufactured soft magnetic Fe-3.7%w.t.Si toroidal samples with solid and novel partitioned cross-sectional geometries are characterized through magnetic measurements. This study focuses on the effect of air gaps and annealing temperature on AC core losses at the 50 Hz frequency. In addition, DC electromagnetic material properties are presented, showing comparable results to conventional and other 3D-printed, high-grade, soft magnetic materials. The magnetization of 1.5 T was achieved at 1800 A/m, exhibiting a maximum relative permeability of 28,900 and hysteresis losses of 0.61 (1 T) and 1.7 (1.5 T) W/kg. A clear trend of total core loss reduction at 50 Hz was observed in relation to the segregation of the specimen cross-sectional topology. The lowest 50 Hz total core losses were measured for the toroidal specimen with four internal air gaps annealed at 1200 ◦C, exhibiting a total core loss of 1.2 (1 T) and 5.5 (1.5 T) W/kg. This is equal to an 860% total core loss reduction at 1 T and a 510% loss reduction at 1.5 T magnetization compared to solid bulk-printed material. Based on the findings, the advantages and disadvantages of printed air-gapped material internal structures are discussed in detail.
Acoustic noise computation of electrical motors using the boundary element method
(2020-01-03) Sathyan, Sabin; Aydin, Ugur; Belahcen, Anouar
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This paper presents a numerical method and computational results for acoustic noise of electromagnetic origin generated by an induction motor. The computation of noise incorporates three levels of numerical calculation steps, combining both the finite element method and boundary element method. The role of magnetic forces in the production of acoustic noise is established in the paper by showing the magneto-mechanical and vibro-acoustic pathway of energy. The conversion of electrical energy into acoustic energy in an electrical motor through electromagnetic, mechanical, or acoustic platforms is illustrated through numerical computations of magnetic forces, mechanical deformation, and acoustic noise. The magnetic forces were computed through 2D electromagnetic finite element simulation, and the deformation of the stator due to these forces was calculated using 3D structural finite element simulation. Finally, boundary element-based computation was employed to calculate the sound pressure and sound power level in decibels. The use of the boundary element method instead of the finite element method in acoustic computation reduces the computational cost because, unlike finite element analysis, the boundary element approach does not require heavy meshing to model the air surrounding the motor.
Adapting geometry-based polygonal contacts for simulating faulty rolling bearing dynamics
(2024-02) Vehviläinen, Milla; Rahkola, Pekka; Keränen, Janne; Halme, Jari; Sopanen, Jussi; Liukkonen, Olli; Holopainen, Antti; Tammi, Kari; Belahcen, Anouar
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Rolling bearings are a leading cause of equipment breakdowns in electrical machines, underscoring the significance of predictive maintenance strategies. However, the given methods require high-quality big data, which is challenging to acquire, especially for faulty cases. Simulation models offer an alternative by generating large data sets to complement experimental data. However, bearings involve complex contact-related phenomena, such as slipping and clearance. Therefore, generating realistic data comparable to the real-world necessitates accuracy. Our study presents a multibody simulation system of a motor bearing, incorporating a geometry-based polygonal contact method (PCM), which accurately captures nonlinear bearing dynamics and allows for the simulation of various contact geometries. We introduce a systematic approach to adjust the PCM contact properties for rolling bearings, referencing the well-established Hertzian theory. Both healthy and faulty bearings with a local outer ring fault were simulated. The simulated output was a relative shaft displacement, experimentally validated using a capacitive sensor. Our model successfully demonstrates the potential to employ geometry-based contacts for generating realistic data on faulty bearings with the aim of predictive maintenance.
Additive manufacturing and performance of E-Type transformer core
(2021-06-03) Tiismus, Hans; Kallaste, Ants; Belahcen, Anouar; Rassõlkin, Anton; Vaimann, Toomas; Ghahfarokhi, Payam Shams
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Additive manufacturing of ferromagnetic materials for electrical machine applications is maturing. In this work, a full E-type transformer core is printed, characterized, and compared in terms of performance with a conventional Goss textured core. For facilitating a modular winding and eddy current loss reduction, the 3D printed core is assembled from four novel interlocking components, which structurally imitate the E-type core laminations. Both cores are compared at approximately their respective optimal working conditions, at identical magnetizing currents. Due to the superior magnetic properties of the Goss sheet conventional transformer core, 10% reduced efficiency (from 80.5% to 70.1%) and 34% lower power density (from 59 VA/kg to 39 VA/kg) of the printed transformer are identified at operating temperature. The first prototype transformer core demonstrates the state of the art and initial optimization step for further development of additively manufactured soft ferromagnetic components. Further optimization of both the 3D printed material and core design are proposed for obtaining higher electrical performance for AC applications.
Additive Manufacturing of Prototype Axial Flux Switched Reluctance Electrical Machine
(2021-03-22) Tiismus, Hans; Kallaste, Ants; Vaimann, Toomas; Rassõlkin, Anton; Belahcen, Anouar
A4 Artikkeli konferenssijulkaisussa
The fast-evolving additive manufacturing (AM) technologies are considered vital for the next industrial revolution as it is capable for cost-effective production of highly customizable complex components. Its freeform design and fabrication flexibility also suggest the production of embedded electromechanical components or even electrical machines with enhanced performance. Presently, due to the maturity of single-material additive manufacturing methods, prototyping of 3D printed electrical machines has taken the path of printing and assembling of individual highperformance machine components. This paper describes the design, the printing, the post-processing, the assembly and the controller of a printed prototype 4/6 axial flux switched reluctance electrical machine. The machine components were fabricated with selective laser melting system from 3 % silicon steel in a total print time of 57 hours. Commercially available bearings and conventional copper windings were added as part of the assembly.
Alternating and Rotational Loss Prediction Accuracy of Vector Jiles-Atherton Model
(2021-06-01) Upadhaya, Brijesh; Rasilo, Paavo; Perkkiö, Lauri; Handgruber, Paul; Benabou, Abdelkader; Belahcen, Anouar; Arkkio, Antero
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
In 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.
Analysis of effect of additional airgaps on the magnetic flux density in a synchronous machine
(2022-08-22) Jagadeesan, Yogesh
Sähkötekniikan korkeakoulu | Master's thesis
Designing a model for synchronous machines that are used in industrial applications is a challenging yet quintessential process. Owing to the huge size of the machine and its complex geometry, it has always been a tedious process to develop a full model of the machine and perform its analysis. Since the industrial synchronous machines are very huge, they are not manufactured in one single piece but are manufactured in many symmetrical pieces which are combined at the last. Because of this process, one major irregularity occurs which is additional air gaps in the rotor which may affect some machine parameters. So, in this thesis paper, a 2-D finite element model of a separately excited synchronous machine is created in FEMM 4.2 software with the additional air gaps in the rotor and the machine is analyzed for changes in the magnetic flux density due to the additional air gaps. After doing the finite element analysis of the machine with additional air gaps it was observed that the magnetic flux density in the air gap decreased with increase in the width of the additional air gaps.
Analysis of Electromagnetic Force Ripple in a Bearingless Synchronous Reluctance Motor
(2021-02) Mukherjee, Victor; Rasilo, Paavo; Martin, Floran; Belahcen, Anouar
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
A bearingless machine should be designed to maximize the average and to minimize the ripple in the electromagnetic torque and levitating force. In a bearingless synchronous reluctance machine (BSynRM), the complex rotor design and the levitation winding create a rich spatial and temporal spectrum of the magnetic flux density in the airgap, which affects both the torque and force ripple. In this article, a novel method is introduced to compute the electromagnetic forces from the spatial harmonics of the airgap flux density. A new indexing method is introduced to classify the spatial harmonic wavenumbers and temporal harmonic frequencies of the flux density in the electromagnetic force. The proposed model enables the understanding of the spatial harmonic footprint on the temporal frequencies of the electromagnetic force ripple. The study is carried out through finite element simulations, which are verified by prototype measurements.
Analysis of Loss Components in a Synchronous Generator under Non-ideal Operating Conditions
(2019-05-06) Rajamäki, Joona
Sähkötekniikan korkeakoulu | Master's thesis
The wide use of high-power salient pole synchronous generators (SPSG) makes the understanding of losses and efficiency important. Factors such on-site conditions and applications affect the power losses of an SPSG. Recently, the effect of torque oscillation on the power losses of an SPSG have been studied and it was shown that torque oscillations may generate additional losses. Furthermore, it is well known, that current unbalance and temperature generate additional losses. All the mentioned effects may be present in on-site use of an SPSG. This thesis determines the effects of torque pulsations, unbalance phase currents and temperature rise on power losses of an SPSG. The different effects were simulated by in-house finite element software FCSMEK. In order to determine the effects of non-ideal conditions on the losses, the limitations for the simulation cases were defined. IEC standards effectively restrict the maximum temperatures and current unbalances of an SPSG. However, the torsional vibrations are not directly limited. Therefore, the measured torque profile of an internal combustion engine (ICE) was used in order to determine the torque oscillation frequencies and amplitudes. The results indicate that current unbalance and temperature increase power losses significantly. The low frequency torque pulsation of an ICE had less effect on the power losses probably due to the low amplitude of the torsional vibration. The temperature rise increases the losses linearly. However, constant temperature was assumed, thus meaning that the effect of the losses on the final temperature was not accounted for. The effect of temperature rise on losses is significant, but more predictable and the effect can be limited by cooling. Furthermore, results show that the negative sequence current may cause significant additional losses. Further investigation could involve introducing the losses into a thermal network to determine the total temperature rise.
Analysis of the Local and Global Forces Acting on the Coil Structure of a Modular Slotless Permanent Magnet Generator
(2019-09) Kallaste, Ants; Vaimann, Toomas; Belahcen, Anouar; Ghahfarokhi, Payam Shams; Rassõlkin, Anton
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This paper investigates the local and global forces acting on the coil structure of a low-speed modular permanent magnet generator for wind energy application. Two different configurations of the coil structure are studied. The first one consists of separately replaceable single-coil modules, whereas the second consists of three-phase coil-module assemblies. The purpose of the analysis is to investigate the advantages and disadvantages of each configuration in terms of vibrations and mechanical robustness. The investigations also provide the load for the mechanical analysis needed in the design of the retaining structure of the generator. The results show that there are strong fluctuations in the radial forces acting on the single-coil structure. The three-phase coil-module assembly reduces the fluctuations of the radial forces, but it results in an increase of the cogging torque, which is not suitable for the slotless design. Namely, the advantage of the slotless design is to reduce the cogging torque. The computed forces are then used in a structural mechanical simulation, the results of which are validated through strain measurements. The validation procedure is carried out on a specially built mock-up as accessing the generator on site is not possible.
Analysis of the Magneto-Mechanical Anisotropy of Steel Sheets in Electrical Applications
(2020-01-08) Martin, Floran; Aydin, Ugur; Ruzibaev, Avaz; Ge, Yanling; Daniel, Laurent; Bernard, Laurent; Rasilo, Paavo; Benabou, Abdelkader; Belahcen, Anouar
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
We investigate the effect of magneto-mechanical and magnetocrystalline anisotropies in a test application by coupling a multiscale magneto-mechanical model with a finite element method. This first application is composed of a cylindrical conductor surrounded by a ring composed of a non-oriented FeSi 3 % steel sheet which contains 396 representative grain orientations. Such an application can reveal the anisotropy due to the texture of the material by inducing a rotational flux density within the ring. Moreover, the effect of the texture and the magneto-mechanical characteristic of the steel sheets is analyzed in an axially laminated synchronous reluctance machine. The effect of stress strongly emphasizes the anisotropic behavior of NO steel sheets.
Analytical Model for magnetic Anisotropy Dedicated to Non-Oriented Steel Sheets
(2015) Martin, Floran; Singh, Deepak; Belahcen, Anouar; Rasilo, Paavo; Arkkio, Antero
School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Recent investigations on magnetic properties of Non-Oriented steel sheets enhance the comprehension of the magnetic anisotropy behavior of widely employed electrical sheets. Our investigation consists of developing an analytical model to consider these magnetic properties while modelling electromagnetic systems. From rotational measurements, the anhysteretic curves are interpolated in order to extract the magnetic energy density for different directions and amplitudes of the magnetic flux density. Furthermore, the analytical representation of this energy is suggested based on statistical distribution which aims to minimize the intrinsic energy of the material. Our model is finally validated by comparing measured and computed values of the magnetic field strength.
Analytical model including rotor eccentricity for bearingless synchronous reluctance motors
(2018-09-03) Saarakkala, Seppo E.; Mukherjee, Victor; Sokolov, Maksim; Hinkkanen, Marko; Belahcen, Anouar
A4 Artikkeli konferenssijulkaisussa
This paper deals with modelling of rotor eccentricity in a dual three-phase winding bearingless synchronous reluctance motors (BSyRMs). The motor includes two separate sets of three-phase windings: one for torque production and the other one for radial force production. For this motor, an improved analytical model with linear magnetic material is presented. The accuracy of the model depends on the accuracy of the inverse-airgap function. Typically, a series expansion is used for approximating the inverse-airgap function. In order to make the main-winding inductances depend on the radial position, at least the first two terms have to be included in the expansion, enabling calculation of the radial forces caused by unbalanced magnetic pull. The improved model is applicable, e.g., for stability analysis, time-domain simulations, or developing real-time control methods.
An Anisotropic Model of a Synchronous Machine with a Rotor Made of Grain-oriented Electrical Steel
(2020-08-17) Davidsson, Timo
Sähkötekniikan korkeakoulu | Master's thesis
Salient pole synchronous machines are widely used in the industry, which is why there is a desire to continuously improve their efficiency. The electrical steel sheets used in the construction of the synchronous machines have a significant influence on the operating characteristics of the machine. All electrical steel sheets, especially grain-oriented electrical steel sheets, represent anisotropic behavior. The anisotropy has major effect on the magnetic properties of the electrical steel sheets depending on the direction of magnetization. This thesis determines the effects of grain-oriented electrical steel sheets in the rotor of a salient pole synchronous machine. The effect of anisotropy in the pole shoe of a salient pole machine is studied with the material model developed in the thesis. The developed material model is implemented into an in-house finite element program FCSMEK, which is used to analyze electrical machines. The effect of anisotropy is studied by simulating the operating characteristics of two salient pole synchronous machines. The results indicate that the shape of the pole shoes is not optimal for grain-oriented electrical steel sheets. The design of the pole shoe has been optimized for isotropic materials, and when the material of the pole shoe is changed into anisotropic material, the operating characteristics change significantly. Further research is needed in order to study the effect of anisotropy on the losses of the synchronous machines.