[article] Sähkötekniikan korkeakoulu / ELEC

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  • Motion of Heavy Particles on a Submerged Chladni Plate
    (2019) Latifi, Kourosh; Wijaya, Harri; Zhou, Quan
     School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Heavy particles are traditionally believed to gather at the nodes of a resonating plate, forming standard Chladni patterns. Here, for the first time, we experimentally show that heavy particles, i.e., sub-mm particles, can move towards the antinodes of a resonating plate. By submerging the resonating plate inside a fluidic medium, the acoustic radiation force and the lateral effective weight become dominant at the sub-mm scale. Those forces, averaged over a vibration cycle, move the particles towards the antinodes and generate sophisticated patterns. We create a statistical model that relates the complex motion of particles to their locations and plate vibration frequencies in a wide spectrum of both resonant and nonresonant frequencies. Additionally, we employ our model to control the motion of single particles and a swarm of particles on the submerged plate. Our device can move particles with sufficient power at an exceptionally wide frequency range, potentially opening a path to new particle manipulation techniques at sub-mm scale in fluidic media.
  • Reduced Basis Finite Element Modeling of Electrical Machines with Multiconductor Windings
    (2017) Lehikoinen, Antti; Arkkio, Antero; Belahcen, Anouar
     School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Finite element analysis of electrical machines withmulti-conductor windings can be computationally costly. Thispaper proposes a solution to this problem, using a reducedbasis approach. The field-circuit problem is first solved in asingle slot only, with a set of different boundary conditions.These pre-computed solutions are then used as shape functionsto approximate the solution in all slots of the full problem. Apolynomial interpolation method is also proposed for couplingthe slot domains with the rest of the geometry, even if thegeometries or meshes do not fully conform on the boundary.The method is evaluated on several test problems both inthe frequency- and time-domains. According to the simulations,accurate solutions are obtained, 54-90 times faster compared tothe established finite element approach.
  • Domain Decomposition Approach for Efficient Time-Domain Finite-Element Computation of Winding Losses in Electrical Machines
    (2017) Lehikoinen, Antti; Ikaheimo, Jouni; Arkkio, Antero; Belahcen, Anouar
     School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Finite element analysis of winding losses in electrical machines can be computationally uneconomical. Computationally lightermethods often place restrictions on the winding configuration or have been used for time-harmonic problems only. This paperproposes a domain decomposition type approach for solving this problem. The slots of the machine are modelled by their impulseresponse functions and coupled together with the rest of the problem. The method places no restrictions on the winding and naturallyincludes all resistive AC loss components. The method is then evaluated on a 500 kW induction motor. According to the simulations,the method yields precise results 70–100 faster compared to the established finite element approach.
  • Reduced basis finite element modelling of electrical machines with multi-conductor windings
    (2016) Lehikoinen, Antti; Arkkio, Antero; Belahcen, Anouar
     School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Finite element analysis of electrical machines withmulti-conductor windings can be computationally costly. Thispaper proposes a solution to this problem, using a reducedbasis approach. The field-circuit problem is first solved in asingle slot only, with a set of different boundary conditions.These pre-computed solutions are then used as shape functionsto approximate the solution in all slots of the full problem. Apolynomial interpolation method is also proposed for couplingthe slot domains with the rest of the geometry, even if thegeometries or meshes do not fully conform on the boundary. The method is evaluated on several test problems. Accordingto the simulations, accurate solutions are obtained. Furthermore,a speed-up factor of 30 is observed when analysing asix-slot phase belt of a high-speed induction machine.
  • Transparent, Flexible, and Passive Thermal Touch Panel
    (2016) Ruoho, Mikko; Juntunen, Taneli; Alasaarela, Tapani; Pudas, Marko; Tittonen, Ilkka
     School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This work presents a touch panel concept, which is enabled by a novel designof thin film thermocouples. The design offers a simple implementation byutilizing a single thin film to function as an array of thermocouples. Theconcept is demonstrated as a flexible, passive, and highly transparent touchpanel. The passive nature of the thermoelectric touch recognition allows theperformance of the presented sensor to be optimal at moderate sheet resistancevalues of the transparent conductive layers. Hence, the concept is highlypotential for low-cost large-area applications and does not rely on costlylow sheet resistance materials such as indium tin oxide. The demonstratorpresented in this work achieves a signal-to-noise ratio of 20 with a rise timeof 90 ms and is able to distinguish individual touches, sweeping with finger,as well as touching by multiple fingers at the same time. In addition, the conceptmay also be used in other thermal distribution mapping applications.
  • Magneto-Mechanical Model for Hysteresis in Electrical Steel Sheet
    (2016) Singh, Deepak; Martin, Floran; Rasilo, Paavo; Belachen, Anouar
     School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A coupled magneto-mechanical model for hysteresis in an electrical steel sheet is presented. The foundation of the model developed is the classical Sablik-Jiles-Atherton (SJA) model. A comprehensive model for the stress dependent magnetostriction is also proposed and implemented in the SJA model. Improvements in the SJA model as well, are proposed and validated with simultaneous measurements of magnetostriction, magnetic field and flux density. The measurements were performed on a single electrical steel sheet under various levels of stress (-35 MPa to 100 MPa). The proposed model was found to adequately model the permeability change and the local bowing of the BH-loop due to stress.
  • Effect of Mechanical Stress on Excess Loss of Electrical Steel Sheets
    (2015) Singh, Deepak; Rasilo, Paavo; Martin, Floran; Belahcen, Anouar; Arkkio, Antero
     School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Effect of mechanical stress on the magnetic loss of electrical steel sheets is analyzed utilizing the statistical loss theory. The focus of the study is on the variation of the excess loss component with the applied stress and its correlation with the hysteresis loss. The model and its correlation are validated by performing comprehensive measurements at various combination of induction levels, frequencies and stresses. It is found that the excess losses can be modeled with sufficient accuracy by their correlation with the hysteresis losses over a wide range of stresses, frequencies and flux densities.
  • Homogenization Technique for Axially Laminated Rotors of Synchronous Reluctance Machines
    (2015) Martin, Floran; Belahcen, Anouar; Lehikoinen, Antti; Rasilo, Paavo
     School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    In this paper, we propose a homogenization technique to model the axially laminated rotor of synchronous reluctance machines. Thus, the computational effort can be significantly reduced by replacing the laminated parts of the rotor by some equivalent anisotropic media. The proposed method is validated in terms of flux density and electromagnetic torque. Some small discrepancies can be noticed due to the air-gap fluctuations caused by the steel sheets and the interlaminar insulation sheets of the rotor. With the test machine, the homogenization method reduces by the number of elements to one fourth and the computation time to one third.
  • Model of Magnetic Anisotropy for Non-Oriented Steel Sheets for Finite Element Method
    (2016) Martin, Floran; Singh, Deepak; Rasilo, Paavo; Belahcen, Anouar; Arkkio, Antero
     School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Even non-oriented steel sheets present a magnetic anisotropic behavior. From rotational flux density measurements at 5 Hz, the model of magnetic anisotropy is derived from two surface Basis-cubic splines with the boundary conditions matching with ferromagnetic theory. Furthermore, the investigation of the magnetic anisotropy shows that the H(B) characteristic is not strictly monotonous due to the angle difference between the field and the flux density. Hence, standard non-linear solvers would eitherdiverge or converge towards the closest local minimum. Thus, we propose two different specific solvers: a combined Particle Swarm Optimization with a relaxed Newton-Raphson and a Modified Newton Method.
  • 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.
  • Estimation of additional losses due to random contacts at the edges of stator of an electrical machine
    (2015) Shah, Sahas Bikram; Rasilo, Paavo; Belahcen, Anouar; Arkkio, Antero
     School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The burrs of electrical machine formed during punching process impair the insulation and make random galvanic contacts between the electrical sheets. This paper presents the modeling of random galvanic contacts in a 37 kW induction machine using a surface boundary layer model. Several thousand time stepping finite element simulations were performed, varying the conductivity randomly at the edges of electrical sheets. Then, the additional losses were computed using a vector potential formulation and the surface boundary layer model. The preliminary result showed the increase of total electromagnetic loss by 7.7%
  • Discrete-Time Observer Design for Sensorless Synchronous Motor Drives
    (2016) Awan, Hafiz Asad Ali; Tuovinen, Toni; Saarakkala, Seppo E.; Hinkkanen, Marko
     School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This paper deals with the speed and position estimation of interior permanent-magnet synchronous motor (IPM) and synchronous reluctance motor (SyRM) drives. A speed-adaptive full-order observer is designed and analyzed in the discrete-time domain. The observer design is based on the exact discrete-time motor model, which inherently takes the delays in the control system into account. The proposed observer is experimentally evaluated using a 6.7-kW SyRM drive. The analysis and experimental results indicate that major performance improvements can be obtained with the direct discrete-time design, especially if the sampling frequency is relatively low compared to the fundamental frequency. The ratio below 10 between the sampling and fundamental frequencies is achieved in experiments with the proposed discrete-time design.
  • Estimation of additional losses due to random contacts at the edges of stator of an electrical machine
    (2015) Shah, Sahas Bikram; Rasilo, Paavo; Belahcen, Anouar; Arkkio, Antero
     School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The burrs of electrical machine formed during punching process impair the insulation and make random galvanic contacts between the electrical sheets. This paper presents the modeling of random galvanic contacts in a 37 kW induction machine using a surface boundary layer model. Several thousand time stepping finite element simulations were performed, varying the conductivity randomly at the edges of electrical sheets. Then, the additional losses were computed using a vector potential formulation and the surface boundary layer model. The preliminary result showed the increase of total electromagnetic loss by 7.7%
  • Modeling of Losses Due to Inter-Laminar Short-Circuit Currents in Lamination Stacks
    (2013) Shah, Sahas Bikram; Rasilo, Paavo; Belahcen, Anouar; Arkkio, Antero
     School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The cores of electrical machines are generally punched and laminated to reduce the eddy current losses. These manufacturing processes such as punching and cutting deform the electrical sheets and deteriorate its magnetic properties. Burrs are formed due to plastic deformation of electrical sheets. Burr formed due to punching on the edges of laminated sheets impairs the insulation of adjacent sheet and make random galvanic contacts during the pressing of stacked sheets. The effect of circulating current occurs if the burrs occur on the opposite edges of the stacks of laminated sheets and incase of bolted or wielded sheets, induced current return through it. This induced current causes the additional losses in electrical machine. The existence of surface current on the boundary between two insulated regions causes discontinuity of tangential component of magnetic field. Hence, based on this principle, the boundary layer model was developed to study the additional losses due to galvanic contacts formed by burred edges. The boundary layer model was then coupled with 2-D finite element vector potential formulation and compared with fine mesh layer model. Fine mesh layer model consists of finely space discretized 950028 second order triangular elements. The losses were computed from two models and were obtained similar at 50 Hz. The developed boundary layer model can be further used in electrical machines to study additional losses due to galvanic contacts at the edges of stator cores.
  • The Effect of Common-Mode Voltage Elimination on the Iron Loss in Machine Core Laminations of Multilevel Drives
    (2015) Salem, A.; Abdallh, A.; Rasilo, P.; De Belie, F.; Ibrahim, M. N.; Dupre, L.; Melkebeek, J.
     School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This paper studies the effect of common-mode voltage elimination (CMVE) on the iron loss of electrical machine core laminations under multilevel converter supply. Three identical magnetic ring cores are excited by either a three-level converter or a five-level voltage source converter to study the behavior of CMVE on a three-phase system. Both multilevel converters are controlled by using a space vector pulse width modulation as it is one of the most often used techniques for CMVE. These experimental results are confirmed numerically with a dynamic iron loss model. In addition, the effect of CMVE, at different switching frequencies, on the core loss of a synchronous machine is numerically studied. The results presented in this paper show that the core loss is considerably increased when the CMVE is implemented. However this iron loss increase in five-level drive systems is lower compared to the three-level ones. Therefore, it is important that the designers of drive systems take such effects into consideration.
  • Effect of Multilevel Inverter Supply on Core Losses in Magnetic Materials and Electrical Machines
    (2015) Rasilo, Paavo; Salem, Aboubakr; Abdallh, Ahmed; De Belie, Frederik; Dupre, Luc; Melkebeek, Jan A.
     School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The effect of multilevel inverter supply on power losses in magnetic cores and electrical machines is studied. A dynamic numerical model for the hysteresis, eddy current, and excess losses in a core lamination is first developed. By both measurements and simulations for a ring-core inductor, we demonstrate how increasing the number of inverter voltage levels decreases the iron losses when compared with traditional two-level supply. Although the switching frequency has a significant impact on the iron losses in the case of a traditional two-level inverter, using three or five voltage levels makes the losses almost independent of the switching. Finally, finite-element simulations show that simi-lar reductions are also possible for the core losses of 150-kVA and 12.5-MW wound-field synchronous machines, in which rather low switching frequencies are typically used. Calorimetric loss measurements are also presented for the 150-kVA machine in order to confirm the significant effect of switching frequency on the core losses with two-level inverter supply.
  • Closure to Discussion on “Effect of Multilevel Inverter Supply on Core Losses in Magnetic Materials and Electrical Machines”
    (2015) Rasilo, Paavo; Salem, Aboubakr; Abdallh, Ahmed; Belie, Frederik De; Dupre, Luc; Melkebeek, Jan A.
     School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • Identification of Synchronous Machine Magnetization Characteristics From Calorimetric Core-Loss and No-Load Curve Measurements
    (2015) Rasilo, Paavo; Abdallh, Ahmed Abou-Elyazied; Belahcen, Anouar; Arkkio, Antero; Dupre, Luc
     School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The magnetic material characteristics of a wound-field synchronous machine are identified based on global calorimetric core-loss and no-load curve measurements. This is accomplished by solving a coupled experimental-numerical electromagnetic inverse problem, formulated to minimize the difference between a finite-element (FE) simulation-based Kriging surrogate model and the measurement results. The core-loss estimation in the FE model is based on combining a dynamic iron-loss model and a static vector Jiles-Atherton hysteresis model, the parameters for which are obtained by solving the inverse problem. The results show that reasonable hysteresis loops can be produced for a grid-supplied machine, while for an inverter-supplied machine the limitations in the FE and iron-loss models seemingly exaggerate the area of the loop. In addition, the effect of the measurement uncertainty on the inverse problem is quantitatively estimated.
  • Analysis of 37 kW Converter-Fed Induction Motor Losses
    (2016) Aarniovuori, Lassi; Rasilo, Paavo; Niemelä, Markku; Pyrhönen, Juha
     School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This paper presents an energy efficiency analysis of a 37 kW standard squirrel-cage induction motor under sinusoidal and non-sinusoidal supply. The motor losses are analyzed using the conventional IEC loss segregation method and also numerically modeled using finite element simulations. The measured and simulated loss components are compared with three different modulation methods. The overall simulated losses are in good agreement with the measured ones, but there exist differences in the loss components.
  • Modeling of Hysteresis Losses in Ferromagnetic Laminations under Mechanical Stress
    (2015) Rasilo, Paavo; Singh, Deepak; Aydin, Ugur; Martin, Floran; Kouhia, Reijo; Belahcen, Anouar; Arkkio, Antero
     School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A novel approach for predicting magnetic hysteresis loops and losses in ferromagnetic laminations under mechanical stress is presented. The model is based on combining a Helmholtz free energy -based anhysteretic magnetoelastic constitutive law to a vector Jiles-Atherton hysteresis model. This paper focuses only on unidirectional and parallel magnetic fields and stresses, albeit the model is developed in full 3-D configuration in order to account also for strains perpendicular to the loading direction. The model parameters are fitted to magnetization curve measurements under compressive and tensile stresses. Both the hysteresis loops and losses are modeled accurately for stresses ranging from –50 to 80 MPa.