International Journal of Applied Electromagnetics and Mechanics - Volume 48, issue 2-3

Authors: Zurek, Stan

Article Type: Research Article

Abstract: Measurements of magnetic properties of toroidal samples of magnetically soft materials are defined by the group of international standards IEC 60404. These standards do not specify the actual value of the shunt resistor, but for instance just the fact that it should be ``non-inductive''. This study provides more information on the topic of selection of shunt resistance, which is crucial for many studies of magnetic measurements. It was found that the resistance value of a shunt resistor has no direct effect on the measurement results of magnetic properties. The quality of calibration of the value does have a …direct effect, but not the value itself and it could have any value from 0.1 Ω to 10.0 Ω (as investigated). Care must be taken so that additional device-specific effects are not induced in the measurement equipment (e.g. reduced accuracy at the lowest or highest input ranges). The value of the shunt resistor should be such that the voltage drop across it would coincide with the most accurate input range of the voltmeter or data acquisition device. Show more

Keywords: Magnetic measurements, magnetic properties, shunt resistor

DOI: 10.3233/JAE-151986

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 48, no. 2-3, pp. 187-194, 2015

Authors: Usarek, Zbigniew | Augustyniak, Boleslaw

Article Type: Research Article

Abstract: Influence of two factors: the variable cross-section and the localized plastic deformation, which affect the stray magnetic field profile of a ferromagnetic sample have been studied. Evaluation of an effect size is based on the analysis of the stray magnetic field component which is tangential to the longest dimension of a sample. However, in order to describe the nature of the stray magnetic field, the normal component (perpendicular to the tangential one and to the largest surface of a sample) was also measured. It was found that the impact of the localized plastic deformation is qualitatively similar to the …impact of the geometric narrowing. For the assessment one used a comparison of so called k coefficient that was determined as the absolute value of the derivative of the tangential component. Although some authors treat its distribution as information about residual stess distribution, the results indicate that a characteristic curve with two maxima stems from a cross-section reduction as well as plastic deformation presence. Show more

Keywords: Stray magnetic field, magnetic flux leakage, metal magnetic memory, plastic deformation, low carbon steel

DOI: 10.3233/JAE-151987

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 48, no. 2-3, pp. 195-199, 2015

Authors: Arbenz, Laure | Benabou, Abdelkader | Clénet, Stéphane | Mipo, Jean-Claude | Faverolle, Pierre

Article Type: Research Article

Abstract: In electrical machines, knowing the electrical conductivity is of importance for the eddy current calculation, especially when massive iron parts are involved. Generally the conductivity is measured on samples of raw materials with simple geometries. Indeed, a simple geometry is suitable for applying an analytical approach to deduce the electrical conductivity from the measured electrical quantities. Nevertheless, when a non destructive measurement is required, the measurement of the electrical conductivity can become rather difficult on parts with complex geometry. To that end, with the help of the Finite Element Modeling approach (FEM), a strategy is developed to characterize the local …electrical properties of parts with a non-trivial geometry. Show more

Keywords: Electrical conductivity, non-trivial geometry, finite element modeling, experiment

DOI: 10.3233/JAE-151988

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 48, no. 2-3, pp. 201-206, 2015

Authors: Ghibaudo, Olivier | Chazal, Hervé | Galopin, Nicolas | Garbuio, Lauric

Article Type: Research Article

Abstract: The decrease of coercive magnetic field strength according to applied mechanical stress at audible and inaudible frequencies is investigated. To this aim, an experimental setup is introduced to both measure mechanical and magnetic behaviors. The mechanical resonant modes of a magnetic ring core sample are tracked to allow large longitudinal bendings and to reduce significantly the hysteresis loop width. Results are then set forth to show that elastic mechanical applied stress is relevant to describe the reduction of coercive field strength measured for both steady and transient states.

Keywords: Coercive field, magneto-elastic, mechanical stress, iron-cobalt

DOI: 10.3233/JAE-151989

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 48, no. 2-3, pp. 207-212, 2015

Authors: Pfützner, Helmut | Shilyashki, Georgi

Article Type: Research Article

Abstract: The paper describes a novel concept for the determination of 3-dimensional interior flux distributions in laminated magnetic cores. Magnetic dummy sensors - e.g. calibrated in Epstein testers - yield local values of induction in a tangential way or in thin channels, respectively.

Keywords: Magnetic sensors, induction distribution, transformer cores

DOI: 10.3233/JAE-151990

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 48, no. 2-3, pp. 213-218, 2015

Authors: Mori, Takahiro | Takahashi, Yasuhito | Fujiwara, Koji

Article Type: Research Article

Abstract: Evaluating magnetic properties accurately under various flux conditions is necessary to reduce iron losses in designing motors and transformers. Particularly, two-dimensional (2-D) magnetic property is one of the most important factors for highly efficient electrical machines. In order to evaluate 2-D magnetic properties of electrical steel sheets, several types of 2-D single sheet testers (2-D SSTs) have been proposed. The structure of magnetizing yoke and coils in a 2-D SST is more complex than an SST for measuring one-dimensional (1-D) magnetic properties of electrical steel sheets (1-D SST). Therefore, leakage inductance of a 2-D SST is generally much larger than …that of a 1-D SST, which results in the fact that it is very difficult to measure magnetic properties up to high flux density region with a 2-D SST. In this paper, a round rotational 2-D SST (RRSST) is developed based on motor stator core. The RRSST is compared with the 2-D SST using a square specimen (SRSST) from the standpoint of 2-D magnetic measurement in high flux density region under rotational and alternating flux conditions. Show more

Keywords: 2-D magnetic properties, rotational single sheet tester, stator of motor

DOI: 10.3233/JAE-151991

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 48, no. 2-3, pp. 219-224, 2015

Authors: Bartolo, James Borg | Klimczyk, Piotr | Tiwisina, Kai | Denke, Patrick | Siebert, Stefan | Gerada, Christopher

Article Type: Research Article

Abstract: In recent years, the field-metric method for measuring the joule losses set up in an electrical steel laminate when subjected to a rotating field has gained popularity. The ideal geometry of the magnetiser required to set up such a field is still however the subject of much debate. The work presented in this paper aims at providing some useful guidelines which might be considered when undertaking the construction of the simplest of such magnetizing setups having four salient poles excited by a two phase system and using a square sample. A 3D model for this rotational power loss tester was …simulated for different pole geometries with the induction uniformity being assessed for every alteration. Show more

Keywords: Two-dimensional magnetisers, iron losses

DOI: 10.3233/JAE-151992

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 48, no. 2-3, pp. 225-232, 2015

Authors: Kai, Yuichiro | Enokizono, Masato

Article Type: Research Article

Abstract: The magnetic properties of electrical steel sheet used in motor cores are influenced by mechanical stress due to the inverse effect of the magnetostriction. Therefore, it is necessary to measure the magnetostriction of the electrical steel sheet in order to clarify the relationships between the stress and magnetic properties. The present paper investigates the influence of shear stress on the two-dimensional magnetostriction of a non-oriented electrical steel sheet. The principal magnetostriction in the two-dimensional magnetostriction of a non-oriented electrical steel sheet is measured while varying the shear stress. The obtained results revealed that the amplitude of the principal magnetostriction along …the 45° and 135° directions varied significantly when the shear stress was applied. Show more

Keywords: Non-oriented electrical steel sheet, vector magnetic property, shear stress, two-dimensional magnetostriction

DOI: 10.3233/JAE-151993

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 48, no. 2-3, pp. 233-238, 2015

Authors: Barrière, Olivier de la | Appino, Carlo | Fiorillo, Fausto | Lécrivain, Michel | Ragusa, Carlo | Vallade, Patrice

Article Type: Research Article

Abstract: The magnetic materials used in embedded applications need characterization and modeling in the kilohertz range. This problem is well addressed under conventional alternating induction, but with rotational and two-dimensional induction loci, which are ubiquitous in electrical machines, there is lack of results, because of the difficult task of reaching such high frequencies at technically interesting induction values with the conventional laboratory test benches. To overcome this difficulty, a novel three phase magnetizer has been designed, exploiting 3D finite element calculations, and applied in the lab. This device permits one to measure magnetization curve and losses in soft magnetic steel sheets …and soft magnetic composites under alternating and circular induction up to about 5 kHz. We provide a few significant examples of loss measurements in 0.20 mm thick Fe-Si and Fe50 Co50 laminations, and in soft magnetic composites. These measurements bring to light the role of skin effect under one- and two-dimensional fields. Show more

Keywords: Soft magnetic materials, soft magnetic composites (SMC), magnetic loss, 2-dimensional magnetizer

DOI: 10.3233/JAE-151994

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 48, no. 2-3, pp. 239-245, 2015

Authors: Appino, C. | Hamrit, O. | Fiorillo, F. | Ragusa, C. | de la Barrière, O. | Mazaleyrat, F. | LoBue, M.

Article Type: Research Article

Abstract: By means of a newly developed broadband measuring setup we have overcome the usual upper limit for the test frequency, around a few hundred Hz, which is encountered in the two-dimensional characterization of magnetic steel sheets at technical inductions and we have measured the rotational losses in low-carbon steels up to 1 kHz and peak induction 1.7 T. An important piece of information is thus retrieved upon a frequency range useful to predict the performance of high-speed electrical machines. Our experiments, performed on thick (0.640 mm) laminations, have brought to light the emergence of the skin effect under rotational fields. …This is revealed by an abrupt deviation of the excess loss component, calculated under the conventional loss separation procedure, from its well-known linear dependence on the square root of the frequency. A simple magnetic constitutive law under rotating induction is proposed and introduced into the electromagnetic diffusion equation, which is solved by finite elements coupled to a non-linear algorithm. The classical rotational eddy current loss, largely prevalent with respect to the hysteresis and excess loss components on approaching the kHz frequencies in low-carbon steels, is then calculated in the presence of skin effect, permitting one to achieve full analysis of the rotational losses and good predicting capability upon a broad range of frequencies and peak inductions. Show more

Keywords: Magnetic loss, circular induction, non-oriented magnetic steel, skin effect

DOI: 10.3233/JAE-151995

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 48, no. 2-3, pp. 247-254, 2015

Authors: Wanjiku, John | Pillay, Pragasen

Article Type: Research Article

Abstract: Two-dimensional (2-D) core loss measurements have low reproducibility and repeatability, due to several errors such in data acquisition, sensing systems and the magnetizer. The latter contributes to the variation in the sample's flux density (B) under rotational magnetization. The variation in B requires a reduction of the measurement region, stresses the power source, lowers the circularity of B and modifies its locus. This variation is analysed in four magnetizers, where sinusoidal distribution of the magnetizing winding and increasing the yoke depth, are proposed. A deep yoke will be shown to increase the magnetic loading of the sample, and mitigates the …variation in B in magnetizers with non-sinusoidal fields such as the square tester. The location of B-coils can result to the overestimation or underestimation of the measured B values; affecting the core loss. Experiments showed a 14% (at ∼ 0.8 T) and 6% (at ∼ 1.6 T) difference at two locations. B-holes also increase non-uniformity in the sample; spiking of B and H at the hole regions. Numerical results will show that it has minimal effects on B (< 1%), but the local increase in the field (H) is in the order of 10$4 $ A/m at saturation. Show more

Keywords: Magnetic measurements, measurement errors, standards, rotational, core losses, single sheet testers

DOI: 10.3233/JAE-151996

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 48, no. 2-3, pp. 255-262, 2015

Authors: Cardelli, Ermanno | Faba, Antonio | Laudani, Antonino | Riganti Fulginei, Francesco | Salvini, Alessandro

Article Type: Research Article

Abstract: In this work we present a possible approach to predict the magnetic behavior of electric steels using a vector hysteron model implemented in a ``moving'' way, because the position of the elementary magnetic particles used to represent the magnetic material changes in function of the magnetization state. The moving functions are identified using a suitable set of experimental data and a numerical procedure based on a Metric-Topological-Evolutionary optimization. The accuracy and effectiveness of the method proposed are proved by comparison between computed and measured data related to circular magnetic induction loops at different amplitudes from the virgin state to the …saturation region. Show more

Keywords: Magnetic hysteresis, magnetic measurements, electrical steels

DOI: 10.3233/JAE-151997

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 48, no. 2-3, pp. 263-270, 2015

Authors: Bottauscio, Oriano | Chiampi, Mario | Zucca, Mauro | Serra, Giovanni

Article Type: Research Article

Abstract: This paper aims at analyzing electric motor-generators specifically designed for the avionics application in More Electric Aircraft, where the machine is included inside the main gas turbine. Because of the harsh environment the problem of evaluating and reducing the losses produced in these machines becomes crucial. For such a purpose, this paper presents an accurate estimate of the magnetic and Joule losses produced inside the machine, when operating as generator in a range of frequencies from 200 Hz up to 400 Hz. Particular attention is paid to the investigation of the effects introduced by the use of a high number …(6 and 12) of phases, due to fault tolerance reasons. The analysis is developed on a small (10 kW) prototype, consisting of a four-pole twelve-phase induction machine. The numerical computations are performed through a validated 2-D finite element code, based on a step-by-step procedure and on the sliding mesh technique. A sophisticated laminated dynamic Preisach model, whose parameters are identified from a large set of measurements, provides an accurate estimate of the iron losses and their separation into the three fundamental components also under skin effect regime. The results show that six and twelve phase configurations produce significant loss decrease. Show more

Keywords: Electromagnetic modeling, fault tolerant systems, induction machines, magnetic losses

DOI: 10.3233/JAE-151998

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 48, no. 2-3, pp. 271-276, 2015

Authors: Shilyashki, Georgi | Pfützner, Helmut | Hamberger, Peter | Aigner, Martin | Palkovits, Martin | Trenner, Gerald | Gerstbauer, Erich

Article Type: Research Article

Abstract: For the development of new strategies for reduction of energy losses and audible noise of transformer cores, the assessment of the induction distribution is essential. The results confirm that the core represents a strongly inhomogeneous 3-dimensional magnetization system. For a full understanding of distributions, measurements in the core interior are necessary. For the first time the paper presents detailed analyses of induction distribution in a multi-package model core. Automatic measurements were performed in 112 local positions within 3-phase, 3-limb transformer core stacked from three packages of different width of grain oriented material. As a completely novel approach, a soft magnetic …Fe-pin (of 2.4 mm diameter) with pick up coil was used as an a priori calibrated pin sensor. 25 measurement channels (of 3 mm diameter) were established through the entire core. Z-profiles of the induction through the channels were determined in an automatic way for a nominal induction of 1.7 T. They confirm that the core represents a system that is magnetized in a strong inhomogeneous way. Strong variations of the induction up to 10% were observed not only for the in-plane direction, but also along the normal direction (off-plane). Maximum induction values were detected in the widest main package, minimum ones in the narrowest peripheral package. An exception is the corner area where the inhomogeneity of B decreases, linked with a balancing off-plane flux. The paper proposes a model for the flux distribution through the three packages of the core. Show more

Keywords: Magnetic sensors, induction distribution, transformer cores

DOI: 10.3233/JAE-151999

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 48, no. 2-3, pp. 277-282, 2015

Authors: Fiorillo, F. | Beatrice, C.

Article Type: Research Article

Abstract: We present and discuss methods, setups, and results concerning the characterization of Mn-Zn and Ni-Zn ferrites in the frequency range DC -1 GHz, by which we bring to light the physical mechanisms responsible for the observed frequency behavior of magnetic losses W and permeability μ and provide thorough assessment of the broadband response of the material. A comprehensive array of polarization Jp and frequency f values is investigated. A fluxmetric approach is applied up to a few MHz, which is substituted by a transmission line method at higher frequencies, up to 1 GHz. The fluxmetric measurements are made …at defined Jp value, typically from a few mT to some hundred mT. The waveguide characterization, centered on the use of a network analyzer, is instead made under defined exciting power. But a full experimental W(Jp , f) matrix up to 1 GHz and Jp values typically belonging to the Rayleigh region is in any case retrieved, thanks to the linear response of the material at high-frequencies. Disaccommodation measurements are the route followed in these experiments to separate the rotations from the domain wall process at all frequencies. Whatever the magnetization mode, the role of eddy currents in Mn-Zn ferrite losses is put in evidence by means of resistivity measurements and ensuing multiscale numerical modeling, the loss experiments being made on progressively thinned ring samples. It is concluded that an eddy current free W(Jp , f$) behavior can always be obtained, which can be decomposed into domain wall and rotation related contributions. The latter can be calculated assuming a suitable distribution of the effective internal anisotropy fields and its introduction in the Landau-Lifshitz-Gilbert derivation of the rotational susceptibility. Show more

Keywords: Soft ferrites, magnetic losses, spin damping, eddy currents, magnetic disaccommodation

DOI: 10.3233/JAE-152000

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 48, no. 2-3, pp. 283-294, 2015

Authors: Magni, Alessandro

Article Type: Research Article

Abstract: This paper describes the broadband investigation of the magnetization process in transverse amorphous ribbons. The use of stroboscopic Kerr imaging allows one to quantitatively measure the relaxation of the domain wall motion. This confirms the result obtained by fluxmetric measurements, which show how the classical loss contribution, originating in the rotational processes, is the only loss term remaining beyond the megahertz range.

Keywords: Amorphous ribbons, magnetooptics, magnetic loss, domain wall motion

DOI: 10.3233/JAE-152001

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 48, no. 2-3, pp. 295-300, 2015

Authors: Soinski, Marian | Leszczynski, Jacek | Swieboda, Cezary | Kwiecien, Marcin

Article Type: Research Article

Abstract: Nanocrystalline Fe-based soft magnetic materials are more and more common not only in power electronics but also in power energy conversion systems. The use of different treatments (stacking and annealing methods) allows to achieve predefined properties of magnetic cores under consideration. This fact increase the applicability level of such magnetic cores. Different concepts of nanocrystalline magnetic stacked cores were discussed in the paper. Obtained results were compared to magnetic cores used up to now.

Keywords: Magnetic cores, nano structured materials, energy conversion, power industry

DOI: 10.3233/JAE-152002

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 48, no. 2-3, pp. 301-307, 2015