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

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