Magnetostriction in non-oriented electrical steels (original) (raw)
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Journal of Magnetism and Magnetic Materials, 2007
Magnetostriction and Barkhausen noise are investigated in non-oriented electrical steels, with composition FeSi 3.2% , corresponding to the E110 grade produced by ACESITA (Brazil), as a function of both, the magnetic induction level and the angle between the applied magnetic field and the rolling direction. The aim of this study is to understand the magnetization and hysteresis loss processes for this steel, identifying the magnetization mechanism taking place when magnetic field is applied in directions not aligned with the rolling direction, mainly at high magnetic induction levels (above 0.8 T). It is shown that the Barkhausen noise is always present at these high induction levels which can be associated to domain wall motion and to the nucleation and annihilation of 1801 and 901 domains as well as to their evolution with the applied field. Thus, it is shown that the origin of the high induction loss in these samples is the motion of domain walls, irrespective to the angle with respect to the rolling direction.
red.pe.org.pl
Surface domain patterns in electrical steel, which appear under rotational magnetisation, were noted to be comparable to those which are observed under high compressive stress. This paper presents comparison of peak to peak magnetostriction of Epstein strips under high compression magnetised along rolling and transverse directions, and disc samples under rotational and uniaxial magnetisation with no external stress applied. Good correlation was found between magnetostriction measurement results obtained in the rolling direction of non-oriented Epstein strips under high compression and disc samples under rotational magnetisation. Also it was observed that the rotational magnetostriction of grainoriented electrical steel is greater than its uniaxial value under compressive stress. Streszczenie. Artykuł prezentuje porównanie magnetostrykcji pasków Epsteina magnesowanych wzdłuż i prostopadle do kierunku walcowania (podanych naprężeniu) oraz próbek w formie dysku poddanych magnesowaniu osiowemu i rotacyjnemu (bez naprężenia). W przypadku blach niezorientowanych znaleziono korelację między magnetostrykcją w kierunku walcowania oraz stratami przy magnesowaniu rotacyjnym. W przypadku blach zorientowanych magnetostrykcja rotacyjna była większa niż jednoosiowa przy naprężeniu próbki. (Porównanie jednoosiowej i rotacyjnej magnetostrykcji blach elektrotechnicznych zorientowanych i niezorientowanych)
Magnetic Properties of Electrical Steels
A short development of magnetic domain theory and the properties of ferromagnetic materials can be explained by the macroscopic properties and the principle of energy minimisation. In ferromagnetic materials the magnetic domains exist in large volumes which the atomic magnetic moments are aligned parallel due to the strong molecular field. The magnetostatic, magnetocrystalline, magnetoelastic, exchange and domain wall energies determine the domain structure in a ferromagnetic crystal. The domain wall has an optimum thickness due to the exchange and magnetocrystalline anisotropy energies within the wall. A certain number of 180 degree domains occur as a result of an interaction between the magnetoelastic and domain wall energies in an iron crystal.
iris.elf.stuba.sk
Magnetostriction data of non-oriented electrical steel is needed for calculation of deformation and vibration of electrical machine cores. It is characterised on various sample shapes using several measurement techniques which may give different results. In this paper, measurement results of AC magnetostriction of two commercial non-oriented steels magnetised at angles to the rolling direction in standard Epstein strip and disc samples are presented. Magnetostriction measured in disc samples magnetised in a twodimensional magnetisation system revealed that the highest magnetostriction in the sheet plane may not occur along the magnetisation direction if the material is anisotropic. Sample geometry also caused differences of magnetostriction measured in the Epstein and disc samples due to the form effect. The results show that magnetostriction measured in Epstein strip form should be used with caution for calculation of core deformation and vibration of large electrical machines.
Measurement and Modeling of 2-D Magnetostriction of Nonoriented Electrical Steel
IEEE Transactions on Magnetics, 2000
Magnetostriction of nonoriented electrical steel was measured under rotating flux magnetization conditions which occur in AC electrical machine stator cores, and compared with the magnetostriction calculated from a model based on a mechanical elasticity analogy. Shear magnetostriction and magnetostriction perpendicular to the magnetization direction are accounted for in the model which leads to an accurate representation of magnetostriction throughout the electrical steel lamination plane. This has the potential for improving the accuracy of stator core deformation and vibration calculations.
Magnetostriction Anisotropy and Rotational Magnetostriction of a Nonoriented Electrical Steel
IEEE Transactions on Magnetics, 2000
Magnetostriction in nonoriented (NO) electrical steel is a possible source of vibration and acoustic noise in electrical machines. The anisotropy of the magnetostriction of NO steel can be far greater than that of its specific power loss which is often quoted. Also magnetostriction under rotational magnetization can be much higher than under alternating magnetization. This paper shows the relevance of magnetostrictive anisotropy to the rotational magnetostriction of a NO steel. An investigation of the effect of anisotropy in magnetostriction was carried out, followed by rotational magnetostriction measurements. A model based on an analogy of mechanical elasticity was used to describe the effect of magnetostrictive anisotropy on the rotational magnetostriction. Results show that a high value in rotational magnetostriction is mainly driven by its high magnetostriction in the transverse direction. The phenomenon is shown to be a source of asymmetrical deformation in the back iron of electrical machine cores where rotational flux predominates.
Effect of metallurgical factors on the bulk magnetic properties of non-oriented electrical steels
Journal of Magnetism and Magnetic Materials, 2014
Non-oriented electrical steel (NOES) is one of the most common material used in electrical motors. Core loss and permeability are the most important properties that the motor manufacturers look for. Both these properties are structure sensitive and depend on several metallurgical factors; such as chemistry, grain size, crystallographic texture, cleanliness and stress states in non-oriented electrical steels. It has been observed in this course of the study that the grain size and Si content of NOES are the primary controlling factors to core loss, especially at higher frequencies. On the contrary, crystallographic texture plays an important role at lower frequencies. At higher frequency, core loss increases with increasing grain size and decreasing Si content of the steels. Small difference in grain size ( $ 50 μm) at lower frequency range has little influence on the magnetic properties but has significant adverse effect as frequency reaches high enough.
Magnetostriction and Magnetization of Common High Strength Steels
IEEE Transactions on Magnetics, 2009
Some common high strength steels possess enough magnetostriction to serve as the active material in sensors, e.g. torque sensors, while simultaneously performing their usual structural role. The magnetization and magnetostriction of six common high strength steels have been measured as a function of stress. Measurements were made in a hydraulic load frame at compressive stresses of 1, 50, 100, and 150 MPa with fields up to 135 kA/m (1700 Oe). With two exceptions, all of the samples displayed "normal" strain-field curves. The exceptions were Maraging 300 steel whose magnetostriction was continuing to increase with stress even at 150 MPa and an SAE 4130 steel that showed an "inverted " shape. curves of all of the samples showed some small dependencies on stress but were otherwise unremarkable. The saturation magnetostrictions (S = 1 10 6) and saturation magnetization (tesla) were: AerMet 100
The angular dependence of magnetic properties of electrical steels
2002
The magnetic property anisotropy of the so called nonoriented electrical steels is well known. The Epstein frame test procedure recognizes it, but it assumes that the average value of the magnetic properties is the average of the value at the rolling direction (RD) and the value at 90 o from that direction (TD)[1, 2]. Honda and coworkers [3] have shown that, for some of the most common electrical steels, the magnetic properties were at worst when measured with Epstein strips cut at 55 o from RD.
Magnetic aging anisotropy of a semi-processed non-oriented electrical steel
Materials Science and Engineering: A, 2005
Electric motor cores are made of semi-processed non-oriented electrical steels. These steels are processed in such a way that the final heat treatment, which causes decarburization and improves magnetic properties, is made by the core producers. Depending on the effectiveness of this heat treatment, the core can heat during motor operation, causing carbide precipitation/coalescence in the metallic matrix, impairing the magnetic properties of the steel. This phenomenon is known as magnetic aging. The present study shows that magnetic aging takes places under anisotropic conditions. In a semi-processed steel, the largest magnetic loss variation occurs at 0 • , around 40 • and 90 • in relation to the rolling direction. This anisotropy can be attributed to the crystallographic structure of this kind of material, in combination with the oriented precipitation of the carbides during aging.