Wyniki 1-10 spośród 10 dla zapytania: authorDesc:"Stan ZUREK"

Static and dynamic rotational losses in non-oriented electrical steel

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The total rotational losses were measured in the non-oriented electrical steel (grade M600-50A) over a range of frequency from 2 Hz to 500 Hz. The static (hysteresis) loss was obtained as an extrapolation to zero frequency of the approximating function: P/f=Ph+Pe-f +Pa-f 0.5.The static loss shows rapid drop at very high flux density. The comparison of static and dynamic losses suggests that the peak in power loss characteristic should vanish at higher frequencies, which is confirmed by the experiments. Streszczenie. Zmierzono straty rotacyjne dla nieorientowanej blachy krzemowej M600-50A w zakresie częstotliwości od 2 Hz do 500 Hz. Straty statyczne (histerezowe) wyznaczono poprzez ekstrapolację wartości do zerowej częstotliwości z równania: P/f=Ph+Pe-f +Pa-f 0.5.Straty statyczne wyka[...]

Qualitative 3D FEM study of B and H distribution in circular isotropic samples for two-dimensional loss measurements DOI:10.15199/48.2015.12.09

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This paper investigates the effect of the approximation of an ellipsoidal shape by three laminations. The calculations are carried out with three-dimensional finite-element method for a non-linear isotropic sample with 60 mm diameter and with both lamination thickness and spacing between laminations as 0.5 mm. It is possible to find an optimum configuration for which the uniformity of B and H distribution is improved, but there is no universal configuration because the distribution is affected even by the amplitude of excitation. Streszczenie. Artykuł opisuje badanie wpływu aproksymacji kształtu epsoidalnego przez trzy warstwy. Obliczenia wykonane są przy użyciu trójwymiarowej metody elementów skończonych dla nieliniowej izotropowej próbki o średnicy 60 mm i o grubości o odstępach 0.5 mm. Możliwym jest znalezienie optymalnej konfiguracji, dla której jednorodność rozkładu B i H jest ulepszona, ale nie ma uniwersalnej konfiguracji, ponieważ rozkład zmienia się nawet przy zmianie amplitudy magnesowania. (Badanie 3D FEM jednorodności pola magnetycznego w jedno- i trójwarstwowych izotropowych próbkach do pomiarów dwuwymiarowych strat mocy). Keywords: two-dimensional power loss, rotational power loss, rotational magnetisation, 3D FEM, ellipsoidal sample Słowa kluczowe: dwuwymiarowe straty mocy, obrotowe straty mocy, magnesowanie obrotowe, 3D FEM, próbka elipsoidalna Introduction Power loss dissipated under rotational magnetisation in electrical steels remains relevant for design of rotating machines and it is a leading topic for an international conference [1]. Measurements under rotational magnetisation are more difficult to perform than under the more conventional alternating (uni-directional) excitation as standardised by the group of international standards IEC 60404. The absolute reproducibility of rotational measurements are significantly worse between different laboratories and measurement systems [2], so that international standard[...]

Example of vanishing anisotropy at high rotational magnetisation of grain-oriented electrical steel DOI:10.15199/48.2017.07.04

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1. Introduction Grain-oriented electrical steels (GO) are materials commonly used for magnetic cores of transformers and other electric machines. GO exhibit high anisotropy of magnetic properties due to their crystallographic structure. A cubic crystallite has a shape for which the planes and directions can be defined as shown in Fig. 1. The alignment of crystallites in each grain is controlled during production so that one "easy" magnetisation direction is produced [1]. In this so-called Goss structure (from the name of its inventor [2]) the crystallites are aligned in such a way that all three important crystallographic directions are located within the plane of the sheet (Fig. 1). The "easy" direction is along the rolling direction (RD) and it caused by all the crystallites having their [100] directions aligned with it. The direction [110] is the face diagonal (Fig. 1a) and is in the transverse direction (TD, perpendicular to RD). The direction [111] is the cube diagonal. Fig.1. Goss structure in GO: a) directions in a crystallite, b) alignment of crystallites in GO sheet [3,4] B-H curves measured for the three crystallographic directions for a single crystal are shown in Fig. 2 [1,3 4]. At lower excitations, within practically applicable range, the [100] direction (0° with respect to RD) has the highest permeability. The [110] direction (90° with respect to RD) has significantly lower permeability, and [111] has the lowest permeability (55° with respect to RD). 0 0.5 1 1.5 2 0 5 10 15 20 25 30 J (T) H (kA/m) [100] [110] [111] Fig.[...]

Practical implementation of universal digital feedback for characterisation of soft magnetic materials under controlled AC waveforms DOI:10.15199/48.2017.07.05

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International standards specify sinusoidal magnetising conditions for measurement of magnetic properties of soft magnetic materials [1-3]. At high excitations the specimen exhibits strongly non-linear behaviour which produces distorted output signal if uncontrolled. The concept of negative feedback loop is fundamental in general control theory (Fig. 1a). The operating point is controlled by reference signal (Vref) supplied to the positive input of the summing point (error detector). The controlled object produces output signal (Vout), which is inverted and connected back to the summing point (negative feedback). As a result, the output can be controlled even if the object is non-linear and other disturbances are present, like noise or environmental factors [4, 5]. Functionality of the summing point can be also accomplished by using an operational amplifier [6] (Fig. 1b), which is suitable for waveshape control in magnetising systems [7-11]. Fig.1. Analogue electronic feedback: a) block diagram of a system with a negative feedback loop, b) implementation with operational amplifier and power amplifier; R1 = R2 = 4.7 kΩ; power supplies and decoupling power supply capacitors are not shown for OP177 The waveforms in Fig. 2 were recorded with an analogue feedback circuit based on OP177 (Fig. 1b) [12]. It should be noted that the distortion in Vout occurs after the peak current and results from bandwidth not power limitations. Even though closed-loop bandwidth is specified as 0.4 MHz the limitations of available voltage swing begin to develop as low as 3 kHz [12], thus the distortion occurs at the fastest slope of the magnetising current. Fig.2. Signals recorded for a toroidal sample of grain-oriented electrical steel, magnetised at 1.55 T and 50 Hz, form factor of Vout diverged by 0.99%; only half-cycle is shown for clarity Analogue circuits are sometimes preferred in magnetic measurements but they can also act in highly und[...]

Systematic measurement errors of local B-coils due to holes DOI:10.15199/48.2018.03.02

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Magnetic properties of soft magnetic materials like electrical steels are measured with the help of induction coils (also referred to as B-coils or search coils [1-10]) which detect flux density B averaged over the active crosssection area of the coil (Fig. 1). According to Faraday's law, voltage induced in the coil is proportional to the number of turns n of the coil, the active cross-section area A, and the rate of change of B with respect to time t but averaged over A. The information about time variation of spatially-averaged B is thus obtained by integration of the function: (1) V = n·A·dB/dt (V) It should be noted if equation (1) is to define the measured voltage across a B-coil then there is no minus on the right-hand-side. This minus appears only for the induced electromotive force. Fig.1. Concept of B-coil Sometimes it is desirable to measure localised properties, which requires the use of the needle probes [1, 5, 8-10], or localised B-coils for which appropriate holes must be drilled in the sample under test [1-3, 5, 6-9]. The performance of needle probes can be severely affected by asymmetrical magnetisation [1, 9]. This can lead to indication of non-physical values of B, even significantly larger than the saturation of the material; results up to 4 T were reported in the literature [10]. B-coils are more immune to such problems and hence also used extensively for localised measurement [5]. However, the method is more destructive because holes must be drilled in the sample under test (Fig. 2). The holes represent non-magnetic discontinuity and severely distort distribution of B in the immediate vicinity of holes. Qualitatively such effects are indeed well known and documented in the literature with both finite element modelling (FEM) [3] as well as surface scanning measurements [11]. However, from the viewpoint of uncertainty analysis these effects do not seem to be quantified sufficiently well in t[...]

LabVIEW as a tool for measurements, batch data manipulations and artificial neural network predictions

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A package of programs written in LabVIEW 5.1 was used in a research project aimed at investigation of industrially important magnetic properties of magnetic cores: power loss (active and apparent) and permeability. The software was developed to perform three distinct roles: i) controlling the test conditions and performing measurements of power loss and permeability, ii) batch manipulation of th[...]

Asymmetry of magnetic properties of conventional grain-oriented electrical steel with relation to 2D measurements

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Samples of 3% Si-Fe 0.27 mm thick conventional GO in a form of single strips 30 x 305 mm, cut at every 10 degrees from 0 degrees (synonymous with rolling direction) to 170 degrees were measured under sinusoidal flux density up to 1.5 T at 50 Hz and 400 Hz. The measured results show that the anisotropy of power loss and permeability is symmetrical about the rolling direction. The irregularities in the curves are caused mainly by the quality of the laser cutting and differences in the local properties of the steel sheet. Streszczenie. Artykuł opisuje pomiary wykonane na próbkach elektrotechniczej blachy zorientowanej 3% Si-Fe pociętych w paski o wymairach 30 x 305 x 0.27 mm pod kątami od 0 do 170 stopni (z krokiem co 10 stopni). Próbki zmierzono w warunkach sinusoidalnej indukcji do war[...]

Influence of digital resolution of measuring equipment on the accuracy of power loss measured in Epstein frame

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Digital and computerised equipment are widely used in the measurements of magnetic properties of soft magnetic materials. The manufacturers of digital data acquisition cards strive for improved accuracy and resolution of voltage measurements. The total accuracy of such devices is an important feature. However, high resolution and high sampling frequency of voltage measurement is not necessarily [...]

Development of an induction motor core model for measuring rotational magnetostriction under PWM magnetisation

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This paper presents development of an experimental induction motor core model for measuring rotational magnetostriction under practical PWM magnetisation. It was found that the magnetostrictive strain (measured with strain gauges) at stator teeth is much greater than that in other regions due to the influence of Maxwell force in the air gap. The magnetostriction on the motor core was also compared with that measured from a rotational single sheet tester. Streszczenie. Artykuł opisuje pomiary magnetostrykcji w warunkach przemagnesowania obrotowego i PWM (modulacji szerokości impulsów) wykonanych na prototypie stojana silnika indukcyjnego. Badania przy użyciu tensometrów wykazały, że wartości magnetostrykcji zmierzone na zębach pakietu blach są znacznie większe niż w innych miejscach r[...]

Correlation between surface magnetic field and Barkhausen noise in grain-oriented electrical steel

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Samples of 3% Si-Fe 0.27 mm thick conventional GO in a form of single strips 30 x 305 mm, cut at every 10 degrees from 0 degrees (synonymous with rolling direction) to 170 degrees were measured under sinusoidal flux density up to 1.5 T at 50 Hz and 400 Hz. The measured results show that the anisotropy of power loss and permeability is symmetrical about the rolling direction. The irregularities in the curves are caused mainly by the quality of the laser cutting and differences in the local properties of the steel sheet. Streszczenie. Artykuł opisuje pomiary wykonane na próbkach elektrotechniczej blachy zorientowanej 3% Si-Fe pociętych w paski o wymiarach 30 x 305 x 0.27 mm pod kątami od 0 do 170 stopni (z krokiem co 10 stopni). Próbki zmierzono w warunkach sinusoidalnej indukcji do war[...]

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