scholarly journals STUDY OF CONDUCTIVE MATERIALS BY MEANS OF A MULTI-FREQUENCY MEASUREMENT SYSTEM BASED ON MICROMINIATURE EDDY CURRENT TRANSFORMERS

Dependability ◽  
2017 ◽  
Vol 17 (4) ◽  
pp. 49-52
Author(s):  
S. F. Dmitriev ◽  
A. V. Ishkov ◽  
A. O. Katasonov ◽  
V. N. Malikov ◽  
A. M. Sagalakov
Keyword(s):  
Magnetic Field ◽  
Eddy Current ◽  
Measurement System ◽  
Distinctive Feature ◽  
Current Transformer ◽  
Eddy Current Method ◽  
The Core ◽  
Useful Signal ◽  
The Magnetic Field ◽  
Excitation Winding

A measurement system has been developed that is based on an eddy current transformer and allows evaluating the applicability of the eddy current method for detecting local defects of products made of an aluminium-magnesium alloy. The paper describes the design of a microminiature eddy current transformer (ECT) with an excitation, measurement and compensation windings that uses a pyramidal core that enables localization of the magnetic field within an area about 2500 square мm. The distinctive feature of the measurement system consists in the ability to detect deep defects (up to 5 mm). The paper sets forth the primary parameters of the transformer that enable the magnetic field localization (shape, material and size of the core, number of the windings and number of loops). It also describes the process of preparation and application of several ECTs with different core and winding parameters. That allowed the ETCs generating different electromagnetic fields and reacting to the changes in that field with varied efficiency. Optimal ECT size for identifying defects in aluminium-magnesium alloys was established (pyramidal shape of the core, base 400 мm in diagonal, edge 4 mm long, 20 loops of the excitation winding, 200 loops of the measurement winding, 200±40 loops of the compensation winding). The paper describes the design of the measurement system and the measurement method that allows finding defects with the linear size of 0.25 mm situated 5 mm below the surface or more depending on the signal received from the eddy current transformer. The measurement system includes two microminiature transformers controlled by special C++ software. Voltage to the excitation winding was applied by an integrated rectangular wave generator. This setup allowed creating a magnetic field with minimal noise. The voltage of the excitation winding varied from 2 to 3V. The transformers output signal was processed in a hardware filtering system described in this paper. The distinctive feature of the measurement system is the synchronous change of the measurement signal generation frequency and filtration frequency. That enables efficient extraction of the useful signal that carries information on the defects of the tested object. The paper sets forth data that demonstrate the dependence of the amplitude part of the signal from the defects of various sizes and experimentally establishes the limit defect sizes under which such measurements are possible. The research covered objects in the form of aluminium-magnesium plates (94% Al, 3% Mg). Amplitude changes due to the linear sizes of the defects and the depth of their situation. The nature of such changes allows identifying the defects’ parameters. Depending on the size and depth of the defects, the change of the amplitude associated with the transformer passing above the defect were from 2.5V (for a defect 0.25 mm wide situated 1 mm from the surface) to 0.1V (for a defect 0.25 mm wide situated 5 mm from the surface).

Design of TSV-based Inductors for Internet of Things

2016 ◽  
Vol 2016 (DPC) ◽  
pp. 002111-002130 ◽  
Author(s):  
Bruce C Kim ◽  
Saikat Mondal
Keyword(s):  
Magnetic Field ◽  
Internet Of Things ◽  
Power Electronics ◽  
Eddy Current ◽  
Electronics Packaging ◽  
High Density ◽  
Metal Core ◽  
The Core ◽  
Iot Applications ◽  
The Magnetic Field

This paper describes the design of a Through Silicon Via based high density 3D inductors for Internet of Things (IoT) applications. We present some possible challenges for TSV-based inductors in IoT applications. The current trend towards Internet of Things (IOT), System in Package (SiP) and Package-on-Package (PoP) requires meeting the power requirements of heterogeneous technologies while maintaining minimum package size. 3-D chip stacking has emerged as one of the potential solutions due to its high density integration in a 3D power electronics packaging regime. As an integral part of many power electronics applications, TSV-based inductors are becoming a popular choice because of their high inductance density due to the reduced on-chip footprint compared to conventional planar inductors. Depending on the requirement, values of these inductors could range from a few nanohenries to hundreds of microhenries. Small inductors with a high quality factor are mainly used for RF filter applications, whereas large inductors are used in power electronics packaging. For high inductance it is necessary to use ferromagnetic materials. A conventional ferromagnetic metal core like nickel could offer high permeability, which can help to boost the inductance. However, the magnetic field lines within a metal core induce eddy current which can have multiple adverse effect in power electronics packaging. For example, it has long been known that the current can increase the resistance in transformer winding [1]. Eddy current can also heat up the core of the inductor which makes the heat sink process in 3D packaging even more challenging. One way to decrease the eddy current, is to pattern and laminate the core block into multiple segments orthogonal to the direction of the magnetic field line [2]. Another method is to increase the resistivity of the core material so that the eddy current is limited to a very small magnitude [3].

Identification of the eddy current method features in the implementation of computer simulation algorithms for controlling the characteristics of the food production equipment parts

2019 ◽  
Vol 1 (97) ◽  
pp. 31-40
Author(s):  
N.M. Zashchepkina ◽  
V.G. Zdorenko ◽  
V. Sebko ◽  
O.M. Markina
Keyword(s):  
Magnetic Field ◽  
Computer Simulation ◽  
Eddy Current ◽  
Current Transformer ◽  
Geometrical Parameters ◽  
Parameter Control ◽  
Contact Method ◽  
Transformer Transducer ◽  
Simulation Algorithms ◽  
The Magnetic Field

Purpose: The purpose of this article is to study the theoretical provisions of the operation of a vortex device in the implementation of a non-contact method of controlling the details of brewing equipment using computer simulation algorithms. Design/methodology/approach: The theoretical positions of thermal ECT operation with a copper product are obtained, which is controlled while maintaining a constant value of the magnetic field frequency f1 = 70.0 Hz, with small values of the generalized parameter x≤1.1 and increasing the parameter x due to the increase in the frequency of thermal ECT, that is, at x≥3.5. Findings: On the basis of computer simulation algorithms the results of the joint measuring control of diameter d, electrical resistance ρ and temperature t of the sample made of copper (in the temperature range from 20-160°C) and the results of determination of thermally dependent thermal ECT signals with the sample of equipment details and the values of specific normalized values that relate the ECT signals to the physical and mechanical characteristics of the samples of the equipment being monitored. Research limitations/implications: Product diameters range is 5 mm to 50 mm. The lower boundary is limited by the frequency of the magnetic field f = 20 Hz and the upper boundary by the diameter of the frame of the thermal eddy current transformer transducer is 50 mm. Perspective positions of work require further development in the direction of extending the limits of control of geometrical parameters of the samples due to the use of automated control systems based on overhead eddy current transformer transducers. Practical implications: The practical value of the work is to increase the overall likelihood of control of the parameters of brewing equipment parts by increasing its instrumental component Di, due to the reduction of measurement errors due to instrumental techniques and on the basis of computer modelling algorithms for three-parameter control of parts of brewing equipment, electrical and temperature parameters, allows to obtain the value of the overall control probability Dz = 0.998. Originality/value: The originality of the article is the study of the theoretical provisions of the eddy current transformer transducer and the implementation of a non-contact method of controlling the details of brewing equipment using computer simulation algorithms that take into account the modes of joint three-parameter control: at high values of the generalized parameter x (with three-parameter surface control), at small values of x (while controlling the value of the average cross section geometry, electrical, temperature settings) at a fixed frequency magnetic field (get information on the diameter d, resistivity ρ and temperature t with a certain depth of penetration of the magnetic field in the sample Δ).

STUDY OF PHASE PROPAGATION IN SUPERCONDUCTING ALUMINUM BY ULTRASONIC ATTENUATION MEASUREMENTS

1959 ◽  
Vol 37 (5) ◽  
pp. 614-618 ◽  
Author(s):  
K. L. Chopra ◽  
T. S. Hutchison
Keyword(s):  
Magnetic Field ◽  
Eddy Current ◽  
Ultrasonic Attenuation ◽  
Cylindrical Specimen ◽  
Current Theory ◽  
Superconducting Phase ◽  
Rate Of Change ◽  
Time Rate ◽  
Phase Propagation ◽  
The Magnetic Field

The phase propagation in superconducting aluminum has been studied by measuring the time rate of change of ultrasonic attenuation. The time taken for the destruction of the superconducting phase in a cylindrical specimen, by means of a magnetic field, H, greater than the critical field, Hc, is approximately proportional to{H/(H–Hc)} in agreement with eddy-current theory. In the converse case, where the superconducting phase is restored by switching off the magnetic field H (>Hc), the total time taken is nearly independent of the temperature (or Hc) as well as H. The superconducting phase grows at a non-uniform volume rate which is considerably less than the uniform rate of collapse.

Quantitative Research on Cracks in Pipe Based on Magnetic Field Response Method of Eddy Current Testing

2021 ◽  
Vol 36 (1) ◽  
pp. 99-107
Author(s):  
Feng Jiang ◽  
Shulin Liu ◽  
Li Tao
Keyword(s):  
Magnetic Field ◽  
Eddy Current ◽  
Quantitative Research ◽  
Three Dimensional ◽  
Impedance Analysis ◽  
Eddy Current Testing ◽  
Element Analysis ◽  
Defect Parameter ◽  
Current Testing ◽  
The Magnetic Field

The quantitative evaluation of defects in eddy current testing is of great significance. Impedance analysis, as a traditional method, is adopted to determine defects in the conductor, however, it is not able to depict the shape, size and location of defects quantitatively. In order to obtain more obvious characteristic quantities and improve the ability of eddy current testing to detect defects, the study of cracks in metal pipes is carried out by utilizing the analysis method of three-dimensional magnetic field in present paper. The magnetic field components in the space near the crack are calculated numerically by using finite element analysis. The simulation results confirm that the monitoring of the crack change can be achieved by measuring the magnetic field at the arrangement positions. Besides, the quantitative relationships between the shape, length of the crack and the magnetic field components around the metal pipe are obtained. The results show that the axial and radial magnetic induction intensities are affected more significantly by the cross-section area of the crack. Bz demonstrates obvious advantages in analyzing quantitatively crack circumference length. Therefore, the response signal in the three-dimensional direction of the magnetic field gets to intuitively reflect the change of the defect parameter, which proves the effectiveness and practicability of this method.

Magneto-inertial waves and planetary rotation

2021 ◽  
Author(s):  
Jérémy Rekier ◽  
Santiago Triana ◽  
Véronique Dehant
Keyword(s):  
Magnetic Field ◽  
Polar Motion ◽  
Density Stratification ◽  
Length Of Day ◽  
Inertial Waves ◽  
Torsional Oscillations ◽  
The Core ◽  
The Earth ◽  
Planetary Rotation ◽  
The Magnetic Field

<p>Magnetic fields inside planetary objects can influence their rotation. This is true, in particular, of terrestrial objects with a metallic liquid core and a self-sustained dynamo such as the Earth, Mercury, Ganymede, etc. and also, to a lesser extent, of objects that don’t have a dynamo but are embedded in the magnetic field of their parent body like Jupiter’s moon, Io.<br>In these objects, angular momentum is transfered through the electromagnetic torques at the Core-Mantle Boundary (CMB) [1]. In the Earth, these have the potential to produce a strong modulation in the length of day at the decadal and interannual timescales [2]. They also affect the periods and amplitudes of nutation [3] and polar motion [4]. <br>The intensity of these torques depends primarily on the value of the electric conductivity at the base of the mantle, a close study and detailed modelling of their role in planetary rotation can thus teach us a lot about the physical processes taking place near the CMB.</p><p>In the study of the Earth’s length of day variations, the interplay between rotation and the internal magnetic field arrises from the excitation of torsional oscillations inside the Earth’s core [5]. These oscillations are traditionally modelled based on a series of assumptions such as that of Quasi-Geostrophicity (QG) of the flow inside the core [6]. On the other hand, the effect of the magnetic field on nutations and polar motion is traditionally treated as an additional coupling at the CMB [1]. In such model, the core flow is assumed to have a uniform vorticity and its pattern is kept unaffected by the magnetic field. </p><p>In the present work, we follow a different approach based on the study of magneto-inertial waves. When coupled to gravity through the effect of density stratification, these waves are known to play a crucial role in the oscillations of stars known as magneto-gravito-inertial modes [7]. The same kind of coupling inside the Earth’s core gives rise to the so-called MAC waves which are directly and conceptually related to the aforementioned torsional oscillations [8]. </p><p>We present our preliminary results on the computation of magneto-inertial waves in a freely rotating planetary model with a partially conducting mantle. We show how these waves can alter the frequencies of the free rotational modes identified as the Free Core Nutation (FCN) and Chandler Wobble (CW). We analyse how these results compare to those based on the QG hypothesis and how these are modified when viscosity and density stratification are taken into account. </p><p>[1] Dehant, V. et al. Geodesy and Geodynamics 8, 389–395 (2017). doi:10.1016/j.geog.2017.04.005<br>[2] Holme, R. et al. Nature 499, 202–204 (2013). doi:10.1038/nature12282<br>[3] Dumberry, M. et al. Geophys. J. Int. 191, 530–544 (2012). doi:10.1111/j.1365-246X.2012.05625.x<br>[4] Kuang, W. et al. Geod. Geodyn. 10, 356–362 (2019). doi:10.1016/j.geog.2019.06.003<br>[5] Jault, D. et al. Nature 333, 353–356 (1988). doi:10.1038/333353a0<br>[6] Gerick, F. et al. Geophys. Res. Lett. (2020). doi:10.1029/2020gl090803<br>[7] Mathis, S. et al. EAS Publications Series 62 323-362 (2013). doi: 10.1051/eas/1362010<br>[8] Buffett, B. et al. Geophys. J. Int. 204, 1789–1800 (2016). doi:10.1093/gji/ggv552</p>

Modelling the core magnetic field of the Earth

1982 ◽  
Vol 306 (1492) ◽  
pp. 179-191 ◽  
Keyword(s):  
Magnetic Field ◽  
Spherical Harmonics ◽  
Secular Variation ◽  
Long Wavelength ◽  
Core Field ◽  
The Core ◽  
The Earth ◽  
High Degree ◽  
Current Systems ◽  
The Magnetic Field

The magnetic field generated in the core of the Earth is often represented by spherical harmonics of the magnetic potential. It has been found from looking at the equations of spherical harmonics, and from studying the values of the spherical harmonic coefficients derived from data from Magsat, that this is an unsatisfactory way of representing the core field. Harmonics of high degree are characterized by generally shorter wavelength expressions on the surface of the Earth, but also contain very long wavelength features as well. Thus if it is thought that the higher degree harmonics are produced by magnetizations within the crust of the Earth, these magnetizations have to be capable of producing very long wavelength signals. Since it is impossible to produce very long wavelength signals of sufficient amplitude by using crustal magnetizations of reasonable intensity, the separation of core and crustal sources by using spherical harmonics is not ideal. We suggest that a better way is to use radial off-centre dipoles located within the core of the Earth. These have several advantages. Firstly, they can be thought of as modelling real physical current systems within the core of the Earth. Secondly, it can be shown that off-centred dipoles, if located deep within the core, are more effective at removing long wavelength signals of potential or field than can be achieved by using spherical harmonics. The disadvantage is that it is much more difficult to compute the positions and strengths of the off-centred dipole fields, and much less easy to manipulate their effects (such as upward and downward continuation). But we believe, along with Cox and Alldredge & Hurwitz, that the understanding that we might obtain of the Earth’s magnetic field by using physically reasonable models rather than mathematically convenient models is very important. We discuss some of the radial dipole models that have been proposed for the nondipole portion of the Earth’s field to arrive at a model that agrees with observations of secular variation and excursions.

scholarly journals ALMA resolves the hourglass magnetic field in G31.41+0.31

2019 ◽  
Vol 630 ◽  
pp. A54 ◽  
Author(s):  
M. T. Beltrán ◽  
M. Padovani ◽  
J. M. Girart ◽  
D. Galli ◽  
R. Cesaroni ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Velocity Gradient ◽  
Flux Ratio ◽  
High Mass ◽  
Continuum Emission ◽  
Mass Star ◽  
Star Forming ◽  
The Core ◽  
Molecular Core ◽  
The Magnetic Field

Context. Submillimeter Array (SMA) 870 μm polarization observations of the hot molecular core G31.41+0.31 revealed one of the clearest examples up to date of an hourglass-shaped magnetic field morphology in a high-mass star-forming region. Aims. To better establish the role that the magnetic field plays in the collapse of G31.41+0.31, we carried out Atacama Large Millimeter/ submillimeter Array (ALMA) observations of the polarized dust continuum emission at 1.3 mm with an angular resolution four times higher than that of the previous (sub)millimeter observations to achieve an unprecedented image of the magnetic field morphology. Methods. We used ALMA to perform full polarization observations at 233 GHz (Band 6). The resulting synthesized beam is 0′′.28×0′′.20 which, at the distance of the source, corresponds to a spatial resolution of ~875 au. Results. The observations resolve the structure of the magnetic field in G31.41+0.31 and allow us to study the field in detail. The polarized emission in the Main core of G31.41+0.41is successfully fit with a semi-analytical magnetostatic model of a toroid supported by magnetic fields. The best fit model suggests that the magnetic field is well represented by a poloidal field with a possible contribution of a toroidal component of ~10% of the poloidal component, oriented southeast to northwest at approximately −44° and with an inclination of approximately −45°. The magnetic field is oriented perpendicular to the northeast to southwest velocity gradient detected in this core on scales from 103 to 104 au. This supports the hypothesis that the velocity gradient is due to rotation of the core and suggests that such a rotation has little effect on the magnetic field. The strength of the magnetic field estimated in the central region of the core with the Davis–Chandrasekhar-Fermi method is ~8–13 mG and implies that the mass-to-flux ratio in this region is slightly supercritical. Conclusions. The magnetic field in G31.41+0.31 maintains an hourglass-shaped morphology down to scales of <1000 au. Despite the magnetic field being important in G31.41+0.31, it is not enough to prevent fragmentation and collapse of the core, as demonstrated by the presence of at least four sources embedded in the center of the core.

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