Research of leakage magnetic field in deenergized transformer

2018 ◽  
Vol 37 (5) ◽  
pp. 1657-1667
Author(s):  
Jacek Horiszny
Keyword(s):  
Magnetic Field ◽  
Magnetic Induction ◽  
Power Transformer ◽  
Three Dimensional ◽  
Magnetic Sensors ◽  
Three Dimensional Model ◽  
Content Type ◽  
The Core ◽  
Leakage Field ◽  
The Magnetic Field

Purpose The paper presents the analysis of magnetic field that surrounds the power transformer after it has been switched off. The purpose of this paper is to determine the possibility of defining the residual fluxes in the legs of the transformer based on the measurement of this field. It was also intended to determine the type and the location of magnetic sensors. Design/methodology/approach Numerical analysis of the magnetic field was performed. A three-dimensional model of the transformer’s magnetic core was created in the Flux 3D simulation program. The analysis was concerned with an oil-filled transformer and a dry transformer. The magnetic field of Earth was taken into account. Findings The research has shown that magnetic induction of the leakage field produced by residual magnetization of the core is comparable to the magnetic induction of the Earth’s field. It was also found that the measurement of the magnetic induction should be performed as close as possible to the core. The interior of the tank turned out to be a convenient space for the placement of the sensors. Research limitations/implications The influence of external ferromagnetic objects, and devices generating magnetic field, on the measurement was not considered. It should be taken into account in the future work. Originality/value On the basis of the analysis, it was proposed to measure the magnetic induction vector of the leakage field at three points. The sensors should be placed in front of the columns at a position that is half of their height. The measurement can be performed with satisfactory accuracy by sensors located on the surface of the windings.

Optimization of magnetic hat for quartz flexible accelerometer

Sensor Review ◽  
2016 ◽  
Vol 36 (1) ◽  
pp. 71-76 ◽  
Author(s):  
Cuo Wang ◽  
Xingfei Li ◽  
Ke Kou ◽  
Chunguo Long
Keyword(s):  
Magnetic Field ◽  
Field Distribution ◽  
Cylindrical Symmetry ◽  
Air Gap ◽  
Magnetic Sensors ◽  
Magnetic Field Distribution ◽  
Navigation Systems ◽  
Pole Piece ◽  
Content Type ◽  
The Magnetic Field

Purpose – This study aims to ameliorate the strength and uniformity of the magnetic field in the air-gap of quartz flexible accelerometers. Quartz flexible accelerometers (QFAs), a type of magneto-electric inertial sensors, have wide applications in inertial navigation systems, and their precision, linearity and stability performance are largely determined by the magnetic field in operation air-gap. To enhance the strength and uniformity of the magnetic field in the air-gap, a magnetic hat structure has been proposed to replace the traditional magnetic pole piece which tends to produce stratiform magnetic field distribution. Design/methodology/approach – Three-dimensional analysis in ANSYS workbench helps to exhibit magnetic field distribution for the structures with a pole piece and a magnetic hat, and under the hypothesis of cylindrical symmetry, two-dimensional finite element optimization by ANSYS APDL gives an optimal set of dimensions of the magnetic hat. Findings – Three structures of the QFA with a pole piece, a non-optimized magnetic hat and an optimized magnetic hat are compared by the simulation in ANSYS Maxwell and experiments measuring the electromagnetic rebalance force. The results show that the optimized hat can supply stronger and more uniform magnetic field, which is reflected by larger and more linear rebalance force. Originality/value – To the authors ' knowledge, the magnetic hat and its dimension optimization have rarely been reported, and they can find significant applications in designing QFAs or other similar magnetic sensors.

Effect of transverse and parallel magnetic fields on thermal and thermo-hydraulic performances of ferro-nanofluid flow in trapezoidal microchannel heat sink

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mojtaba Sepehrnia ◽  
Hossein Khorasanizadeh ◽  
Mohammad Behshad Shafii
Keyword(s):  
Magnetic Field ◽  
Heat Flux ◽  
Heat Sink ◽  
Hartmann Number ◽  
Three Dimensional ◽  
Microchannel Heat Sink ◽  
Nanofluid Flow ◽  
Content Type ◽  
Trapezoidal Microchannel ◽  
The Magnetic Field

Purpose This paper aims to study the thermal and thermo-hydraulic performances of ferro-nanofluid flow in a three-dimensional trapezoidal microchannel heat sink (TMCHS) under uniform heat flux and magnetic fields. Design/methodology/approach To investigate the effect of direction of Lorentz force the magnetic field has been applied: transversely in the x direction (Case I);transversely in the y direction (Case II); and parallel in the z direction (Case III). The three-dimensional governing equations with the associated boundary conditions for ferro-nanofluid flow and heat transfer have been solved by using an element-based finite volume method. The coupled algorithm has been used to solve the velocity and pressure fields. The convergence is reached when the accuracy of solutions attains 10–6 for the continuity and momentum equations and 10–9 for the energy equation. Findings According to thermal indicators the Case III has the best performance, but according to performance evaluation criterion (PEC) the Case II is the best. The simulation results show by increasing the Hartmann number from 0 to 12, there is an increase for PEC between 845.01% and 2997.39%, for thermal resistance between 155.91% and 262.35% and ratio of the maximum electronic chip temperature difference to heat flux between 155.16% and 289.59%. Also, the best thermo-hydraulic performance occurs at Hartmann number of 12, pressure drop of 10 kPa and volume fraction of 2%. Research limitations/implications The embedded electronic chip on the base plate generates heat flux of 60 kW/m2. Simulations have been performed for ferro-nanofluid with volume fractions of 1%, 2% and 3%, pressure drops of 10, 20 and 30 kPa and Hartmann numbers of 0, 3, 6, 9 and 12. Practical implications The authors obtained interesting results, which can be used as a design tool for magnetohydrodynamics micro pumps, microelectronic devices, micro heat exchanger and micro scale cooling systems. Originality/value Review of the literature indicated that there has been no study on the effects of magnetic field on thermal and thermo-hydraulic performances of ferro-nanofluid flow in a TMCHS, so far. In this three dimensional study, flow of ferro-nanofluid through a trapezoidal heat sink with five trapezoidal microchannels has been considered. In all of previous studies, in which the effect of magnetic field has been investigated, the magnetic field has been applied only in one direction. So as another innovation of the present research, the effect of applying magnetic field direction (transverse and parallel) on thermo-hydraulic behavior of TMCHS is investigated.

Health Monitoring of Adhesive Joints Using Magnetostrictive Fillers

2008 ◽  
Author(s):  
Yarden B. Weber ◽  
Daniel Schweitzer ◽  
Hedva Bar ◽  
Doron Shilo
Keyword(s):  
Magnetic Field ◽  
Smart Materials ◽  
Three Dimensional ◽  
Local Stress ◽  
Magnetic Sensors ◽  
Clear Correlation ◽  
Stress Profile ◽  
Stress Monitoring ◽  
Load Bearing ◽  
The Magnetic Field

One major application for smart materials is measuring stresses or strains in load bearing structures. The ability to monitor structural health, and observe real time stress levels in load bearing platforms is a field of great interest. In this work, we develop and characterize a method for stress monitoring adhesively bonded joints by incorporating a magnetostrictive filler into the polymeric matrix. Magnetostrictive materials create a change in their surrounding magnetic field when subjected to strain, and thus serve as natural strain sensors, that require neither power supply nor any kind of wiring. A clear correlation between the stress and the magnetic field, which is measured at a distance of 20–60 mm from the specimen, is observed under both shear and compression loads. Moreover, there is a significant stress region in which the relationship between the stress and the magnetic field is approximately linear. This behavior demonstrates the possibility of monitoring the average stress in a specimen by a single magnetic sensor mounted at a distance from the specimen. Additionally, complete three dimensional mapping of the magnetic field around loaded specimens reveals that the specimen magnetization is not uniform and implies the existence of a correlation between the specimen magnetization and the stress field which was numerically computed. This behavior indicates the potential of mapping the local stress profile within a specimen by using an array of several magnetic sensors. The effects of magnetostrictive particle size and of applying a magnetic field during specimen polymerization are also discussed.

Electrostatic plasma turbulence Part 1. Turbulent plasma diffusion across a magnetic field

1976 ◽  
Vol 15 (2) ◽  
pp. 279-292 ◽  
Author(s):  
H. C. Barr ◽  
T. J. M. Boyd
Keyword(s):  
Magnetic Field ◽  
Three Dimensional ◽  
Particle Energy ◽  
Dimensional Model ◽  
Fluctuation Spectrum ◽  
Three Dimensional Model ◽  
Continuous Transition ◽  
Strong Magnetic Fields ◽  
Plasma Diffusion ◽  
The Magnetic Field

The turbulent diffusion of plasma across a magnetic field is studied theoretically using a three-dimensional model which includes the full dynamics of the diffusing particles and which is valid for arbitrary magnetic field strengths. The theory is confined to perpendicular turbulence, i.e. where the build-up of the fluctuations lies primarily in the plane perpendicular to the magnetic field (although it is more generally applicable). A single expression for the diffusion is derived in terms of the fluctuation spectrum, particle energy, the dispersion characteristics of the excited modes and the magnetic field. Earlier results for equilibrium plasmas are confirmed. We demonstrate the continuous transition from anomalous (1/B) diffusion in regimes of low fluctuation levels (or strong magnetic fields) to classical (1/B2) diffusion in regimes where the fluctuation level destroys the coherence sustained by the magnetic field. In this latter regime, the particles behave as if unmagnetized except for a turbulent drift which appears in the presence of anisotropic spectra.

An experimental study on characterizing damage and fracture of a rock-like material based on three-dimensional magnetic field imaging

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Wenping Yue ◽  
Mingyang Yang
Keyword(s):  
Magnetic Field ◽  
Imaging System ◽  
Three Dimensional ◽  
Fracture Pattern ◽  
Content Type ◽  
Damage And Fracture ◽  
Magnetic Marker ◽  
Magnetic Field Imaging ◽  
The Magnetic Field ◽  
Field Imaging

Purpose The results showed that the use of a magnetic marker could relatively accurately reflect the fracture pattern inside the rock-like material (RLM). Design/methodology/approach This study investigated the internal structure and fracture pattern of a fractured RLM. Magnetized iron oxide powder, which was used as a magnetic marker, was mixed with water and glue to form a magnetic slurry, which was subsequently injected into a fractured RLM. After the magnetic slurry completely filled the cracks inside the RLM and became cemented, the distribution and magnitude of the magnetic field inside the RLM were determined using a three-dimensional (3D) magnetic field imaging system. Findings A model for determining the magnetic field strength was developed using MATLAB. Originality/value This model of 3D magnetic will further be used as a finite element tool to simulate and image cracks inside the rock.

Analysis of Three-Phase Power Transformer Inrush Current Magnetic Field

2010 ◽  
Vol 44-47 ◽  
pp. 1719-1723
Author(s):  
Hong Kui Li
Keyword(s):  
Magnetic Field ◽  
Power Transformer ◽  
Short Circuit ◽  
Three Dimensional ◽  
Inrush Current ◽  
Three Phase ◽  
Dimensional Finite Element ◽  
Element Computation ◽  
Three Dimensional Finite Element ◽  
The Magnetic Field

This research studies the magnetic field and forces on the windings of transformer due to short circuit. Three dimensional finite element computation of three-phase power transformer is carried out. The model developed have been applied to power transformer and the results are verified experimentally. To verify the computation results, they are compared with those obtained using ANSYS software simulation.

Magnetic Emission Mapping for Passive Integrated Components Characterisation

2003 ◽  
Author(s):  
O. Crépel ◽  
Y. Bouttement ◽  
P. Descamps ◽  
C. Goupil ◽  
P. Perdu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Mobile Phone ◽  
Printed Circuit Board ◽  
Magnetic Sensors ◽  
Circuit Board ◽  
Magnetic Disturbance ◽  
Passive Components ◽  
Printed Circuit ◽  
Integrated Inductor ◽  
The Magnetic Field

Abstract We developed a system and a method to characterize the magnetic field induced by circuit board and electronic component, especially integrated inductor, with magnetic sensors. The different magnetic sensors are presented and several applications using this method are discussed. Particularly, in several semiconductor applications (e.g. Mobile phone), active dies are integrated with passive components. To minimize magnetic disturbance, arbitrary margin distances are used. We present a system to characterize precisely the magnetic emission to insure that the margin is sufficient and to reduce the size of the printed circuit board.

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