Three-dimensional Current Distribution Research Articles

Analytical Torque Ripple Reduction Strategy for Flux Modulated Doubly-Salient Reluctance Motor Drives Based on ZSC Harmonic Regulation

Compared to the conventional doubly-salient reluctance motor (DRM) drives, the novel flux modulated DRM (FMDRM) drives can achieve a better overall torque performance due to the dc-biased sinusoidal current excitation. However, previous investigations only focus on the dc-biased and fundamental current components, and the contributions of current harmonics to the torque production are not clear. This paper proposes an analytical torque ripple reduction strategy for open-winding FMDRM drives based on zero-sequence current (ZSC) harmonic regulation. Firstly, the contribution of third-order ZSC harmonic to the electromagnetic torque is investigated together with the dc-biased sinusoidal current components. Secondly, an alternative torque component cancellation method is put forward, where the additional third-order ZSC is utilized to counteract the dominating part of the alternative torque generated by the dc-biased sinusoidal current for torque ripple reduction. Both the amplitude and initial phase angle of the additional third-order ZSC are calculated by the analytical equation of electromagnetic torque. Moreover, the corresponding three-dimensional current distribution is investigated to achieve the desired ZSC regulation. With the proposed scheme, the torque ripple can be effectively suppressed while maintaining high output torque capability and efficiency. Furthermore, experimental results are presented on a three-phase FMDRM prototype to verify the proposed strategy. <fn fn-type="other" id="fn3" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> </fn>

In Situ Study of the Magnetic Field Gradient Produced by a Miniature Bi-Planar Coil for Chip-Scale Atomic Devices.

The miniaturization of quantum sensors is a popular trend for the development of quantum technology. One of the key components of these sensors is a coil which is used for spin modulation and manipulation. The bi-planar coils have the advantage of producing three-dimensional magnetic fields with only two planes of current confinement, whereas the traditional Helmholtz coils require three-dimensional current distribution. Thus, the bi-planar coils are compatible with the current micro-fabrication process and are quite suitable for the compact design of the chip-scale atomic devices that require stable or modulated magnetic fields. This paper presents a design of a miniature bi-planar coil. Both the magnetic fields produced by the coils and their inhomogeneities were designed theoretically. The magnetic field gradient is a crucial parameter for the coils, especially for generating magnetic fields in very small areas. We used a NMR (Nuclear Magnetic Resonance) method based on the relaxation of 131Xe nuclear spins to measure the magnetic field gradient in situ. This is the first time that the field inhomogeneities of the field of such small bi-planar coils have been measured. Our results indicate that the designed gradient caused error is 0.08 for the By and the Bx coils, and the measured gradient caused error using the nuclear spin relaxation method is 0.09±0.02, suggesting that our method is suitable for measuring gradients. Due to the poor sensitivity of our magnetometer under a large Bz bias field, we could not measure the Bz magnetic field gradient. Our method also helps to improve the gradients of the miniature bi-planar coil design, which is critical for chip-scale atomic devices.

Development of Self-Discharge Point Visualization Technique inside Lithium-Ion Battery

With the rapid spread of electric vehicles and hybrid vehicles in recent years, the energy density of lithium-ion batteries, which are the power sources of them, tends to increase.This means that the risk of ignition is further increased as represented by some fire accident case of an EV vehicle that had taken long time to extinguish, and thus eventually makes the requirement of safety management in the battery manufacturing process be expected stricter.To prevent ignition due to internal short circuit of battery, and eliminate a short-life battery product, we have been developing a technology to non-destructively visualize the self-discharged part inside the storage battery. In this technology, on the first, electric current is applied to the battery from external power source, and the leakage magnetic field that generated due to the internal electric current in the battery is sensed on outside of the battery. Next, the electric current density distribution inside the battery can be reconstructed and visualized three-dimensionally by using the spatial distribution of the measured magnetic field as the boundary condition and solving the inverse problem analytically.To measure leakage magnetic field with high sensitivity, it is necessary to take steps against disturbances as like DC magnetic field derived from magnetism or magnetic materials (often Ni is used for the collector foil), and AC magnetic fields generated from external circuits. In this method, two steps are used in combination for detection sensitivity of the pico-tesla order;(1) An AC current is applied to the battery, and the AC magnetic field generated in synchronization is phase-detected.(2) Install a small coil near the sensor and generate a DC cancel magnetic field by feedback control.By this method, it is possible to detect only the AC magnetic field corresponding to the applied current with high sensitivity in the linear operating region of the magnetic sensor. In actual detection of the leakage magnetic field, a DC voltage that balances with the output voltage of the battery is applied to the AC output of the AC current source connected to the battery so that the SOC of the storage battery is kept constant voltage. In addition to the above, the frequency of the AC output is usually set to 10 Hz or less to avoid the shielding effects of electrodes and the metallic package of the battery.By these steps and scanning two-dimensional of magnetic sensors or using a sensor array in which magnetic sensors are arranged two-dimensionally, the spatial distribution of the two-dimensional magnetic field outside the storage battery can be obtained. Since the sensor detects only one direction component of magnetic field, changing the direction of the sensor by 90 ° is needed.On data processing, some realistic structural assumptions are required to solve the inverse problem.(1) Defining that the plane parallel to the storage battery electrode plane is the XY plane, the Z component of the magnetic field vector is zero around the battery, and only X component and Y component remains as magnetic field vector components generated from internal current of the battery.(2) The thickness of the battery is sufficiently smaller than the size of the battery in the plane direction, that is, the three-dimensional current in the battery is confined in the thin two-dimensional plane.In the first step of the reconstruction, under the fact of (1), Laplace's equation is analytically solved in the "free space from the measurement surface to just above the electrode surface in the battery, without a magnetic source", and derive the two-dimensional magnetic field distribution directly above the electrode surface. In the next step, it is possible to obtain a three-dimensional current distribution inside the battery by analytically solving the Poisson-type equation and the electric current continuity equation under the realistic structural assumption of (2) with first calculation result as the boundary condition.In the presentation, we will introduce in detail the experiment and data processing for identifying the self-discharge point with this technology, including examples of visualizing the magnetic field distribution and current density distribution inside a battery after aging test.

Estimating particulate organic carbon flux in a highly dynamic estuary using satellite data and numerical modeling

Quantitative estimates of the flux, transportation, and burial of riverine particulate organic carbon (POC) in estuaries and shelf areas are crucial for understanding the carbon cycle in marginal seas. The complexity of the hydrodynamic environment and estuarine processes in the Changjiang River estuary (CRE) results in a POC flux with high spatiotemporal variability. In this study, we proposed a new method for time series monitoring of riverine POC flux by combining satellite ocean color and numerical modeling data. We used 500-m resolution geostationary satellite data from the Geostationary Ocean Color Imager (GOCI) to retrieve surface POC concentrations in the CRE and used the numerical Finite Volume Community Ocean Model (FVCOM) to simulate three-dimensional (3D) current and sediment distribution. Diurnal, seasonal, and annual variations in POC flux through the lower reaches (Datong Hydrological Station), upper estuary (Xuliujing Hydrological Station), and outlets of the CRE, as well as transportation and deposition outside the CRE, were examined from July 2011 to June 2018. The annual mean POC fluxes through the Datong, Xuliujing, and outlet sections were 1.16 ± 0.16 Tg C/yr, 1.29 ± 0.11 Tg C/yr, and 1.17 ± 0.11 Tg C/yr, respectively. After passing through the estuary, 35.2% of POC was deposited in the sandbar outside the outlets, 52.9% was transported to the south, and a small amount entered the eastern shelf. Thus, these results indicated that POC flux through the river and estuary sections differed from the effective riverine POC flux into the sea. The proposed method combining high spatiotemporal-resolution satellite data and numerical modeling not only makes full use of their advantages, but also reduces the uncertainty of their individual estimates. This approach also supports long-term monitoring of riverine fluxes to the sea and helps clarify the effects of terrestrial inputs on marginal seas under multiple stresses from human activities and climate change.

Modeling discontinuous potential distributions using the finite volume method, and application to liquid metal batteries

The electrical potential in a battery jumps at each electrode-electrolyte interface. We present a model for computing three-dimensional current and potential distributions, which accounts for such internal voltage jumps. Within the framework of the finite volume method we discretize the Laplace and gradient operators such that they account for internal jump boundary conditions. After implementing a simple battery model in OpenFOAM we validate it using an analytical test case, and show its capabilities by simulating the current distribution and discharge curve of a Li‖Bi liquid metal battery.

Optimal Three-Dimensional Current Computation Flux Weakening Control Strategy for DC-Biased Vernier Reluctance Machines Considering Inductance Nonlinearity

An optimal three-dimensional current computation flux weakening control strategy for dc-biased Vernier reluctance machines (VRMs) is proposed in this paper. Compared with permanent magnet synchronous machines, dc-biased VRMs have an additional degree of freedom to regulate the rotor flux through variable dc-biased armature current. The conventional flux weakening control strategy does not utilize the adjustable dc field current, and the output capacity in the flux weakening region is limited. In this paper, the optimal three-dimensional current distribution is calculated at the intersection of current and voltage constraint. Meanwhile, in order to maintain the armature voltage within the voltage constraint, the inductance nonlinearity is reflected by constructing the inductance table. The algorithm provides maximum output capability and high efficiency for dc-biased VRMs despite the changes in inductance parameters in the whole flux weakening region. Finally, the effectiveness of the proposed control strategy is validated by experimental results for a prototype machine.

Implementation of 16-Channel AMR Sensor Array for Quantitative Mapping of Two-Dimension Current Distribution

Implementation of 16-Channel AMR Sensor Array for Quantitative Mapping of Two-Dimension Current Distribution

High-Frequency Nanocapacitor Arrays: Concept, Recent Developments, and Outlook.

We have developed a measurement platform for performing high-frequency AC detection at nanoelectrodes. The system consists of 65 536 electrodes (diameter 180 nm) arranged in a sub-micrometer rectangular array. The electrodes are actuated at frequencies up to 50 MHz, and the resulting AC current response at each separately addressable electrode is measured in real time. These capabilities are made possible by fabricating the electrodes on a complementary metal-oxide-semiconductor (CMOS) chip together with the associated control and readout electronics, thus minimizing parasitic capacitance and maximizing the signal-to-noise ratio. This combination of features offers several advantages for a broad range of experiments. First, in contrast to alternative CMOS-based electrical systems based on field-effect detection, high-frequency operation is sensitive beyond the electrical double layer and can probe entities at a range of micrometers in electrolytes with high ionic strength such as water at physiological salt concentrations. Far from being limited to single- or few-channel recordings like conventional electrochemical impedance spectroscopy, the massively parallel design of the array permits electrically imaging micrometer-scale entities with each electrode serving as a separate pixel. This allows observation of complex kinetics in heterogeneous environments, for example, the motion of living cells on the surface of the array. This imaging aspect is further strengthened by the ability to distinguish between analyte species based on the sign and magnitude of their AC response. Finally, we show here that sensitivity down to the attofarad level combined with the small electrode size permits detection of individual 28 nm diameter particles as they land on the sensor surface. Interestingly, using finite-element methods, it is also possible to calculate accurately the full three-dimensional electric field and current distributions during operation at the level of the Poisson-Nernst-Planck formalism. This makes it possible to validate the interpretation of measurements and to optimize the design of future experiments. Indeed, the complex frequency and spatial dependence of the data suggests that experiments to date have only scratched the surface of the method's capabilities. Future iterations of the hardware will take advantage of the higher frequencies, higher electrode packing densities and smaller electrode sizes made available by continuing advances in CMOS manufacturing. Combined with targeted immobilization of targets at the electrodes, we anticipate that it will soon be possible to realize complex biosensors based on spatial- and time-resolved nanoscale impedance detection.

Effect of three-dimensional current distribution on characterizing parasitic resistance of FinFETs

A thorough analysis of the FinFET resistance and current distribution is presented. By combining multiple conventional and novel measurement techniques, the key components that contribute to the parasitic resistance of FinFETs can be quantified. Through a three-dimensional (3D) FinFET resistance network model, the impact of the FinFET 3D structure on the current distribution and parasitic resistance is analyzed. The heterogeneous current distribution, known as the current crowding effect, is also discussed with possible alleviation methods through 3D simulation.

Inversion of Meg Data for a 2-D Current Distribution

The support of a localized three-dimensional neuronal current distribution, within a conducting medium, is not identifiable from knowledge of the exterior magnetic flux density, obtained via Magnetoencephalographic (MEG) measurements. However, this is not true if the neuronal current is supported on a set with dimensionality less than three. That is, the support of a dipolar current distribution can be recovered if it is a set of isolated points, a segment of a curve, or a surface patch. In this work we provide an analytic algorithm for this inverse MEG problem and apply it to the case where the current is supported on a localized disk having arbitrary position and size within the brain tissue. The proposed recovery algorithm reduces the identification of the characteristics of the current to the solution of a nonlinear algebraic system, which can be handled numerically.

On the Inverse EEG Problem for a 1D Current Distribution

Albanese and Monk (2006) have shown that, it is impossible to recover the support of a three-dimensional current distribution within a conducting medium from the knowledge of the electric potential outside the conductor. On the other hand, it is possible to obtain the support of a current which lives in a subspace of dimension lower than three. In the present work, we actually demonstrate this possibility by assuming a one-dimensional current distribution supported on a small line segment having arbitrary location and orientation within a uniform spherical conductor. The immediate representation of this problem refers to the inverse problem of electroencephalography (EEG) with a linear current distribution and the spherical model of the brain-head system. It is shown that the support is identified through the solution of a nonlinear algebraic system which is investigated thoroughly. Numerical tests show that this system has exactly one real solution. Exact solutions are analytically obtained for a couple of special cases.

Investigation of Three-Dimensional Current Distribution at Silver Diffusion Joint of RE-123 Coated Conductors Based on Magnetic Microscopy Combined With Finite Element Method

Combining scanning Hall-probe microscopy (SHPM) with finite element method (FEM), we have investigated three-dimensional current distribution at a silver diffusion joint of RE-123 coated conductor (CC). This research aims at the understanding of electromagnetic behaviors in a jointed CC and at the establishment of an analysis model for it. Two-dimensional distribution of sheet current density in a jointed sample was visualized by a SHPM measurement with a spatial resolution of a few hundred micrometers. Then, it was found that such a distribution included information about current transfer between the jointed pieces. Furthermore, the experimental results were successfully reconstructed by a three-dimensional FEM analysis. We believe that these will be very important findings for the establishment of jointing processes on CCs and for the designs of practical applications which need such processes.

Monte Carlo study of charge transport in organic sandwich-type single-carrier devices: Effects of Coulomb interactions

We present the results of Monte Carlo simulations of transport of charge carriers of a single type in devices consisting of a disordered organic semiconductor sandwiched in between two electrodes. The simulations are based on hopping of carriers between sites with a Gaussian energetic distribution, which is either spatially uncorrelated or has a correlation based on interactions with randomly oriented dipoles. Coulomb interactions between the carriers are taken into account explicitly. For not too small injection barriers between the electrodes and the organic semiconductor, we find that the current obtained from the simulations can be described quite well by a one-dimensional drift-diffusion continuum model, which takes into account the long-range contributions of Coulomb interactions through the space-charge potential. For devices with low injection barriers, however, the simulations yield a considerably lower current than the continuum model. The reduction of the current for uncorrelated disorder is larger than for correlated disorder. By performing simulations in which the short-range contributions of the Coulomb interactions between the carriers are omitted, we demonstrate that the difference is caused by these short-range contributions. We can rationalize our results by analyzing the three-dimensional current distributions and the in-plane radial distribution function of the carriers resulting from the simulations for different injection barriers with and without taking into account these short-range contributions.

Three-dimensional numerical analysis of mixed ionic and electronic conducting cathode reconstructed by focused ion beam scanning electron microscope

Three-dimensional microstructure of mixed ionic and electronic conducting cathode, La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF6428), is obtained by a dual-beam focused ion beam-scanning electron microscope, and its overpotential is predicted by the lattice Boltzmann method. Gaseous, ionic and electronic transport equations coupled with electrochemical reaction at the gas/solid interface in the three-dimensional microstructure are solved with an assumption of local equilibrium in the solid oxide. The gas transport is modeled by the dusty gas model. The numerical simulation is conducted under the current density conditions of 0.01, 0.05, 0.1 and 0.2A/cm2. Predicted cathode overpotentials agreed well with the experimental results. However, predicted overpotential was very large at O2=20%, T=973K and i=0.2A/cm2 case due to the decline of ionic conductivity at low oxygen partial pressure. Three-dimensional chemical potential and current vector distributions inside LSCF microstructure are presented. Ionic and electronic current stream lines are uniform and smooth, which indicates good ionic and electronic conductions as well as wide electrochemically active areas inside the LSCF microstructure. Present method will be an effective tool for investigating local oxygen potential field which affects local reactions, diffusions and physical properties of the MIEC cathodes.

Correlation between three-dimensional current distribution profiles and surface scatterings in nanostructured materials

Intensive heat generation associated with surface scattering is a major obstacle for minimizing high performance electronic circuit components beyond submicron scale, a regime in which the device length scale is comparable to the electron inelastic scattering mean free path. In this work, the fundamental physics of surface scattering during the electrical transport process is addressed by quantum mechanical modeling of the current distribution profile in a three-dimensional conduction channel. The results show that the surface potentials act as local scatters that deflect the current from the topmost surface layer, leading to an accumulation of the current density in the subsurface layer. The possible size dependency in such a current distribution profile is proposed based on the scaling theory in weak localization regime. It suggests that for Gaussian-like surface potential profile, the inelastic scattering mean free path decreases as the full width half maximum of the potential profile increases. Surface scatterings are also likely to play an important role in producing the resistivity of extremely narrow conducting channels.

Back Cover: Phys. Status Solidi C 7/7‐8

physica status solidi cVolume 7, Issue 7-8 Back Cover Back Cover: Phys. Status Solidi C 7/7-8 First published: 20 July 2010 https://doi.org/10.1002/pssc.201090012AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract Researchers at the Semiconductor Photonics Lab., Hanyang University, Ansan, Korea, led by Jong-In Shim, study, evaluate, and improve the performance and reliability of light-emitting diodes (LEDs). The lab has various unique simulation and characterization techniques, including an efficient in-house simulation tool for three-dimensional current distribution analysis in the LED device and a system that extracts the internal quantum efficiency from the electroluminescence measurement. On p. 2133ff. Dongpyo Han et al. demonstrate that the current crowding in the LED device causes nonuniform light emission and local heat generation, eventually affecting the LED performance badly. The large figure shows the simulated current distribution in an LED device, obtained by the in-house simulation tool. The second figure, placed on the upper right, is the light distribution image of the same device, taken by a charge-coupled-device (CCD) camera. The last figure on the lower right is the temperature distribution image of the same device taken by an infrared camera. Volume7, Issue7-8Special Issue: 8th International Conference on Nitride Semiconductors (ICNS‐8)July 2010 RelatedInformation

A Nuclear Disaster Prevention Support System : MEASURES

At the time of nuclear emergency, it is important to identify the type and the cause of the accident. Besides with these, it is also important to provide adequate information for the emergency response organization to support decision making by predicting and evaluating the development of the event and the influence of the release of radioactivity for the environment. Recently, a new type of nuclear disaster prevention support system called MEASURES (Multiple Radiological Emergency Assistance System for Urgent Response) was developed which provides not only the current state of the nuclear power plant and the influence of the radioactivity for the environment, but also the future prediction of the accident development. In order to provide the accurate results of these analyses quickly, MEASURES utilizes the various techniques, such as multiple nesting method, which narrows down the calculation area gradually, and parallel processing computer for three-dimensional analyses, such as air current distribution analysis. In this paper, the outline and the feature of MEASURES are presented, especially focused on the usage of parallel processing computer for the threedimensional air current distribution analysis with Regional Atmospheric Modeling System (RAMS) developed by Colorado State University.

Effect of three-dimensional current and temperature distributions on void formation and propagation in flip-chip solder joints during electromigration

Effect of three-dimensional current distribution on void formation in flip-chip solder joints during electromigration was investigated using thermoelectrical coupled modeling, in which the current and temperature redistributions were coupled and simulated at different stages of void growth. Simulation results show that a thin underbump metallization of low resistance in the periphery of the solder joint can serve as a conducting path, leading to void propagation in the periphery of the low current density region. In addition, the temperature of the solder did not rise significantly until 95% of the contact opening was eclipsed by the propagating void.

Two- and three-dimensional connectivity and current distribution in YBa2Cu3Ox-coated conductors

The microstructure of YBa2Cu3Ox sYBCOd-coated conductors depends strongly on the deposition method and thickness of the YBCO layer. This letter shows how the clear qualitative difference in grain connectivity between vacuum-deposited and solution-grown layers has direct consequences for the spatial distribution of the critical current density sJcd. Pulsed-laser-deposited YBCO conductors usually have a columnar grain structure that results in a two-dimensional current network, as demonstrated with magneto-optical imaging. Consequently, their transport Jc varies considerably on length scales from 50 mm up to 5 mm, with current suppression occurring even at defects that run parallel to the macroscopic current. In contrast, the thicker YBCO coatings in metalorganic-deposited samples have a layered structure, leading to a three-dimensional current path. Magneto-optically, this is deduced from sample-wide shielding currents, while transport experiments reveal much smaller spatial variations in Jc. These results are encouraging for the further development of nonvacuum produced YBCO-coated conductors, since such three-dimensional systems are inherently more “forgiving” of local defects.

B206 GVSPM法による3次元電流分布の可視化

In recent years, faulty operation by mutual interference among electric and electronic devices has become a social problem, which is occurred by widely spreading in use of the personal computers and cellular phones. This is a typical EMC(Electromagnetic Compatibility) problem. The electromagnetic field visualization in the electronic devices is of paramount importance to checking up the EMC problem for developing and designing the modern electronic devices. We have studied the visualization of the current distributions from the locally measured magnetic fields. In order to visualize the current distributions, it is intrinsically reduced into solving an ill-posed inverse problem. In this paper, we carried out the estimation of the three-dimensional current vector distributions with GVSPM method of inverse problem from the locally measured six two-dimensional magnetic fields around the square cubic box.