Flux Concentrator Research Articles

High-Precision Tunneling Magnetoresistance (TMR) Current Sensor for Weak Current Measurement in Smart Grid Applications

To meet the demand for high-precision, high-resolution measurement of weak currents in smart grids, this article presents the design of a current sensor based on the tunneling magnetoresistance (TMR) effect. To improve the detection accuracy of the sensor, this design adopts a low-noise, high-sensitivity TMR chip as its chip selection; in the sensor circuit, a high-linearity interface circuit is used to eliminate fixed bias; and a magnetic flux concentrator is used to improve sensitivity and anti-interference capability. Experimental results indicate that the sensor achieves a sensitivity of 29.4 mV/V/mA, a linearity of 0.19%, and an accuracy of 0.045% within a ±100 mA range, supporting current measurement from DC up to 10.5 kHz. The proposed sensor demonstrates several advantages, including a wide measurement range, high accuracy, high resolution, and non-invasive measurement capability, making it well suited for weak current detection in smart grid applications.

Development of a novel multi-constriction superconducting magnetic flux concentrator and its application in magnetoresistance-superconducting composite magnetic sensors

Development of a novel multi-constriction superconducting magnetic flux concentrator and its application in magnetoresistance-superconducting composite magnetic sensors

Design of magnetic flux concentrator composed of nanospheres for high-sensitivity magnetometers

Design of magnetic flux concentrator composed of nanospheres for high-sensitivity magnetometers

Accelerated Induction Heating and Fast Bonding of Microchips Based on a Design of Hollow Magnetic Flux Concentrator

Accelerated Induction Heating and Fast Bonding of Microchips Based on a Design of Hollow Magnetic Flux Concentrator

The Development of a High-Efficiency Small Induction Furnace for a Glass Souvenir Production Process Using Multiphysics

A small induction furnace (SIF), which has the important components of copper coils, a ceramic jig, and a graphite crucible, employed for a glass souvenir production process, has been developed as a form of clean technology for multiphysics, consisting of electromagnetics analysis (EA) and thermal analysis (TA). First, two experiments were established to measure parameters for multiphysics results validation and boundary condition settings. Then, the parameters were applied to multiphysics, in which the EA revealed magnetic flux density (B) and ohmic losses, and the TA reported a temperature consistent with the experimental results, confirming the multiphysics credibility. Next, a ferrite flux concentrator was added to the SIF during development. Multiphysics revealed that PC40 ferrite, as a flux concentrator with a suitable design, could increase B by about 159% compared to the conventional SIF at the power of 1000 W. As expected, the B increases alongside the increase in power applied to the coils, and is more densely concentrated in the flux concentrator than in other regions, enhancing the production process efficacy. Lastly, the developed SIF was employed in the actual process and received good feedback from users. The novel research findings are the developed SIF and methodology, exclusively designed for this research and practically employed for a glass souvenir production process.

Induction assisted autogenous plasma arc welding of HSLA steel

In this work, a high frequency induction heating (HFIH) assisted plasma arc welding (IPAW) technique is proposed to weld 6 mm thick S690QL high strength low alloy steel plates in square butt joint configuration and without using any filler material. A 3D finite element based coupled electromagnetic-thermal analysis is carried out to ascertain the weld's thermal characteristics. Microstructure evolution and mechanical performance are investigated using scanning electron microscopy, electron back scattered diffraction, transmission electron microscopy, tensile test, Charpy impact test and micro hardness test. The results demonstrate that 15 s initial static heating using a co-directional current coil with magnetic flux concentrator predominantly improves the weld penetration by 48 % and joint efficiency reaches 90 % to the base plate strength. Microstructural study shows that the addition of HFIH promotes low angle grain boundaries (LAGB) with bainite ferrite and granular bainite micro-constituents in the fusion zone, which causes localised yielding and failure in this zone during tensile test. Further investigation reveals that the HFIH encourages the formation of BI-type bainite ferrite laths of 1.3–2.2 μm width, combined with slender martensite-austenite (M-A) island at the bainite ferrite lath boundaries. The results also reveal that the induction heating promotes the formation of M23C6 precipitates and B2 structured Cu-enrich nano precipitates in the fusion zone (FZ). The microhardness distribution indicates that the FZ and coarse grain heat affected zone are significantly reduced due to the assistance of the HFIH. The impact test result shows a lower energy absorption by the IPAW weldments due to dominance of the LAGB with unfavourable strain distribution.

Heat flux concentrator based on nanophononic metamaterials

Heat flux concentrators have important potential applications in thermoelectric generators. In this study, we demonstrated the heat flux concentration characteristic in nanophononic metamaterials using molecular dynamics simulations. The ratio of heat flux (RHF) is used to evaluate the concentration performance, the RHF can reach 1.62. The performance is optimized by varying the height of the nanopillar and the atomic mass of the atoms in the nanopillar. Increasing the atomic mass of the atoms in the nanopillars yields better performance. We found that the main mechanism for concentration is phonon localization in the nanopillar region. Furthermore, when the distance from the surface increases, the low-frequency peak of phonon density of states (PDOS) decreases, the high-frequency peak increases, and the mode participation rate (MPR) transforms from localized to delocalized. This work provides a new design of heat flux concentrator based on nanophononic metamaterials for regulating thermal conduction.

Magnetic Flux Concentration Technology Based on Soft Magnets and Superconductors

High-sensitivity magnetic sensors are fundamental components in fields such as biomedicine and non-destructive testing. Flux concentration technology enhances the sensitivity of magnetic sensors by amplifying the magnetic field to be measured, making it the most effective method to improve the magnetic field resolution of magnetic sensors. Superconductors and high-permeability soft magnetic materials exhibit completely different magnetic effects. The former possesses complete diamagnetism, while the latter has extremely high magnetic permeability. Both types of materials can be used to fabricate flux concentrators. This paper compares superconducting and soft magnetic flux concentration technologies through theoretical simulations and experiments, investigating the impact of different structural parameters on the magnetic field amplification performance of superconducting and soft magnetic concentrators. This research is significant for the development of magnetic focusing technology and its applications in weak magnetic detection and other fields.

Induction heating simulation for aircraft RTM toolings

Aircraft CFRP parts as sharklets are produced in resin transfer molding (RTM) tooling. The parts need to be heated up homogenously over the whole area with a constant temperature. The complex shape and accessibility of the tooling make it hard to introduce a common heating system. In addition, the heat must be transferred through the Invar metal tooling structure onto the CFRP. Infrared lamp, air fan and microwave heating are concepts in development. Electrical heating layer mats and cages are laborious in applying. Induction has the advantage of contact-less, efficient, and fast heating. Induction heating was tested for the structural bonding of CFRP frames and stringers showing high bonding strengths. To apply this technology for the RTM tooling, the placement and distance of the induction coils is important. Simulation can help to find the right adjustments and power needed for induction heating. With the program COMSOL the surface and the coils are modeled, and the numerically structured net is divided in small tetrahedron and quadratic sub elements. Since there is no magnetic streamline in the middle of the coil-section, a symmetric halving of the structure is applied as a boundary condition. The temperature-time development and the distance of the coils are simulated in 2D and 3D. Due to the material properties of the magnetic flux concentrator (MFC), higher flux concentration of the magnetic field occurred only in 2D. The results are validated by experiments and are in good agreement.

A sensitivity-enhanced sunlight-driven quantum magnetometer via level anti-crossing

Nitrogen-vacancy (NV) centers in diamond have emerged as a robust room-temperature solid-state platform for weak magnetic field detection. Several NV-based magnetometers have been proposed in the past decades, but they still suffer from either low sensitivity or high power consumption. This is a challenge for sensors deployed in remote locations on Earth or in space that are not connected to the power grid. Although sunlight-driven quantum magnetometry, which does not rely on conventional energy sources, has been proposed as a possible solution, its sensitivity remains a limitation. Here, we present an impressive improvement in the sensitivity of the sunlight-driven NV-diamond quantum magnetometer. A crucial aspect of our approach involves leveraging the ground-state level anti-crossing properties of the NV centers, coupled with magnetic flux concentrators. This integration enables us to achieve a magnetic-field sensitivity of 26 pT/Hz in a laboratory environment and 49 pT/Hz when the magnetometer operates outdoors under sunlight. We also illustrate the promising potential of further improving the sensitivity to the subpicotesla level by using cutting-edge technologies. Furthermore, we reveal the capability of this quantum magnetometer as a receiver of extremely low-frequency magnetic signals and pave the way for communication applications. These advancements represent a significant leap toward attaining high-sensitivity and energy-efficient magnetic field sensing and expanding the range of possible applications for these environmentally sustainable quantum technologies.

Numerical investigation into the Nd doped YAG rod grooving impact on the sunlight-pumped-laser performance

This paper presents a numerical analysis of the impact of grooving the Nd doped YAG rod on the sunlight-pumped lasers performance. The study analyzes laser systems that utilize side-exciting and end-side-exciting approaches to activate both grooved and non-grooved Nd doped YAG laser rods. The effects of the rod surface groove on the performance of the sunlight-pumped-lasers are thoroughly examined using ZEMAX© and LASCAD© software. To excite the grooved and non-grooved Nd doped YAG rods alternately, a ring-array sunlight flux concentrator is employed. Moreover, in the side-exciting technique, the head of the laser system contains a rectangular light guide of an extremely transparent glass made from fusing silica and an excitation cavity with a V-shaped configuration, housing the Nd doped YAG rod. This exciting method with a grooved laser rod resulted in a 13.70% increase in laser power and a 28.20% reduction in stress intensity compared to the non-grooved rod. In the end-side-exciting technique, the head of the laser system comprises an aspheric lens made of a fused silica glass and a conical-shaped excitation cavity, accommodating the Nd doped YAG rod. Results indicate that using grooved laser rod in this exciting system did not lead to an amelioration in output laser power. However, this technique enhanced the stress intensity by a reduction of 35.03%.

A Study on Magnetic Flux Concentrator to Enhance Sensitivity of SQUID in Magnetoenterogram

A Study on Magnetic Flux Concentrator to Enhance Sensitivity of SQUID in Magnetoenterogram

Half bridge configurated magneto-resistive sensors with flux guide structure for enhancing sensitivity

We demonstrate the enhancement in sensitivity of half Wheatstone bridge configurated magneto-resistive sensors with a design of the magnetic flux guide. The efficacy of our flux guide design, in comparison to the conventional micro-magnetic flux concentrator for improving the flux gain, is studied using finite element method and verified with the experimental result. We observed a sensitivity of 260%/mT for our half Wheatstone bridge sensor with a very small coercivity of 0.01 mT at room temperature. Our work will contribute to paving a road map for mass production of sensitive magneto-resistive sensors with small footprints (2.5 mm2 in this study).

Study on Performance Improvement through Reducing Axial Force of Ferrite Double-Layer Spoke-Type Permanent Magnet Synchronous Motor with Core Skew

Recently, due to the price fluctuation and supply instability of rare earth mineral resources, there has been a lot of development of electric motors using non-rare-earth permanent magnets. As a result, motors using Dy-free permanent magnets and ferrite permanent magnets are being researched, and, in particular, ferrite permanent magnets often utilize spoke-type structures, which are magnetic flux concentrators, to compensate for their low coercivity and residual flux density. However, in general, spoke-type PMSMs do not use much reluctance torque, so double-layer spoke-type PMSMs have been studied for their more efficient design. Unlike general spoke-type PMSMs, double-layer spoke-type PMSMs can utilize high reluctance torque by increasing the difference between d-axis and q-axis reluctance. However, as the difference in magnetic resistance increases, vibration and noise are generated, which adversely affects the mechanical part and shortens the life of the motor. Although this problem seemed to be solved by applying core skew in the previous study, it was confirmed that the axial force caused by the axial leakage flux occurred in the maximum torque per ampere (MTPA) control section and the torque ripple was increased. Therefore, in this paper, a model that can apply symmetrical core skew and reduce axial force is proposed. First, the causes of the axial force generated in previous studies were analyzed. Based on the analysis of these causes, a new symmetrical core skew structure was proposed, and its justification was verified through FEA.

Three-Axis Vector Magnetometer with a Three-Dimensional Flux Concentrator.

This research proposes a magnetic field sensor with spatial orientation ability. Through the assistance of a magnetic flux concentrator, out-of-plane magnetic flux can be concentrated and guided into the planar magnetic cores of a fluxgate sensor. A printed circuit board is used to construct the basic planar structure, on which the proposed three-dimensional magnetic flux concentrator and magnetic cores are assembled. This reduces the alignment error of the coils and improves the reliability of the sensor. Three-axis sensing is achieved by using the second harmonic signals from selected sensing coil pairs. The magnetometer exhibits a linear range to 130 μT. At an excitation frequency of 50 kHz, the measured sensitivities are 257.1, 468.8, and 258.8 V/T for the X-, Y-, and Z-axis sensing modes, respectively. This sensor utilizes only one sensing mechanism for the vector field, making it suitable for IoT applications, especially for assessing mechanical posture or position.

Broadband stripline Lenz lens achieves 11 × NMR signal enhancement

A Lenz lens is an electrically passive conductive element that, when placed in a time-varying magnetic field, acts as a magnetic flux concentrator or a magnetic lens. In the realm of nuclear magnetic resonance (NMR), Lenz lenses have been exploited as electrically passive metallic radiofrequency interposers placed between a sample and a tuned or untuned NMR detector in order to focus the B1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${B}_1$$\\end{document}-field of the detector onto a smaller sample space. Here we explore a novel embodiment of the Lenz lens, which acts as a non-resonant stripline interposer, i.e., the B1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${B}_1$$\\end{document}-field acts along the longitudinal volume of a sample container, such as a capillary or other microfluidic channel that is coincident with the axis of the stripline. The almost vanishing self-resonance of the stripline Lenz lens, at frequencies relevant for NMR, leads to a desirable B1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${B}_1$$\\end{document}-field amplitude that is nearly perfectly uniform across the sample and hence lacking a characteristic sinusoidal modal shape. The action of Lenz’ law ensures that no stray B1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${B}_1$$\\end{document}-field is found outside of the stripline’s active volume. Because the stripline Lenz lens does not rely on its own geometry to achieve resonance, its frequency response is thus widely broadband for field enhancements up to a factor of 11, with only the external driving resonator properties governing the overall resonant behaviour. We explore the use of the stripline Lenz lens with a sub-nanolitre sample volume, readily detecting 4 isotopes with resonances ranging from 125.76 to 500 MHz. The concept holds potential for the NMR study of thin films, small biological samples, as well as the in situ study of battery materials.

Wireless Power Transfer with Magnetic Flux Concentrator and Its Equivalent Circuit

This paper proposes a novel loosely coupled transformer (LCT) with a planar magnetic flux concentrator (MFC) for the wireless power transfer (WPT) in smart grid, which can improve the power of the receiving (Rx) coil. The MFC is a planar copper plate with a radial slit and a center hole, which is made of a printed circuit board (PCB). A simulation model and an experimental platform are built to investigate the performance of the LCT with and without an MFC. The results show that in the case of the transmitting (Tx) side with an MFC, the power of the receiving (Rx) coil increase by 33.82%. Besides, we propose the equivalent T-circuit for the LCT with an MFC.

Two-dimensional synchronous motion modulation MEMS structure for suppressing 1/f noise in magnetoresistive sensors

Magnetoresistive (MR) sensors have great application prospects in the field of weak magnetic field detection due to their high sensitivity, small size, and low power consumption. However, 1/f noise greatly limits the low-frequency detectivity of MR sensors. In order to suppress 1/f noise, this paper proposes a two-dimensional synchronous motion modulation (TDSMM) structure based on microelectromechanical systems (MEMS). This structure can effectively reduce 1/f noise by modulating the frequency of the measured magnetic field in the high-frequency band. Theoretical analysis and finite element simulation were conducted on three different modulation models: TSDMM, magnetic flux concentrators motion modulation, and MR components longitudinal motion modulation. The results showed that the modulation efficiency of the TDSMM reached as high as 127%, which is currently the highest value in MR-MEMS sensors. The TDSMM MEMS structure has been successfully manufactured, and the resonant frequency of the transverse resonator is twice that of the longitudinal resonator, enabling extremely high modulation efficiency. The noise spectral density of giant-magnetoresistive components on a silicon-on-insulator substrate was tested, and the noise level in the high-frequency band was three orders of magnitude lower than that in the low-frequency band. These results position MR-MEMS sensors with TDSMM structures as highly competitive candidates in the field of ultra-weak magnetic field detection.

MAGNETIC FIELD CONTROL IN AN ANALYTIC PLATFORM FOR ASSESSMENT OF PATHOGENIC BACTERIA

The paper presents a conceptual, analytical platform with various pathogen detection applications, based on a hybrid magnetic field source, comprised of permanent magnets and solenoid coils fixed on the same magnetic yoke that acts as a magnetic flux concentrator. The magnetic field creates magnetization forces that guide functionalized paramagnetic microparticles through the volume of an analyte sample, in order to capture targeted pathogens. The presence of bacteria is sensed with an additional electrical impedance spectroscopy (EIS) module attached to the system, at high-frequency electrical fields. The magnetic field control is studied using mathematical modeling and numerical simulation in several geometry setups, coil excitation, and remanent flux density values.

High sensitivity of diamond nitrogen-vacancy magnetometer with magnetic flux concentrators via enhanced fluorescence collection

Diamond nitrogen-vacancy (NV) centers magnetometer is attracting more and more attention due to their room-temperature solid-state property. High sensitivity is crucial for practical applications of diamond NV magnetometers. However, the sensitivity of the diamond magnetometer needs to be improved for weak magnetic measurement. Recent studies have shown that diamond with magnetic flux concentrators (MFC) makes it feasible to achieve low-frequency sensitivity at fT/Hz level. Here, we demonstrate an enhanced fluorescence collection method to improve the sensitivity of diamond NV magnetometer with MFC. A high magnetic field sensitivity of 0.47 pT/Hz (>100Hz) is achieved under resonance conditions, which is about two times higher than that without improved fluorescence collection. We then integrate the diamond magnetometer (probe size ∼8×9×13 cm3) with a shielded sensitivity of 1 pT/Hz (>30Hz). Our method offers a solution for the high-sensitivity diamond NV magnetometer. Thus, this work enables an ultra-compact and scalable platform for quantum sensing based on the diamond NV center technique. Future, diamond NV magnetometers could be proposed used in shipwreck detection, cardiac magnetic field measurement, explosives detection, etc.