Magnetic Properties Of Core Research Articles

Analyzing the impact of interlocking on non-oriented electrical steel (NOES) laminations: A microstructural and mechanical property perspective

Non-oriented electrical steel laminations are widely used in electric motor cores and are manufactured using various techniques such as cutting, punching, interlocking, and welding. These manufacturing processes can have a detrimental effect on the performance of the electric motor. Thus, in order to enhance the performance of the electric motor, it is essential to comprehend the microstructural, mechanical, and magnetic property changes resulting from manufacturing. The current study focuses on the microstructural modifications caused by interlocking, which is known to impact the core magnetic properties of motors, and its relation to mechanical properties like hardness. Six interlocked non-oriented electrical steel samples were prepared by incomplete punching at different loads from 500 N to 4000 N. Scanning Electron Microscopy (SEM) and Electron backscattered diffraction (EBSD) analysis was performed on the interlocked samples to study the microstructure and crystallographic texture near the edge whereas nanoindentation was used to determine the hardness profile. Pop-in analysis was done to study the extent of work hardening due to punching and its effect on hardness. The hardness change due to residual stress was determined, which was used to estimate the induced residual stress near the edge. It ranged from 0.04 GPa at 550 N load to 11 GPa at 4000 N load near the punched edge.

Effect of low magnetic field heat treatment process on grain sizes and soft magnetic properties of Finemet cores

In this study, we investigate the effect of low transverse magnetic field annealing on the soft magnetic properties of cores made of industrial Finemet ribbons. The variation of static/dynamic magnetic properties and average grain size of the cores obtained by zero-field annealing (ZFA), secondary-field annealing (SMA) and direct-field annealing (DMA) are studied in detail. It is found that the average grain size obtained by DMA decreased compared to that of the ZFA sample, while the average grain size increased slightly after SMA. The effective permeability (μe) of the ZFA sample after SMA decrease less than that of the ZFA sample with increasing frequency. The μe of the DMA sample decreases significantly at the low-frequency stage but tends to decrease smoothly overall, maintaining high effectiveness at high frequencies magnetic permeability. For example, at 100 kHz, the μe of ZFA at 550 °C temperature is only 0.6 × 104, while the μe of SMA and DMA are 2.0 × 104 and 2.2 × 104, respectively. Meanwhile, the Hc = 1.85 A/m, Br = 0.59 T after ZFA and Hc = 1.67 A/m after DMA show no significant decrease compared to ZFA. While Hc = 0.55 A/m, Br = 0.08 T after SMA. Due to the field anisotropy constant Ku generated after SMA and DMA, the average anisotropy constant is dominated by Ku, the domain structure becomes simple and uniform, and the domain width becomes larger. This leads to a decrease in core losses with increasing frequency and improves the high-frequency characteristics of the core. These results can provide good guidance for performance optimization for Finemet alloys in a wide frequency range.

Effect of magnetic field annealing on the soft magnetic properties of CoFeSiB ribbon and its fluxgate performance

As a key part of fluxgate, the properties of magnetic core determine the performance of fluxgate sensor. We studied the effects of zero magnetic field annealing (ZFA) and longitudinal magnetic field annealing (LFA) on soft magnetic properties, magnetic anisotropy and magnetic domain structure of the Co70Fe5Si15B10 amorphous ribbon and its fluxgate sensor performance. It is found that LFA can effectively modulate the magnetic domain from irregular shape and size to wide regular strip domains. As a result, pinning effect, magnetic anisotropy and coercivity decrease, while the initial permeability increases. And finally, the sensitivity of the fluxgate become higher, and noise become less. The results show that the optimal soft magnetic properties of the ribbons are obtained after LFA at 440 °C, with the initial permeability of 21,020 and the coercivity of 0.2 A/m. We applied a square wave excitation signal of current 30 mA and frequency 2.4 kHz to test the performance of the fluxgates. It is found that the fluxgate sensitivity increases from the original 36.54 to 41.82 mV/μT after magnetic field annealing treatment, and the peak-to-peak noise (Noisep-p) value at 10 Hz bandwidth in 250 s decreases from the original 5.22 to 2.14 nT. The results show that the LFA treatment of the core has a significant effect on its magnetic properties and fluxgate performance enhancement, and these results have good implications for the construction of high-performance fluxgate.

Microstructure, Magnetic Properties, and Application of FINEMET-Type Alloys with Co Addition

The choice of materials for cores of electrotechnical devices is currently related to energy saving and global warming problems. Nanocrystalline alloys are emerging as materials for cores in these devices in addition to amorphous materials already commonly used due to their better magnetic properties at high operating frequencies. The thermal stability of the magnetic properties of cores is also an important criterion. Keeping these criteria in mind, a study of microstructure and magnetic properties was carried out in this work, and FeCoNbBCu-type material was selected for use as the core of a choke operating in a DC/DC converter in interleaved topology. On the basis of the conducted studies, it was found that good magnetic properties and the best thermal stability were shown by Fe58Co25Nb3B13Cu1 alloy. Using RALE software, the technical parameters of the choke core were determined and compared with the same parameters for a choke core made of FINEMET-type alloy.

New Approach for Ampacity Calculation of Overhead Lines With Steel-Cored Conductors

Due to increasing energy demand and penetration of renewable energy sources into the grid, the transmission system has often been operated closer to its operating limit. This scenario requires the accurate calculation of the lines' ampacity in order to ensure their safe operation and the full use of their capacity. This paper proposes a new approach for calculating the ampacity of overhead lines with steel-cored conductors, using an accurate resistance calculation model in a straightforward way. The alternating current (AC) resistance of this type of conductors can be affected by the core magnetization depending on factors such as the number of aluminum layers and the core magnetic properties, which are properly considered using the proposed model. Results for the conductor AC resistance variation with the carried current value and the ampacity for different scenarios are presented and compared with those obtained using the resistance calculation models proposed in ampacity calculation methods by IEEE and CIGRE´ . Results show that the lines' ampacity tends to be underestimated using the existing models. However, for conductors with one aluminum layer, the IEEE method may overestimate the line's ampacity by considering a constant conductor resistance value, bringing risks of accidents due to conductor overheating.

Magnetic properties of a high-density iron dust core without binders

Iron dust cores produced from insulated iron particles via the powder metallurgy pressure-forming process are suitable for small motor cores, reactor cores, and inductors because of their high shape flexibility. However, the dust core’s magnetic properties are inferior to those of conventional laminated cores because the insulation materials and silicon resins between iron particles to reduce eddy current losses degrade the magnetic properties of the core. Unfortunately, there is no researches of the iron dust cores without binders such as resin to improve the magnetic properties. Therefore, this paper investigates the magnetic properties of iron dust cores without binders. Assessments revealed that the dust core of gas-atomized iron powder with an average particle size of 49μm had the best magnetic properties. On further assessments, while the insulation layer’s thickness was around 60 nm, the density of gas atomized iron powder core was over 7.6 g/cm3. At 50 Hz and 1 kHz, DC hysteresis iron losses and eddy current loss of 49μm gas atomized iron dust cores without a binder showed lower values than those of the conventional powder core with a binder.

Impact of Manufacturing Stresses On Multiple-Rib Synchronous Reluctance Motor Performance

The effects of manufacturing stresses on the overall magnetic properties of electrical steel core applied in the stator and transversally-laminated rotor of Synchronous Reluctance motors are studied. In addition, it is investigated how the -manufacturing-degraded electrical steel core affects the electromagnetic performance of two different Synchronous Reluctance motors. The traditional transversally-laminated rotor of this kind of a machine requires the adoption of mechanical elements (inner and tangential ribs) to maintain its mechanical integrity. Especially, for high-speed applications, the number of rotor ribs must be increased to make the rotor withstand higher centrifugal forces. Lamination manufacturing typically affects the magnetic properties of electrical steel by reducing its permeability at the machined edge. This machining effect is greater when the overall core layer area surrounded by the machined edges is small i.e., the machined surface area ratio to the total core area is high. Considering this, the degradation of the core magnetic properties in the ribs could improve the performance of the machine, and this effect would be more visible when the machine is designed with a higher number of narrow ribs with the adoption of Topology Optimization. The paper aims to propose some guidelines for the simulation of these effects starting from the measurements on defined core samples and then based on the measured results the simulation model should be updated accordingly. The samples are manufactured from several assembled sheets in order to modify the width of the cut area while maintaining the same external geometry.

Measurement and Modeling of Magnetic Materials under 3D Vectorial Magnetization for Electrical Machine Design and Analysis

The magnetic properties of magnetic cores are essential for the design of electrical machines, and consequently appropriate mathematical modeling is needed. Usually, the design and analysis of electrical machines consider only the one-dimensional (1D) magnetic properties of core materials, i.e., the relationship of magnetic flux density (B) versus magnetic field strength (H), and their associated power loss under 1D magnetization, in which the B and H are constrained in the same orientation. Some studies have also been performed with the two-dimensional (2D) magnetizations in which the B and H are vectorial, rotating on a plane, and they may not be in the same direction. It has been discovered that the 2D rotational property is very different from its 1D alternating counterpart. However, the magnetic fields in an electrical machine, in particular claw pole and transverse flux machines, are naturally three-dimensional (3D), and the B and H vectors are rotational and may not lie on the same plane. It can be expected that the 3D vectorial property might be different from its 2D or 1D counterpart, and hence it should be investigated for the interests of both academic research and engineering application. This paper targets at a general summary about the magnetic material characterization with 3D vectorial magnetization, and their application prospect in electrical machine design and analysis.

Microstructure and Magnetic Properties of Grain Boundary Insulated Fe/Mn0.5Zn0.5Fe2O4 Soft Magnetic Composites.

Mn0.5Zn0.5Fe2O4 nano-powder was coated on Fe microparticles by mechanical ball milling combined with high-temperature annealing. The effects of milling time on the particle size, phase structure and magnetic properties of core–shell powder were studied. Scanning electron microscopy (SEM), energy-dispersive spectroscopy and X-ray diffraction showed that the surface of the milled composite powder was composed of thin layers of uniform Mn0.5Zn0.5Fe2O4 insulating powder. SEM also revealed a cell structure of Fe particles, indicating that the Fe particles were well separated and isolated by the thin Mn0.5Zn0.5Fe2O4 layers. Then, Fe/Mn0.5Zn0.5Fe2O4 soft magnetic composites were prepared by spark plasma sintering. The amplitude permeability of Fe/Mn0.5Zn0.5Fe2O4 SMCs in the Fe/Mn0.5Zn0.5Fe2O4 soft magnetic composites was stable. The resistivity decreased with the increase in sintering temperature. The loss of the composite core was obviously less than that of the iron powder core. Hence, the preparation method of Mn0.5Zn0.5Fe2O4 insulating iron powder is promising for reducing core loss and improving the magnetic properties of soft magnetic composites.

A detailed investigation of the core@shell structure of exchanged coupled magnetic nanoparticles after performing solvent annealing

Solvent annealing at around 300 °C resulted in a significant modification of the structure and the magnetic properties of core–shell metal oxide nanoparticles as shown by DANES and XMCD.

A preliminary study on the application of paramagnetic composite nanoparticles in the navigation of hepatectomy

As the preferred treatment strategy for primary liver cancer, hepatic resection surgery can effectively improve the survival of liver cancer patients without relying on other treatments. However, traditional hepatic resection surgery cannot achieve precise localization of the cancer foci boundary. Therefore, improving hepatectomy targeting and reducing the metabolic rate of contrast agents in vivo has become an urgent challenge. This study constructed a novel indocyanine green nanocomposite fluorescent contrast agent, known as indocyanine green-carboxymethyl chitosan/superparamagnetic iron oxide nanoparticle (ICG-CMCS/SIO NP), based on a superparamagnetic iron oxide. The carboxymethyl chitosan and indocyanine green (ICG)’s graft copolymer served as a nanomaterial shell. This shell enhanced ICG targeting’s control ability and stability while effectively retaining its core magnetic properties. Thus, ICG-CMCS/SIO NPs should provide a novel idea for the study of clinical hepatocellular carcinoma resection surgery navigation.

Effect of magnetic nanoparticles containing ropivacaine on ankle nerve block in rats

Ropivacaine (RVC), a common pain management drug used for clinical anesthesia and postoperative analgesia, inhibits peripheral nociceptive pain stimulation. However, the potential neurological damage resulting from RVC use must be considered. Developing a strategy to enhance the local anesthetic effect of RVC while reducing its potential acute toxicity to the central nervous system is urgently needed. In this study, a novel RVC nanocomposite drug, magnetic iron oxide/polyethylene glycol-carboxymethyl chitosan/ropivacaine nanoparticle (mCMCS-PEG/RVC NPs), was synthesized with magnetic iron oxide. The inherent shell–core structure of mCMCS-PEG retained core magnetic properties, improved the stability and biocompatibility of magnetic nanoparticles, and avoided excessive degradation. Thus, mCMCS-PEG/RVC NPs are expected to provide a new pain management strategy for perioperative patients.

High-Frequency Loss Modeling of Amorphous and Nanocrystalline Cores With Different Air Gaps

In general, an air gap plays an important function in the magnetic core. It will enhance the stability of the inductance value of a reactor, increase the power density of the inductor, and optimize the properties of a high-frequency transformer. Hence, it is of great significance to study the influence of the air gap on the properties of magnetic cores. Based on a novel designed tester, the dynamic magnetic properties of the C-type amorphous (AMCC025) core and nanocrystalline (F3CC0125) core with different lengths of the air gaps are measured and analyzed when the cores are excited at different frequencies. In addition, the modified Steinmetz empirical formula which takes the fringing magnetic flux near the air gap into account is proposed. The calculated magnetic properties obtained from the modified formula show great agreement with the measured results. The average prediction error of the modified model is confined in 10%. Both the calculated and experimental results indicate that the influence of the fringing magnetic flux could be ignored when the length of the air gap is less than 5% length of the equivalent magnetic circuit. In particular, the frequency-dependent losses decrease to a minimum value and then increase with the increase in flux density accordingly. The modified loss model and results would be beneficial to the design of high-frequency inductors and transformer cores.

Preparation and magnetic properties of core–shell structured Fe-Si/Fe3O4 composites via in-situ reaction method

The Fe-Si/Fe3O4 soft magnetic composites (SMCs) have been fabricated via in-situ reaction method. A layer of Fe3O4 was formed on the Fe-Si particles in the KNO3 solution, and the growth mechanism of the Fe3O4 coating layer has been studied, and its formation and thickness can be controlled by adjusting the concentration of KNO3 solution to obtain the microstructure of the composites and then adjust the magnetic performance of SMCs. The formation of Fe3O4 shell on Fe-Si particles can effectively reduce the core loss of the composites. The samples in-situ reacted in 0.1 mol/L KNO3 solution exhibit excellent comprehensive properties with high saturation magnetization, relatively high permeability (34), great frequency stability of permeability, and very low core loss of 13.6 w/kg (measured at 20 mT and 150 kHz).

Improved Electromagnetic Model for Steel-Cored Conductors

The core magnetization of steel-cored conductors can affect their alternating current resistance and the current distribution between their aluminum layers, depending on several aspects such as the current carried by the conductor, the number of aluminum layers, and the steel core magnetic properties. Electromagnetic models can consider these aspects when calculating the effects of the core magnetization and also be used to optimize the conductor's design in order to reduce losses. However, as the existing models represent the steel core in a simplified way, calculations may not be accurate for high currents and the design optimization is restricted to changes in the aluminum layers only. This work presents a new electromagnetic model for calculating the resistance and current distribution of steel-cored conductors, in which their core is appropriately represented. Results show good accuracy for a conductor with three and a single aluminum layer over the whole current range analyzed. It is also shown that the magnetic fields produced in the steel layers can play an important role in reducing the core magnetization and that it is possible to further reduce losses by optimizing the core design.

Microstructural and magnetic properties of core–shell FeSiAl composites with Ni0.4Zn0.45Co0.15Fe2O4 layer by sol–gel method

FeSiAl/Ni0.4Zn0.45Co0.15Fe2O4 ferrite core–shell particles and cylindrical magnetic cores have been synthesized by sol–gel auto-combustion method. The magnetic cores were prepared by pellet molding process and high temperature annealing at 700 °C for 1 h. The reaction, surface morphology and magnetic properties of FeSiAl/ Ni0.4Zn0.45CoFe2O4 ferrite cores have been investigated by Differential thermal analysis-thermogravimetry (DTA-TG), X-ray diffraction (XRD), the impedance analyzer and Vibration sample magnetometer (VSM). The results indicates that there are three stages to form ferrite. The cores of unphosphated FeSiAl/Ni0.4Zn0.45CoFe2O4 ferrite will be oxidized in air at 700 °C. The spinel ferrites are successfully prepared by sol–gel and form a homogeneous as well as porous structure on the surface of the cores. The maximum permeability is 41 at 6 wt% ferrite. Ms decreases from 106.6 emu/g to 103.6 emu/g, with the increase of ferrite content.

Magnetic properties of an ACSR conductor steel core at temperatures up to 230 ∘C and their impact on the transformer effect

The current density distribution between layers of steel-reinforced conductors having an odd number of aluminum layers is modified by the transformer effect, as a result of the steel core magnetisation. This redistribution of current affects the conductor alternating current resistance, the transitory temperature radial distribution, and depends on the total current intensity, and the core permeability, which varies with temperature. Although some steel-cored conductors are designed to operate at high temperatures to maximise their current capacity, the core magnetic properties in this scenario need to be further investigated. This paper presents the results of experimental work on an ACSR conductor, and on its steel core to investigate the steel core magnetic properties over an extended temperature range, and how they affect the transformer effect. Results show an unexpected hump-shaped variation of the permeability with temperature in a specific range of magnetic field strength, with maximum permeability values occurring at a temperature ranging from 150 to 170 ∘ C , which were not covered in previous studies. A similar behaviour is seen in the variation of the axial magnetic flux with increasing conductor temperature, causing the flux to decrease at high temperatures, and thus weakening the transformer effect during the conductor operation.

Examination of Stress-Relief Annealing Method of Ring Core Material by Using Induced Magnetic Field Strength

Magnetic properties of motor cores are deteriorated due to residual stress and outside load during manufacturing process. In this paper, new stress-relief annealing method of ring cores will be suggested by applying an induced magnetic field. The temperature distribution and temperature characteristic on the surface of the ring core is examined by changing the lamination number of the ring core. In addition, the ring core which cut by punching, wire discharge and laser process are annealed and the magnetic properties of these cores before and after the annealing is evaluated.

Photocatalytic activity of magnetic core-shell CoFe2O4@ZnO nanoparticles for purification of methylene blue

Magnetic core–shell CoFe2O4@ZnO nanoparticles have been successfully synthesized by using coprecipitation method to provide easy separated nanomaterials and high photocatalytic activity performance. Core–shell nanoparticles with various CoFe2O4-to-ZnO molar ratio (1:2, 1:3, 1:4, 1:5) have been investigated over x-ray diffraction (XRD), transmission electron microscopy (TEM), UV-visible spectroscopy, and vibrating sample magnetometer. XRD spectra confirm the cubic spinel ferrite phase structure of CoFe2O4 and the hexagonal wurtzite phase of ZnO. The crystallite size is found within the range of 14.9–20.6 nm. TEM measurement confirms the good crystallinity of the samples. The magnetic hysteresis shows that CoFe2O4@ZnO has high saturation magnetization of about 30 emu g−1 and coercivity of about 300 Oe. Photocatalytic investigation was carried out using methylene blue (MB) under UV irradiation. Our result yields the enhancement of MB degradation as ZnO content increases. The maximum photodegradation achieved by the core–shell nanoparticles is 57.2%, 60.5%, 65.5%, and 78.3% for molar ratio of 1:2, 1:3, 1:4, and 1:5, respectively. The enhancement of MB degradation can be attributed to the formation of internal structure between CoFe2O4 and ZnO in the form of heterojunction structure. The magnetic properties of core–shell lead to the easy separation between the magnetic core–shell nanoparticles and the final degraded solution by permanent magnet.

Structural characterization and magnetic properties of core–shell Fe@Fe3O4 nanowires

Core–shell Fe@Fe3O4 nanowires (NWs) were successfully prepared on a homemade anodic aluminum oxide (AAO) template by the anodic oxidation of Fe NWs followed by annealing reduction. A field-emission scanning electron microscope was used to observe the morphology of the AAO template, which shows that the diameter of AAO template was 30 nm. TEM results confirm a thin oxide layer was formed on Fe NWs, confirming the core–shell nature of Fe NWs. The TEM analysis shows that with the increase in anodizing time, the oxide layer thickness was increased from 2.4, 4.6, 5.9 nm, respectively. The elemental composition of core–shell Fe NWs was confirmed by energy-dispersive X-ray spectrometer. The oxide phase of Fe could not be easily distinguished by X-ray analysis, because of the line width broadening of nanocrystals; thus, the valence states of Fe in Fe@Fe2O3 and Fe@Fe3O4 NWs were further analyzed by X-ray photoelectron spectroscopy (XPS). XPS results confirm the oxide nature of Fe2O3 and Fe3O4 in core–shell Fe NWs. The influence of oxide layer thickness on the magnetic properties of core–shell Fe@Fe3O4 NWs was investigated by vibrating sample magnetometry. Magnetic measurement revealed that the coercivity and squareness values of core–shell Fe@Fe3O4 NWs gradually increased with the increase in the Fe3O4 shell thickness. Results clearly showed that the size and magnetism of the core–shell Fe@Fe3O4 NWs can be adjusted to a certain extent by this synthetic method, so as to meet different requirements in desired biomedical applications.