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Due to the high conductivity and low permeability of giant magnetostrictive materials (GMMs), eddy currents and temperature rise caused by these materials are unavoidable. These factors will significantly impact the output efficiency and reliability of giant magnetostrictive transducers (GMTs). It is essential to conduct precise evaluations of the output characteristics in various temperature settings to effectively design and optimize the transducer. However, to reduce the eddy current loss of GMMs, a radial slit is introduced. The intricate geometry also contributes to the complexity of analysis. According to the practical engineering requirements, this paper initially established a testing system for GMM characteristic and analyzed the mechanism between material temperature and output characteristics. Second, improvements have been made to the equivalent circuit method. Research has been conducted on the influence of temperature and eddy currents on the electrical and mechanical equivalent circuits, leading to the creation of a comprehensive equivalent circuit model for GMTs. Finally, a testing platform has been set up to assess the temperature-output characteristics of the transducer. The impedance and displacement characteristics of a GMT were examined to validate the proposed model. The test results demonstrated that within the 20 – 100 °C range, the discrepancy between the model and the measured impedance is under 1%, and the displacement amplitude error is less than 5%, thus confirming the precision of the proposed model. [ABSTRACT FROM AUTHOR]

Magnetically induced heterogeneous catalysis has been attracting attention due to its high energy efficiency and flexibility for dynamic reactor control. Iron wool is a commercial, low-cost, and versatile heating agent, which has been used in several magnetic catalysis studies, but its heating properties have never been investigated. Here, the properties of three types of Fe wool were studied using optical and electronic microscopy, x-ray diffraction, and measurements of both heating power and high-frequency hysteresis loops. The effects of strand width, packing, and magnetic field amplitude and frequency were studied. A maximum specific absorption rate (SAR) around 700 W/g under a rms field of 47.4 mT at 93 kHz was measured for the larger width Fe wool. High-frequency hysteresis loops were used to quantify the contribution of hysteresis losses and eddy currents to total heating. Eddy currents contribute 65%–90% to the global heating depending on the strand width. Coating the wool with SiO2 and Ni has negative effects on the SAR but none on hysteresis losses. It is interpreted as originating from the cut-off of inter-wire eddy currents due to the insulating (SiO2, oxidized Ni) nature of the coating. Last, it was found that adding more Fe wool in a given volume mostly decreases the SAR. This effect could be not only due to the absorption and/or screening of the field by surface strands but also due to magnetic interactions. The results described in this work give insights into the magnetic heating of microscale magnetic materials and optimize their use for heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

The easy-plane FeSi3.5 composite with excellent magnetic properties and power loss is proposed. The magnetic properties and power loss of the easy-plane FeSi3.5 composite are studied by using the none easy-plane FeSi3.5 composite as a control. This easy-plane FeSi3.5 composite has an initial permeability of 62, resonance frequencies of 100 MHz and 1.5 GHz, and frequency stability of 40 MHz. In addition, the easy-plane FeSi3.5 composite has also excellent loss properties, with a high-frequency power loss of only 108.12 kW/m3. The three kinds of power loss of the easy-plane FeSi3.5 composite are reduced compared with the none easy-plane FeSi3.5 composite through loss separation, especially the eddy current loss and the excess loss. The eddy current loss and the excess loss of the easy-plane FeSi3.5 composite are only 0.03 and 12.93 kW/m3 at 500 kHz, which reduce by 99.44% and 92% compared with the none easy-plane FeSi3.5 composite. Effective reduction of power loss and significant improvement of magnetic properties are important for solving the problem of power loss encountered by power electronic devices at the kHz band. Therefore, the application of the easy-plane FeSi3.5 composite with excellent power loss and high-frequency magnetic properties becomes a novel approach to meet the practical application of power electronics. The method that increases the working frequency and decreases the maximum magnetic flux density keeping the energy transformation efficiency constant is a new method to reduce power loss at the wide frequency band. [ABSTRACT FROM AUTHOR]

The complex permeability and power losses are very important parameters for soft magnetic materials. In this paper, the temperature dependence of these two parameters is investigated for Mn–Zn ferrite. The Hopkinson peak was observed at 440 K below the Curie temperature (TC), and the domain-wall resonance peaks and the natural resonance peaks gradually move to lower frequencies until the Hopkinson temperature (TH). Further, the domain-wall resonance peaks from relaxation type to resonance type are observed by fitting the permeability spectrum, which is related to the reduction of the loss factor. In addition, the power losses were measured from 245 to 365 K and divided into hysteresis loss (Ph), eddy current loss (Pe), and excess loss (Pexc). Each loss contribution was discussed to be dependent on temperature. The results show that at high temperatures and high frequencies, the thermal superposition effect will cause an abnormal increase in excess loss. [ABSTRACT FROM AUTHOR]

In this work, we utilized an in-situ chemical synthesis method to fabricate a Fe 3 O 4 /K-geopolymer (KGP) composite to be applied in a microwave absorbent field. This material, as a type of ceramic precursor, is highly expected to be a 3D printing material to prepare microwave absorbing components with complex shapes. The investigation results demonstrate that the material possesses a large effective microwave absorbing bandwidth of 3.7 GHz with the minimum reflection loss reducing to −12.2 dB when the generated Fe 3 O 4 percent reaches 12 wt% in the KGP composite. This microwave absorbent performance can be attributed to a synergistic effect between the eddy current loss caused by the improved electrical conductivity of magnetic nanoparticles and the interfacial polarization effect from the geopolymer matrix and magnetic medium interface. Also, we used direct ink writing technology to print two-dimensional components with desirable patterns. Thickness-dependent wave absorption evaluation results confirmed a maximum reflection loss of −25.9 dB at 15.2 Hz was obtained from the printed sample containing 9.0 wt% Fe 3 O 4 for a layer thickness of 10 mm, indicating that wave consumption effectiveness was determined by porous microstructures, magnetic loss of Fe 3 O 4 nanoparticles as well as suitable impedance matching. The preparation method and synthesized material pave the way for integrated manufacturing of 3D printing components with microwave absorbing performance. • Fe 3 O 4 /KGP composite was fabricated using an in-situ chemical synthesis method. • The Fe 3 O 4 /KGP composite slurry could be printed into components with wave-absorbing properties. • The microwave dissipation capacity and intrinsic mechanism of the composite were investigated. [ABSTRACT FROM AUTHOR]

ABSTRACT To address the issue of significant loss increase in planar transformers at high frequencies in LLC resonant converters, the winding width of the transformer was optimized. This design minimizes losses due to eddy currents and skin effects, thereby optimizing the transmission efficiency of the LLC resonant converter. This paper developed a mathematical model of the transformer windings, analyzed the losses in the windings and the core of the planar transformer, and summarized the design rules for three commonly used winding geometries. By determining the optimal winding width, the transformer losses were optimized. Using the finite element simulation software Maxwell3D, a 3D simulation model of the transformer was constructed. The simulation results were compared, and a 500‐W full‐bridge LLC prototype was built to validate the principles summarized in the paper. [ABSTRACT FROM AUTHOR]

The air gap magnetic field of a magnetic coupling plays a crucial role in the examination of its static torque and eddy current losses. Precise characterization of the air gap magnetic field is essential for ensuring the accuracy of performance assessments of the magnetic coupling. This study focuses on the cylindrical magnetic coupling as the subject of investigation, employing mathematical analysis and finite element methods to evaluate and quantify the magnetic field properties. The study establishes a mathematical model of the magnetic field of a magnetic coupling based on electromagnetic field principles and the superposition theorem. An analytical formula for the magnetic flux density distribution of the air-gap magnetic field is derived. Subsequently, a three-dimensional magnetic field finite element model is created using the finite element method to numerically calculate the air gap magnetic field and validate the analytical formula. The research also explores the periodic distribution characteristics of the magnetic field in the air gap, analyzing axial differences in magnetic flux density value and direction distribution influenced by end effects. [ABSTRACT FROM AUTHOR]

Despite their advantages of light weight, complete coating and good formability, the poor high-temperature stability of organic materials limits their use as insulation coatings for soft magnetic powders. Therefore, a polyethyleneimine (PEI)/silicone resin (SR) double organic insulation layer was exploited to release internal stress and maintain insulation stability during the high-temperature annealing process, which achieved low core losses (Pcv) and high effective permeability (μe). Cross-sectional scanning transition images indicate that the PEI/SR layer undergoes the following evolution during annealing at 500–900°C: coating → densification → crack → rupture, implying thermal stability up to 700°C. Because of the integrity of double inorganic shells and the weak pin on magnetic domain movement, FeSiAl@PEI/SR cores annealed at 800°C deliver remarkable AC soft magnetic performance at 50 and 100 kHz, that is, low Pcv of 61.6 mW/cm3 (50 mT, 100 kHz), 121.2 mW/cm3 (100 mT, 50 kHz) and 307.3 mW/cm3 (100 mT, 100 kHz), high μe of 55.6 up to 1 MHz and 140°C, and DC bias of 51.5% at 100 Oe. Eddy current loss reaches the minimum value at 700°C and deteriorates at 800°C, and hysteresis loss continues to decrease with increasing annealing temperature, confirming the evolution of the insulation layer. Moreover, cores annealed at 700°C deliver μe of 57.6 at 1 MHz and Pcv of 278 mW/cm3 (20 mT, 1 MHz), exhibiting great potential for 1 MHz frequency power applications. [ABSTRACT FROM AUTHOR]

Here, the core-shell structured FeSiBCuNb/Fe 3 O 4 soft magnetic composites (SMCs) were successfully designed and fabricated by coating Fe 3 O 4 magnetic nanoparticles on the surface of phosphorylated FeSiBCuNb powder. The effects of Fe 3 O 4 and Polyvinylpyrrolidone (PVP) contents on the micromorphology, interface structure, and soft magnetic properties of SMCs were systematically investigated. The results demonstrate that the Fe 3 O 4 magnetic nanoparticles are uniformly distributed on the surface of magnetic powders, which fill up the air gap in-between the magnetic powder and increase the resistivity. It shows that the permeability gradually decreases with the increase of Fe 3 O 4 from 0 wt% to 1 wt%, while the loss decreases first and then increases. The loss separation of SMCs indicates that the Fe 3 O 4 nanoparticles effectively reduce the hysteresis loss and eddy current loss. Furthermore, the FeSiBCuNb/Fe 3 O 4 SMCs with the addition of PVP as a binder enhance the binding force between Fe 3 O 4 nanoparticles and the powder matrix, which facilitates the formation of a uniform and dense interface structure. When adding 0.3 wt% PVP + Fe 3 O 4 nanoparticles, the FeSiBCuNb/Fe 3 O 4 SMCs exhibit excellent soft magnetic properties with ultra-low loss of 138.5 kW/m3 (100 mT/50 kHz), high permeability of 54, and good frequency stability. The presented results provide a new strategy for synthesizing ultra-low core loss and frequency stability of core-shell structured SMCs, which has great potential for applications at high frequencies. [ABSTRACT FROM AUTHOR]

As an important part of the primary circuit system of a nuclear power plant, the safe and stable operation of the canned motor of a nuclear main pump is crucial. The existence of stator can and rotor can in the air gap of a canned motor will generate additional eddy current loss during the operation of the motor, which will be detrimental to the long-term stable operation of the motor. Therefore, in this paper, in order to analyze and weaken the eddy current loss generated on the shielding can, using the empirical formula method, the eddy current loss generated by the shielding can before optimization is calculated, and the relationship among the eddy current loss, can thickness, and motor speed is derived. Subsequently, two shielding can structure optimization schemes were proposed, and the reduction of eddy current loss after optimization was calculated using finite element simulation software. The effects of different optimization schemes were compared. Finally, peak torque and current experiments are conducted on the original motor to verify the accuracy of the finite element calculation results. The results show that both optimization schemes proposed in this paper can reduce the eddy current loss, and the axial segmentation scheme has a better reduction effect on the shielding can. [ABSTRACT FROM AUTHOR]

According to the different excitation methods, automotive eddy current retarders (ECRs) can be divided into electrically excited retarders (EERs) and permanent magnet excited retarders (PMERs), and EERs and PMERs have certain complementarity in control and braking characteristics. Therefore, based on literature research, this article proposes a hybrid excitation rotary electromagnetic retarder (HERER) and conducts numerical simulation analysis and experimental research on the braking performance of the HERER. Firstly, the structure and working principle of the HERER are introduced. Secondly, based on the principles of electromagnetics, an equivalent magnetic circuit analysis model of the HERER is established. Then, a finite element analysis model of the HERER is established using Jmag 14 electromagnetic simulation software, and the braking performance of the HERER under different current and speed conditions is studied. Finally, bench tests are conducted on the air loss torque and eddy current braking performance of the HERER. The effectiveness of the finite element analysis model and equivalent magnetic circuit model of the HERER is verified. [ABSTRACT FROM AUTHOR]

Soft magnetic composites (SMCs) are key materials in electronic devices. Conventional SMCs incorporate too much insulating material in order to reduce eddy current loss at high frequency, resulting in severe magnetic dilution and demagnetization field, which leads to deterioration of the magnetic performance. In this paper, ZnO precursor is homogeneously deployed on the surface of FeSiAl, which in situ generates a thin and dense Al2O3 layer on the surface of FeSiAl through the interfacial solid phase reaction between Al and O atoms during annealing process. Meanwhile, ferromagnetic ZnO layer is simultaneously obtained due to the loss of O. The formed Al2O3/ZnO layers effectively reduce power loss and endow high frequency stability with less influence on effective permeability. Finally, FeSiAl/ZnO‐0.4% SMC exhibits low power loss of 83.2 mW cm−3 (50 mT/100 kHz), high effective permeability of 92, and cut‐off frequency as high as 40 MHz. This study provides an efficient route for high performance SMCs and broadens high frequency application of soft magnetic devices. [ABSTRACT FROM AUTHOR]

The present study focuses on synthesizing a composite material comprising of nickel ferrite and carbon derived from cotton, to exhibit exceptional microwave absorption capabilities over a wide frequency range. By adopting a mechanical alloy method, the microwave-absorbing composite is developed. The microwave absorption characteristics of the developed composites are further unearthly in terms of their permittivity and permeability. Combining magnetic and dielectric phases produces better eddy current loss and polarization, which are primarily responsible for absorption characteristics. The developed composites are cast into rectangular pallets to evaluate microwave absorption characteristics and examined using a vector network analyzer within the 8.2–12.4 GHz frequency range. With a pallet thickness of 2.55 mm, the entire X-band frequency is effectively covered, yielding a remarkable minimum reflection loss of −20.46 dB at 10.01 GHz. The current work's findings, owing to the synergistic combination of nickel ferrite and carbonized carbon provide a practical approach for developing a hybrid material with remarkable electromagnetic performance. [Display omitted] • The composite comprising of both magnetic and non-magnetic phases has been developed with the mechanical alloying method. • Impedance matching characteristics of the developed lightweight NCF tailored effectively with varying weight percentages. • Achieved minimum reflection loss of −20.46 dB for NCF25 composition at 10.01 GHz with 2.55 mm coating thickness. [ABSTRACT FROM AUTHOR]

Advancements in electronics and digitization have led to concerns about electromagnetic interference (EMI), necessitating effective EMI shielding measures. This study investigates the electromagnetic wave absorption properties of La n+1 Ni n O 3n+1 (n = 1, 2, 3) Ruddlesden-popper (RP) phases. While a single phase, La 2 NiO 4 , was obtained for n = 1, mixed phases of La 3 N 2 O 7-δ /La 4 Ni 3 O 10-δ were observed for n = 2 and 3. Electron paramagnetic resonance spectroscopy revealed superparamagnetic behavior for La 2 NiO 4 and multi-resonance peaks for La 3 Ni 2 O 7-δ , suggesting increased surface defects. La 3 Ni 2 O 7-δ exhibited enhanced absorption properties, with a minimum reflection loss of −19.4 dB and a broader (less than −10 dB) bandwidth covering 4.2 GHz (X-band) at a thickness of 1.4 mm, attributed to optimal conductivity, magnetic resonance, eddy current losses, and synergistic dielectric loss. The sample with n = 2 demonstrates potential for EMI absorption and electrostatic discharge (ESD) applications. [ABSTRACT FROM AUTHOR]

In order to effectively comprehend the impact of alloying element equilibrium relationship of binary nano‐magnetic particles on their electromagnetic wave absorption performance, four sets of binary nano FeNi magnetic particles with Fe:Ni alloy ratios of 2:8, 4:6, 6:4, and 8:2 were prepared with liquid‐phase reduction and the microstructure, static magnetic properties, and electromagnetic wave absorption performance of the particles were studied. The results show that the nano FeNi magnetic particles exhibit a spherical geometric structure, with a decrease in crystallinity as the Fe:Ni alloy ratio increases. The remanence and coercivity initially increase and then decrease with the increased Fe:Ni alloy ratio, with a 270 % decrease in saturation magnetization intensity as the alloy ratio changes from 2:8 to 8:2. With the increase in the Fe:Ni alloy ratio, the real and imaginary parts of the complex permittivity exhibit a decreasing trend, while the real part of the magnetic permeability decreases with increasing frequency. Aside from the 8:2 Fe:Ni alloy ratio, significant polarization relaxation losses were observed in the prepared magnetic particles, with eddy current losses was not the main mechanism of magnetic losses. The attenuation constant shows a peak at high frequencies, and the impedance matching performance increases with the increase in the Fe:Ni alloy ratio. When the Fe:Ni alloy ratio changes from 2:8 to 8:2, the minimum reflection loss decreased by 3340 %, and at a thickness of 2.1 mm and a frequency of 12 GHz, the FeNi alloy particles with a ratio of 2:8 exhibited a minimum reflection loss of −17.2 dB with an effective absorption bandwidth of 1.92 GHz. [ABSTRACT FROM AUTHOR]

Silicon steel sheets (SSSs), serving as the principal constituent of the magnetic circuit in electric machines, necessitates precise modelling and accurate computation using magnetic circuit theory as a prerequisite for analysing the characteristics of electric machines. Nevertheless, the conventional magnetic circuit theory, limited to a single reluctance component, fails to address the phase relationship between magnetomotive force and magnetic flux, and inadequately represents the magnetic flux distribution observed under high‐frequency conditions. Consequently, the existing magnetic circuit model for SSSs remains imperfect in its current state. Fortuitously, the advent of magductance has effectively addressed these challenges. Building upon magductance, this study deduces the fundamental laws and theorem within the vector magnetic circuit theory. Subsequently, a distributed parameter vector magnetic circuit model for the SSSs is constructed, accompanied by the derivation of expressions pertaining to its reluctance and magductance. The authors propose the transfer function composed of reluctance and magductance parameters, successfully resolving the phase between the magnetic circuit vectors, the magnetic flux distribution, and the magnetic circuit loss under different frequencies for SSSs. Finally, experimental findings affirm the efficacy and validity of the distributed parameter vector magnetic circuit model for SSSs. The proposal of vector magnetic circuit theory opens a whole new door for the analysis, computation, and optimisation of electric machines. [ABSTRACT FROM AUTHOR]

Permanent magnet coupling (PMC) generates a large amount of thermal energy due to the eddy current induced in the metal isolation cylinder, resulting in performance degradation. The magnetic-thermal-mechanical coupling analysis has an important impact on the design and operation of PMC devices. In this paper, the Maxwell equations are solved based on the separated variable method; the 3D eddy current loss and magnetic torque equations are proposed; and the electrical conductivity, the convective heat transfer coefficient, and the magnetic-thermal-mechanical properties of PMC are presented. The 3D analytical coupling model calculates the temperature field and presents an uneven distribution of temperature along the coolant flow direction, and it then obtains a more precise magnetic field and torque under various temperatures. Furthermore, the working conditions such as rotor speed, coolant flow rate, and applied load are taken into consideration in the 3D analytical model. The results show that the eddy current loss is proportional to the square of the speed. With an increase in the load, the eddy current decreases. However, with an increase in the coolant flow, more eddy current loss would be produced, but the generated heat would be taken away by the increased coolant flow, resulting in a decrease in the temperature. The 3D analytical coupling model results are in good agreement with the experimental data, which is helpful to the design and optimization of the PMC system. [ABSTRACT FROM AUTHOR]

Coatings play a crucial role in minimizing eddy current loss in soft magnetic composites (SMCs). The powder atomic layer deposition (PALD) technique was utilized to coat Fe–Ni–Mo soft magnetic powder in this study. The Al 2 O 3 coating fabricated via PALD enhanced corrosion resistance and reduced core loss in SMCs. Additional deposition cycles increased the resistivity of the Fe–Ni–Mo powder and the corrosion resistance of the Fe–Ni–Mo SMCs, indicating that the density and integrity of the amorphous Al 2 O 3 coating were enhanced. Thinner coatings (20 cycles) exhibited anodic passivation in corrosion, which was attributed to insufficient density. Nevertheless, an excessively thick coating (100 cycles) resulted in a decrease in effective permeability and an increase in hysteresis loss. The fabricated Fe–Ni–Mo SMCs (50 cycles) demonstrated a core loss of 603.1 mW/cm3 at 100 kHz/100 mT, coupled with an effective permeability of 108.5 and a Q value of 97.8 at 100 kHz. [ABSTRACT FROM AUTHOR]

The properties of the solid magnetic core of the stator of a slotless torque motor with permanent magnets are considered. It is noted that the solid stator under the conditions of low rotation speed has some advantages over the traditional laminated magnetic circuit. These advantages consist in the cost reduction of the design, its compactness and the low time of production preparation. The mathematical model's assumptions and the input data's limitations are formulated. A model of a static magnetic field with a moving electrically conductive medium is chosen. The two-dimensional model is implemented in the "Magnetic fields" interface of the "COMSOL Multiphysics" software. The maximum torque values were obtained and the optimal number of pole pairs was found. The method of calculating the torque based on eddy current losses in the magnetic medium is used. The decrease in torque with increasing rotor speed is calculated. The correction coefficients of the maximum moment were obtained to correct the results of two-dimensional modelling using a three-dimensional model. [ABSTRACT FROM AUTHOR]

Abstract Silicon steel sheets (SSSs), serving as the principal constituent of the magnetic circuit in electric machines, necessitates precise modelling and accurate computation using magnetic circuit theory as a prerequisite for analysing the characteristics of electric machines. Nevertheless, the conventional magnetic circuit theory, limited to a single reluctance component, fails to address the phase relationship between magnetomotive force and magnetic flux, and inadequately represents the magnetic flux distribution observed under high‐frequency conditions. Consequently, the existing magnetic circuit model for SSSs remains imperfect in its current state. Fortuitously, the advent of magductance has effectively addressed these challenges. Building upon magductance, this study deduces the fundamental laws and theorem within the vector magnetic circuit theory. Subsequently, a distributed parameter vector magnetic circuit model for the SSSs is constructed, accompanied by the derivation of expressions pertaining to its reluctance and magductance. The authors propose the transfer function composed of reluctance and magductance parameters, successfully resolving the phase between the magnetic circuit vectors, the magnetic flux distribution, and the magnetic circuit loss under different frequencies for SSSs. Finally, experimental findings affirm the efficacy and validity of the distributed parameter vector magnetic circuit model for SSSs. The proposal of vector magnetic circuit theory opens a whole new door for the analysis, computation, and optimisation of electric machines.

To meet the needs for higher energy efficiency and a wide operating temperature range of electric vehicles, the low‐loss MnZn ferrites in a wide temperature range have been developed by optimizing the Fe content and the oxygen partial pressure (PO2) during the sintering process in this work. For the optimal sample, power loss at 300 kHz/100mT is 204 kW/m3 at 25°C and remains below 290 kW/m3 in the wide temperature range from ‐10 to 120°C. The loss separation method was employed to clarify the effects of the Fe content and PO2 on power loss. The equivalent circuit model has been employed to fit the complex impedance and it is found that the increase of PO2 enhances both the grain resistance Rg and the grain boundary resistance Rgb. The enhancement of Rgb is mainly responsible for the reduction of eddy current loss and consequently power loss. Dielectric permittivity is as large as about 15000 in this series of samples due to the electric polarization at the rich grain boundaries. Dielectric loss is very low between ‐50 and 150°C and has little contribution to the energy loss. [ABSTRACT FROM AUTHOR]

Magnetic coupling is an approach employed to prevent gas leakage by transforming the dynamic seal into a non-contact static seal for the recovery of natural gas pressure energy. The impact of thermal demagnetization necessitates the consideration of the heat dissipation characteristics resulting from eddy current losses in the rotating magnetic field. We performed a numerical study of thermal-magnetic coupling in a magnetic transmission validated by experimental results. The Maxwell software was utilized to simulate the distribution characteristics of induced current, while the Fluent software was employed to analyze the dissipation of heat caused by eddy currents. The obtained simulation results reveal a proportional increase in induced current and eddy current losses with the rotation speed. Also, the eddy current losses increase together with the thickness of the isolation cover, since more volume of the conducting media is affected by the eddy currents. Furthermore, reducing the electrical conductivities of the isolation cover and enhancing the internal flow rates can effectively decrease the temperature of the magnetic coupling and mitigate thermal demagnetization. These research findings offer valuable insights for the design and optimization of non-contact transmission methods, ultimately enhancing the safety of natural gas top-pressure energy recovery equipment. [ABSTRACT FROM AUTHOR]

Abstract The authors present the multi‐physical field performances comparative research for a 30 kW, 30,000 r/min high‐speed permanent magnet motor (HSPMM) when the motor is powered by the sinusoidal pulse width modulation (SPWM) voltage inverter and sinusoidal voltage source, respectively. Firstly, electromagnetic performances including torque, voltage and current of the HSPMM with different driving methods are compared and analysed by the finite element method (FEM). Considering the effects of high operation frequency, power losses of the HSPMM with different driving methods under full‐load conditions are calculated and compared with the skin effect and the proximity effect considered for HSPMM winding copper loss estimation. Based on the above analysis, a prototype driven by the SPWM voltage inverter is manufactured, with its electromagnetic and thermal performances tested and verified. In addition, several influencing factors of the HSPMM rotor eddy current loss are studied, with their effects on the HSPMM under different driving methods further analysed and compared as well. A novel equivalent power supply method is proposed to effectively save the calculation time with a negligible error. Finally, in order to further improve the heat dissipation capacity of the HSPMM, a novel cooling method is intensively studied with its influencing factors further analysed. The cooling effect of the novel cooling method and the temperature of the motor components are verified and calculated by the computational fluid dynamics (CFD) method.

A feasibility study on cobalt ferrite-barium titanate (CFO-BTO) core-shell nanocomposite as a potential candidate to induce localized hyperthermia is performed through finite element analysis (FEA). The applied field in the radio frequency range (RF) to the simulated nanosized magneto-electric (ME) CFO-BTO core-shell nanocomposites is translated to heat energy due to (i) eddy current loss (ii) hysteresis loss and (iii) relaxation loss. A quantitative estimation of the hysteresis loss and eddy current loss is evaluated. The required temperature for hyperthermia is approximately 315K and the Pennes bioheat equation is used to study the rate of change in the temperature of the surrounding dielectric tissue. The FEA is used to study the temperature gradient as a function of time for four cases: (i) no nanoparticles (ii) using CFO-BTO to generate hyperthermia (iii) using cobalt ferrite (CFO) to generate hyperthermia (iv) increasing the concentration of CFO-BTO to generate hyperthermia. It was evident that the rate of temperature increase is higher for CFO-BTO compared to CFO. This can be attributed to the acoustic translation of energy between the magnetostrictive and piezoelectric shells. The results also indicate that increasing the concentration of CFO-BTO allows a faster rate of applied field energy translation to internal energy due to close interparticle interaction. [ABSTRACT FROM AUTHOR]

Optimizing the interface between a magnetic powder matrix and an oxide-insulating layer is an effective method to improve the permeability and lower eddy current loss of iron-based soft magnetic composites. In this study, in order to improve the bonding strength of the substrate and insulation layer, soft magnetic composites were prepared by pressing and heat treating with reduced iron powder as a magnetic matrix, high-temperature MgO nanoparticles as insulating coating, and phenolic resin as an adhesive. The effects of MgO content on the microstructure and magnetic properties of the composites were investigated. The results of a scanning electron microscopy and an energy-dispersive spectrometer analysis corroborate that the results obtained regarding the frequency characteristics and the resistivity of the iron powder agree with the scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) analysis and confirm their improvement by the presence of an insulating layer of MgO. The resistivity of the sample coated with 4 wt.% MgO is nearly 45 times higher than that of the uncoated sample under the same conditions. The MgO-insulating film formed on the surface of iron powder makes the coated sample have low effective grain size, high resistivity, and low magnetic loss at a high frequency. At 1 kHz, the magnetic loss of the 4 wt.% MgO-coated sample is reduced by 77.3%, and the magnetic loss is only 5.8% compared with the uncoated sample at 50 kHz. This magnetic loss separation study shows that the addition of MgO insulation material can effectively reduce the eddy current loss of the magnetic powder core. The 4 wt.% MgO-coated sample has the lowest hysteresis loss factor and relatively low eddy current loss factor, so it can be determined that the addition of 4 wt.% MgO is the optimum content to attain a low magnetic loss. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synergistic etching-assembly strategy toward hierarchical Fe-based microspheres engineering. • Successive regulation of magnetic-dielectric components and microstructure for balanced magnetic-dielectric synergy. • Fe@C-1/NC exhibits minimum reflection loss of-70.7 dB and effective absorption bandwidth of 3.75 GHz at 2.3 mm. Hierarchical engineering of magnetic-dielectric composite microspheres has attracted increasing attention owing to its potential to enhance electromagnetic wave absorption (EMA) through magnetic-dielectric synergy. However, optimizing magnetic-dielectric balance in composite microspheres at the nanoscale remains a formidable task due to their limited component optimization and microstructural regulation. Herein, a novel approach is proposed to modify conventional carbonyl iron powder (CIP) microspheres via synergistic etching-assembly strategy. By applying a polydopamine coating, successive tannic acid (TA) etching-assembly, and pyrolysis, hierarchical iron@carbon-1/ N -doped carbon (Fe@C-1/NC) composite microspheres are obtained. This overcomes the drawbacks of CIP microspheres, including their high density and poor impedance matching, which hinder EMA performance. Hierarchical carbon layer engineering can introduce abundant dipole centers, heterogeneous interfaces, and conductive networks to induce dielectric loss, while magnetic components contribute to magnetic resonance and eddy current loss, as demonstrated by the results. Accordingly, Fe@C-1/NC composite microspheres demonstrate a minimum reflection loss (RL min) of −70.7 dB and an effective absorption bandwidth of 3.75 GHz at a matching thickness of 2.3 mm. Generally, this work paves the way towards CIP engineering to provide guidance to the future exploration of hierarchical magnetic-dielectric EMA materials. [ABSTRACT FROM AUTHOR]

The balise transmission system (BTS) is essential for train position sensing and safe operation. Transmission loss is a key parameter particularly required for the evaluation of systems. The eddy current loss (ECL), caused by the conductivity of debris, affects the transmission performance of the BTS when the balise is immersed in water. This study proposes an effective modeling for the BTS using S-parameters. Utilizing the electromagnetic coupling analysis in the near-field region, we derived an equivalent circuit with the frequency and conductivity of water taken into consideration. The S21 can be predicted accurately by using the proposed equivalent circuit. For validation, a BTS system was implemented and measured to compare with theoretically calculated results and electromagnetic simulation results in the main lobe zone. The measurement results, simulation, and calculation were in good agreement. Moreover, the modeling was used to predict the I/O characteristics of the balise. The power of the balise uplink FSK signal was measured in the water debris and found to be approximately 0.62 dB less than in air. These findings aligned well with theoretical predictions. [ABSTRACT FROM AUTHOR]

This study investigates the impact of the amount and types of absorbent added on the compressive strength, flexural strength, and microwave absorption performance of modified sulfur magnesium cement. The X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) were used to analysis the microstructures. The results indicate that the incorporation of ferrite makes the microstructure more compact. The filling effect of ferrite particles and their greater hardness contribute to the enhancement of concrete strength, whereas graphite, with its weaker interlayer van der Waals forces, negatively affects the mechanical properties of concrete. When co-doped with 10% graphite and 15% ferrite, at 7.8 GHz, the reflectivity curve reaches its lowest point, with the electromagnetic wave reflectivity at 13.5 GHz reaching − 13.2 dB, and within the 5.4–18 GHz frequency range, the reflectivity remains below − 10 dB. With the combined effect of ferrite and graphene, the electromagnetic wave penetration of the cement matrix is enhanced, increasing the electromagnetic absorption efficiency and improving the interaction and eddy current loss capabilities of sulfur magnesium cement towards electromagnetic waves. [ABSTRACT FROM AUTHOR]

Compared to the traditional wet-mate underwater power supply method, Magnetic Coupling Resonant Wireless Power Transfer (MCR-WPT) technology boasts advantages such as excellent insulation, high safety, and convenient operation, showing promising application prospects in the field of power supply for underwater vehicles and other mobile underwater devices. In order to explore the transmission characteristics of this technology underwater, this article first establishes a traditional mathematical model, and then modifies the underwater model through analysis of changes in coil self-inductance and mutual inductance, as well as the impact of eddy current losses. Using the modified mathematical model of the underwater MCR-WPT system, the transmission characteristics are analyzed, and simulations and experimental validations are performed using MATLAB R2022a software. In the study of frequency characteristics, it is found that the system operates optimally when both ends of the circuit work at the resonant state; that is, when finput = fresonance = 100 kHz, the output performance is at its best, and the optimal resonant frequency significantly improves power and transmission efficiency. When the input frequency is less than 87.3 kHz or greater than 122.9 kHz, the output power decreases to less than half of the maximum power. In the investigation of load effects, the optimal load for maximizing system output power was identified, but the load that maximizes transmission efficiency is different from this optimal load. This study provides strong theoretical support and guidance for improving the performance of underwater wireless power transmission systems. [ABSTRACT FROM AUTHOR]

The authors present the multi‐physical field performances comparative research for a 30 kW, 30,000 r/min high‐speed permanent magnet motor (HSPMM) when the motor is powered by the sinusoidal pulse width modulation (SPWM) voltage inverter and sinusoidal voltage source, respectively. Firstly, electromagnetic performances including torque, voltage and current of the HSPMM with different driving methods are compared and analysed by the finite element method (FEM). Considering the effects of high operation frequency, power losses of the HSPMM with different driving methods under full‐load conditions are calculated and compared with the skin effect and the proximity effect considered for HSPMM winding copper loss estimation. Based on the above analysis, a prototype driven by the SPWM voltage inverter is manufactured, with its electromagnetic and thermal performances tested and verified. In addition, several influencing factors of the HSPMM rotor eddy current loss are studied, with their effects on the HSPMM under different driving methods further analysed and compared as well. A novel equivalent power supply method is proposed to effectively save the calculation time with a negligible error. Finally, in order to further improve the heat dissipation capacity of the HSPMM, a novel cooling method is intensively studied with its influencing factors further analysed. The cooling effect of the novel cooling method and the temperature of the motor components are verified and calculated by the computational fluid dynamics (CFD) method. [ABSTRACT FROM AUTHOR]

High speed permanent magnet synchronous motor for Hydrogen fuel has high loss, and its temperature rise is related to the coupling of high-speed AC (Alternating current) steady electromagnetic field, flow field and temperature field, which makes it difficult to predict its temperature rise. On the basis of deriving the two-dimensional electromagnetic field control equation of a high-speed permanent magnet synchronous motor using the Maxwell's equations, this paper uses the Bertotti iron loss discrete model to calculate the motor iron loss, introduces the Reynolds coefficient to calculate the wind friction loss, uses the classical calculation formula to calculate the winding copper loss and eddy current loss, and converts the loss value into a volumetric heat generation rate applied to each heating component of the motor as a heat source for temperature field analysis. Considering the temperature variation characteristics of materials and the anisotropy of thermal conductivity of stator amorphous alloy, a temperature rise prediction model of high-speed permanent magnet motor is established by using the fluid solid coupling method. Based on the established model, numerical analysis was conducted using Maxwell and Fluent software to study the effects of air gap slot width, slot shoulder height, and air gap length on the magnetic field and temperature field of the motor. The influence curve was drawn, and it was found that the air gap slot width had a small impact on the magnetic field of the motor. Increasing the air gap slot width appropriately was beneficial for motor heat dissipation, providing theoretical support for electromagnetic field analysis and temperature rise prediction of high-speed permanent magnet synchronous motors. [ABSTRACT FROM AUTHOR]

Nonoriented electrical steel for new energy vehicles should have high strength and excellent magnetic properties simultaneously. However, it is challenging to optimize mechanical and magnetic properties simultaneously during nonoriented electrical steel processing. This article prepares nonoriented electrical steel with high strength and excellent magnetic properties by Cu–Ni alloying, and the evolution of properties of Cu–Ni‐alloyed nonoriented electrical steel during aging and underlining mechanisms is studied. The optimal strength is achieved when aging for 10 min with a yield strength of 773 MPa, where the magnetic induction intensity (B50) is 1.66 T, and the iron loss (P1.0/400) is 18.07 W Kg−1. The optimal strength is attributed to the Cu–Ni recombination, which induces a rapid precipitation of numerous small‐sized Cu‐rich phases within a short period. Besides, the main strengthening mechanisms of the small‐size Cu‐rich phases are modulus strengthening and ordered strengthening. Furthermore, the small‐size Cu‐rich phases with B2 and body‐centered cubic structure in the earlier aging period do not deteriorate the magnetic properties of the steel. Nevertheless, in the late aging period, due to the coarsening of the precipitated Cu‐rich phase with face‐centered cubic structure and the abnormal growth of some grains, the eddy current loss increases, leading to worsen magnetic properties. [ABSTRACT FROM AUTHOR]

The FeSiBCuNb soft magnetic composities (SMCs) with five different particle size distribution (PSD) were prepared. The PSD of powders was quantified by using the logarithmic distribution width (Δ) and particle size (D50), respectively. Moreover, the thickness of the coating layers (δ) for powders and the density (ρ) of SMCs, as key factors affecting permeability (μe) and eddy current loss (Pe) of SMCs, were also estimated in detail. The results showed that the PSD has an effective effect on the ρ and μe of SMCs. The ρ and μe of SMCs increased with the increase of the Δ. The δ of powder surface was positively correlated with D50. The results of loss separation showed that the total losses (Pcv) were influenced by both D50 and Δ. The hysteresis losses and residual losses dominated the Pcv and were closely related to Δ, while Pe was mainly affected by D50. The present works had a guiding significance for the selection of PSD for the preparation of SMCs. [ABSTRACT FROM AUTHOR]

Compared with traditional actuators, the giant magnetostrictive actuator has the merits of fast response, high accuracy, and high reliability and has been widely applied. However, its performance is affected by the electromagnetic loss and the temperature, prestress, and magnetic coupling effect. In order to accurately analyze its performance, it is necessary to establish a nonlinear dynamic model including the electromagnetic loss and the magnetic–prestress–thermal coupling effect. First, based on the field separation approach, the magnetic fields generated by the eddy current loss and the anomalous loss are obtained and added to the Jiles–Atherton model. Second, the magnetostrictive model is given with the magnetic–prestress–thermal coupling effect. Finally, assuming the transmission of the giant magnetostrictive actuator as a mass–spring–damper system, a nonlinear dynamic hysteresis model with magnetic–prestress–thermal coupling effect and dynamic electromagnetic losses of a giant magnetostrictive actuator is developed. Based on this model, the output displacement curves of the giant magnetostrictive actuators under different driving currents and frequencies are given. The comparison with the experimental results shows that this model agrees well with the experiment. [ABSTRACT FROM AUTHOR]

Accurate calculation of power losses has always been important for the design and optimization of magnetic components consisting of windings and magnetic cores, such as inductors and transformers. Focusing on windings, litz wire outperforms its counterparts in terms of eddy current losses, making it particularly suitable for high-frequency (HF) applications. The power loss calculation of litz wire is however challenging due to its complex structure of thin strands twisted in multiple levels. This article therefore aims to review various kinds of litz wire power loss calculation methods from analytical methods, numerical methods to coupling ones. In addition to, the principles and applications of each method, their inherent correlation and differences are also highlighted in this article. On this basis, a comprehensive review and comparison of different calculation methods of litz-wire power loss are provided. Finally, future challenges and directions are then summarized, whose ultimate goal is to calculate the power loss of litz wire accurately and efficiently. [ABSTRACT FROM AUTHOR]

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This paper investigates the use of fractional-slot concentrated windings (FSCWs) in large-scale (MW level) offshore wind generators. It focuses specifically on a power rating of 3 MW and uses an existing direct-drive synchronous PM machine (DD-SPM) with 480s/160p and dual three-phase integer-slot winding (ISW) as a baseline. A multiple of the common 12s/10p FSCW machine is used that matches the electrical frequency of the ISW machine, yielding a 192s/160p dual three-phase machine. The hybrid star–delta connection has grown increasingly popular owing to its unique harmonic cancellation properties, which can help reduce rotor and PM eddy current losses in FSCW machines. In this paper, two dual three-phase star–delta-wound machines are scaled to 3 MW and included in the investigation. Specifically, a 384s/160p dual three-phase and dual star–delta winding machine, which is a multiplication of the 24s/10p machine, and a 192s/176p dual three-phase and dual star–delta winding machine, which is a multiplication of the 24s/22p machine, are used. These machines are investigated using finite element analysis (FEA) and compared on the basis of their air-gap flux density harmonics, open-circuit electro-motive force (EMF), torque performance, and losses and power. It is found that the proposed 384s/160p dual star–delta winding machine has the best electromagnetic performance of all, with a stator power that is 1.2% greater than that of the baseline ISW machine. However, this machine has a coil pitch of 2 and so loses the manufacturing and fault-tolerant advantage of having concentrated windings. If concentrated windings are desired, then the proposed 192s/176p dual star–delta winding machine is the best choice, with the stator power only 2.6% less than that of the baseline ISW machine, but unfortunately still has significant rotor and PM eddy current losses. [ABSTRACT FROM AUTHOR]

Soft magnetic composite (SMC) products have been widely used in electromagnetic applications due to their unique properties, including extremely low eddy current loss and relatively low total core loss at medium and high frequencies. However, there were few studies that investigated the contradictory of mechanical and magnetic properties to process FeSiCr SMC powders. To ensure that the parts fabricated by selective laser melting (SLM) satisfy the application requirements and to assist manufacturing engineers in choosing optimal process parameters, the relationship of four key process parameters (oxygen concentration, laser power, scanning speed, and hatch distance) and three fabricated part properties (permeability, core loss, and ultimate strength) was established by the machine learning models. Three experiments based on the L9 orthogonal array design were conducted to optimize the material properties and to collect data for modeling. Five machine learning algorithms were investigated, and the better ones were adopted to estimate the part properties with the input SLM parameters, which were outperformed the inference based on the regression method. A manufacturing parameter suggestion system was developed with the selected machine learning models and a multi-objective optimal algorithm, NSGA-II, to assist engineers in determining the optimal process parameters regarding the conflictive mechanical and magnetic property requirements. [ABSTRACT FROM AUTHOR]

In this paper, three typical permanent magnet machines for All-Electric aircraft propulsion are designed, optimized and compared. Firstly, the necessary performances are determined based on the requirements of high power/torque density and an aircraft with a maximum takeoff weight of 1500 kg. The initial structures of interior permanent magnet (IPM) synchronous machine, vernier permanent magnet (VPM) machine and flux-switching permanent magnet (FSPM) machine are designed with identical stator outer radius and rotor shaft length. Then, parametric sensitivity analysis and multi-objective particle swarm are combined as an optimization methodology to optimize these machines. Based on the finite element analysis, the electromagnetic performances such as no-load airgap flux density harmonic spectrum, cogging torque, average output torque, losses, efficiency and power factor, etc., are generally compared and analyzed. Subsequently, the discussions are carried out, where the strength and weakness of these three machines are concluded and the future prospects are suggested. Finally, it is concluded that if effective measures are implemented to reduce the permanent magnet eddy current loss and improve the power factor, the VPM machine would be the most suitable choice among these machines for All-Electric aircraft propulsion. [ABSTRACT FROM AUTHOR]

The DC bias may affect the transient transfer characteristics of the current transformer (CT), threatening the correct action of the relay protection and the safe operation of the power system. Compared with the high voltage direct current (HVDC) transmission in the unipolar-earth loop operation mode and geomagnetically induced current (GIC), the amplitude of the stray current is smaller, and the randomness and fluctuation are larger and accompanied by sudden changes. Combining the characteristics of stray current and the CT equivalent model considering the eddy current loss of the iron core, the mechanism of local transient saturation under the influence of bias magnetization is explained, and the CT saturation phenomenon caused by stray current and its effect on line distance protection are simulated and analyzed. The research shows that the influence of low amplitude and high duration of stray current will make the magnetic flux of CT grow and affect the transmission of steady-state and transient-state so that the measurement impedance appears amplitude-phase shift, which leads to under-range rejection of distance protection. [ABSTRACT FROM AUTHOR]

In order to solve the problem of large eddy current losses and high temperature rises caused by a large number of permanent magnets, a new type of combined-magnetic-pole permanent magnet motor is proposed in this paper. The sinusoidally distributed subdomain model of a non-uniform-air-gap rotor was established using the Laplace equation, and the analytical expression of eddy current losses in the rotor in a uniform air gap and non-uniform air gap was derived. The effect of the rotor's eccentricity on eddy current losses was obtained. According to the characteristics of the distributed winding of the non-uniform-air-gap combined-pole permanent magnet motor, an equivalent treatment was performed to obtain the equivalent thermal conductivity value; to establish an equivalent thermal network model of the motor; determine the temperature of each component of the motor; and verify the correctness of the thermal network model through magnetothermal bidirectional coupling. Finally, an experimental platform was set up to carry out temperature rise experiments on the two prototypes. The experimental results show that a non-uniform-air-gap rotor structure can effectively reduce a rotor's eddy current losses and motor temperature rise, as well as verify the accuracy of the analytical model's calculation results. [ABSTRACT FROM AUTHOR]

This document discusses the design and fabrication of micro/nano sensors and actuators, specifically focusing on micro-electromechanical systems (MEMS). MEMS devices integrate various components such as sensors, converters, and actuators into one or more chips. These devices are made from materials like silicon, metal, ceramics, and glass, which greatly influence their performance. The document also highlights the importance of process manufacturing in determining the reliability and performance of MEMS devices. The Special Issue included in the document features 11 papers that explore different aspects of MEMS/NEMS, including device design, materials, and manufacturing processes. [Extracted from the article]

This work introduces a 2D model that calculates power losses in coaxial magnetic gears (CMGs). The eddy current losses of the magnets are computed analytically, whereas the core losses of the ferromagnetic segments are computed using an analytical–finite element hybrid model. The results were within 1.51% and 3.18% of those obtained from an FEA for the eddy current and core losses in the CMG for an indicative inner rotor speed of 2500 rpm. In addition, the significance of the circumferential magnet segmentation is demonstrated in the CMGs. Furthermore, a parametric investigation of the efficiency of the system for different applied external loads is carried out. Finally, a mesh sensitivity analysis is performed, along with the computation of the average power losses throughout one full period, resulting in an at least 80% reduction in computational costs with a negligible effect on accuracy. The developed model could be a valuable tool for the minimization of power losses in CMGs since it combines high accuracy with a low computational cost. [ABSTRACT FROM AUTHOR]

Abstract A variable coefficient segmented iron loss calculation model is proposed for high‐voltage multi‐pole asynchronous motors, which fully considers the influence of high‐order harmonic magnetic density on such motors. This model introduces additional hysteresis loss, improved eddy current loss coefficients, and rotation magnetisation coefficients to account for changes in losses due to small hysteresis loops and skin effect, as well as rotation magnetisation losses. A 710 kW 10‐pole asynchronous motor is used as the research object. A full‐domain iron loss calculation model considering stator and rotor tooth top surface losses is developed. The model can be used to accurately calculate the overall and local harmonic iron losses in the stator and rotor cores of high‐voltage multi‐pole asynchronous motors. And quantitatively analyse the distribution pattern of any harmonic iron loss at any location in the motor core. It realises the refinement calculation and analysis of iron losses in the whole domain of high‐voltage multi‐pole asynchronous motor. Finally, no‐load and load tests were conducted on the 710 kW 10‐pole asynchronous motor. The iron losses of the 710 kW 10‐pole asynchronous motor at no load and load are calculated using the above mentioned model and the classical trinomial constant factor model. The results are compared with the measured iron loss values. It is proved that the iron loss model is more accurate in calculating the iron loss of high‐voltage multi‐pole asynchronous motor. The result helps researchers to calculate the iron loss distribution of high voltage motors more accurately. Thus, the design and operating parameters of the motor can be optimised to improve the efficiency and performance of the motor. It provides the necessary technical support and key basis for the reduction of loss and energy saving of high‐voltage motors and the optimisation of their core structure.

Abstract In‐plane eddy‐current loss in permanent‐magnet synchronous machines has been comprehensively and analytically studied by using three‐dimensional (3D) finite element method. Considering the accuracy and calculation time, the electrical conductivity in the stack direction should be set to zero in 3D analysis. Stacking factor is also an important analytical parameter in this kind of calculation. The influences of slot number and coil‐end height have been clarified. Harmonics caused by an inverter in pulse‐width‐modulation or one‐pulse mode result in additional in‐plane eddy‐current loss, which is independent of the slot number. This behaviour can be explained by a theoretical equation of the eddy‐current loss. These results are useful for the analysis and design of highly efficient electrical machines.

The use of heterostructures in electromagnetic wave absorption applications has been limited by the problem of homogeneous dispersion in composites. In this study, three-dimensional (3D) cross-linked electromagnetic wave absorbing composites with the carbon nanofiber/Fe3O4 (CNF/Fe3O4) core–shell structure were synthesized by expanding the interface of the heterogeneous structure with Fe3O4 nanocrystals uniformly modified on the surface of the carbon nanofiber. The 3D cross-linked structure of the composites contributes to the generation of conductive loss and macroscopic eddy current loss. The heterogeneous interface formed by graphite nanocrystals and amorphous carbon in the carbon nanofiber is identified by high-resolution transmission electron microscopy and Raman spectroscopy as having a strong electromagnetic wave absorption capacity for boundary-type defects. The Fe3O4 nanocrystal particles on the surface of the carbon nanofiber not only have the strong magnetic loss capability of magnetic materials but also form a new heterogeneous interface with the carbon nanofiber surface, which further enhances the interfacial polarization of the composite and improves the electromagnetic wave absorption properties. With the synergistic effects of interfacial polarization, macroscopic and microscopic eddy current losses, conductive losses, and magnetic losses, the electromagnetic wave absorption performance of the composites is further enhanced based on the carbon nanofiber. The reflection loss reaches −51.11, −42.99, and −55.98 dB at 9, 12 (X-band), and 17 GHz (Ku-band), respectively, corresponding to the thicknesses of 2.0, 1.5, and 1.0 mm. In addition, the widest effective absorption bandwidth is 3.3 GHz at 14.7–18 GHz (only 1.09 mm). [ABSTRACT FROM AUTHOR]

A variable coefficient segmented iron loss calculation model is proposed for high‐voltage multi‐pole asynchronous motors, which fully considers the influence of high‐order harmonic magnetic density on such motors. This model introduces additional hysteresis loss, improved eddy current loss coefficients, and rotation magnetisation coefficients to account for changes in losses due to small hysteresis loops and skin effect, as well as rotation magnetisation losses. A 710 kW 10‐pole asynchronous motor is used as the research object. A full‐domain iron loss calculation model considering stator and rotor tooth top surface losses is developed. The model can be used to accurately calculate the overall and local harmonic iron losses in the stator and rotor cores of high‐voltage multi‐pole asynchronous motors. And quantitatively analyse the distribution pattern of any harmonic iron loss at any location in the motor core. It realises the refinement calculation and analysis of iron losses in the whole domain of high‐voltage multi‐pole asynchronous motor. Finally, no‐load and load tests were conducted on the 710 kW 10‐pole asynchronous motor. The iron losses of the 710 kW 10‐pole asynchronous motor at no load and load are calculated using the above mentioned model and the classical trinomial constant factor model. The results are compared with the measured iron loss values. It is proved that the iron loss model is more accurate in calculating the iron loss of high‐voltage multi‐pole asynchronous motor. The result helps researchers to calculate the iron loss distribution of high voltage motors more accurately. Thus, the design and operating parameters of the motor can be optimised to improve the efficiency and performance of the motor. It provides the necessary technical support and key basis for the reduction of loss and energy saving of high‐voltage motors and the optimisation of their core structure. [ABSTRACT FROM AUTHOR]

• Preliminary exploration of radial wave rotors in refrigeration applications. • Radial configuration simplifies refrigeration cycle. • Two strategies are posited to augment equipment adaptability. • The dynamics of radial heat transfer and power consumption have been investigated. • The refrigeration coefficient peaks when φ = φ i and n = 2750 rpm. Gas wave refrigeration technology is an innovative refrigeration technique that harnesses pressure waves to facilitate energy exchange. In this paper, the wave rotor undergoes a transformation from its original axial structure to a radial structure. The self-pressurization capability of radial structure is proven to facilitate autonomous gas circulation, obviating the necessity for a drive fan, according to numerical simulations. We explore two methods to regulate the cycling ability for improved adaptability: altering exhaust ports and controlling exhaust resistance. The former offers a broader range of adjustment, while the latter is suitable for fine-tuning due to associated throttling pressure loss. Additionally, the mechanism of radial heat transfer is probed, revealing its intensification correlating with rising rotational speeds. The study also delves into the power consumption dynamics unique to the radial configuration. Influenced by these two factors, the device attains its peak efficiency near the specific internal circulation state of φ = φ i. The optimal rotational speed is determined to be 2750 rpm, which offers a balance between eddy current loss and power consumption. This study demonstrates that a radial gas wave refrigerator enables the integration of the pressurization and refrigeration processes. It serves as the foundation for subsequent structural optimization and experimental research on radial configurations. [ABSTRACT FROM AUTHOR]

Soft magnetic composites (SMCs) play a crucial role in modern electronics and electrical devices, for which challenges remain in maintaining magnetic performance and reducing loss at megahertz (MHz) frequencies. Here, CeFeCo/FeSiAl@ polyurethane (PU) SMCs have been rationally designed with the simultaneous achievement of large relative permeability, high domain-wall resonance frequency, and low power loss. As a rare-earth soft magnetic alloy, the CeFeCo is promising for high-frequency applications due to its easy-plane anisotropy, whereas FeSiAl is advantageous with increased electrical resistivity as well as approaching-zero magnetocrystalline anisotropy and magnetostriction. Hot pressing has been adopted to achieve a dense and homogeneous distribution of CeFeCo and FeSiAl powders in the PU for reduced magnetic dilution and eddy current loss. The resultant SMCs exhibit optional soft magnetic performance with large relative permeability of 21.0, low power loss of 3677.5 kW·m−3 at 5 MHz, and high domain-wall resonance frequency of 386.1 MHz. As such this work provides insights into the design of high-frequency SMCs incorporating novel rare-earth soft magnetic alloys. [ABSTRACT FROM AUTHOR]

In this work, distinct-morphological Co 3 O 4 /Nickel foams were prepared through a simple hydrothermal method and a subsequent heat treatment process. The morphology of Co 3 O 4 can be efficiently modulated from hexagonal nanosheets to nanobunches and urchin-like microspheres by manipulating the NH 4 F concentration. For the urchin-like Co 3 O 4 /Nickel foam composites, the minimum reflection loss (RL min) value can reach −42.53 dB at a matching thickness of 2.7 mm. Theoretical analysis shows that the enhanced microwave absorption intensity is mainly originated from dielectric losses including significant interfacial polarization of the abundant interfaces, intrinsic dipoles of Co 3 O 4 and magnetic losses containing natural resonance and eddy current loss are favorable for the impedance matching. Simultaneously, multiple scattering occurring within the 3D Ni network skeleton are considered to promote the microwave absorption performance. Furthermore, a quadrilateral cone array of the resultant urchin-like Co 3 O 4 /Nickel foam composites has a RL min of −56.7 dB and an effective absorption bandwidth can achieve 9.44 GHz. This work could be beneficial for exploiting high-efficient magnetic-dielectric microwave absorption materials via the microstructural design. [ABSTRACT FROM AUTHOR]