Search Results (57)

Grain-oriented silicon steel is a key soft magnetic material for transformer cores, and femtosecond laser scribing provides a potential approach for achieving high-precision magnetic-domain refinement while reducing thermal damage. However, the near-surface electronic response and charge-imbalance behavior of grain-oriented silicon steel during femtosecond laser irradiation are still not well understood. In this study, a two-temperature model coupled with an electron transport model was employed to investigate the evolution of electron temperature and net charge density under different laser fluences and pulse durations. The results showed that laser fluence and pulse duration jointly affected the near-surface electron-temperature response, electron-emission process, and net charge-density evolution in grain-oriented silicon steel. Increasing laser fluence enhanced electron excitation and the degree of charge-distribution imbalance. Meanwhile, increasing pulse duration promoted the extension of the net charge distribution along the depth direction, which indicated that there was a pulse-duration range that can simultaneously promote charge accumulation at the surface and in the near-surface region. These results provided comprehensive insight into the near-surface charge-imbalance behavior during femtosecond laser etching of grain-oriented silicon steel. Full article

Inspired by the key hole concept in micro-surgery, we developed a “magnetic key hole concept” for basic studies of localized characteristics of soft magnetic laminations (electric steel, Fe-based amorphous ribbon) under exactly defined conditions of induction B(t). A material sample of 50 cm length and 10 cm width is magnetized in a novel multi-frequency SST that allows for exact sinus up to 10 kHz. A priori, the tester offers global results for permeability µ_G, power function p_G(t) and total loss P_G, as averaged over the entire sample material. But beyond that, a so-called Experimental Window (EW) offers additional information on local characteristics, as determined in a small central “key hole” region of defined magnetization. Here, a scanning adapter is mounted to study localized crystallographic features of the grain structure, as well as inhomogeneities, like failures, structure modifications, or specific technological treatment. Out of several types of sensor units a linear motor drive takes up a specific one within little manual effort. Already-developed sensor concepts concern the local tangential field, permeability, power, loss, and local widths of main domains and spike domains. The paper discusses several examples of analyses. Full article

The Axial Flux Permanent Magnet Synchronous Motor (AFPMSM) has gained significant attention as a core power source for next-generation industrial sectors, including electric vehicles, wind turbines, robot joints, and drone propulsion motors, due to its high power density from a short axial length and large radial dimensions. Despite these structural advantages, cogging torque caused by magnetic interaction between the stator teeth and permanent magnets remains a critical drawback, inducing noise and vibration. While conventional Soft Magnetic Composite (SMC) core methods facilitate 3D flux paths, they suffer from low magnetic permeability, insufficient mechanical strength, and manufacturing complexity. To address these issues, this study proposes a stepped structure model utilizing electrical steel sheets to effectively reduce cogging torque. This structure features radial stacking of identical electrical steel sheets with varying widths, where each layer’s center is incrementally shifted in the rotational direction. This configuration achieves an effect analogous to continuous skewing without specialized 3D machining. To validate the proposed design, 3D Finite Element Analysis (FEA) was conducted. Results demonstrate that the peak-to-peak cogging torque was reduced to approximately 86% of the conventional model’s value, while maintaining the back-EMF reduction rate within 5%. By presenting a novel skewing technique, this research provides a practical alternative for high-precision and high-power AFPMSM. Full article

This paper presents a real-time magnetic adhesion force estimation framework for wall-climbing robots equipped with Halbach permanent magnet arrays (PMAs) and air-gap–adjustable mechanisms. Accurately computing the magnetic adhesion force between a PMA and a large ferromagnetic surface is challenging due to the nonlinear magnetization behavior of soft magnetic materials and the strongly coupled, highly nonuniform magnetic fields generated by Halbach arrays. Conventional analytical models fail to capture these effects, while finite element methods (FEM) incur prohibitive computational cost for real-time applications. To address this, we propose an analytical magnetic-force estimation model based on the magnetostatic MoI (Method of Images), which replaces the unknown magnetization inside the steel plate with an equivalent image magnet distribution that satisfies boundary conditions at the air–steel interface. The method avoids solving complex magnetization in soft magnetic media and enables a unified force computation for arbitrarily oriented magnet elements. Additionally, complex Halbach PMA geometries are approximated through cuboid-element segmentation into cuboid magnet array, allowing efficient force evaluation. Comparative studies demonstrate that the proposed method achieves accuracy comparable to FEM while reducing computation time by several orders of magnitude. Experimental validation using a linear Halbach array and a large steel plate proved that the framework can reliably estimate magnetic adhesion force across varying air-gap distances, meeting the real-time requirements of air-gap–adjustable wall-climbing robots. Full article

Tubular flux-switching permanent-magnet linear machines (TFSPMLMs) are difficult to optimize using a single core material because conventional axial laminations suffer from severe in-plane eddy-current loss, whereas soft magnetic composites (SMCs) exhibit lower permeability and higher hysteresis loss. To address this trade-off, three hybrid SMC–laminated steel core configurations were investigated: H1, with radially laminated steel in the yoke; H2, with axially laminated steel in the tooth; and H3, with circumferential laminated steel segments. A reference SMC model (R1) and the three hybrid models were comparatively evaluated using three-dimensional finite element analysis (3D FEA). H1 and H2 showed degraded performance due to an interfacial micro-gap along the main flux path and additional in-plane eddy currents in the laminated steel regions. To mitigate these limitations, circumferential segmentation was applied to the laminated steel parts. With eight segments, H2 achieved a thrust force of 278.8 N, comparable to that of R1, while reducing iron loss by 22.5%; even a two-segment structure provided noticeable improvement. Among the investigated models, H3 showed the best overall performance by avoiding a micro-gap on the main flux path, achieving 285.5 N, and 3.9% higher thrust force and 18% lower iron loss than R1. These results indicate that H3 is the most effective hybrid-core configuration for maximizing both thrust force and loss reduction, whereas segmented H2 is an attractive practical option when manufacturability and low-loss operation are considered. Full article

Amorphous soft magnetic materials (AMMs) have demonstrated significant advantages in electric machines due to their low core losses, high permeability, high tensile strength, and superior energy efficiency at high operating frequencies. Despite these benefits, their adoption in electric vehicle (EV) motors remains limited. This review explores the key technological, economic, and industrial barriers preventing the widespread use of AMMs in EV applications. An overview of the AMM fundamentals, including the material composition, manufacturing processes, and recent advancements, is first presented. To quantitatively assess their potential in traction applications, a numerical study is conducted on two 5.5 kW synchronous reluctance machines with identical geometries, employing AMM and conventional silicon steel stators, respectively. The machines are compared in terms of electromagnetic torque and efficiency, highlighting the impact of AMM properties on machine performance. These results are discussed alongside the findings from the existing literature to evaluate the core loss reduction, electromagnetic behavior, mechanical robustness, and thermal considerations. Special attention is given to the emerging commercial applications of AMMs in EV motors, which have only recently begun to materialize. Finally, the study highlights the gap between academic research and industrial implementation and identifies critical research areas needed to accelerate AMM adoption. Full article

Grain oriented electrical steel is the most common core material used in power and distribution transformers. Compressive mechanical stress has a detrimental effect on the magnetic properties of the steel; thus, it is important to develop techniques and models that might be useful for the designers of magnetic circuits in non-rotating electrical machines. The present paper proposes an approach to address this issue. The approach is related to previous research by Garikepati et al., yet it uses more easily accessible measurement data (coercive field strength). The phenomenological T(x) model is used as part of the computational chain. The results might interest engineers working on the nondestructive testing of soft magnetic materials. Full article

Iron-based metallic glasses are gaining increased interest due to their good glass-forming ability, high compressive strength, high corrosion resistance, catalytic properties, excellent soft magnetic properties, and relatively low cost. Cold spraying was successfully used to produce amorphous coatings from commercially available powder without any crystallization due to its high cooling rate and short processing time, minimizing thermal influences. Thick and dense amorphous coatings were obtained. The effect of a substrate on the microstructure, phase composition, microhardness, flexural strength, and wear behaviour of the coatings was investigated. The cold sprayed coatings revealed an almost complete amorphous structure and negligible porosity. The coating deposited on the steel substrate showed higher microhardness, better resistance to loose abrasive wear, and a slightly lower wear index tested in the coating and Si₃N₄ ball tribological association than that cold sprayed on an Al alloy. The force required to destroy the durability of the coating–steel substrate system estimated during three-point bending tests was also much higher. Both coatings were characterized by a comparable friction coefficient. Full article

430 stainless steel exhibits soft magnetic properties, excellent formability, and corrosion resistance, making it widely used in industrial applications. This study investigates the effects of different cold working rates on the properties of 430 stainless steel subjected to various magnetic annealing atmospheres (F-1.5Si, F-1.5Si-10%, F-1.5Si-40%, F-1.5Si-10% (MA), F-1.5Si-40% (MA), F-1.5Si-10% (H₂), and F-1.5Si-40% (H₂)). The results indicate that increasing the cold working rate improves the material’s mechanical properties; however, it negatively impacts its magnetic and corrosion resistance properties. Additionally, the magnetic annealing process improves the mechanical properties, while atmospheric magnetic annealing optimizes the overall magnetic performance. In contrast, magnetic annealing in a hydrogen atmosphere does not enhance the magnetic properties as effectively as atmospheric magnetic annealing. Still, it promotes the formation of a protective layer, preserving the mechanical properties and providing better corrosion resistance. Furthermore, regardless of whether magnetic annealing is conducted in an atmospheric or hydrogen environment, materials with 10% cold work rate (F-1.5Si-10% (MA) and F-1.5Si-10% (H₂)) exhibit the lowest coercive force (286 and 293 A/m in the 10 Hz test condition), making them ideal for electromagnetic applications. Full article

Magnetic gears (MGs) are attracting increasing attention in power transmission systems due to their contactless operation principles, low frictional losses, and high efficiency. However, the broad application potential of these technologies requires a comprehensive evaluation of engineering parameters, such as material selection, energy efficiency, and structural design. This review focuses solely on solid-core magnetic gear systems designed using laminated electrical steels, soft magnetic composites (SMCs), and high-saturation alloys. This review systematically examines the topological diversity, torque transmission principles, and the impact of various core materials, such as electrical steels, soft magnetic composites (SMCs), and cobalt-based alloys, on the performance of magnetic gear systems. Literature-based comparative analyses are structured around topological classifications, evaluation of material properties, and performance analyses based on losses. Additionally, the study highlights that aligning material properties with appropriate manufacturing methods, such as powder metallurgy, wire electrical discharge machining (EDM), and precision casting, is essential for the practical scalability of magnetic gear systems. The findings reveal that coaxial magnetic gears (CMGs) offer a favorable balance between high torque density and compactness, while soft magnetic composites provide significant advantages in loss reduction, particularly at high frequencies. Additionally, application trends in fields such as renewable energy, electric vehicles (EVs), aerospace, and robotics are highlighted. Full article

This work presents a comparative study of five rare earth compounds—Erbium nitrate pentahydrate lll (Er), Neodymium nitrate pentahydrate (Nd), Samarium III Nitrate Hexahydrate (Sm), Yterbium III Chloride Hexahydrate (Yb) and Praseodymium nitrate hexahydrate lll (Pr)—protecting API 5L X70 steel from corrosion in saline medium that uses electrochemical impedance spectroscopy (EIS) and polarization curves (CPs) at different concentrations and in static mode. The results show that Erbium is the best corrosion inhibitor, containing 50 ppm and reaching an inhibition efficiency of about 89%, and similar result was shown by Sm with an IE~87.9%, while the other rare earths (Nd, Yb and Pr) showed a decrease in corrosion protection at the same concentration, since they were below an IE~80%. On the other hand, with the Langmuir model it was possible to describe that the adsorption process of the three rare earths follows a combined physisorption–chemisorption process to protect the metal’s surface. The observed adsorption free energy, ΔG°ads, reaches −38.7 kJ/mol for Er, −34.4 kJ/mol for Nd, and −33.6 kJ/mol for Pr; whereas Sm and Yb have adsorption free energies of −33.9 and −35.0 kJ/mol, respectively. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) further confirmed the formation of a protective film. Their characterization using density functional theory showed the transference of charge from the iron cluster towards the rare earth metal compounds. The adsorption process produced a slightly polarized region of interaction with the metal surface. Also, it was found that the adsorption of the rare earths affected the magnetic properties of the surface of the iron cluster. Quantum chemical descriptors, such as Pearson’s HSAB (Hard and Soft Acids and Bases) descriptors, were useful in predicting the behavior of the flow of electrons between the metal surface and the interacting rare earth ions. Full article

Fe-Co alloy has the highest saturation magnetic flux density among soft magnetic materials, and Fe₅₀Co₅₀ has the maximum permeability of Fe-Co alloys. However, Fe-Co alloy is difficult to use in applications due to its brittleness. Various attempts have been made to improve its mechanical properties for applications, but its magnetic properties have not been retained. This research focuses on improving the magnetic properties of Fe-Co electrical steels at various heat treatment temperatures with the addition of 2 at.% vanadium. To reveal the ordered body-centered cubic phase, which has good soft magnetic properties, the thermal properties of the steels were investigated with differential scanning calorimetry. The microstructure of the electrical steels after heat treatment was analyzed by scanning electron microscopy, and the tendencies of their magnetic properties, measured by a DC B-H loop tracer and a vibrating sample magnetometer, were explored in connection with the microstructure. The decrease in coercivity up to 800 °C was due to stress relief and grain growth, and its increase at 850 °C is believed to be due to the pinning effect of the V-rich phase in the grain boundary. The optimal heat treatment temperature was found to be 800 °C because the steel had reasonable magnetic saturation (2.28 T) and hysteresis loss (0.47 W/kg), the highest magnetic flux density at 5000 A/m, and the lowest coercivity (56.7 A/m). Full article

Demand is high for small, lightweight, and power-dense machines. However, as power increases and size decreases, rejecting losses becomes more difficult. Many novel cooling systems have been developed, which have allowed machines to be made smaller while increasing power. This paper proposes a cooling system making use of soft magnetic composite (SMC) cores to improve cooling specifically in a high-speed axial-flux machine via the use of an integrated cooling channel in the SMC core. A series of experiments on a prototype machine are performed and the experimental data are used to determine a set of parameters for the FEA thermal model. Using the thermal FEA model, a comparison is completed with a traditional closed cooling system using laminated steels and an attached cooling plate.The SMC machine is then simulated at speeds up to 160 krpm and currents up to 8 A. To achieve the same coil temperature between the two designs, the laminated steel model required 4 MPa contact pressure at 10 krpm and 5 MPa contact pressure at 20 krpm. At the same time, the novel design removed approximately 20% more heat per shear air gap surface area and approximately 15% more heat per total machine surface area than the version with the attached cooling plate. Extending the operating range of the model to 160 krpm demonstrated that the maximum temperature rise remained below 180 °C. Full article

A magnetic-wheeled robot is a type of robot that inspects large steel structures instead of humans, and it can run on a three-dimensional path by using wheels with built-in permanent magnets. For the robots to work safely, their magnetic wheels require both magnetic attractive forces and friction forces. Planetary-geared magnetic wheels, which we have developed, make direct contact with their yokes on the running surface to ensure their magnetic attractive force. However, this design decreases their frictional performance more than common magnetic wheels covered with soft materials. Therefore, the yokes require methods that can improve their frictional performance without decreasing their attractive force. To consider the best method for the use of magnetic wheels, this study has run experiments with five types of yokes, which have different processing. As a result, the yokes with corroded surfaces could have maintained the attractive force more than 90% of the time and increased their traction forces by about 36% in static conditions and about 30% in dynamic conditions compared to yokes with no machining. The main reasons for these experimental results are that the rust layer has stable irregularities on the surface and includes ferromagnetic materials. Full article

With the rise of eco-friendly policies, advanced motor technologies are being developed to replace fossil fuel-based engines in the mobility industry. Axial flux motors, known for their ability to reduce size and increase output torque compared to radial flux motors, require different materials and manufacturing techniques. Specifically, the production of complex stator cores and segmented magnets presents significant challenges, often leading to higher costs. To address this issue, soft magnetic composite (SMC) materials, which offer greater design flexibility, are being explored for use in stator cores. However, soft magnetic composite materials exhibit lower permeability and saturation flux density compared to laminated silicon steel, resulting in reduced output torque and efficiency. This paper investigates the effects of stator geometry on axial flux motor performance and explores cladding core technology, which combines soft magnetic composite materials with silicon steel. By conducting finite element method (FEM) analysis to evaluate the output torque and efficiency based on the shape of the silicon steel within the cladding core, this study proposes an optimized cladding core design to enhance the efficiency and output torque of axial flux motors. Full article