Low Core Loss Research Articles

Significant improving magnetic properties and thermal conductivity of FeBSiPCNbCu nanocrystalline powder cores by designing novel ZnO insulating layer

As the application scenarios of soft magnetic composites (SMCs) tend to be high frequency, reducing their high-frequency core loss (Pcv) and improve the heat-sinking capability to avoiding thermal failure of electronic system are still greatly challenging. In present work, we successfully designed and prepared novel ZnO insulating layers on the surface of FeBSiPCNbCu nanocrystalline powders and discussed their growth processes. In addition, we investigated the effects of the ZnO insulating layers on the magnetic properties and heat-sinking capability of the FeBSiPCNbCu nanocrystalline magnetic powder cores (NMPCs) and explored the related mechanisms. The experimental results show that the hydrolysis of 1.75 wt% zinc acetate dihydrate under the coupling of 1 wt% polyvinylpyrrolidone forms uniform and thin ZnO insulating layers on the powders surface. The FeBSiPCNbCu@ZnO NMPCs annealed at 510 °C for 60 min exhibit excellent magnetic properties and superior heat-sinking capability with a low core loss of 698.4 mW/cm3 (20 mT, 2 MHz), high DC bias permeability of 68.3% (100 Oe) and heat conductivity coefficient of 2.22 W/(m•K) as compared with those of 859.8 mW/cm3, 57.1% and 1.86 W/(m•K), respectively, for the NMPCs without ZnO insulating layer.

Optimal Design and Analysis of High-Frequency Isolation Transformer for Switched-Mode Power Converters

High-frequency (HF) transformers have gained great interest in recent years due to the advent of powerful soft magnetic materials with low core loss in semiconductor power switches. Also, the optimal design of the HF transformer is a significant issue for high-performance energy conversion systems. In this paper, a 40W 50/12.5/25 V universal input and two output discontinuous-conduction mode (DCM) flyback transformer is designed by using mathematical calculations and analyzed via 3D ANSYS/Maxwell simulation including electromagnetic and loss analysis. It is shown that the simulation results accounting for hysteresis losses, eddy current losses, copper losses, and magnetic flux density determine the accuracy of the mathematical model calculation. Analyzes are performed at 100 kHz frequency levels. Results obtained will include core magnetic flux density, core/copper losses, leakage/magnetizing inductances, windings parasitic capacitances, input/output voltage, current values, and all design parameters. Finally, the proposed HF transformer's overall efficiency is calculated and presented. Significantly, the HF transformer achieves 97.8% efficiency thanks to the transformer's core and coil selection, B-H and B-P characteristics, one-to-one dimension design, and mesh operation. The dynamic and mathematical results of the designed transformer demonstrate the design and efficiency success

Formation, thermal stability and soft magnetic properties of Fe-Co-B-Si amorphous alloys with ultrahigh saturation magnetic induction of 2.0 T

This paper studies the influence of metallic element composition on the formation ability, thermal stability and magnetic properties of melt-spun (Fe1-xCox)B15–19Si1 (x =0.2–0.4) amorphous alloy ribbons. The maximum metal concentration at which an amorphous phase is formed during melt spinning has been determined in conjunction with the metal content dependence of crystallization processes and crystallized phases. The amorphous (Fe0.8Co0.2)84B15Si1 alloy with the highest metal content in an optimally annealed state exhibits an extremely high saturation induction (MS) of 2.0 T, low coercive force of 7.6 A m−1, high effective permeability of 13500 at 1 kHz and low core losses of 5.5 W kg−1 at 100 mT and 19.7 W kg−1 at 200 mT at 10 kHz which have not been simultaneously obtained for all kinds of soft magnetic materials up to date. The replacement of Fe with Co significantly increases the Curie temperature of the amorphous phase, resulting in very high thermal stability of the high MS alloys. The combination of excellent soft magnetic properties with ultrahigh MS value makes them candidates for use in highly loaded high-speed electric motors capable of operating at temperatures up to 473 K.

Influence of Polytetrafluoroethylene Content, Compaction Pressure, and Annealing Treatment on the Magnetic Properties of Iron-Based Soft Magnetic Composites.

To improve the magnetic properties of iron-based soft magnetic composites (SMCs), polytetrafluoroethylene (PTFE) with excellent heat resistance, electrical insulation, and extremely high electrical resistivity was chosen as an insulating coating material for the preparation of iron-based SMCs. The effects of PTFE content, compaction pressure, and annealing treatment on the magnetic properties of Fe/PTFE SMCs were investigated in detail. The results demonstrate that the PTFE insulating layer is successfully coated on the surface of iron powders, which effectively reduces the core loss, increases the resistivity, and improves the frequency stability and the quality factor. Under the combined effect of optimal PTFE content, compaction pressure, and annealing treatment, the iron-based SMCs exhibit a high effective permeability of 56, high saturation magnetization of 192.9 emu/g, and low total core losses of 355 mW/cm3 and 1705 mW/cm3 at 50 kHz for Bm = 50 mT and 100 mT. This work provides a novel insulating coating layer that optimizes magnetic properties and is advantageous for the development of iron-based SMCs. In addition, it also provides a comprehensive understanding of the relationship between process parameters and magnetic properties, which is of great guiding significance for scientific research and industrial production.

Magnetic domain structure and electromagnetic performance of amorphous and nanocrystalline soft magnetic composites treated by magnetic field assisted annealing

Soft magnetic composites (SMCs) based on flaky amorphous and nanocrystalline powders have less applications in SMCs than conventional alloys due to their insufficient stress relief during low-temperature annealing and relatively low comprehensive electromagnetic properties. Here, transverse and longitude magnetic field assisted annealing (MFAA) processes are applied for FeSiB amorphous and FeSiBCuNb nanocrystalline SMCs. Excellent electromagnetic performance of the amorphous/nanocrystalline SMCs can be obtained by MFAA. The SMCs of FeSiB treated by longitude field with induced current of 40 A and FeSiBCuNb treated by transverse field of 750 Gs exhibit high effective permeability of 41 and 68 at 100 kHz, and low core loss of 304 and 149 mW/cm3 at 100 kHz and 50 mT, respectively. Dynamic magnetic domain observation and loss separation are carried out to reveal the physical mechanisms for the property enhancement. Strip-like domain with small size and smooth edge appear in the amorphous/nanocrystalline SMCs after MFAA, indicating the induced magnetic anisotropy. The loss separation results show that the MFAA can induce the magnetic anisotropy, effectively improve the permeability and reduce the core loss of SMCs. This work provides an insightful understanding of magnetic field heat treatment on the electromagnetic properties for amorphous and nanocrystalline SMCs.

Structural evolution mechanism and magnetic properties of soft magnetic composites transformed from FeSiAl/Co3O4 composites

Simultaneous optimization of core loss and saturation magnetization in soft magnetic composites (SMCs) is crucial for the development of high frequency and high power in power electronic devices. In this work, FeSiAl/(Al2O3-Co) and FeSiAlCo/Al2O3 SMCs were prepared by sintering FeSiAl/Co3O4 composite powders at different temperatures. The corresponding structural evolution mechanism and magnetic properties of the prepared SMCs were studied systematically. When the sintering temperature was below 950 ℃, a chemical reaction at the FeSiAl/Co3O4 interface occurred and led to the formation of Al2O3-Co composite coating. The Al2O3 coating, as an isolation band, can effectively hinder the interdiffusion between Co coating and FeSiAl magnetic powder. When the sintering temperature increased to above 1000 ℃, the interdiffusion began to occur and was accelerated by the high temperature and chemical potential educed by concentration gradient, finally resulting in the formation of FeSiAlCo alloy. The prepares SMCs exhibited a low core loss due to the high integrity of Al2O3 coating. Its saturation magnetization and permeability significantly increased with the sintering temperature due to the generation of Co coating with ferromagnetism. This work provides a new strategy for the construction of ceramic oxide coating with high integrity and elemental doping of magnetic powder in SMCs, which is expected to be applied to the preparation of high-performance SMCs.

Statistical characterization of the effect of random core loss on the intercore crosstalk in long-haul uncoupled multicore fiber links

We characterize the statistical properties of direct average intercore crosstalk (ICXT) in long-haul uncoupled multicore fiber (MCF) links consisting of concatenated MCF segments, where core dependent loss (CDL) in each segment varies randomly. Numerical simulation results show that the direct average ICXT power at the output of long-haul MCF links with random CDL is well described by a Gaussian distribution. A statistical distribution, which accounts for only two values of core loss (the highest and lowest core loss) with equal probability, is proposed as the worst-case distribution of core loss resulting in the maximum excess of direct average ICXT power. With this distribution, practical values of random CDL, 20 MCF segments per span and 2000 km-long links, analytical and simulation results show the maximum excess of direct average ICXT power does not exceed 0.25 dB, being further lower for a higher number of segments. An analytical approximation for the maximum excess of direct average ICXT power in long-haul uncoupled MCF links with similar spans is presented. Demonstrating high accuracy (with less than 0.02 dB discrepancy relative to simulation results in all cases evaluated), this approximation provides a simple and efficient means for estimating the worst-case impact of random CDL on ICXT power in long-haul MCF links.

Effect of initial grain size on microstructure, texture and magnetic properties of non-oriented electrical steel

The effect of initial grain size prior to cold rolling on the microstructure, texture evolution, and magnetic properties of Fe-3.5 wt% Si non-oriented electrical steel (NOES) was investigated through the introduction of normalization. There were massive intragranular shear bands in {111}<110> and {111}<112> deformed grains in the cold-rolled sheet with large initial grain size, providing nucleation sites for new recrystallized grains with Goss ({110}<001>), λ-fiber, γ-fiber, and {113}<631> components. Subsequent annealing resulted in weaker γ-fiber ({111}<110>−{111}<112>), stronger α*-fiber concentrated at {113}<631>, along with Goss and λ-fiber ({100}<001>−{100}<012>) textures. In addition, appropriate final annealing temperature effectively reduced iron loss. The simultaneous optimization of texture and grain size by normalization and annealing treatments led to improved magnetic properties, with the superior magnetic induction (B50 = 1.719) T, and the lowest core loss (P15/50 = 2.69 W/kg, P10/400 = 16.337 W/kg).

Fabrication of FeSiBPCNbCu nanocrystalline soft magnetic powders with high saturation magnetization and low core loss

Fabrication of FeSiBPCNbCu nanocrystalline soft magnetic powders with high saturation magnetization and low core loss

Data-driven composition design and property optimization of solid solution and precipitation simultaneously strengthened non-oriented silicon steel

Limitations on data volume and quality are key bottlenecks in using machine learning for property prediction and property-oriented composition design of non-oriented silicon steel. In response, this study employed a Gaussian Mixture Model (GMM) to generate virtual samples for enhancing the in-house experimental data, by which the generated virtual data well captured the distribution of the raw experimental data. As a result, compared with the model without data augmentation, the enhanced prediction model (composition → property) fitted by virtual samples improved its R2 value from 0.52 to 0.86. Based on this model, a multi-properties-oriented (yield strength σs, magnetic induction B50, and iron loss P10/400) composition prediction model (property → composition) was established to rapidly discover high-performance non-oriented silicon steel. Experimental characterization and theory calculation of the explored candidate alloys exhibited that their yield strength was above 750 MPa, which primarily results from solid solution strengthening (50 %) and precipitation strengthening (36 %). Moreover, the alloys possessed magnetic induction B50 of over 1.72 T and low core losses with P10/400 of 12.1 W/kg (0.2 mm) and 17.0 W/kg (0.35 mm). Further microstructural characterization exhibited that such satisfactory performance is associated with copper (Cu)-rich nanoprecipitates that dramatically improved the yield strength without deteriorating the magnetic properties.

High permeability Fe@SiO2@ Mn0.5Zn0.5Fe2O4 soft magnetic composite (SMC) materials which formed via high temperature in-situ reaction

The permeability of the Fe Soft Magnetic Composite (SMC) materials need further improve to broaden their application prospect. This research work presents a novel high permeability SMC material which has a low core loss (Pcv). The Fe particles formed an elongated strip shape structure through the ball milling process, and the high permeability Mn0.5Zn0.5Fe2O4 ferrite phase was formed around the elongated strip shape Fe particles via a high temperature in-situ reaction process (ZnO + MnO + Fe2O3–Mn0.5Zn0.5Fe2O4). While the added high resistive SiO2 phase aggregated at the long strip shape Fe particle outer surface and effectively increased the resistivity of the SMCs. As the percentage of the Mn0.5Zn0.5Fe2O4 ferrite coating increase, the permeability of the double layer coated SMCs gradually increased from 38 for the 1 wt% Mn0.5Zn0.5Fe2O4 coated SMCs to 170 for the 18 wt% Mn0.5Zn0.5Fe2O4 coated SMCs. The 3 wt% Mn0.5Zn0.5Fe2O4 coated SMCs has the lowest core loss (Pcv) of 86.9 W/kg at 10 mT, 500 kHz.

Low core loss and high DC bias performance of FeSiAl soft magnetic composites cores with hybrid insulating layers of MgO/SiO2

Soft magnetic composites (SMCs) play an indispensable role in electromagnetic conversion, transmission, and storage. However, in order to achieve miniaturization, energy conservation, and meet the application requirements of premagnetisation in direct-current (DC) components, SMCs are required to have low core loss and high DC bias performance. In this work, FeSiAl SMCs with hybrid insulating layers of MgO/SiO2 have been successfully prepared by the decomposition of magnesium acetate tetrahydrate and silicone resin. The presence of MgO and SiO2 insulating layers can effectively compensate for each other's coating defects, thereby forming complete insulating layers on the surface of FeSiAl powders to reduce the core loss. Finally, the FeSiAl@MgO/SiO2 SMC gets remarkable comprehensive magnetic properties with a low core loss (Pcv) of 163.7 mW/cm3 at 50 mT/100 kHz, a high DC bias performance of 53.7 % at 100 Oe, and an effective permeability (μe) of 46, which is promising for high-frequency and high-power applications.

Optimizing FeSiCr-Based Soft Magnetic Composites Using the Deionized Water as the Phosphating Solvent.

To prepare a soft magnetic powder core, the magnetic powder surface has to be insulated by phosphating treatment. Organic chemicals such as ethanol and acetone are generally used as solvents for phosphoric acid, which may cause serious environmental problems. This work proposed deionized water as the environmentally friendly phosphating solvent for FeSiCr powder. The soft magnetic composites (SMCs) were prepared using phosphoric acid for inorganic coating and modified silicon polymer for organic coating. The effect of different phosphating solvents, including deionized water, ethanol, and acetone, on the structure and magnetic properties of SMCs were investigated. It is found that the solvent affects the phosphating solution's stability and the phosphoric acid's ionization. The phosphoric acid is more stable in deionized water than in ethanol and acetone. The phosphating reaction in deionized water is also more stable in deionized water, resulting in a dense phosphate coating on the particle surface. The effects of phosphoric acid concentration and temperature on the magnetic properties of FeSiCr-based SMCs were further studied. With the increase in phosphoric acid concentration and temperature, the magnetic permeability and saturation magnetization of the powder core decrease, and the core loss decreases, followed by an increase. The optimized combination of properties was obtained for the SMCs phosphated with 0.2 wt.% phosphoric acid in deionized water at 35 °C, including a high effective permeability μe of 25.7, high quality factor Q of 80.2, low core loss Pcv of 709.5 mW/cm3 measured at 0.05 T @ 100 kHz, and high withstanding voltage of 276 V, due to the formation of uniform and dense insulating coating layers. In addition, the SMCs prepared with phosphated powder show good corrosion resistance. The anti-corrosion properties of the SMCs using deionized water as a phosphating solvent are better than those using ethanol and acetone.

The Balance Between Low Core Loss, High Permeability, and Large DC Bias Performance in FeSiAl Cores Covered by Polydopamine/Polyethyleneimine

The Balance Between Low Core Loss, High Permeability, and Large DC Bias Performance in FeSiAl Cores Covered by Polydopamine/Polyethyleneimine

Critical state-induced emergence of superior magnetic performances in an iron-based amorphous soft magnetic composite

Soft magnetic composites (SMCs) play a pivotal role in the development of high-frequency, miniaturization and complex forming of modern electronics. However, they usually suffer from a trade-off between high magnetization and good magnetic softness (high permeability and low core loss). In this work, utilizing the order modulation strategy, a critical state in a FeSiBCCr amorphous soft magnetic composite (ASMC), consisting of massive crystal-like orders (CLOs, ∼1 nm in size) with the feature of α-Fe, is designed. This critical-state structure endows the amorphous powder with the enhanced ferromagnetic exchange interactions and the optimized magnetic domains with uniform orientation and fewer micro-vortex dots. Superior comprehensive soft magnetic properties at high frequency emerge in the ASMC, such as a high saturation magnetization (M s) of 170 emu g−1 and effective permeability (μ e) of 65 combined with a core loss (P cv) as low as 70 mW cm−3 (0.01 T, 1 MHz). This study provides a new strategy for the development of high-frequency ASMCs, possessing suitable comprehensive soft magnetic performance to match the requirements of the modern magnetic devices used in the third-generation semiconductors and new energy fields.

Development of FeCoMnAl multi-principal element alloys and soft magnetic powder cores with excellent magnetic properties and high temperature magnetic stability

In order to develop a multi-principal element alloy with outstanding soft magnetic properties and high thermal stability, a Fe35Co35Mn30−xAlx (x = 9, 12, 15, 18, 21, 24) alloy system was designed. The findings demonstrated that the optimal Al/Mn content ratio contributes to the formation of a BCC and B2 dual-phase structure, which leads to a significant increase in the saturation magnetic flux density (Bs) and a considerable decrease in the coercivity of the alloy. The as-cast Fe35Co35Mn15Al15 alloy with a co-lattice structure exhibits exceptional soft magnetic properties, with a resistivity of 324 μΩ·cm, a Bs of 1.46 T and a Hc of 167.2 A/m. Corresponding soft magnetic powder cores (SMPCs) were fabricated and the impact of heat treatment temperature on the properties of the SMPCs was examined. The SMPCs after annealing at 660 °C exhibits high stable permeability (μe) of 48 up to 10 MHz, a low core loss (Pcv) of 1208 mW/cm3 (at 1 MHz, 20 mT), and excellent direct current bias performance. In addition, these SMPCs possess excellent high temperature magnetic stability, and the variation of both μe and Pcv at a high frequency (1 MHz) is less than 2 % over a wide temperature range of 25–150 °C.

Fe-based amorphous powder cores with low core loss and improvement of permeability

Fe-based amorphous powder cores of Fe–Si–B–Cr–C magnetic powder and phenolic binder were fabricated, and the effects of annealing and compaction pressure on the soft magnetic properties and core loss were investigated. The formation of Fe–B and α-Fe (Si) phases was confirmed at the annealing temperature above 773 K. The density gradually increased from 5.3 to 5.5 g/cm3 as annealing temperature increased, resulting in the saturation magnetization 4πMs increased to 1.0 T at 773 K. The effect of compaction pressure was studied by using samples annealed at 723 K. Both the density and 4πMs enhanced with compaction pressure from 980 to 1960 MPa. The real part of permeability µ’ remained constant for the frequency up to 2 MHz. The initial value of µ’ increased from 25 to 38 with compaction pressure. Consequently, at Bm of 50 mT and frequency of 100 kHz, the considerably low core loss of 67 kW/m3 was obtained. The low core loss and moderately high permeability of Fe–Si–B–Cr–C amorphous powder core across a wide frequency range indicate its potential for application in high frequency electronic components.

Size effect configuration modeling for the high-performance hybrid Fe-Si directional alloyed soft magnetic material (DASMM)

This work presents a novel hybrid gas/water atomized Fe-Si directional alloyed soft magnetic materials (DASMM), they have a combination of low core loss (Pcv), constant permeability (μ) and high compatibility. The particle size has a big influence upon the Fe-Si DASMP magnetic properties, the study result revealed that the coarse powder DASMM merely have a steady permeability of 60 in the frequency range between 10 and 100 kHz; while the fine particle (≥200 meshes) DASMM could maintain its constant permeability of 40 in the whole range between 10 and 500 kHz. The Pcv of Fe-Si DASMM rapidly decreased as the consisting powder particle size decrease, dramatically decreased from 277.36 W/kg for the 100 mesh to 62.00 W/kg for the 300 mesh Fe-Si DASMM. While the resistivity (Rs) sharply increased, it increased 9 times from 5.93 mΩ·cm for the 100 mesh to 54.33 mΩ·cm for the 300 mesh Fe-Si DASMM.

Design and analysis of a hybrid permanent magnet variable leakage flux motor for low core loss and wide speed range

In this paper, a new hybrid permanent magnet variable leakage flux (VLF-HPM) motor is proposed. In order to enhance motor speed range, short arc-shaped and elliptical-shaped magnetic barriers are placed on the q-axis magnet circuit, realizing the so-called leakage flux effect. In addition, ferrite PMs are artfully designed, so self-leakage flux can be reduced while main flux is enhanced. The relationship among PM topology, flux barrier and flux-regulation capability are also investigated in detail. Finally, the electromagnetic performance of VLF-HPM motor is evaluated by the finite element analysis and compared with a conventional V-typed PM motor. It is noted that, compared with conventional V-typed PM motor, the VLF-HPM motor possesses lower core losses and a wider speed range, which offers a new research path for high-performance PM motor.

Fe/amorphous-Al2SiO5 composites fabricated by low-temperature solid-phase reaction densification achieve synergistically enhanced structural and soft magnetic properties

To date, an urgent problem for various metal-based soft magnetic composites (SMCs) is that it is difficult to simultaneously achieve high strength and optimum magnetic performance, which actually restricts their large-scale applications in many electromagnetic fields. In this work, we have tried to resolve this basic problem by proposing a new concept of low-temperature solid-phase reaction densification instead of conventional particle-deformation densification to fabricate high-performance metal-based SMCs. Specifically, fully-densified nanoscale amorphous Al2SiO5 coating layers are formed through a solid phase reaction at 500 °C between initially-prepared nano-sized amorphous SiO2 and amorphous Al2O3, and meanwhile coated in situ on the surface of deformed Fe to fabricate novelly-structured Fe/amorphous-Al2SiO5 SMCs. The low-temperature solid-phase reaction for fabrication of Fe/amorphous-Al2SiO5 SMCs can avoid negative effects of high processing temperature for conventional metal-based SMCs on their structure and magnetism resulting in their high strength, increased resistivity, low core loss and high saturation magnetic inductions. Thus, Fe/amorphous-Al2SiO5 SMCs show synergistically enhanced structural and soft magnetic properties, which exceed those of most conventional metal-based SMCs. This work also provides a special and useful insight into the design and applications of metal-based composites needing both functional and structural properties.