Low Total Core Loss Research Articles

Formation mechanism and magnetic performance of Fe-Si soft magnetic composites coated with MnO-SiO2 composite coatings

Fe-Si soft magnetic composites (SMCs) coated with MnO-SiO2 composite coatings were fabricated via sintering the ball milled Fe-Si/MnO2 composite powders. The transformation mechanism from MnO2 coating to MnO-SiO2 composite coatings was studied. The effect of MnO2 content on the microstructure and magnetic properties of Fe-Si soft magnetic composites has also been investigated systematically. The analysis results indicated that MnO2 would be reduced to MnO by Si in the Fe-Si particles at 780.1 ℃. When the temperature reached 985.8 ℃, the generated MnO and SiO2 would further combine to form 2MnO·SiO2, finally forming the MnO-SiO2 composite coatings. With the increase of the MnO2 content from 0.0 wt% to 10.0 wt%, the MnO-SiO2 composite coatings became thicker, thus the saturation magnetization and permeability decreased gradually. However, exorbitant MnO2 content above 5.0 wt% would result in excessive in-situ Fe existed in the composite coatings and obvious reduction of Si content in the Fe-Si particles due to the above solid-state reactions. Therefore, the increasing trend of the resistivity was weakened. And the 5.0 wt% MnO2 coated Fe-Si SMCs exhibited superior comprehensive performance such as high saturation magnetization (186.5 A·m2/kg), good permeability (71), low total core loss (362.6 mW/cm3 at 50 kHz).

Insulation layer design for soft magnetic composites by synthetically comparing their magnetic properties and coating process parameters

The soft magnetic performances of the Fe-6.5 wt.%Si (FeSi) soft magnetic composites (SMCs) insulated with different materials, including organic, inorganic, and soft magnetic materials with high resistivity, and composite coating of inorganic-magnetic layer, under the same fabrication condition have been compared and analyzed by synchronously considering their coating preparation parameters. The core–shell structure of the coated powder was characterized by using a combination of SEM-EDS, FTIR, and XRD. Loss separation fitting model was established to evaluate the source of each part loss for the corresponding FeSi SMCs above. Due to the fact that the SMCs insulated with inorganic or/and magnetic ferrite materials exhibit high bulk resistivity more than 1.4 Ω·m, their eddy current losses account for lower contribution of only 20.2 ~ 22.1% of total core loss compared with that of 61.9% for the SMCs coated alone with organic resin. As compared to the other insulation materials, the SMCs coated using inorganic material (SiO2 or TiO2) exhibit a better DC-bias over 75.5%, higher retain real-part permeability exceed 44.6 at an applied field of 7960 A/m, a relatively low total core loss of 1040.6 kW/m3 at 100 kHz, 0.1 T, and can be fabricated at room temperature with a total preparation time of 70 min, which is favorable for being widely used in industry. The results of this work offered a referable ideal to design insulating layer for other SMCs.

Microstructure and magnetic properties of MnO2 coated iron soft magnetic composites prepared by ball milling

In this paper, Fe soft magnetic composites (SMCs) coated with MnO2 were prepared successfully by ball milling and following spark plasma sintering. The effect of MnO2 content on microstructure and magnetic properties for the Fe/MnO2 SMCs was investigated in detail. The analysis results show that a uniform MnO2 coating layer can be formed on the surface of the Fe particles via low speed ball milling with agate balls. When the MnO2 content increases from 0.0 wt% to 10.0 wt%, the thickness of the MnO2 coating layer exhibits a growth trend. As a consequence, the increased nonmagnetic phase leads to the magnetic dilution, finally resulting in the reduced saturation magnetization and deteriorated coercivity. Moreover, the enhanced resistivity induced by the increased thickness, significantly reduces the generation of the inter-particle eddy current, which leads to more stable permeability and lower total core loss at high frequencies. This study provides a novel insulating coating layer to reduce total core loss and is advantageous for the development of iron-based SMCs.

Prepared novel Fe soft magnetic composites coated with ZnO by Zn(CH3COO)2 pyrolysis

In this work, Fe/ZnO soft magnetic composite (SMC) is prepared successfully by sol-gel method combined with a pyrolysis process. Formation mechanism and effect of annealing on magnetic properties for the Fe/ZnO SMCs are studied in detail. The results show that Fe/zinc acetate hydrogel mixture will be decomposed into the Fe/ZnO composites by heating above 340 °C. And ZnO is well coated on the surfaces of Fe particles. The Fe/ZnO composite compact has lower total core loss and better frequency stability of magnetic permeability compared with pure Fe compact. In addition, annealing treatment shows an enhanced effect on the magnetic properties for the Fe/ZnO composite compact such as reduced coercivity and increased permeability. The annealed Fe/ZnO SMCs can keep stable magnetic permeability (26) from 50 Hz to 10 kHz, high magnetic induction (1.65 T) and a relatively low core loss of 91.11 kW/m3 measured under a magnetic flux density of 30 mT at 10 kHz. Therefore, the Fe/ZnO soft magnetic composites prepared by the above-mentioned method provide a great potential application in electromagnetic conversion equipment.

Hybrid Phosphate-Alumina Iron-Based Core-Shell Soft Magnetic Composites Fabricated by Sol-Gel Method and Ball Milling Method

Novel Fe-based soft magnetic composites (SMCs) with hybrid phosphate-alumina layers were prepared by both sol–gel and ball-milling methods. The effects of the fabrication methods and the addition of Al2O3 particles on the microstructure and the soft magnetic performance of SMCs were studied. The formation of the hybrid phosphate-Al2O3 shell not only leads to the decrease of the total core loss, but also results in the reduction of the permeability and saturation magnetization. However, the degree of decrease caused by the different methods were not identical. The sample with 8% Al2O3 prepared by the sol–gel method showed the best magnetic performance, exhibiting a high-amplitude permeability (μa) of 85.14 and a low total core loss (Ps) of 202.3 W/kg at 50 mT and 100 kHz. The hysteresis loss factor and the eddy current loss factor were obtained by loss separation. The results showed that the samples with the same Al2O3 content prepared by different methods exhibited almost the same total core loss. However, the contribution of the hysteresis loss and the eddy current loss showed an obvious difference in behavior because of the change of the particle shapes and the refinement of the particle size during the ball-milling process.

Effects of compaction and heat treatment on the soft magnetic properties of iron-based soft magnetic composites

Iron-based soft magnetic composites (SMCs) are promising substitutes for laminate steels in electromagnetic applications due to their excellent magnetic properties and productivity. However, the preparation process is a key factor in deciding the magnetic performance of SMCs. In this work, the Fe-based soft magnetic composites with improved soft magnetic properties were achieved by optimizing the compaction and the annealing process. Results showed that the core–shell structure of powders which would directly have an impact on the permeability and the core loss of the SMCs could be affected by the compaction and the annealing process. In addition, the magnetic properties were enhanced by tuning the microstructure. As a result, the optimal magnetic performance of the compact with high permeability and low total core loss was obtained. The real part of the permeability of the soft magnetic composites could reach a maximal value of 336.8 and a rather low core loss of 2.5 W Kg−1 (measured at 50 mT and 5 kHz). Therefore, soft magnetic composites with enhanced magnetic properties were obtained by optimizing the powder metallurgy (PM) process in this study.

Influence of iron powder core on the switched reluctance motor performance enhancement

Soft Magnetic Composite (SMC) materials possess isotropic magnetic and thermal properties, very low eddy current loss and relatively low total core loss at medium and higher frequencies. This paper presents the application potential of iron powder SMC in switched reluctance machine (SRM) and its performance enhancement. The results of extensive finite element simulation and experimental validation of the proposed fabricated prototype are delineated. The study concludes that the use of SMC as magnetic core of a switched reluctance motor enhances its thermal and vibration characteristics in comparison with the conventional lamination counterpart.

Enhancements of preparation efficiency and magnetic properties for Fe-based amorphous magnetic flake powder cores upon the adoption of a novel double-paralleled slits nozzle

The thick and brittle amorphous ribbons with the maximum thickness up to 58 μm were successfully fabricated using melt-spinning method upon the adoption of a novel double-paralleled slits nozzle (DPSN). The magnetic properties of the two magnetic flake powder cores (MFPCs) prepared from the conventional thin ribbon pulverization and the thick ribbon pulverization were analyzed and compared. Hereinto, a coupling model of fluid flow with free surface and surface tension, and heat transfer with phase transform was developed to design the slit spacing for the DPSN, and sol-gel method was employed to create SiO2 insulation layer on the surfaces of the magnetic flake powders to improve electrical resistivity. Results show that a quasi-steady-state can be reached for the puddle with the upstream and downstream menisci in crescent and slope shapes, respectively, by adopting the DPSN with slit spaces of 2.0 mm and 2.5 mm. The embrittlement process for the conventional thin ribbon can be omitted to enhance the efficiency of the powder preparation when using the thick ribbon before the ribbon pulverization. The MFPCs fabricated using the thick amorphous ribbon pulverization exhibit a higher permeability of 65.27, lower total core loss with the frequency being less than 234 kHz for Bm = 0.08 T, and a better DC-bias property of 70.97% as compared to the MFPCs made from the conventional thin amorphous ribbon pulverization. This work provides a promising approach to further development of Fe-based amorphous MFPCs with high preparation efficiency and excellent magnetic properties at the frequency below 234 kHz.

Effects of annealing on the magnetic properties of Fe-based amorphous powder cores with inorganic-organic hybrid insulating layer

In order to improve the magnetic properties of soft magnetic composites (SMCs), the Fe-based amorphous powder cores (AMPCs) based on spherical FeSiBCCr amorphous magnetic powders coated with inorganic-organic (TiO2-epoxy resin) hybrid insulating layer were prepared. The influence of annealing temperature on the soft magnetic properties of the AMPCs has been systematically researched in this work. It was found that the reasonable annealing temperature could increase the permeability and decrease the core loss of the AMPCs. The AMPCs annealed at 480 °C showed a constant permeability of 81.5 up to 10 MHz, and low total core loss of 275 mW/cm3. This study demonstrated that the present Fe-based AMPCs with inorganic-organic hybrid insulating layer have a great promising future in the field of medium and high frequency for the various electronic components.

Controllable SiO2 insulating layer and magnetic properties for intergranular insulating Fe-6.5wt.%Si/SiO2 composites

In this study, the intergranular insulating Fe-6.5wt.%Si/SiO2 soft magnetic composites (SMCs) were prepared successfully using in-situ chemical deposition followed by the spark plasma sintering (SPS) process. The effects of ammonia concentration on the microstructure and magnetic properties of the composites have been studied systematically. The Fe-6.5wt.%Si alloy particles could be well insulated by the uniform SiO2 insulating layer, and its thickness increases with increasing the ammonia concentration from 0 to 0.02 ml/g. However, further increasing the ammonia concentration to 0.03 and 0.04 ml/g would result in the discontinuous and uneven SiO2 insulating layer. Correspondingly, the saturation magnetization and effective permeability of the composite compacts first decrease and then increase with increasing the ammonia concentration from 0.00 to 0.04 ml/g, whereas the coercivity and resistivity vary in the opposite tendency. Note that the overall performances such as the frequency stability of effective permeability, higher resistivity and lower total core loss, reach the optimal value for the sample with the ammonia concentration of 0.02 ml/g.

In-situ formation of Fe3O4 and ZrO2 coated Fe-based soft magnetic composites by hydrothermal method

In this paper, the soft magnetic composite was prepared using a powder metallurgy method with the Fe3O4 and ZrO2 co-coated iron powder which was synthesized though the in-situ hydrothermal method. Energy dispersive spectroscopy (EDS) coupled with X-ray photoelectron spectroscopy (XPS) revealed that the Fe3O4 and ZrO2 were uniformly coated on the surface of iron powders. The addition of ZrO2 in the coating effectively improves the properties of the soft magnetic composite. ZrO2 can further improve the insulating properties, and enhance the thermostability of the coating simultaneously which will lead to resistivity increase and eddy current loss decrease. By controlling the additive amount of zirconium cation and annealing temperature, high magnetic induction of 1.002 T (measured at 8000 A/m), relatively high permeability of 83 (measured at 100 kHz), and low total core loss of 255.2 W/kg (measured at 100 kHz and 50 mT) were achieved. The Fe@ZrO2&Fe3O4 SMCs show high electrical resistivity and saturation induction, which may be widely used in high speed electric motor, transformer, inductance and switching power supply.

Structure and magnetic properties of iron-based soft magnetic composite with Ni-Cu-Zn ferrite–silicone insulation coating

This paper investigates the structure and magnetic properties of Ni-Cu-Zn ferrite-silicone coated iron-based soft magnetic composites (SMCs). Scanning electron microscopy coupled with a energy-dispersive spectroscopy (EDS) analysis revealed that the Ni-Cu-Zn ferrite and silicone resin were uniformly coated on the surface of iron powders. By controlling the composition of the coating layer, low total core loss of 97.7 mW/cm3 (eddy current loss of 48 mW/cm3, hysteresis loss of 49.7 mW/cm3, measured at 100 kHz and 0.02 T) and relatively high effective permeability of 72.5 (measured at 100 kHz) were achieved. In addition, the as-prepared SMCs displayed higher electrical resistivity, good magnetic characteristics over a wide range of frequencies (20–200 kHz) and ideal the D-C bias properties (more than 75% at H = 50 Oe). Furthermore, higher elastic modulus and hardness of SMCs, which means that the coating layer has good mechanical properties and is not easily damaged during the pressing process, were obtained in this paper. The results of this work indicate that the Ni-Cu-Zn ferrite-silicone coated SMCs have desirable properties which would make them suitable for application in the fields of the electric-magnetic switching devices, such as inductance coils, transformer cores, synchronous electric motors and resonant inductors.

Core loss analysis of Finemet type nanocrystalline alloy ribbon with different thickness

Nanocrystalline soft magnetic materials are widely used in power electronic applications due to their high permeability, magnetization and low core loss. In this paper, Fe73.5Cu1Nb3Si15.5B7 (at%) nanocrystalline alloy ribbons, with ultra-thin thickness of 14µm, and also 18 and 22µm, were prepared by a planar flow casting method with a single roller device. Soft magnetic properties of these ribbons were analyzed after nanocrystallization annealing. The experiments were conducted on toroidal samples using IWATSU B-H Analyzer over a frequency range of 10–100kHz, at induction amplitudes of 100–500mT, at room temperature. It was found that the excess eddy current loss Pex was the dominant factor in the overall core loss above 10kHz. The toroidal samples made of the 14µm thickness ribbon exhibit very low total core loss of 48W/kg at a frequency of 100kHz and magnetic flux density of 300 mT. The ratio of the Pex was up to 89% at 100kHz. The ribbon with lower thickness exhibits lower Pex and therefore lower total core loss. The domain structure evidences were found. It indicates that the ribbons with small thickness are preferable for application in high frequency condition.

Interplay of crystallization, stress relaxation and magnetic properties for FeCuNbSiB soft magnetic composites

Fe73.5Cu1Nb3Si15.5B7 amorphous alloy was fabricated into nanocrystalline soft magnetic composites (SMCs). Crystallization process and the evolution of stress relaxation of the SMCs during annealing have been investigated and their effects on the magnetic properties are revealed. Crystallization of the amorphous alloy is accomplished by increment of nucleation sites with the annealing temperature ranged from 500 °C to 600 °C. Stress induced by milling and compaction relieves with increased annealing temperature and complete relaxation can be achieved at around 575 °C. Coupling of small grains (9.1 nm–12.8 nm) and stress relaxation ensures the FeCuNbSiB SMCs of relatively low coercivity, high permeability and low loss. Further raised annealing temperature above 600 °C leads to dominating growth and coalescence of the existing α-Fe(Si) grains and the precipitation of the Fe23B6 phase, which deteriorates the magnetic properties. Optimized soft magnetic properties of the SMCs such as small coercivity (4.5 Oe), large effective permeability (115) and low total core loss (200 mW/cm3 measured when Bm = 0.1 T and f = 50 kHz) can be achieved by post-annealing at 575 °C.

Magnetic Properties of Soft Magnetic FeSi Composite Powder Cores

Soft magnetic composites (SMCs), which are used in electromagnetic applications, can be described as ferromagnetic powder particles surrounded by an electrical insulating lm. These composite materials o er several advantages over traditional laminated steel cores such as reduction in weight and size. They have some unique properties, including three-dimensional isotropic ferromagnetic behaviour, very low eddy current loss, relatively low total core loss at medium and high frequencies, high electrical resistivity and good relative magnetic permeability. FeSi powder was used as a base ferromagnetic material for preparation of soft magnetic composites. The commercial FeSi particles of a precise spherical shape were prepared in two granulometric fractions (up to 150 μm or up to 356 μm). The phenol-formaldehyde resin modi ed by SiO2 nanoparticles was used as an electroinsulating layer. The FeSi particles covered by the synthesized resin were compacted at 800 MPa into the ring samples for magnetic measurements. The nal samples were treated thermally under the curing schedule, which was suggested according to thermal degradation of the modi ed resin.

Soft magnetic composite materials (SMCs)

Abstract Soft magnetic composites (SMCs), which are used in electromagnetic applications, can be described as ferromagnetic powder particles surrounded by an electrical insulating film. SMC components are normally manufactured by conventional PM compaction combined with new techniques, such as two step compaction, warm compaction, multi-step and magnetic annealing followed by a heat treatment at relatively low temperature. These composite materials offer several advantages over traditional laminated steel cores in most applications. The unique properties include three-dimensional (3D) isotropic ferromagnetic behavior, very low eddy current loss, relatively low total core loss at medium and high frequencies, possibilities for improved thermal characteristics, flexible machine design and assembly and a prospect for greatly reduced weight and production costs. With expanded applications of soft magnetic composite materials expected in the future, a review of the magnetic properties, characteristics, processing and applications of SMCs is presented in this article.

Applications of soft magnetic composite materials in electrical machines

Soft magnetic composite (SMC) materials and their uses in electrical machines have undergone significant development in the past decade. The major advantages of the materials include isotropic magnetic and thermal properties, very low eddy current loss and relatively low total core loss at medium and higher frequencies, and low cost fabrication with good tolerance and surface finish using the well developed powder metallurgical techniques that require no further machining. It is even anticipated that the application of SMC may lead to a revolutionary development in the electrical machine manufacturing industry. This paper reviews the application of SMC in electrical machines. Both successful experiences and existing difficulties are discussed, and possible further work required for the commercial success of SMC machines is proposed.