Ferrite Magnets Research Articles

Study on Performance Improvement through Reducing Axial Force of Ferrite Double-Layer Spoke-Type Permanent Magnet Synchronous Motor with Core Skew

Recently, due to the price fluctuation and supply instability of rare earth mineral resources, there has been a lot of development of electric motors using non-rare-earth permanent magnets. As a result, motors using Dy-free permanent magnets and ferrite permanent magnets are being researched, and, in particular, ferrite permanent magnets often utilize spoke-type structures, which are magnetic flux concentrators, to compensate for their low coercivity and residual flux density. However, in general, spoke-type PMSMs do not use much reluctance torque, so double-layer spoke-type PMSMs have been studied for their more efficient design. Unlike general spoke-type PMSMs, double-layer spoke-type PMSMs can utilize high reluctance torque by increasing the difference between d-axis and q-axis reluctance. However, as the difference in magnetic resistance increases, vibration and noise are generated, which adversely affects the mechanical part and shortens the life of the motor. Although this problem seemed to be solved by applying core skew in the previous study, it was confirmed that the axial force caused by the axial leakage flux occurred in the maximum torque per ampere (MTPA) control section and the torque ripple was increased. Therefore, in this paper, a model that can apply symmetrical core skew and reduce axial force is proposed. First, the causes of the axial force generated in previous studies were analyzed. Based on the analysis of these causes, a new symmetrical core skew structure was proposed, and its justification was verified through FEA.

Investigation into the Influencing Factors of the Center Magnetic Force of Anisotropic Permanent Ferrite Magnets in Motor Stator Application

Investigation into the Influencing Factors of the Center Magnetic Force of Anisotropic Permanent Ferrite Magnets in Motor Stator Application

Comparative Analysis and Design Optimization of Ferrite-Based Surface PM Vernier Machines

This paper presents the results of a comprehensive investigation into the comparative analysis and design optimization of ferrite-based surface permanent magnet vernier machines (SPMVMs). While SPMVMs boast a simple mechanical structure and enhanced torque density attributed to the flux modulation effect, they suffer from a persistent challenge of low power factor. Several factors hinder the adoption of low-cost ferrite magnets in SPMVMs. First, ferrite magnets are prone to irreversible demagnetization, constraining the allowable range of magnet thickness. Second, the reduced residual magnetic flux density of ferrite magnets exacerbates the decrease in power factor and machine efficiency. Thus, achieving optimal performance in ferrite-based SPMVMs necessitates the careful selection of various design parameters. To address these issues, this study employs a surrogate-based metaheuristic optimization algorithm with adaptive sampling to identify the optimal solution. Additionally, the integration of a Halbach array is explored to further enhance the performance of the three-slot/two-pole SPMVM topology. Subsequently, two ferrite-based SPMVM baseline models—one with a conventional SPM structure and another with a Halbach magnet array—are thoroughly designed, optimized, and subjected to detailed performance analysis using the 2D finite element method.

Effect of Bismuth Oxide on the Structure, Electrical Resistance, and Magnetization of Lithium Zinc Ferrite

Effect of Bismuth Oxide on the Structure, Electrical Resistance, and Magnetization of Lithium Zinc Ferrite

Site-selective cobalt substitution in La–Co co-substituted magnetoplumbite-type ferrites: 59Co-NMR and DFT calculation study

The La–Co co-substituted magnetoplumbite-type (M-type) ferrites AFe12O19 (A = Ca, Sr and Ba, ion sizes Ca2+ < Sr2+ < Ba2+) with Co compositions around 0.2 have been subjected to 59Co-NMR. The results show that Co occupies the 4f1, 2a and 12k sites, and that the smaller the A ion, the more Co tends to occupy the 4f1 minority spin site, which is effective in enhancing both uniaxial anisotropy and magnetisation. First-principles total energy calculations based on density functional theory (DFT) of undoped AFe12O19 and a supercell ( 2×2×1 of the unit cell) in which 1/96 of Fe3+ is replaced by Co2+ were performed to predict the stable structure and Co occupancy sites. The results show that regardless of A, Co is most stable when it occupies the 4f1 site, followed by the 2a and 12k sites with energy differences on the order of 100 meV, and Co practically does not occupy the 2b and 4f2 sites. As the A ion becomes smaller, the energy difference when Co occupies each Fe site tends to increase, and the Co occupancy of the 4f1 site also increases. The site selectivity of Co can be roughly explained as a result of the difference in uniaxial strain along the c-axis associated with the difference in A. However, the influence of the A ion differs between the R and S blocks and the local strain also has a secondary effect on the Co distribution. Based on these results, the guidelines for improving the performance (anisotropy and magnetisation) of La–Co co-substituted M-type ferrite magnets with a limited amount of Co can be summarised as follows: It is effective to select as small A ions as possible and to post-anneal at low temperature or cool slowly to concentrate Co at the 4f1 site in tetrahedral coordination.

Surface magnetic flux density optimization considering effect of aligned magnetic field molding conditions of ring-shaped multi-pole anisotropic ferrite permanent magnet for DC motors

The ring-shaped anisotropic ferrite magnet with multiple poles boasts significant benefits for brushless DC motors (BDCMs). However, the prevalent production method involves dry magnetic field molding, making it challenging to enhance the magnetic properties. Herein, ferrite powder made from iron oxide, a by-product of the steel industry, is used as the starting material of magnets, and the differences between dry and wet molding approaches on the surface magnetic flux density of a ring-shaped multi-pole anisotropic ferrite magnet are first investigated. ANSYS MAXWELL conducted an initial simulation to achieve the design specifications of the wet molding mold. Following this, the mold was prepared for the fabrication of ring magnets. Compared to magnets prepared via dry molding, those produced through wet molding exhibit a peak surface magnetic flux density of approximately 15.9% higher, demonstrating significant potential for industrial applications and substantial enhancement of the key magnetic properties of wet molded ferrite ring magnets. To achieve increased surface flux density of ring magnets, it is common practice to utilize magnetic powders with greater magnetic properties when molding the magnets. However, this requires a costly mold redesign. In this study, higher surface magnetic flux densities can be achieved for ring magnets by simply adjusting the shape, size and magnetization direction of NdFeB permanent magnets that provide a constant aligned magnetic field in the mold without requiring any alterations to the existing mold's dimensions. The findings of this study could improve the effectiveness of existing motor designs. The usage of ring-shaped multi-pole anisotropic ferrite magnets is anticipated to witness a surge in the coming years, driven by the growth of energy-efficient motors in diverse sectors.

SAB-YOLOv5: An Improved YOLOv5 Model for Permanent Magnetic Ferrite Magnet Rotor Detection

Surface defects on the permanent magnetic ferrite magnet rotor are the primary cause for the decline in performance and safety hazards in permanent magnet motors. Machine-vision methods offer the possibility to identify defects automatically. In response to the challenges in the permanent magnetic ferrite magnet rotor, this study proposes an improved You Only Look Once (YOLO) algorithm named SAB-YOLOv5. Utilizing a line-scan camera, images capturing the complete surface of a general object are obtained, and a dataset containing surface defects is constructed. Simultaneously, an improved YOLOv5-based surface defect algorithm is introduced. Firstly, the algorithm enhances the capability to extract features at different scales by incorporating the Atrous Spatial Pyramid Pooling (ASPP) structure. Then, the fusion of features is improved by combining the tensor concatenation operation of the feature-melting network with the Bidirectional Feature Pyramid Network (BiFPN) structure. Finally, the introduction of the spatial pyramid dilated (SPD) convolutional structure into the backbone network and output end enhances the detection performance for minute defects on the target surface. In the study, the SAB-YOlOv5 algorithm shows an obvious increase from 84.2% to 98.3% in the mean average precision (mAP) compared to that of the original YOLOv5 algorithm. The results demonstrate that the data acquisition method and detection algorithm designed in this paper effectively enhance the efficiency of defect detection permanent magnetic ferrite magnet rotors.

Investigation and formulation of cobalt content of ultra-thin diamond blades and dicing performance manufactured by fused deposition modeling and sintering (FDMS)

Achieving appropriate cobalt concentration within the matrix when fabricating ultra-thin diamond blades with fused deposition modeling and sintering (FDMS) leads to improved machining performance. This study investigates the effects of cobalt content on mechanical properties such as hardness, relative density, and holding strength of ultra-thin diamond blades by FDMS. It also examines the fragmentation characteristics, chipping size, and surface quality of diced surfaces with these ultra-thin diamond blades. The experimental findings show that increasing the cobalt content of the matrix enhances its mechanical properties and reinforces the bond between the matrix and diamond particles, thereby improving the flatness, sharpness, and overall quality of the blades. Additionally, it has been observed that ultra-thin diamond blades containing less cobalt are more effective at processing ferrite magnets, whereas those containing more cobalt perform better at machining alumina ceramics. The cobalt content of ultra-thin diamond blades has an additional impact on the surface quality and surface topology of diced surfaces in various materials. This results in microstructured surfaces with the lowest surface roughness values of 0.282 μm and 0.367 μm for alumina ceramics and ferrite magnets, respectively. In conclusion, understanding the effects of cobalt content within the matrix of diamond thin blades could assist in the availability of good formulas in FDMS, improving blade quality and dicing performance, and ultimately advancing FDMS's capability to produce high-quality diamond cutting tools for a wide range of applications.

Broadband, thin thickness and low filling ratio microwave absorption by constructing Sm2Fe17/Fe(Sm) hard/soft magnetic nanoparticles in Sm2O3-doped porous carbon matrix

Exchange-coupled hard/soft magnetic composites are supposed to be promising microwave absorber, due to the multiple-resonance peaks in permeability. However, due to insufficient magnetization and dielectric loss, soft/hard ferrite magnets are difficult to achieve further breakthroughs in microwave absorption performance. In this work, the special hard/soft magnetic composites are successfully fabricated, in which Sm2Fe17/Fe(Sm) hard/soft hybrid nanoparticles are embedded in ∼5 nm Sm2O3-doped porous carbon matrix. The hard/soft magnetic exchange-coupling result in the multiple-resonance peaks beyond Snoek’s limitation at broad wave band and the Sm2O3-doped carbon supplements dielectric loss capacity. Multiple-resonance effect is modified by adjusting the ratio of hard and soft magnetic components and the dielectric loss capacity is supplemented by Sm2O3-doped carbon. Herein, the hard/soft magnetic exchange-coupling and dielectric matrix are dexterously integrated to achieve broad absorption band with thin matching thickness and low filling ratio. By varying the ratio of Fe3+/Sm3+ in raw material, 20 wt% Sm2Fe17/Fe(Sm)-paraffin composites can reach the maximum effective absorption bandwidth of 6.8 GHz with matching thickness of 1.6 mm, the minimal reflection loss of −47.15 dB with 1.5 mm and the optimal microwave absorption efficiency of 71.1 dB·GHz/mm with 1.4 mm. Overall, this work provides a simple approach to introduce multi-resonance effect, which broadens the path for advanced absorbers with broad band and thin thickness and low filling ratio.

Effect of surfactant-assisted low-temperature annealing on the refinement of particle size and enhancement of magnetic properties of SrFe12O19 ferrite

The fabrication of SrFe12O19 ferrite powders with good magnetic properties is a key process in the industrial production of permanent magnets. Remanence and coercivity of the powders was seriously decreased due to the generation of surface lattice defects produced during the crushing of pre-sintered ferrite powders. And the traditionally applied high-temperature annealing above 800 °C can only partially restore the magnetic properties. In this work, the effects of types, adding mode and contents of surfactant (hexadecyl trimethyl ammonium bromide, triethanolamine) on the magnetic properties of crushed powders of the pre-sintered SrFe12O19 ferrite under a low-temperature annealing of 400 °C process were systematically explored. The results showed that surfactants are beneficial to restore or even enhance the magnetic properties of the crushed powders compared with the pre-sintered ferrite due to the refinement of the particles and repairing the surface defects. The surfactant-assisted low-temperature annealing process proposed in this work will promote the commercial production of high performance ferrite powders and ferrite magnets, which can also effectively reduce the production energy consumption.

Investigating magnetization of permanent magnets by magnetic flux viewing film

Permanent magnets are used in many current industrial as well as home appliances today. Frequently, kitchen plastic magnets could be found at the refrigerators at home. However, the magnetic domain structure of such permanent plastic foils is not known and understood to the users at all. The purpose of this paper is to explain the magnetic domain structure of plastic magnets with Halbach array and ferrite or neodymium magnet polarization orientation. Principles of magnetic field visualization foils (magnetic flux detector and colour changing viewing film) is explained and demonstrated on multipole magnetic structures. Experiments with magnetic polarization reversal by the strong neodymium magnet in weaker ferrite magnetic material is demonstrated. All presented principles are collected in the simple magnetic set and suggested for education of school children of different ages. Elementary school children below 10 years age are mostly interested only in making hidden pictures in magnetic paper and ferrite magnet. Older school children of 11–12 years are able to absorb more knowledge about behaviour and properties of magnets.

Sintering temperature optimization for enhanced magnetic performance in La–Ca–Co doped strontium ferrite

The effectiveness of employing La-Ca-Co co-doping has been demonstrated as the optimal approach for enhancing the magnetic performance of strontium ferrite. However, limited studies have explored the evolution of the magnetoplumbite phase and its correlation with the sintering temperature. In our research, La-Ca-Co doped strontium ferrite permanent magnets were fabricated using a conventional ceramic process and a two-step sintering technique. After sintering at different temperatures, all the samples possess proper c-axis orientation. When the sintering temperature was raised from 1175 °C to 1205 °C, there was an upward trend observed in the remanence Br, increasing from 430 mT to 439 mT. The coercivity Hcj exhibited an increase from 380 kA/m and reached its peak at 397 kA/m at 1185 °C. Although the Br value remained favorable, the coercivity experienced substantial deterioration, reaching its lowest point at 303 kA/m at 1205 °C. Under a sintering temperature of 1195 oC, magnetic performance with optimal energy product was achieved, with Br of 439 mT, Hcj of 379 kA/m, Hcb of 318 kA/m, and (BH)max of 35.5 kJm-3.

Effects of SmCo Co-substitution on the magnetic and electrical properties of low temperature sintering synthesized strontium hexaferrite

In order to mitigate the rapid grain growth, a sintered ferrite magnet exhibiting stable characteristics was successfully synthesized. M-type strontium ferrite Sr1-xSmxFe12-xCoxO19 (x = 0.00, 0.01, 0.02, 0.03, 0.04, 0.05 and 0.10) was synthesized via a low-temperature co-firing method, incorporating an appropriate quantity of Bi2O3 and CuO as additives within the solid-phase reaction process. The magnetic and electrical properties of the resulting composites were meticulously examined, and X-ray diffraction (XRD) analysis was performed for structural characterization. The findings reveal that a pure hexagonal strontium phase is achieved consistently when the substitution level, x, remains below 0.5. With an increase in the substitution level, a heterogeneous phase α-Fe2O3 becomes apparent within the phase structure. Upon introducing doping elements, the subtle incorporation of SmCo (x ≤ 0.02) enhances the saturation magnetization, remanent magnetization, and coercivity of the composite material. Moreover, the resistances of grain and grain boundary (Rg, Rgb) have been downscaled from 1.856 × 106Ω and 3.61 × 106Ω to 3.182 × 104Ω and 4.37 × 105Ω respectively. Consequently, the Sr1-xSmxFe12-xCoxO19 ferrite sintered under low-temperature conditions demonstrates outstanding electromagnetic characteristics, presenting a viable option for materials in microwave device applications.

Comparison of single and multi-coil self-powered MR damper subjected to cyclic and earthquake loading for structural vibration control

A promising solution for semi-active vibration control of different dynamic systems is to use magnetorheological (MR) dampers. In the present study, the investigation focuses on developing a novel single and multi-coil self-powered magnetorheological (MR) damper system using electromagnetic induction (EMI) for seismic mitigation. The conventional MR dampers, which rely on external power sources, can be unreliable and impractical in earthquake-prone locations. Thus, the EMI device connected to the MR damper can be used as an effective and alternative power source for the MR damper, results in a self-powered system. The proposed energy-harvesting system is an MR damper placed above the top of the piston. The coil is wound around the piston, and the outer casing with a ferrite magnet is fixed. As the mechanical energy of the piston is converted into electrical energy, its self-tuning capacity is a perfect fit for structural vibration control applications. The MR damper is subjected to cyclic and time-history loading. At a maximum amplitude of 15 mm, the damper generated 1767.8 N for cyclic loading and -1780 N for earthquake loading, the El Centro earthquake 1940 is considered for the study. By placing EMI, the mechanical energy is converted into electrical energy and powers the damper to avoid external power. The experimental results showcase enhanced damping forces and adaptability, thereby establishing it as an innovative and effective it can be alternative to conventional MR dampers for vibration control in future

Electromagnetic design, sensitivity analysis, optimization and Multiphysics capability of rare-earth-free synchronous reluctance motor for electric trike vehicle

&lt;p&gt;As a part of last-mile transportation, electric three-wheelers, popularly known as trikes, are considered as an important aspect of the future of the auto industry. The appropriate choice of electric traction motor drive is imperative to the design of an electric motor power train. In this paper, six main types of sinusoidal-fed electric motor power trains—Ferrite-Assisted Synchronous Reluctance Motor (FASRM), Synchronous Reluctance Motor (SyncRelM), Ferrite-based Spoke motor, Ferrite-based Surface-Mounted Permanent Magnet Synchronous Motor (SMPMSM), Wound-Field Synchronous Motor (WFSM), and Induction Motor (IM)—are compared for their performance in electric trike applications. The permanent magnet machines presented here utilize ferrite magnets, in line with the recent trend of not using rare-earth magnets. The comprehensive comparative analysis establishes that SyncRelM, FASRM, and Spoke motors are superior in terms of overall electromagnetic, thermal, and vibration performance. This paper also focuses on an optimal design of the FASRM due to its high torque density, lower torque ripple, and minimal use of ferrite magnets. A Design of Experiments (DoE)-based statistical analysis tool is used to identify the key parameters needed for robust motor performance in the optimization step. Furthermore, an Extreme Learning Machine (ELM)-based interpolation technique is employed for estimating the performance parameters during each step of the optimization routine. A 1.2 kW FASR motor prototype is developed and tested. A comparison of Finite-Element-Analysis-based modeling results is presented along with Indian drive-cycle results for the FASRM for trike application.&lt;/p&gt;

Improved Design of Synchronous Homopolar Motor With Ferrite Magnets With Increased Resistance to Irreversible Demagnetization for Subway Train

Improved Design of Synchronous Homopolar Motor With Ferrite Magnets With Increased Resistance to Irreversible Demagnetization for Subway Train

Study on the relationship between structure and magnetic properties of τ-phase MnAl prepared by cryo-milling

The unique characteristics, such as high magnetic moment, high Curie temperature, large magnetic crystalline anisotropy, and low cost, make the τ-phase MnAl a promising candidate as the market alternatives which could fill the gap between the rare earth magnets and ferrite magnets. Because at low temperatures the metal will become more brittle, the cryomilling technology may allow the τ-phase MnAl to be broken quickly and introduce few crystal defects, and then obtain better permanent magnetic properties. In this study, the cryomilling technology was used to grind the τ-phase MnAl, and the structural and magnetic properties of the obtained powder sample were investigated. It was found that compared to room-temperature ball milling, the morphology of cryomilled powders is granular and the powder agglomeration is dramatically suppressed at a low temperature, and as a result the larger particles tend to be broken down into smaller ones rather than being agglomerated to larger thin layers. The grain size D reduced continuously from 145 nm to 36 nm when the sample was milled for 120 minutes. The coercivity increased with increasing the cryo-milling time, while the saturation magnetization decreased. The maximum coercivity of up to 4.9 kOe was obtained by cryo-milling for 100 minutes. By the neutron diffraction analysis, it was confirmed that the decrease of the saturation magnetization with increasing milling time is mainly due to the migration of Mn atoms from 1a site to the 1d site and the decrease of Mn atomic magnetic moment.

Study of Magnetic Fields Effects on Antipathogenic, Antioxidant and Anticoagulation Activity of Purified Phycocyanin

This research was performed with the purpose of investigating the effect of a magnetic field on the antipathogenic, antioxidant, and anticoagulant activities of purified phycocyanin (PC) from the cyanobacterium &lt;i&gt;Spirulina laxa&lt;/i&gt;. Magnetic fields of 30 and 60 mT generated by an electric current and ferrite magnets were applied for 21 days. After biomass production and purification of PC, different analyses of antibacterial, antioxidant, and anticoagulant activity were performed. The results showed that magnetic fields of 30 mT showed the highest intensity of PC absorption. While the magnetic field of 60 mT caused the highest purity of PC compared to the control sample (&lt;i&gt;P&lt;/i&gt; &amp;#60; 0.05), Moreover, the highest antibacterial and antifungal activity was found against &lt;i&gt;Yersinia enterocolitica&lt;/i&gt; 33114 and &lt;i&gt;Saprolegnia parasitica &lt;/i&gt;CBS 223.65 in both 30 and 60 mT magnetic fields. Moreover, the highest anticoagulation and antioxidant activity of PC and also glutathione peroxidase, glutathione reductase, superoxide dismutase, and catalase enzymes were observed under 60 mT magnetic fields. In conclusion, the use of magnetic fields can be a novel strategy for analyzing cyanobacterial pigments for their antibacterial, antioxidant, antifungal, and anticoagulation activities.

Design and Analysis of a New Dual-Stator Hybrid Magnet Flux Modulation Machine

This paper proposes a new dual-stator hybrid-magnet flux modulation machine (DS-FMHMM) for direct-drive applications, which employs NdFeB magnet excitation and Ferrite magnet excitation on the rotor and outer stator sides, respectively. With this design, the proposed DS-FMHMM can not only fully use the bidirectional flux modulation effect, but also effectively alleviate the magnetic saturation issue. The machine configuration is described, together with the operating principle. Then, the design parameters of DS-FMHMM are globally optimized for obtaining high torque quality, and the influence of magnet dimensions on torque is analyzed. To evaluate the merits of the proposed DS-FMHMM, the electromagnetic performances of machines under different magnet excitation sources are analyzed, and a comprehensive electromagnetic performance comparison of DS-FMHMM and two existing dual-stator flux modulation machines (DSFMMs) is developed.

Theoretical analysis of effects of ferrite geometrical parameters on tokamak magnetic field perturbations

In this paper, a magneto-dynamic approach has been developed to investigate the probable enhancing effect of a magnetizing material like ferrite on the mitigation of the edge-localized mode instabilities. It has been assumed that the ferrite is placed on the first wall of the tokamak. The Landau–Lifschitz–Gilbert equation has been used to calculate the ferrite contribution to the equilibrium and the perturbed magnetic fields in the plasma. Simulations have shown that the ferrite can alter the magnetic field topology. Investigating the effects of the ferrite geometrical parameters such as the length, the width and the angle have shown that increasing the values of these parameters elevates the ferrite magnetization contribution in the plasma. Because of the type of the perturbation initially defined, this contribution was especially strong at the bottom of the ferrite. Since the ferrite can increase the total perturbation field in the plasma, it can help to mitigate the edge-localized modes by the resonant magnetic perturbation phenomenon. The simulation has shown that for an optimum geometry of the ferrite, the magnetic flux surfaces near the edge can be modified from an opened-line topology to a closed-line topology. Thus, the ferrite can prevent the magnetic flux from touching the wall which is necessary to have a good confinement and to reduce the edge instabilities.