Saturation Induction Research Articles

Measurement Method of Deeply Saturated Excitation Characteristics of Converter Transformer Under AC-DC Hybrid Excitation

During operation, converter transformers enter a saturation state, leading to phenomena such as magnetising inrush currents. Accurately measuring the excitation characteristic curve of an iron core under deep-saturation conditions is essential for analysing low-frequency transient phenomena in transformers. This paper presents a method for calculating the excitation characteristics of a converter transformer under deep iron core saturation. The method involves establishing an improved T model for the converter transformer and conducting open-circuit experiments in the linear working region to obtain the excitation characteristic curve and knee point parameters. AC-DC hybrid excitation is used to achieve deep saturation, and measurements of saturated inductance at different levels of saturation at the transformer terminals are taken. The mathematical relationship between saturated inductance and magnetic impedance is derived, allowing deduction of the magnetising characteristic curve of the converter transformer under deep-saturation conditions based on measured saturated inductance values. A finite element simulation analysis was performed on a single-phase four-column converter transformer with a capacity of 250 MVA. Additionally, a test platform for toroidal transformers and dry-type transformers has been set up to carry out excitation characteristic measurement and verification. Experimental results demonstrate that errors are maintained within 10% or less, validating this approach’s effectiveness.

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.

Inductance Estimation Based on Wavelet-GMDH for Sensorless Control of PMSM

In permanent magnet synchronous motor (PMSM) sensorless drive systems, the motor inductance is a crucial parameter for rotor position estimation. Variations in the motor current induce changes in the inductance, leading to core magnetic saturation and degradation in the accuracy of rotor position estimation. In systems with constant load torque, the saturated inductance remains constant. This inductance error causes a consistent error in rotor position estimation and some performance degradation, but it does not result in speed estimation errors. However, in systems with periodic load torque, the error in the saturated inductance varies, consequently causing fluctuations in both the estimated position and speed errors. Periodic speed errors complicate speed control and degrade the torque compensation performance. In this paper, we propose a wavelet denoising-group method of data handling (GMDH) based method for accurate inductance estimation in PMSM sensorless control systems with periodic load torque compensation. We present a method to analyze and filter the collected three-phase current signals of the PMSM using wavelet transformation and utilize the filtered results as inputs to GMDH for training. Additionally, a method for magnetic saturation compensation using the inductance parameter estimator is proposed to minimize periodic speed fluctuations and improve control accuracy. To replicate the load conditions and parameter variations equivalent to the actual system, experiments were conducted to measure the speed ripples, inductance variations, and torque component of the current. Finally, software simulation was performed to confirm the inductance estimation results and verify the proposed method by simulating load conditions equivalent to the experimental results.

Comparison of nonlinear solution methods for magnetic equivalent circuits of saturated induction motors

This work compares three nonlinear solution methods for the performance of an induction motor’s magnetic equivalent circuit model with magnetic saturation. The interrelation between magnetic flux density and permeability introduces nonlinearities in the differential system of equations. Three popular nonlinear solution methods are selected for comparison, namely (i) the Gauss–Seidel method, (ii) the Newton–Raphson method and (iii) the inverse Broyden’s method. While all three methods have been applied in this context before, no comparison study has been published to the authors’ best knowledge. The study finds that the inverse Broyden’s method is most performant in terms of the number of required iterations, the computation time per iteration and the resulting total computation time. However, for substantial saturation levels, the authors recommend a hybrid implementation of multiple solution methods to obtain robust and reliable convergence.

Preparation of Fe@Fe3O4/ZnFe2O4 Powders and Their Consolidation via Hybrid Cold-Sintering/Spark Plasma-Sintering.

Our study is focused on optimizing the synthesis conditions for the in situ oxidation of Fe particles to produce Fe@Fe3O4 core-shell powder and preparation via co-precipitation of ZnFe2O4 nanoparticles to produce Fe@Fe3O4/ZnFe2O4 soft magnetic composites (SMC) through a hybrid cold-sintering/spark plasma-sintering technique. XRD and FTIR measurements confirmed the formation of a nanocrystalline oxide layer on the surface of Fe powder and the nanosized nature of ZnFe2O4 nanoparticles. SEM-EDX investigations revealed that the oxidic phase of our composite was distributed on the surface of the Fe particles, forming a quasi-continuous matrix. The DC magnetic characteristics of the composite compact revealed a saturation induction of 0.8 T, coercivity of 590 A/m, and maximum relative permeability of 156. AC magnetic characterization indicated that for frequencies higher than 1 kHz and induction of 0.1 T, interparticle eddy current losses dominated due to ineffective electrical insulation between neighboring particles in the composite compact. Nevertheless, the magnetic characteristics obtained in both DC and AC magnetization regimes were comparable to those reported for cold-sintered Fe-based SMCs.

Effect of ultralow Dy and Gd contents on surface crystallization and domain wall motion of FeCuSiBNbMo alloys

Surface crystallization of Fe-based melt-spun ribbons with high saturation induction leads to the formation of coarse grains after nanocrystallization, which results in a deterioration of the soft magnetic properties. Herein, doping with an ultralow concentration (0.1 at.%) of RE (RE = Dy and Gd) inhibits the surface crystallization of melt-spun FeCuSiBNbMo samples using industrial-grade Nb–Fe raw materials. This inhibition of surface crystallization promotes the formation of uniform and ultrafine nanograins after optimal annealing. Furthermore, the movement of domain wall is significantly affected by the presence of large grains (∼600 nm) in the free surface, which exerts a strong pinning effect on the domain wall motion. This pinning effect can be attributed to the higher magnetic anisotropy energy of the free surface compared to that of the nanocrystal region. The low coercivity observed in the samples with 0.1 at.% Dy and Gd addition is ascribed to the presence of dense and ultrafine nanocrystals, low effective magnetic anisotropy, and a weak pinning effect. This work provides insights into the relationship between surface crystallization, coercivity, domain wall motion, and magnetic anisotropy energy in Fe-based nanocrystalline ribbons.

Correlating the microstructure with magnetic properties of Ti-doped high-frequency MnZn ferrite

In this study, high-frequency MnZn ferrites are prepared for power applications at 10 MHz using solid-state reaction method. The sample doped with 3000 ppm TiO2 yields the optimal comprehensive magnetic properties, with an initial permeability of 792, power loss of 415 kW/m3 (10 MHz, 5 mT, 25 ℃), and saturation induction of 460 mT. This indicates significant progress compared to previously reported results. The mechanisms of property optimisation, microstructure and domain structure evolution also discussed with TiO2 doping. The precipitation of Ti at the grain boundary can promote a high-density microstructure and favour the formation of magnetic monodomain in MnZn ferrites. Our results elucidate the correlations between microstructure, domain structure, and high-frequency performance, and present a potential roadmap for the development of high-frequency soft magnetic ferrites.

Influence of Nb and Mo Substitution on the Structure and Magnetic Properties of a Rapidly Quenched Fe79.4Co5Cu0.6B15 Alloy.

The importance of amorphous and nanocrystalline Fe-based soft magnetic materials is increasing annually. Thus, characterisation of the chemical compositions, alloying additives, and crystal structures is significant for obtaining the appropriate functional properties. The purpose of this work is to present comparative studies on the influence of Nb (1, 2, 3 at.%) and Mo (1, 2, 3 at.%) in Fe substitution on the thermal stability, crystal structure, and magnetic properties of a rapidly quenched Fe79.4Co5Cu0.6B15 alloy. Additional heat treatments in a vacuum (260-640 °C) were performed for all samples based on the crystallisation kinetics. Substantial improvement in thermal stability was achieved with increasing Nb substitution, while this effect was less noticeable for Mo-containing alloys. The heat treatment optimisation process showed that the least lossy states (with a minimum value of coercivity below 10 A/m and high saturation induction up to 1.7 T) were the intermediate state of the relaxed amorphous state and the nanocomposite state of nanocrystals immersed in the amorphous matrix obtained by annealing in the temperature range of 340-360 °C for 20 min. Only for the alloy with the highest thermal stability (Nb = 3%), the α-Fe(Co) nanograin grows, without the co-participation of the hard magnetic Fe3B, in a relatively wide range of annealing temperatures up to 460 °C, where the second local minimum in coercivity and core power losses exists. For the remaining annealed alloys, due to lower thermal stability than the Nb = 3% alloy, the Fe3B phase starts to crystallise at lower annealing temperatures, making an essential contribution to magneto-crystalline anisotropy, thus the substantial increase in coercivity and induction saturation. The air-annealing process tested on the studied alloys for optimal annealing conditions has potential use for this type of material. Additionally, optimally annealed Mo-containing alloys are less lossy materials than Nb-containing alloys in a frequency range up to 400 kHz and magnetic induction up to 0.8 T.

Nanostructural evolution and improved magnetic performance of high saturation-induction Fe-based alloy via two-step combination crystallization

Refining nanoparticles and reducing the average random anisotropy constant (<K1>) are crucial for improving the magnetic properties of nanocrystalline alloys with high magnetic saturation induction. This study systematically investigates the evolution of nanostructure and soft magnetic performance during two-step combination annealing, which includes stress annealing at a flash heating rate followed by normal-annealing. Stress-annealing at 500 °C prior to crystallization reduces the area of the FeB-like short-range-order structure and effectively increases the number density of Cu clusters that act as heterogeneous nucleation sites for α-Fe(Si) nanoparticles. Stress-annealing at 500 °C precipitates tiny (∼ 5 nm) Fe3Si nanoparticles (A6 structure) dispersed in an amorphous matrix, resulting in more Fe clusters in the amorphous matrix and superior crystallinity following the second-step annealing process. The two-step combination annealing process increases the magnetic saturation induction (by ∼3%) and permeability (by∼62%) at 10 kHz in comparison with those obtained for the one-step annealed sample. Moreover, we propose a model for nanostructural evolution and the observed correlation with magnetic performances.

The DC Inductor Current Ripple Reduction Method for a Two-Stage Power Conversion System

This paper proposes a method for minimizing the inductor current ripple of a DC–DC converter in a two-stage power conversion system consisting of a grid-connected PWM converter and an interleaved multiphase three-level DC–DC converter. To reduce the output voltage ripple, the three-level DC–DC converter is configured in parallel and operated interleaved. However, a circulating current generated by the interleaved operation increases the inductor current ripple of each DC–DC converter and causes system loss and inductor saturation. In this paper, the inductor and output current ripple of the interleaved three-phase three-level DC–DC converter is mathematically analyzed and the effect of the DC–DC converter’s duty ratio and output voltage on each current ripple is described. Based on this analysis, a method is proposed for controlling the optimal DC link voltage through the PWM converter, so that the DC–DC converter is controlled with the duty ratio that minimizes the inductor current ripple. The simulation and experimental results under various operating conditions are presented to verify the feasibility of the proposed control method.

Magnetic properties evaluation of Fe-based amorphous alloys synthesized via spark plasma sintering

Fe77.7Si8B10P4Cu0.3 amorphous powder compacts with high relative density (ρr = 94%), high saturated magnetic induction (Bs = 1.34 T), and high permeability (μ = 163 at 20 kHz) were fabricated by spark plasma sintering. In this work, Fe77.7Si8B10P4Cu0.3 spherical amorphous powders with good amorphous forming ability were prepared by regulating the material composition and the particle size distribution by gas atomization at first. The effect of sintering temperature (Ts) on the structure and magnetic properties of powder compacts was systematically investigated. The powder compacts sintered at Ts of 696–712 K were found to remain amorphous structure and exhibit optimal structural and magnetic performance, due to the high temperature and high pressure employed in SPS with high heating rate. These results are promising for the applications of Fe-based amorphous powder alloys in soft magnetic devices requiring tens of kilo-hertz frequency.

Effects of Sn substitution on the microstructural and electromagnetic properties of MnZn ferrite for high-frequency applications

To achieve compact and lightweight power conversion devices, magnetic core materials such as MnZn ferrite are highly desired with low core losses at high frequencies above megahertz. In this work, high-valent Sn4+ ions were doped into MnZn ferrite to manipulate the electromagnetic properties and suppress the high-frequency core losses. The distribution of Sn4+ in MnZn ferrite was investigated by transmission electron microscopy with energy dispersive x-ray analysis, which indicated that most of the substituted Sn4+ ions remained at the grain boundaries rather than dissolving into the lattice, and thus greatly impacted the electromagnetic properties of MnZn ferrite. The initial permeability and saturation induction decreased monotonically with the Sn substitution. The core loss was reduced to 457 kW m−3 at 3 MHz, 30 mT, and 25 °C when the Sn substitution content was 0.003, due to the effective suppression of eddy current loss and residual loss. The sample with a Sn content of 0.003 exhibited excellent overall electromagnetic properties, which could be potentially useful in high-frequency transformers, converters, and power sources.

Investigation of metal amorphous nanocomposite soft magnetic alloys in the (FexNiyCo100−x-y)80B14Nb4Si2 system

Following reports of attractive soft magnetic performance of an (Fe70Ni30)80B14Nb4Si2 alloy [1–3], improvement to this alloy is sought through substitution of small percentages of Co for Fe and/or Ni. Fifteen alloys in the (FexNiyCo100−x-y)80B14Nb4Si2 alloy system are fabricated by small batch planar flow casting and analyzed for various properties relating to their soft magnetic performance. Alloys synthesized are within the range x = 60–70 and y = 20–30. The most important properties studied here are saturation induction (Bsat), coercivity (Hc), saturation magnetostriction (λs), and Curie temperature (Tc). These metrics are important to various aspects of electric motor design. High Tc improves a material’s magnetic performance at elevated temperature, while lower Hc and λs reduce switching losses and larger Bsat is associated with higher torque capability. The resulting alloys have improved amorphous phase Tc of up to 414 ℃ and a λs reduction of up to 40%. This is achieved while keeping Hc of many compositions below 10 A/m and a calculated Bsat at T= 0 K of one alloy over 1.5 T. Given their improvements in the relevant properties, these new alloys present promise as soft magnets for electric motor applications.

Desaturation of sebaceous-type saturated fatty acids through the SCD1 and the FADS2 pathways impacts lipid neosynthesis and inflammatory response in sebocytes in culture.

Sebum is a lipid-rich mixture secreted by the sebaceous gland (SG) onto the skin surface. By penetrating through the epidermis, sebum may be involved in the regulation of epidermal and dermal cells in both healthy and diseased skin conditions. Saturated and monounsaturated fatty acids (FAs), found as free FAs (FFAs) and in bound form in neutral lipids, are essential constituents of sebum and key players of the inflammatory processes occurring in the pilosebaceous unit in acne-prone skin. Little is known on the interplay among uptake of saturated FFAs, their biotransformation, and induction of proinflammatory cytokines in sebocytes. In the human SG, palmitate (C16:0) is the precursor of sapienate (C16:1n-10) formed by insertion of a double bond (DB) at the Δ6 position catalysed by the fatty acid desaturase 2 (FADS2) enzyme. Conversely, palmitoleate (C16:1n-7) is formed by insertion of a DB at the Δ9 position catalysed by the stearoyl coenzyme A desaturase 1 (SCD1) enzyme. Other FFAs processed in the SG, also undergo these main desaturation pathways. We investigated lipogenesis and release of IL-6 and IL-8 pro-inflammatory cytokines in SZ95 sebocytes in vitro after treatment with saturated FFAs, that is, C16:0, margarate (C17:0), and stearate (C18:0) with or without specific inhibitors of SCD1 and FADS2 desaturase enzymes, and a drug with mixed inhibitory effects on FADS1 and FADS2 activities. C16:0 underwent extended desaturation through both SCD1 and FADS2 catalysed pathways and displayed the strongest lipoinflammatory effects. Inhibition of desaturation pathways proved to enhance lipoinflammation induced by SFAs in SZ95 sebocytes. Palmitate (C16:0), margarate (C17:0), and stearate (C18:0) are saturated fatty acids that induce different arrays of neutral lipids (triglycerides) and dissimilar grades of inflammation in sebocytes.

Phase Current Measurement Method for Switched Reluctance Motors With One Current Sensor

Accurate phase currents are necessary for the control and protection of motor drives. In this article, a novel phase current reconstruction strategy for switched reluctance motors (SRMs) with single current sensor is proposed. Firstly, the characteristic of the unsaturated phase inductance is analyzed. Secondly, the location of the single current sensor is rearranged, and all phase currents flow through the sensor in positive direction. The phase current in unsaturated region is directly obtained by dividing the flux linkage by the unsaturated inductance. In the linear region, the phase current is calculated by solving the similar triangles according to the relationship between the unsaturated inductance and saturated inductance. Finally, the overall control strategies of SRM drive integrated with the proposed phase current reconstruction method are implemented. The proposed method can be used for different chopping modes and different control strategies. Simulations and experiments on a three-phase 12/8 SRM validate the effectiveness of the proposed phase current reconstruction scheme.

Improvement of cyclic liquefaction resistance induced by partial saturation: An interpretation using wave-based approaches

Methods to estimate the liquefaction resistance in sandy soils have been proposed in the literature, involving correlations between cyclic resistance ratio and seismic wave velocities measured by in situ and laboratory tests. However, the applicability of these correlations has not been validated in sands improved with the induction of partial saturation. This study addresses the assessment of cyclic liquefaction resistance improvement induced by partial saturation using wave-based approaches. For this purpose, an experimental plan comprising cyclic triaxial and bender elements was carried out in a Portuguese natural sand. The studied soil is TP-Lisbon sand, a historically liquefiable soil collected in the ‘Terreiro do Paço’ site — next to the Tagus River in the centre of Lisbon. Notwithstanding, the results presented herein are compared against other liquefiable sands from Japan. The induced partial saturation was controlled by P-wave velocity measurements, which were contrasted against theoretical predictions performed in the light of Biot’s theory. The results confirmed the increase in liquefaction resistance by inducing partial saturation. Experimental results revealed that P-wave velocity provides a reliable prediction of liquefaction resistance in partially saturated conditions rather than S-wave velocity. The suitableness of these approaches was attributed to the presence of occluded air bubbles in partially saturated soils, which can be detected by the P-wave and not by the S-wave.

Technological developments in amorphous and nanocrystalline soft magnetic ribbons with high saturation induction via patent analysis

Technological developments in amorphous and nanocrystalline soft magnetic ribbons with high saturation induction via patent analysis

Auxiliary Resonant Snubber‐Based Soft‐Switching Converter with Saturable Inductor to Reduce Reverse Recovery Current and Loss

The auxiliary resonant snubber‐based converter (ARSC) has the advantages of low dead‐time effect and low switching loss. However, the auxiliary switches suffer from high reverse recovery loss and high reverse recovery current in high‐switching frequency application. Thus, the ARSC with saturable inductor is proposed to solve the problem above. In this paper, the operating principle of ARSC with saturable inductor is analyzed, and the duty cycle operating range that can realize ZVS in the full load range is deduced. The reverse recovery model of the auxiliary switching device body diode is established to analyze the circuit parameters' influence. Then, the influence of the saturable inductor on the reverse recovery peak current and reverse recovery loss is analyzed. Based on the analysis results, the saturable inductance parameters are designed. Finally, based on the experimental platform of the ARSC, the effectiveness of the proposed method is verified. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Effects of V&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt;-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; sintering aid on properties of low temperature sintered Li-Zn microwave ferrites

With the progress of modern wireless communication technology, microwave communication devices are developing toward miniaturization and integration, and low-temperature co-firing ceramic/ferrite technology is the key to meet the above demands. In this paper, V&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt;-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; (VA) sintering aid is used to realize low-temperature sintering (below melting point of silver that is 950 ℃) of Li-Zn microwave ferrite, which is suitable for radar phase shifter. In this work, firstly, Li-Zn ferrite pre-firing material is prepared by mechanochemical ball-milling method, and then VA composite is selected as sintering aid to prepare Li&lt;sub&gt;0.42&lt;/sub&gt;Zn&lt;sub&gt;0.27&lt;/sub&gt;Ti&lt;sub&gt;0.11&lt;/sub&gt;Mn&lt;sub&gt;0.1&lt;/sub&gt;Fe&lt;sub&gt;2.1&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; ferrite at low temperatures. The effects of adding amount of VA sintering aid and sintering temperature on crystal structure, microstructure and magnetic properties (saturation induction, coercivity, linewidth of ferromagnetic resonance, etc.) of the materials are also studied. The VA sintering aid can reduce the sintering temperature and maintain the spinel crystal structure of Li-Zn microwave ferrite, the diffraction peaks of V&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt; and Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; involved in the sintering process are observed from none of the samples sintered at different temperatures, because the additive amount of VA sintering aid is very low compared with that of Li-Zn ferrite, so no corresponding impurity peaks are detected. The introduction of VA sintering aid can promote the grain growth, with the average grain size increasing from 0.92 μm to 9.74 μm. In the sintering process of Li-Zn ferrite, V&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt; in VA sintering aid will melt first to form liquid phase due to its low melting point, which promotes the growth of grains. At the same time, Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; with higher melting point can inhibit the grain growth and make the grain uniform. It is worth noting that when excessive VA sintering aid is added, the grain size of ferrite will decrease instead, because too much VA sintering aid will form a large number of liquid phases around the grains, thus splitting the grains and hindering the further growth of the Li-Zn grains. Under the condition of optimal VA sintering aid addition (0.18%, weight percentage), the saturation induction of the sample increases from 144 mT to 281 mT; the rectangular ratio increases from 0.57 to 0.78; the coercivity decreases from 705 A/m to 208 A/m; the linewidth of ferromagnetic resonance decreases from 648 Oe to 247 Oe. In summary, VA sintering aid can effectively improve the properties of Li-Zn microwave ferrite, which has a positive significance in developing low- temperature co-firing ceramic/ferrite technology.

Estimation of Number of Cores for Preventing Common-Mode Inductor Saturation in Railway Traction Inverters

In the traction system of rolling stock, the common-mode (CM) voltage is over 500 V, so the inductors that suppress the CM current are prone to saturation. To prevent saturation, the traction inverter needs many numbers of cores inside CM inductors, but the required number of cores has been determined empirically. This paper proposes a method calculate the approximate number of nanocrystalline cores to avoid saturation of CM inductors in railway traction inverters without circuit simulation. Using the only the CM capacitance of traction motor and the core characteristics on the datasheet, the maximum flux density of the inductor is calculated. Comparing calculated results of the maximum flux density with the results measured with a 1500 V DC inverter indicates that the proposed method can better identify the occurrence of saturation than the methods based on CM current presented in the literature. Furthermore, for the entire CM voltage range from 500 V to 3000 V, the minimum number of cores which saturation is prevented by the proposed calculation method is shown to be in reasonable agreement with the simulation results.