Search Results (5,283)

Wireless power transfer (WPT) is increasingly used in smart manufacturing, unmanned platforms, and contactless power-supply applications. However, weak coupling, load-dependent impedance drift, and spatial misalignment can shift the resonant condition, leading to unstable output voltage and reduced transfer efficiency. This paper proposes a constant-voltage WPT method that combines a non-uniform winding coupler, parasitic coils, and dynamic capacitor compensation. A composite magnetic coupler with dense outer windings, loose inner windings, and parasitic coils is first developed, and a region-based electromagnetic model is established to characterise self-inductance, mutual inductance, and coupling coefficients. An improved LCC-S compensation network with a dynamic capacitor compensation matrix is then derived to keep the system close to resonant operation at the nominal 85 kHz operating point under load variation and coil-displacement-induced coupling changes. A zero-voltage-switching-angle tracking method with mutual-inductance correction is further introduced to compensate for phase deviation and maintain soft-switching operation through limited switching-frequency adjustment. Experimental validation demonstrates that the system maintains a stable constant-voltage output across a load range of 20–50 Ω and under 5 cm lateral and longitudinal offsets. The measured efficiency remains above 89% and reaches 93.7% under the optimal coupling and load-matching condition. Full article

All rotating electrical machines are susceptible to vibrations arising from electromagnetic (EM) forces, electrical faults, mechanical defects, imbalance, and structural resonance. In Doubly Fed Induction Generators (DFIGs), such electromechanical vibrations are especially important because they can degrade reliability, increase noise, and lead to severe damage if resonance-prone operating conditions are not identified in time. Although fault diagnosis in DFIGs has been widely investigated using current, voltage, and flux signatures, comparatively fewer studies have examined fault-specific vibration behaviour under stator and rotor interturn faults (ITTFs), particularly through a coupled EM structural framework. In addition, prior vibration-based studies have not examined the influence of end winding ITTFs, its location, severity, and modal interaction investigating resonance risk. This paper considers vibration characteristics of a variable-speed 2.8 MW DFIG used in a grid-connected Type-3 wind turbine unit (WTU) at no-load operating condition. The DFIG is modelled in ANSYS Academic Research v 2022 R2 Maxwell for EM behaviour assessment for ITTFs in both stator and rotor windings along with modal analysis (MA) in ANSYS Workbench to examine the undamped stator and rotor modes over a range of frequencies. This coupled approach enables identification of vibration signatures associated with different ITTF types. The results show the magnetic flux density near faulty end-winding region increases with fault severity and ranges from 4.19 T to 4.39 T in proximity to faulty windings. A dominant modal frequency band of 60–65 Hz is identified, where stator and rotor modes coincide, creating probable resonance conditions. A severe vibration response is observed for single-phase stator ITTF, showing an amplitude of 2116 mm/s at 480 Hz for a larger number of shorted turns, indicating that asymmetric faults can produce stronger EM excitation than multi-phase faults. The main contribution of this paper is demonstration of a fault-specific, MA and vibration-based Condition monitoring system (CMS) implementation workflow for a DFIG. Unlike prior vibration-based studies that primarily focus on general machine vibration, mechanical faults, bearings, etc., this paper links stator and rotor ITTF induced EM excitation to modal characteristics, resonance behaviour, and measurable vibration signatures, establishing vibration analysis (VA) as a practical complementary technique for CMS of ITTFs in DFIGs. Full article

Halide solid electrolytes (HSE) have shown remarkable stability against high-voltage cathodes. Some HSE, such as Li₃InCl₆ (LIC), can be readily synthesized via aqueous routes. Here, we expand the aqueous synthesis of LIC to include Y substitution, which has different hydration coordination strengths, to form Li₃In_xY_1−xCl₆ (LIYC, 0 ≤ x ≤1). This composition is intended to combine the high ionic conductivity of LIC with the superior stability of Li₃YCl₆ (LYC). We compared solution-synthesized products with those derived mechanochemically. We found that adding ammonium chloride in a 3:1 ratio to YCl₃ + InCl₃ produces a phase-pure product, with X-ray diffraction (XRD) revealing structure similarity for both routes. Through nuclear magnetic resonance (NMR) and impedance measurements, we evaluate how the synthesis method affects ionic transport, particularly regarding correlated motion. Despite lower initial grain boundary impedance in mechanochemical samples, full cells made from solution-synthesized samples show superior cycling performance. This work establishes a scalable aqueous synthesis route for LIYC that achieves properties comparable to traditional mechanochemical methods. Full article

To investigate the corrosion resistance and deterioration mechanism of cast-in situ concrete incorporating iron ore tailings aggregate (IOT), specimens with IOT replacement ratios of 0%, 30%, and 50% were exposed to distilled water, endogenous Cl⁻-SO₄²⁻ corrosion, exogenous Mg²⁺-SO₄²⁻ corrosion, and endogenous-exogenous coupled corrosion. The evolution of mass, size, compressive strength, and flexural strength was evaluated, while Nuclear Magnetic Resonance (NMR), Scanning Electron Microscope-Energy Dispersive Spectroscopy (SEM-EDS), X-ray Diffraction (XRD), and Thermogravimetric Analysis/Derivative Thermogravimetry (TG/DTG) were used to characterize pore structure and phase transformation. Results show that distilled water causes limited variation, whereas exogenous and coupled corrosion accelerate product accumulation, size expansion, pore coarsening, and strength degradation. Under exogenous Mg²⁺-SO₄²⁻ corrosion, the peak compressive strengths of specimens with 0%, 30%, and 50% IOT reach 43.30 MPa, 45.60 MPa, and 46.93 MPa, respectively, with the 50% IOT specimen showing an 8.38% increase compared with the specimen without IOT. TG/DTG results show that the Ca(OH)₂ related mass loss decreases from 5.42% under distilled water immersion to 4.37% under exogenous Mg²⁺-SO₄²⁻ corrosion, confirming calcium consumption during sulfate–magnesium attack. Microstructural characterization reveals that sulfate reaction, chloride binding, and Mg²⁺-induced decalcification jointly promote the formation of gypsum, ettringite, Friedel’s salt, magnesium silicate hydrate (M-S-H), and magnesium-associated corrosion products. Overall, 30% IOT provides better pore refinement and mechanical stability under endogenous and exogenous corrosion, whereas 50% IOT improves residual skeleton support under coupled corrosion. These findings provide guidance for durability design and sustainable utilization of IOT aggregate in cast-in situ concrete. Full article

M-type hexaferrites are widely used in magnetic applications, and tailoring their properties via aliovalent substitution requires a detailed understanding of charge compensation and cation distribution. In this work, Mg²⁺/M⁴⁺ (M = Zr, Hf) co-substituted BaFe₁₂O₁₉ was synthesized via Na₂CO₃ flux and comprehensively characterized by wavelength-dispersive X-ray spectroscopy, powder and single-crystal X-ray diffraction, Rietveld refinement, X-ray absorption near-edge structure, and magnetic measurements. Increasing substitution levels x, y in BaFe_12−x−yMg_xM_yO₁₉ result in increasing lattice parameters and decreasing the room-temperature magnetic parameters saturation magnetization, remanence, and coercivity, while remanence and coercivity increase at low temperatures. Secondary phases form for nominal substitution ≥ 1. Zr⁴⁺ and Hf⁴⁺ preferentially occupy the 4f₂ site, whereas Mg²⁺ is distributed over multiple sites, as indicated by polyhedral volume analysis. Wavelength-dispersive X-ray spectroscopy confirms homogeneous elemental distribution within individual crystals but reveals significant variation in substitution levels within batches. The maximum degree of substitution for the tetravalent metals was y ≈ 1.2–1.7, with lower Mg incorporation of x ≈ 0.9–1.1. Charge compensation was found to be partially achieved via vacancy formation, while minor Fe²⁺ contributions cannot be excluded. Full article

The motion of AC electromagnetic actuators exhibits complex electrical–magneto–mechanical coupling characteristics. A three-phase AC contactor is taken as the typical research object in this paper. Using the finite-element method (FEM) and mesh deformation technique, the commercial software COMSOL Multiphysics is adopted to analyze its static electromagnetic characteristics, together with the operational coil current response and movable core displacement. In addition, the static correlation between the magnetic force, air gap, and time-varying magnetic force curves in the movement process are obtained. An experimental platform is established to measure the magnetic force of electromagnetic actuators. The experiment results demonstrate the feasibility of the proposed simulation method. The normalized root mean square errors between simulated and measured static magnetic forces are below 8% under all tested coil voltages. Furthermore, the effect of coil voltage phase angle on dynamic operational characteristics is thoroughly investigated. Combined with the closing time and final velocity of the movable core, the recommended operating window and its corresponding phase angle are determined. Full article

To reveal the nonlinear instability mechanism by which the three-degree-of-freedom rotor system of a magnetic-liquid double suspension bearing transforms from stable suspension to periodic vibration, a nonlinear dynamic model considering electromagnetic suspension force, hydrostatic supporting force, rotor unbalance force, and liquid film resistance is established. The equilibrium point of the system is linearized, and the Hopf bifurcation boundary is determined using the Routh–Hurwitz criterion. Numerical simulations are then carried out to investigate the effects of the initial current i₀, supply flow rate q₀, and different initial disturbances on the displacement time histories, phase trajectories, and spatial phase trajectories of the rotor. The results show that, under the given system parameters, the Hopf bifurcation boundary is 0.61 A for the initial current and 9.62 × 10⁻⁵ m³/s for the supply flow rate. Current variation mainly affects electromagnetic stiffness and nonlinear electromagnetic force, whereas flow rate variation primarily changes the hydrostatic load capacity and oil film damping characteristics. Under different initial disturbances, the system may exhibit amplitude attenuation, recovery to stable suspension, or finite amplitude periodic vibration. Experimental results show good agreement with numerical simulations in terms of frequency spectra, displacement time histories, and phase trajectories, thereby verifying the effectiveness of the proposed three-degree-of-freedom dynamic model and Hopf bifurcation analysis method. The results can provide theoretical guidance for parameter matching, stability evaluation, and self-excited vibration suppression of magnetic-liquid double suspension bearings. Full article

To address quality deterioration in yellowfin tuna during traditional freezing, this study systematically investigated the combined effects of alternating magnetic fields (AMFs) and two cryoprotectants (carboxylated cellulose nanofibers (CCNF); konjac glucomannan (KGM)). Twelve groups were established by combining four magnetic intensities (0, 5, 10, 15 mT) with three treatments (no cryoprotectant, 10 mg/mL CCNF, or KGM). The results show that AMF significantly shortened the freezing phase transition time and mitigated the phase transition delay induced by cryoprotectants. The optimal preservation was achieved by combining a 5 mT AMF with KGM (AMF5-KGM), which significantly reduced thawing, cooking, and centrifugation losses. Mechanistically, the 5 mT AMF and KGM synergistically stabilized the secondary and tertiary structures of myofibrillar proteins, whereas high-intensity AMF (>10 mT) and CCNF exacerbated protein conformational damage. Furthermore, the AMF5-KGM group exhibited maximal structural integrity, with the smallest ice crystal pore area (36.6%). Ultimately, this study demonstrates that a 5 mT, 50 Hz AMF combined with 10 mg/mL KGM synergistically improves the preservation quality of frozen yellowfin tuna, providing a theoretical basis for high-value pelagic fish product. Full article

Spodoptera littoralis (Boisduval, 1833) is one of the most destructive insect pests in Egypt and worldwide. This study was conducted to investigate the impact of exposure to a magnetic field (MF) of 180 milliTesla on the developmental phases of S. littoralis, as well as malform, reproductivity, and genomic DNA mutagenicity. The obtained results concluded that the exposure of S. littorelis to MF significantly affected the malformation and mortality rates in both larvae and pupae. The MF extended the duration of the pupal stage from approximately 0.8 to 5.9 days compared to the untreated pupae. The adult emergence percentages decreased to 68.0 and 74.0% upon exposure to a magnetic field for 60 and 40 min, respectively. The female fecundity decreased by increasing the exposure duration, yielding (7–10), (6–10), and (3–8) mass eggs per female upon exposure intervals of 20, 40, and 60 min, respectively. Meanwhile, the hatchability percentage diminished with prolonged exposure time, recording 77%, 60%, and 53% for MF exposure durations of 20, 40, and 60 min, respectively, compared to 91% hatchability in the control trial. The genetic characterization employing inter-simple sequence repeat (ISSR) markers disclosed genetic mutagenicity, exhibiting a similarity matrix range from 61.6% to 74.1% for larvae, 59.8% to 68.5% for adults, and 36.2% to 49% for pupae, indicating genetic alteration in treated insects. Hence, these findings highlight the implications and prospective application of a magnetic field of 180 milliTesla as a unique approach in integrated S. littoralis control frameworks. Full article

High-intensity magnetic fields in tokamak structures for nuclear fusion generate significant ferromagnetic forces that must be properly estimated for a reliable design of the mechanical structures. Accurate numerical modeling of these electromagnetic problems is likely to entail high computational costs due to the complexity of the geometries and the need to account for nonlinear material behavior. However, electromagnetic forces are not the only loads acting on tokamaks, as other phenomena, such as seismic forces, must also be considered in their design. Therefore, it is highly beneficial to develop coarse estimates of the electromagnetic loads in order to compare their magnitude with that of other loads. Such estimates are useful not only in the early stages of design, but also in the final design phase, particularly if these forces prove to be negligible. To this end, this paper proposes a semi-analytical method to quickly estimate the forces acting on ferromagnetic components located outside the vessel. The method is based on the calculation of the magnetization by means of a well-established integral method after a coarse discretization of the volume occupied by the ferromagnetic materials. The proposed method is implemented in computational routines made available within this paper, enabling the estimation of these forces even for users who lack the expertise required to operate commercial simulation tools. The method is applied to case studies related to some export components of the ITER tokamak, and the validation is carried out with reference to the accurate numerical solutions provided by both commercial and in-house simulation tools. Full article

To address the bottlenecks of conventional valve-controlled marine steering systems—characterized by high throttling losses, low efficiency, and high leakage risk—as well as the insufficient power density and impact resistance of electro-mechanical actuators (EMAs) for high-load steering of large vessels, this paper proposes and validates a high-performance integrated solution for an electro-hydrostatic actuator (EHA) for ship steering. First, a fifth-order electro–hydraulic–mechanical coupled dynamic model comprising a permanent magnet synchronous motor, hydraulic pump, hydraulic cylinder, and load is established. The validity and applicability boundaries of three simplifying assumptions—neglecting leakage, pipeline pressure losses, and steady-state fluid compressibility effects—are quantitatively analysed, with a total introduced error ≤3%. These assumptions are justified under medium-pressure, short-pipeline, and well-sealed conditions typical of marine EHA systems. Second, a composite control architecture combining outer-loop sliding mode control with inner-loop motor PID dual-loop control is proposed. Parameter tuning is performed using pole placement for the sliding surface and the Ziegler–Nichols critical ratio method for the inner loops, effectively suppressing hydraulic system parameter perturbations and random wave-induced load disturbances. Quantitative comparisons show that the proposed method reduces overshoot by 11.63% and improves sinusoidal tracking accuracy by 90.13% compared to conventional single-loop PID control. An integrated drive-control structure is designed, and a three-phase full-bridge inverter main circuit with wide-voltage input capability—including EMI filtering, soft-start, and LC filtering—is developed to accommodate the ±20% voltage fluctuations typical of ship power grids, thereby enhancing system integration and grid adaptability. Phased bench tests demonstrate that the settling time from no-load start-up to 200 r/min is only 0.01 s. When a sudden 20 N·m load is applied, the speed drop is less than 3%, and the recovery time is less than 0.025 s. The steady-state steering angle error does not exceed 0.12°, the maximum average steering rate reaches 3.33°/s, and the steering response time is within 0.3 s. All core performance indicators exceed the general technical standards for marine steering systems, with a 65.7% improvement in steady-state accuracy and a 62.5% improvement in response speed over conventional PID control. The research findings provide an effective general technical solution and experimental data support for the performance optimization and engineering application of marine EHA systems. Full article

Nickel ferrite (NiFe₂O₄) is one of the most studied inverse-spinel ferrites because it combines moderate saturation magnetization, comparatively high electrical resistivity, chemical stability, and broad synthesis flexibility. Yet the literature shows that the measured structure and magnetism of NiFe₂O₄ are not intrinsic constants; they evolve strongly with dimensionality, size, thickness, strain state, cation distribution, surface spin disorder, and synthesis pathway. This review develops a unified theoretical and literature-based interpretation of how dimensionality reshapes the structural and magnetic behavior of NiFe₂O₄ across bulk ceramics, nanoparticles, one-dimensional nanostructures, polycrystalline thin films, and ultrathin epitaxial films. The review is anchored in the two uploaded nickel ferrite attachments and expanded using internet-sourced journal literature on spinel inversion, surface effects, mechanochemical synthesis, sputtered and pulsed laser deposited thin films, and epitaxial ultrathin-film anomalies. The central novelty of this article is the formulation of a dimensionality-dependent framework in which the observed magnetic response is governed by a competition among three coupled factors: (i) the cation-distribution function, which controls the A–B superexchange balance and therefore the net ferrimagnetic moment; (ii) the microstructural coherence function, which measures how crystallinity, strain, defects, and anti-phase boundaries preserve or degrade exchange continuity; and (iii) the surface/interface spin-order parameter, which quantifies the loss or reconfiguration of magnetic order at free surfaces and buried interfaces. Within this framework, bulk NiFe₂O₄ behaves as a near-equilibrium inverse spinel with relatively stable magnetization, whereas nanoscale NiFe₂O₄ experiences strong spin canting and finite-size suppression due to the growing fraction of disordered surface spins. Thin films introduce a distinct regime in which strain, texture, anti-phase boundaries, substrate mismatch, and growth kinetics determine both anisotropy and magnetization. In ultrathin epitaxial films, off-equilibrium cation redistribution and interface-controlled electronic reconstruction may even generate magnetization values far above bulk expectations. The review also compares major synthesis routes—solid-state reaction, sol–gel, co-precipitation, hydrothermal growth, reactive milling, combustion, pulsed laser deposition, and radio-frequency sputtering—and explains why each route biases the final dimensionality-dependent properties differently. A set of word-style equations is provided to formalize spinel inversion, finite-size suppression, anisotropy scaling, coercivity trends, and superparamagnetic crossover. Beyond summarizing the field, the review proposes a regime map linking dimensionality to characteristic structural defects and magnetic signatures, and it identifies unresolved questions concerning the true origin of enhanced magnetization in ultrathin NiFe₂O₄, the interplay between anti-phase boundaries and strain, and the distinction between intrinsic inversion changes and extrinsic substrate artifacts. The resulting article offers a submission-ready, originality-focused review that positions dimensionality as the master variable governing structure–magnetism correlations in nickel ferrite. Full article

Simultaneously enabling wireless charging for multiple electronic devices is a distinctive advantage of wireless power transfer (WPT). Nevertheless, the development of dual-receiver WPT systems is constrained by several challenges, including undesired cross-coupling effects, suboptimal spatial utilization, complex control strategies, and insufficient system stability. To overcome the limitations, this article develops a multipolarity decoupled four-coil WPT system with constant voltage (CV) and constant current (CC). The proposed system suppresses undesired cross-coupling to negligible levels, thereby reducing the system complexity. In addition, the compensation network can be designed in a straightforward manner, providing improved design flexibility. A detailed mathematical derivation is presented to rigorously demonstrate the load-independent CV and CC output characteristics. Meanwhile, the inverter can achieve zero phase angle (ZPA), thereby improving the power factor of the WPT system. In addition, the multipolarity decoupled mechanism of the four-coil magnetic coupler is analyzed in detail theoretically. Finally, an experimental prototype is built and tested. The experimental results demonstrate a strong agreement with the theoretical analysis, ensuring load-independent CV and CC outputs of 68 V and 3.5 A, respectively. The system achieves a measured peak efficiency of 85.97%. Full article

Multiple three-phase machine drives are inherently fault-tolerant due to their multiphase structure; however, they remain susceptible to inverter-related faults. A common fault is the loss of gate signals in one inverter leg, resulting in an open-phase condition. Under such conditions, a reverse conduction path is established through the freewheeling diodes of the faulted leg, leading to uncontrolled freewheeling diode current generation. The resulting freewheeling diode current becomes particularly critical in the field-weakening region, when the back-EMF may exceed the DC-link voltage and a large reverse current can occur. This paper derives an analytical expression for real-time prediction of the freewheeling diode current in a triple three-phase surface-mounted permanent magnet synchronous machine drive. The method is applicable in both the constant-torque and field-weakening regions. The analytical prediction is validated through comparison with both experimentally measured and numerically simulated freewheeling diode current waveforms over a wide range of operating points, including no-load and loaded conditions. The results show that the proposed model accurately reproduces the envelope and conduction boundaries, while maintaining good agreement with simulations and measurements. The predicted current can be utilized in post-fault control, fault detection, and sensorless position estimation. Full article

The transition from sinusoidal to pulse width-modulated (PWM) voltage excitation introduces high-frequency ripple, generating small remagnetization cycles within the main magnetization cycle and increasing total iron losses. Soft magnetic materials are essential for constructing many electrical devices, and accurate loss data are critical for reliable design and thermal dimensioning. However, magnetic material data are typically available only under sinusoidal excitation, and there is no generally accepted method for calculating PWM-induced losses during the design phase. To address this issue, loss measurements under DC-biased magnetization were performed on laminated ring cores, and the data were collected in the form of three-dimensional (3D) loss maps defined by the variables $\Delta B$, ${\displaystyle \frac{\mathrm{d}B}{\mathrm{d}t}}$ and $B_{\mathrm{bias}}$. Based on these maps, a method referred to as 3DLMB is proposed to calculate the contribution of PWM-induced losses to total iron losses by comparing minor-loop variables obtained from AC excitation with those measured under DC bias conditions. The method is experimentally validated on three ring cores with different geometrical parameters, showing agreement between calculated and measured total AC losses within ±5% over a range of switching frequencies. The reported agreement applies to the investigated M400-50A material, ring-core geometries, and operating range, while applying it to other materials or geometries requires constructing the corresponding DC-bias 3D loss map. Full article