Ferrite Core Research Articles

Ferrite Concentrating and Shielding Structure Design of Wireless Power Transmitting Coil for Inductively Coupled Capsule Robot.

High permeability material, especially the ferrite, has been widely used in wireless power transfer (WPT) to enhance the power transfer efficiency (PTE). However, for the WPT system of inductively coupled capsule robot, the ferrite core is solely introduced in power receiving coil (PRC) configuration to enhance the coupling. As for the power transmitting coil (PTC), very few studies focus on the ferrite structure design, and only the magnetic concentrating is taken into account without careful design. Therefore, a novel ferrite structure for PTC giving consideration to the magnetic field concentration as well as the mitigation and shielding of the leaked magnetic field is proposed in this paper. The proposed design is realized by combing the ferrite concentrating part and shielding part into a whole and providing a low reluctance closed path for magnetic induction lines, thereby improving the inductive coupling and PTE. Through analyses and simulations, the parameters of the proposed configuration are designed and optimized in terms of average magnetic flux density, uniformity, and shielding effectiveness. Prototypes of PTC with different ferrite configurations are established, tested, and compared to validate the performance enhancement. The experimental results indicate that the proposed design notably improves the average power delivered to the load from 373 mW to 822 mW and the PTE from 7.47% to 16.44%, with a relative percentage difference of 119.9%. Moreover, the power transfer stability is slightly enhanced from 91.7% to 92.8%.

Investigation of Flux Transfer along Ferrite Core of Probe Coil for Eddy Current Nondestructive Evaluation

Abstract A probe coil with a T-core above a layered conductor with surface hole is investigated for magnetic flux transfer along the ferrite core and enhancement of eddy currents in conductor. The cylindrical coordinate system is adopted and an artificial boundary is added to the solution domain with radius b, and the general formula for calculating the impedance of the T-core coil is derived using the truncated region eigenfunction expansion (TREE) method. For four special cases with different probe configurations, coil impedance changes due to the layered conductor and defect are calculated with Mathematica software over a frequency change ranging from 100 Hz to 20 kHz. The analytical results are in good agreement with those obtained by the finite element method and experimental measurements. The results show that under the same lift-off height and excitation frequency, the impedance change caused by the conductor or defect in the coil of long core column is greater than that of the short core column coil. It indicates that the probe coil with a long core column can transfer magnetic flux to the conductor, thereby enhancing eddy currents in the conductor.

Raman scattering features of nanocrystalline neodymium ferrite

We report on the analysis of the structural properties of nanocrystalline neodymium ferrite produced by the solution combustion method. The Raman spectrum and X-ray diffraction patterns were measured and analyzed by comparison with the literature data. The Raman spectrum demonstrated the superposition of bands assigned to two substances, namely nanocrystalline neodymium ferrite and traces of iron oxide as hematite. The achieved results lend credence to the idea that particles with a crystalline neodymium ferrite core encased in hematite-like iron oxide scatter light.

Magnetic Properties and Exchange Coupling Effects of SrFe12O19@MFe2O4 (M = Co, Ni, Zn) as Hard-Soft Magnetic Ferrite Core–Shell Nanofibers

Magnetic Properties and Exchange Coupling Effects of SrFe12O19@MFe2O4 (M = Co, Ni, Zn) as Hard-Soft Magnetic Ferrite Core–Shell Nanofibers

Magnetic Design Aspects of Coupled-Inductor Topologies for Transient Suppression

Based on the discovery of the surge absorption capability of supercapacitors, a transient protector named supercapacitor-assisted surge absorber (SCASA) was designed and implemented in a commercial device. Despite its simplicity, the circuit topology consisted of a coupled inductor wound around a specially selected magnetic core. This paper elucidates the design aspects of SCASA coupled-inductor topologies with a special focus on the magnetic action of core windings during transient propagation. The non-ideal operation of the SCASA transformer was studied based on a semi-empirical approach with predictions made by using magnetizing and leakage permeances. The toroidal flux distribution through the transformer was also determined for a 6 kV/3 kA combinational surge, and these findings were validated by using a lightning surge simulator. In predicting the possible effects of magnetic saturation, the hysteresis properties of different powdered-iron and ferrite core types were considered to select the optimal design for surge absorption. The test results presented in this research revealed that X-Flux powdered-iron toroid and air-gapped EER ferrite yielded exceptional performance with ∼10% and ∼20% lower load–voltage clamping compared to that of the existing Kool μu design. These prototypes further demonstrated a remarkable surge endurance, withstanding over 250 consecutive transients. This paper also covers details of three-winding design optimizations of SCASA and LTSpice simulations under the IEC 61000/IEEE C62.45 standard transient conditions.

Design of Wireless Power Transfer System for PMBLDC Motor driven Autonomous Vehicle

In the modern age of technology where everything is powered via physical wires, once considered a technical marvel has now become a bane. Wireless power transfer is the key to the future of power transfer, in this paper a 1kW WPT system is designed and simulated for an PMBLDC motor driven autonomous vehicle. This paper focuses in detail about the variation in performance of the coils and the overall system when ferrite cores and aluminum shielding is considered along with the coils. It provides a comprehensive analysis on the misalignment of transmitter and receiver coils in different orientations and distances. The results indicate a significant increase in power transfer and efficiency of the system when extra components such as cores and shielding are also implemented. It is oriented towards increasing the efficiency of powering autonomous vehicles used in various sectors such as automobiles, information technology, aerospace, robotics, precision and domestic equipment, etc.

Modeling and Analysis of Litz Wire Radio Frequency (RF) Coil in Inside-Out NMR Well Logging Sensor

Nuclear magnetic resonance (NMR) well logging is an important method of oil measurement, and the radiofrequency (RF) coil is an important component for obtaining accurate parameters of rock formation. The use of Litz wire as RF coil can help minimize the resistance and increase the signal-to-noise ratio (SNR) of NMR signals. However, the electromagnetic field computing and performance evaluation of Litz wire are complicated and difficult. In this study, we proposed an effective model for analyzing the Litz wire in inside-out NMR logging sensor. Considering the electromagnetic parameters of the coil itself, the frequency response of excitation and tuning and matching circuit, we proposed a new and accurate model for SNR analysis. We then introduced a homogenization-based finite element method to calculate the Litz wire around a ferrite core, and the electromagnetic parameters of Litz wire with different structures were obtained accurately and quickly. We compared the Litz wire and enameled wire through our proposed model. Results show that the SNR of Litz wire is remarkably higher than that of enameled wire, and the model analysis results are consistent with the measured results. Suggestions for further reducing the AC resistance of RF coil composed of Litz wire are provided.

Analysis and Experimental Investigation of High-Frequency Magnetic Flux Distribution in Mn-Zn Ferrite Cores

This article presents a comprehensive investigation of the high-frequency magnetic flux distributions in manganese-zinc ferrite ring cores. New experimental characteristics are presented and used in the flux modeling. The flux distribution is predicted by a one-dimensional analytical model, a transmission-line model, and finite-element analysis. The models are used to investigate the high-frequency effects, such as skin depth and dimensional resonance. A complete experimental validation is presented. The nonuniform magnetic flux distributions are experimentally validated for two Mn-Zn materials: 3F36 and 3E10. The low permeability 3F36 material performance can be significantly degraded by dimensional resonance. However, the high permeability 3E10 material degrades due to the skin effect. The presented analytical methods show a very good correlation with the measurements.

Temperature effects induced by NIR photo-stimulation within Ist and IInd optical biological windows of seed-mediated multi-shell nanoferrites.

Different types of ferrite core-shell structures, namely CoFe2O4@CoFe2O4, CoFe2O4@Fe3O4, CoFe2O4@MnFe2O4, and CoFe2O4@MnFe2O4@ZnFe2O4, were prepared by the seed-mediated approach. We show that this synthetic methodology offers great and important flexibility in the engineering of multi-shell ferrite nanoparticles which can be further used in various advanced applications. This impressive tool can be used for particle size tuning of homo- and heterostructures through convenient control of the concentration of metal acetylacetonates without the necessity of changing synthetic parameters, i.e., temperature, time, and solvent. The contactless conversion of laser light within Ist (808 nm) and IInd (1122 nm) biological optical windows was studied on the fabricated ferrite core-shell materials which showed promising heating effects that can be a basis of their practical exploitation in the biomedical field.

Gold nanoshells with magnetic cores and a urea-based receptor for SERS sensing of fluoride anions: experimental and computational study.

The study demonstrates that a combination of plasmonic nanostructures and artificial receptors can be applied for sensing small molecular species. Gold nanoshells containing magnetic cores are used as the SERS-active substrates, which opens the way for the development of multimodal contrast agents with applicability extended to sensing or for the separation of analytes by magnetic solid-phase extraction. Disubstituted ureas forming hydrogen-bonded complexes with certain anions can be employed as molecular sensors. In this case study, gold nanoshells with silica-coated Mn-Zn ferrite cores were prepared by a multistep procedure. The nanoshells were co-functionalized with an N-(4-mercaptophenyl)-N'-(4-nitrophenyl)urea sensor synthesized directly on the gold surface, and with 4-nitrothiophenol, which is adopted as an internal standard. SERS measurements were carried out with acetonitrile solutions of tetrabutylammonium fluoride (Bu4NF) over a concentration range of 10-10-10-1 mol L-1. The spectral response of the sensor is dependent on the fluoride concentration in the range of 10-5-10-1 mol L-1. To investigate further the SERS mechanism, a model sensor, N-(4-bromophenyl)-N'-(4-nitrophenyl)urea, was synthesized and used in Raman spectroscopy with solutions of Bu4NF, up to a molar ratio of 1 : 20. The spectra and the interactions between the sensors and fluoride anions were also studied by extensive DFT computations.

Equivalent circuit of an inductor on a nanocrystalline core with a high magnetic permeability

Based on the measured impedance of the inductors based on a toroidal core wound from a thin (18 m) nanocrystalline tape, with a different number of winding turns, an equivalent high frequency (0 Hz - 500 MHz) circuit model was built. The equivalent circuit model was built taking into account the physical processes occurring in the inductor: effect of wire resistance, effect of core material, mutual effect of wire and core material. The attempt explaining why the frequency characteristics (modulus and phase) of the inductor complex impedance have such a character in a wide frequency band (up to 500 MHz) was made. It was shown that for constructing an equivalent circuit model (structure and parameters), measuring only the inductors resistance modulus is not enough. It is also necessary to measure the phase of the inductor complex resistance, which is ignored in many works on the synthesis of an e inductor equivalent circuit. The fundamental difference between the operation of a nanocrystalline core and a ferrite core as applied to high-frequency filters is shown.

Performance analysis in a two-phase interleaved DC-DC boost converter with coupled inductors

In this study, the inductor current ripple and output voltage ripple of a two-phase DC-DC boost converter, circuit performance is investigated according to the direct/inverse coupling effect of the coupled inductors. The coupled inductors are modeled with both power electronics circuit and electromagnetic modeling and by using finite element analysis software (FEA). However, the high frequency inductor designs generally use air-gapped composite ceramic ferrite cores and are designed with powder core (Kool Mu) core structures that eliminate air gap requirements. Thus, the fringe flux, which occurs in the air gaps in ferrite cores and reduces the useful flux, and the bad effects such as overheating and electromagnetic noises (EMI/EMC) in the air gaps in high frequency switching are also reduced. Especially in interleaved power converter designs, the performances of coupled inductors affect the output parameters of the power electronics circuit. Considering energy efficiency and more compact circuit topologies, the modeling and simulation approach of high-frequency inductors using finite element analysis software, which is emphasized in this study, popularly and scientifically guides power electronics circuit designers.

A hepatocyte-targeting nanoparticle for enhanced hepatobiliary magnetic resonance imaging.

Hepatobiliary magnetic resonance imaging (MRI) can inform the diagnosis of liver tumours in patients with liver cirrhosis and hepatitis. However, its clinical utility has been hampered by the lack of sensitive and specific contrast agents, partly because hepatocyte-specific nanoparticles, regardless of their surface ligands, are readily sequestered by Kupffer cells. Here we show, in rabbits, pigs and macaques, that the performance of hepatobiliary MRI can be enhanced by an ultrasmall nanoparticle composed of a manganese ferrite core (3 nm in diameter) and poly(ethylene glycol)-ethoxy-benzyl surface ligands binding to hepatocyte-specific transmembrane metal and anion transporters. The nanoparticle facilitated faster, more sensitive and higher-resolution hepatobiliary MRI than the clinically used contrast agent gadoxetate disodium, a substantial enhancement in the detection rate (92% versus 48%) of early-stage liver tumours in rabbits, and a more accurate assessment of biliary obstruction in macaques. The nanoparticle's performance and biocompatibility support the further translational development of liver-specific MRI contrast agents.

ANFIS-based Parameter Estimation of a Single Phase Inverter Circuit with Isolation Transformer

In this study, it is aimed to isolate the output interface of single-phase inverter circuits and the grid from each other. For this purpose, three-dimensional isolation transformers are designed with a software using the In order to determine the leakage inductance behavior of the isolation transformer, whose electromagnetic modeling was carried out with Ferrite N87 core material, the geometric distances of the primary-secondary windings and the diameter sizing of the windings were changed in parametric linear steps, and a data set was obtained as a specific parametric scenario for the leakage inductance values. Thus, the estimation process of the electromagnetic modelling of the transformer has been successfully carried out thanks to the training and testing processes of Adaptive Network Based Fuzzy Inference Systems (ANFIS) with the numerical information obtained from the finite element analysis (FEA) parametric data set. After the estimation processes, the percentage error is calculated as 0.3470% and 0.4448% for training and testing. Thus, the determination of the isolation transformer with the optimum values designed for the inverter circuit has become easier. Also, experimental analysis is performed on inverters to prove the robustness of the proposed method. In this context, first of all, RMS values that vary according to the different operating parameters of the inverters are created. The proposed ANFIS based system estimates RMS values with 7,057 % error.

Implicit iteration calculations using 3D field analyses, to predict the power loss in powder ferromagnets, with their measurement tests

An implicit iterative calculation model with 3D magnetic field analysis has been developed to predict the power losses in the sintered ferromagnetic powders. The integral parameters of the magnetic field such as the losses due to eddy currents and hysteresis ones were calculated for different frequencies and magnetic flux density values. Such prediction of the losses is helpful as the data provided in catalogues is measured for strictly limited ranges of flux density and operation frequency. Moreover, the manufacturers don't give the electrical conductivity and magnetic permeability values of the magnetic cores from the aforesaid materials needed for 3D magnetic field analyses, where ferromagnetic particles cannot be separately included due to enormous computational efforts. The simulated losses in the cores were tested for the magnetically soft composite (SMC) called Somaloy as well as for ferrite cores. A good conformity of the simulated core losses with the measured values was obtained.

Optimal transformer design of DAB converters in solid‐state transformers for maximum power efficiency

AbstractSolid‐state transformers (SST) are a viable solution to replace the conventional low‐frequency transformer in railway vehicles. In the SST, high frequency transformers in dual‐active‐bridge (DAB) converters are essentially used for electrical insulation. Thus, the high‐frequency transformer design becomes so important to increase the high efficiency operation with electrical insulation. Here, an optimal transformer design methodology, which provides a maximum power efficiency operation of the transformer for DAB converters, is proposed. Considering the core loss and copper loss of the transformer, the optimal number of turns for the transformer in a DAB converter N1,op and N2,op can be determined so that the maximum power efficiency for the transformer is achieved at a normal operating point of the DAB converter. To derive the major loss parameters, a finite‐element‐method based simulation was performed for resistive and magnetic loss analysis, which eventually provided the optimal number of turns under the given physical size of ferrite core. The 20 W prototype for a DAB converter with EER2828 and EER3019 of ferrite core shapes were fabricated and verified by simulations and experiments. The results showed that the optimum number of turns N1,op were selected as 12 and 8 turns for two ferrite core models, respectively, which are most highest efficiencies with regard to the different winding turns. To apply the proposed methodology to the SST power level in railway vehicles, 125 kW transformers with inductor set for the SST applications has been fabricated and experimentally verified. As a result, 99.6% of highest efficiency with thermal stable operation was obtained by the proposed transformer design methodology.

Self-Operating Flyback Converter for Boosting Ultra-Low Voltage of Thermoelectric Power Generator for IoT Applications

This article presents a novel self-operating flyback converter to boost the ultra-low voltage produced by thermoelectric power generator (TEG). The proposed converter uses dual transformer, one for low-voltage startup and other to extract power from TEG. The use of separate transformer provides high-voltage transfer ratio, reduces high series resistance loss, and brings down the input impedance of circuit. The copper wire wounds ferrite toroid core transformer provides very low series resistance and negligible core loss, which improves the circuit efficiency. This boost converter operates with an input voltage range of 22–300 mV and provides maximum output power of 0.073 – 147 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\rm{mW}}$</tex-math></inline-formula> correspondingly. The peak efficiency of 68% with output power of 1.32 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\rm{mW}}$</tex-math></inline-formula> (voltage ∼1.83 V) is achieved at an input voltage of 50 mV. For regulated output voltage, a feedback loop is used to keep output voltage constant during sudden voltage rise of TEG. The proposed circuit uses discrete components, ferrite toroid core, and PCB, which has lower cost than available energy harvester module, which uses energy harvesting ICs, discrete components, and tiny transformer. The lower startup voltage, higher output power, and voltage with high conversion efficiency of this boost converter maximize the applications potential of the TEG as a portable power source for Internet of Things (IoT) devices.

Measurement Methods for High-Frequency Characterizations of Permeability, Permittivity, and Core Loss of Mn-Zn Ferrite Cores

Manganese–zinc (Mn-Zn) ferrites are the primary choice for high-frequency and high-power magnetic components. Optimum material selection is essential for high-performance magnetic component design. However, the manufacturers’ material specifications usually do not provide sufficient information to optimize the design. Complex permeability and permittivity, as well as specific power loss, are typically provided as one value, regardless of the core shape and size. Magnetic component design based on these incomplete specifications can result in a poorly optimized component. This article proposes methods to determine the properties of Mn-Zn ferrite at high frequencies, with tests up to 20 MHz. This article also presents experimental complex permeability and permittivity frequency characteristics for four ferrite materials: 3E10, 3F36, 3E65, and 3C95. The resulting fitted parameters for the equivalent-circuit model can be used in any design algorithm or simulation tool. The impacts of physical size, temperature and force on complex permeability and permittivity are also considered.

Large-Area Free-Positioning Wireless Power Transfer to Movable Receivers

This article introduces a method for efficient and robust free-positioning wireless power transfer (WPT) in a large area, which can be applied to many use cases, including wireless charging of industrial robots, drones, and electric scooters. In these large areas of WPT applications, multiple transmitters (Txs) are placed in a pad-like area, and the Tx coils are optimally excited to enable robust and efficient power transfer to movable receivers within the charging area. The proposed configuration enables almost continuous magnetic flux path from a set of Tx coil(s) to another set of Tx coil(s) through the receiver coil ferrite core. Therefore, efficient power transfer is ensured throughout the whole Tx coverage area. The article introduces a novel method to detect the position and orientation of the receiver only from the Tx-side measurements. The proposed solution is experimentally verified in a laboratory prototype, and the experimental results show dc-to-dc efficiency of 91% with only 1% variation in most of the Rx positions.

Model of Ferrite-cored Driver-pickup Coil Probe Application of TREE Method for Eddy Current Nondestructive Evaluation

An analytical model of a driver-pickup coil probe, consists of a cylindrical ferrite core, located above a layered conductor is presented. The truncated region eigenfunction expansion (TREE) method is used and the solution region is truncated with a certain radius around markedasmathitalicz axis. First, the magnetic vector potential of each region of filamentary coil problem is derived and solved with variables separation method using boundary and interface conditions, and then the rectangular cross-section coil problem is solved with superposition method. The expression of induced voltage in pickup coil is obtained and can be calculated with software such as Matlab or Mathematica. Using the proposed analytical model, the influence of the excitation frequency and excitation current in the driver coil on the responses of the pickup coil is examined. Experiments are performed, and the changes of voltage induced in the pickup coil due to the conductor are measured at different excitation frequencies and excitation currents. The analytical calculation results agree with the experimental results very well, verifying the correctness of the proposed analyticalmodel.