External Inductor Research Articles

Construction of a generalized mathematical model and fast calculations of plane-parallel rotating magnetic fields in process reactors with longitudinal currents of cylindrical inductors on a graphical calculator

The object of research is a quasi-stationary rotating magnetic field (RMF) generated by cylindrical inductors with longitudinal windings in the working space of process reactors, in particular reactors designed to work with magnetic particles (MP). The RMF theory in the working space of reactors has not yet been sufficiently developed, which hinders the widespread introduction of the considered, rather complex technologies into practice. The RMF of a specific reactor can be calculated accurately and completely using modern programs based on the finite element method, but it does not replace the general theory and theoretical analysis. In the literature, special cases of circular and elliptical plane-parallel RMF in reactors of the type under consideration have been studied, however, analytical formulas for a plane-parallel RMF for the general case of m-phase cylindrical inductors of external and internal design with symmetrical longitudinal windings are not presented. In this paper, a mathematical model is constructed and generalized analytical formulas for magnetic induction are obtained, linking the characteristics of a plane-parallel RMF in the working space of reactors at idle speed with the main parameters of external and internal cylindrical inductors with an m-phase symmetric longitudinal winding. A physical analysis is carried out and the adequacy of the model is confirmed. Using the proposed formulas and a free, easy-to-use Desmos graphical calculator, quick trial calculations and analysis of RMF in several reactors with two-pole external inductors and various windings for three phases (for 6 and 42 slots) and for six phases (12 slots) are carried out. The calculation results are consistent with experimental and literary data. New analytical formulas, as well as the demonstrated methods of quick evaluation calculations, analysis and experimental studies are recommended for practical implementation in the research, development and operation of reactors of this type. To carry out the calculations, it is enough to have a laptop or smartphone connected to the Internet, the time costs are insignificant. The results of the work will be useful to technologists, engineers and developers of both the reactors of the type under consideration and other devices with a similar purpose with an RMF.

Force effect of a circular rotating magnetic field of a cylindrical electric inductor on a ferromagnetic particle in process reactors

The object of research is the force effect of a circular magnetic field of cylindrical inductors with alternating current windings on the actuator element of technological reactors – a ferromagnetic particle. Technologies using a rotating magnetic field and ferromagnetic particles (RMF and FP) are increasingly used in industry, in devices for fine and ultra-fine grinding, mixing and activation, in the construction and chemical industries, in energy-saving and environmental systems. In previous studies, the authors proposed a method for calculating the force effect on ferromagnetic particles (FP) of an elliptical rotating magnetic field (RMF) of an external cylindrical inductor with a symmetrical alternating current winding. In this work, based on this technique, formulas for the force effect on the FP of the fundamental harmonic of RMF of cylindrical inductors with different numbers of pole pairs are derived and analyzed. It is shown that for a hard magnetic and saturated magnetically soft (soft-magnetic) particle in a circular field of a cylindrical inductor with the number of pole pairs greater than one, the magnitude of the magnetic displacement force does not depend on the orientation of the magnetic moment of the ferromagnetic particle, and the direction of action of this force is determined by the angle between the circular field induction vector and the magnetic moment of the particle. While maintaining the similarity of the inductors and the equality of the amplitude of the magnetic induction on the surface of the inductor bore, the magnetic displacement force does not retain the similarity, in particular, while maintaining the values of the magnetic moment of the particle, this force is inversely proportional to the radius of the bore of the cylindrical inductor. Examples are given of the use of formulas for calculating the ratio of displacement forces to the weight of a particle and the calculation of forces for an unsaturated soft-magnetic particle, where, due to the dependence of the magnetic moment on the field strength, the calculation formulas are modified and take on a slightly different form than the formulas for a particle with a constant modulus magnetic moment. The research results will be useful for engineers and researchers involved in the research, development, design and operation of reactors with RMF and FP technologies.

Modelling and mitigating oscillation in E-mode GaN HEMT: A simulation-based approach to parasitic inductance optimization

The escalating demands in energy conversion necessitate the evolution of efficient power electronic devices beyond the limitations of traditional silicon (Si) counterparts. This research delves into the intricacies of the Enhancement mode Gallium Nitride High Electron Mobility Transistor (E-mode GaN HEMT). A focus is placed on its static characterization, parameter analysis, and the influence of external parasitic inductances, particularly regarding oscillation challenges during its hard switching process. Forward and revise bias are conducted through comparison with Si-MOSFET and Cascade-GaN HEMT, along with its static on-resistance and transfer characteristics. Through rigorous half-bridge double pulse circuit LTSPICE simulations, this study deciphers the turn-on and turn-off dynamics of the E-mode GaN HEMT. By scrutinizing various parasitic inductances, the research elucidates mechanisms instigating high-frequency voltage and current oscillations. Significantly, the research presents a hierarchy of parasitic inductance influences, employing an energy loss comparison. This analysis underscores the prominent impact of the common source parasitic inductance, which exhibits energy loss increases of 23.6 % and 22.7 % at junction temperatures of 25 °C and 75 °C, respectively. Building on these insights, the study recommends strategies to mitigate the effects of external parasitic inductance, underscoring the pivotal role of oscillation suppression in advanced GaN Printed Circuit Board (PCB) and Integrated Circuit (IC) designs. This comprehensive inquiry provides a blueprint for enhancing GaN circuit designs, paving the way for their optimal application in the evolving realm of power electronics.

Dynamics of a fractional order locally-active Memristor with applications in oscillatory systems* *This work is supported by the National Natural Science Foundation of China (Grant No: 52077160) and the Natural Science Foundation of Shaanxi Province (Grant No: 2022JQ-661).

A non-volatile fractional-order Memristor, with two asymptotically stable equilibrium points and locally-active characteristic is presented. A fractional-order small-signal equivalent circuit is used to describe the memristor’s characteristics at an operating point within a locally-active region. Via the equivalent circuit, the memristor is shown to possess an edge of chaos within a voltage range; when connected in series with an inductor, it generates periodic oscillation about the locally-active operating point in the edge of chaos. The oscillating frequency and the external inductance are determined by the small-signal circuit’s admittance. Adding external capacitors and inductors in series/parallel with the memristor, three- and four-dimensional circuits are realized which generates chaotic oscillations. Analysis of the resulting three- and four-dimensional circuits are carried out at the memristor’s equilibrium point, the effects of the memristor’s parameters and the fractional order indexes of the added components on the system dynamics are also investigated using Lyapunov and bifurcation analysis. Numerical simulations show the versatility of the memristor for usages in oscillatory systems.

A self-powered synchronous magnetic flux extraction interface for electromagnetic energy harvesting

In this work, a self-powered synchronous magnetic flux extraction (SP-SMFE) circuit is proposed for electromagnetic energy harvesting. It's a bridgeless direct ac-dc converter, that uses a large-value external inductor L to store and transfer energy. By comparing the voltage across L, SP-SMFE achieves the peak detection of the inductor current Iem without an external power supply and transfers the energy to the load when Iem reaches the peak value, which can maximize the energy extraction from the electromagnetic transducer. Simulation results show that the output power of SP-SMFE is much higher than that of the voltage doubler circuit under the load range of 1–100 kΩ and the frequency range of 20–140 Hz. The input ac voltage with 4 V amplitude is rectified and stepped up to 59 V dc by SP-SMFE at the load of 100 kΩ and the frequency of 40 Hz. Experiment results verify the effectiveness of the SP-SMFE circuit in power harvesting at low frequencies and large loads.

Numerical simulation of supersonic gas flow in a conical nozzlewith local plasma heating and experimental results

The results of the main theoretical calculations and some experiments on local heating of the supersonic flow of gases by an external inductor with low-temperature plasma during the ionization of gases in a ceramic, conical nozzle, carried out by means of a powerful, high-frequency, electromagnetic field, are given. Numerical calculations are based on the provisions of electromagnetic field theory based on the equations of Maxwell, Navier Stokes for gas dynamics, Saha Eggert for ions and electrons, which make it possible to calculate the basic parameters of the inductor and the necessary specific power for heating supersonic, multicomponent, gas flows with low-temperature plasma. A model of vortexless (laminar), supersonic, stationary gas flow was used and mathematical modeling of its movement in a conical nozzle was carried out with the aim of possibly using the effect of additional heating of the gas flow with low-temperature plasma to increase the efficiency of the liquid rocket engine. It was found that in order to effectively heat the gas flow with low-temperature plasma in the design diameter, a conductivity of gases of at least s 200 1/·m is required for the initial temperature Ta = 2528 2674 оK and the frequency f = 27,12 MHz, which is not feasible even in the presence of a high concentration of impurities based on alkali metals. Therefore, a special device was developed an ionizer for the combustion chamber. The use of an ionizer allows to achieve the specified conductivity for the pressure in the combustion chamber of 15 MPa (a link to the article is given in the list of references). Calculations indicate the possibility of effective heating with low-temperature plasma of the supersonic flow of gases in the initial volume of the conical nozzle, which is adjacent to the critical cross-section of the liquid rocket engine. This will allow in the future to significantly increase its specific impulse and thrust at the start, due to an increase in the flow rate of gases in the design section. It has also been determined that the parietal region of a conical nozzle has a significant temperature gradient in the radial direction, whereas along the symmetry axis of the conical nozzle, the temperature increase has a linear relationship. The results of numerical simulations are qualitatively consistent with the experiments conducted in a quartz reactor cooled by water, which made it possible to use a variety of gas and gas-liquid mixtures to select fuel with the optimal composition of components. Preliminary data obtained on a working stand with a thermal power of a quartz reactor not exceeding 4 kW are given.

Impact of Parameter Mismatch on Three-Phase Dual-Active-Bridge Converters

Three-phase dual active bridge converters (DAB3) are a widely used topology in battery charging applications thanks to their numerous advantages, such as bidirectional power flow, galvanic isolation, low output current ripple, and inherent soft-switching. In such applications, three single-phase transformers are commonly employed as the AC-link to simplify manufacturing and reduce costs. These transformers’ leakage inductance can be utilized instead of the external leakage inductance to achieve high power density. However, the assumption of uniformity in these inductances is not always accurate as they can vary significantly during fabrication. This study presents a comprehensive analysis of the impact of transformer leakage inductance variation, which can deviate by up to 24% from the desired value. The effects of this variation are investigated from different perspectives, including power transfer, soft-switching range, root-mean-square (RMS) current, and the temperature rise of the transformer winding. Although the power transfer and total copper loss of transformers are changed insignificantly even under highly mismatched leakage inductance, the currents and thermal distribution among phases are considerably impacted. Based on statistical probability, a maximum leakage inductance variation threshold of 10–15% compared to the desired value is recommended to ensure the maximum acceptable temperature rise among phases. Experimental results are presented to validate the analysis.

Induction system for heating large rings before rolling

The paper considers the issues of designing an induction system for heating large-sized hollow cylindrical billets before rolling. The specific features of the billets heating process at the installation built into the technological processing line are noted. It is shown that for increasing the efficiency of the process of heating large-sized steel billets it is expedient to carry out the system of inductors with the use of a heat shield. A study of the process of heating of workpieces taking into account the nonlinear dependence of the physical characteristics of the metal of heated workpieces on the temperature changing in the process of heating is performed. The parameters of the induction system are calculated on the basis of a two-dimensional model. The geometric parameters of the circular billet resulted in a significant nonuniformity of the current density distribution along the axial coordinate of the billet due to the strongly pronounced boundary effects. The results of numerical calculation of the electromagnetic and thermal fields at different variations of the induction system design are presented. In order to substantiate and select the design of induction system that provides heating of the ring for the time caused by the work rate of the deforming equipment. A series of calculations was made, including three options: heating by an external cylindrical inductor; heating by two inductors: heating by inductor system with a heat shield. Analysis of efficiency of the investigated variants is based on multiple refinement of the results in the process of iterative design. Results of calculation of temperature distribution in the billet during heating are presented. The results of the research can be used to develop design and operating parameters of induction ring heating system in the rolling line.

Programmable resonant and forced mode high-voltage RF generator for dielectric barrier discharge and quadrupole mass filter

Dielectric barrier discharge, originally called silent discharge, is the electrical discharge between two electrodes separated by an insulating dielectric barrier. A high-voltage alternating current is required to generate the discharge process. There are two major principles of operation to implement a high-voltage generator: resonant mode and forced mode. While operating in forced mode, the working frequency is forced by the user using internal electronic devices. On the other hand, in resonant mode, the operating frequency is determined by the resonant circuit, which includes the external capacitance, inductance, and resistance of the load. This work shows a flexible circuit based on a real-time digital signal processor and a full H-bridge that combines the two topologies and can be used as a controller for dielectric barrier discharge and a quadrupole mass filter with varying capacitance.

Measurements of Small Frequency Differences by Dual Mode 4 MHz Quartz Sensors

We proposed a method for measuring frequency differences of the order of a few Hz with an experimental error lower than 0.0001% by using two 4 MHz quartz oscillators, the frequencies of which are very close (a few 10 Hz difference) due to the dual mode operation (differential mode with two temperature-compensated signal frequencies or a mode with one signal and one reference frequency). We compared the existing methods for measuring frequency differences with the new method which is based on counting the number of transitions through zero within one beat period of the signal. The measuring procedure requires equal experimental conditions (temperature, pressure, humidity, parasitic impedances etc.) for both quartz oscillators. To ensure equal resonant conditions for oscillation two quartz crystals are needed, which form a temperature pair. The frequencies and resonant conditions of both oscillators must be almost equal, which is achieved by an external inductance or capacitance. In such a way, we minimized all the external effects and ensured highly stable oscillations and high sensitivity of the differential sensors. The counter detects one beat period by an external gate signal former. By using the method of counting transitions through zero within one beat period, we reduced the measuring error by three orders of magnitude, compared to the existing methods.

A Fully Autonomous SSHIC Interface Circuit With Configurable Multi-Step Bias-Flip for Piezoelectric Energy Harvesting

This brief presents a piezoelectric energy harvesting interface circuit with a multi-step bias-flip strategy to boost the energy extraction capability. The optimized parallel synchronized switch on inductor and capacitor (SSHIC) technique is adopted. Except for the external inductor and capacitors, the proposed interface circuit is designed for fully integrated control without any external adjustment during the bias-flip process. Moreover, the steps for bias-flip can be configured flexibly, and the circuit can work even without an inductor. The interface circuit has been designed and implemented with 0.18- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mu }\text{m}$ </tex-math></inline-formula> CMOS technology. With the 5-step bias-flip SSHIC topology and a 1-mH inductor, the simulated whole current dissipation is 106 nA, the measured maximum flipping efficiency is 90.3%, and the measured maximum power efficiency improvement is 642% compared to the ideal full bridge rectifier (FBR).

Design and Optimization of a Boost Interface for Magnetostrictive Energy Harvesting

Magnetostrictive alloys are very promising for Vibration Energy Harvesting applications to supply power to Wireless Sensor Network (WSN) and Internet of Things (IoT) devices, especially because of their intrinsic robustness. Typically, vibration energy sources are random in nature, usually providing exploitable voltages much lower than the electronic standards 1.6, 3.3 and 5 V. Therefore, a Power Electronic Interface (PEI) is needed to improve the conversion to DC output voltage from AC input over a wide range of frequencies and amplitudes. Very few or no conversion techniques are available for magnetostrictive devices, although several have been presented over the years for other smart materials, such as piezoelectrics. For example, hybrid buck–boost converters for piezoelectrics use one or more external inductors with a high-frequency switching technique. However, because of the intrinsic nature of harvesters based on magnetostrictive materials, such energy conversion techniques are proved to be neither efficient nor applicable. An improved AC–DC boost converter seems very promising for our purpose instead. The key feature is represented by the direct exploitation of the active harvester coil as a storage element of the boost circuit, without using other passive inductors as in other switching methods. Experimental tests of such a converter, driven with a real-time operating Arduino controller to detect the polarity of the input voltage, are presented with the aim to assess the potentiality of the scheme with both sinusoidal and impulse-like inputs. Simulations have been performed with LTspice, and the performance and efficiency have been compared with other energy conversion techniques.

Simplification of Chua corsage memristor and hardware implementation of its neuron circuit

&lt;sec&gt;The Chua corsage memristor (CCM) is a voltage-controlled locally-active memristor, which has complex dynamic behaviors and potential applications in the field of neuromorphic computing. According to the DC &lt;i&gt;V&lt;/i&gt;-&lt;i&gt;I&lt;/i&gt; plot, the CCM can be classified as two-lobe, four-lobe, and six-lobe type. By analyzing their non-volatility and local activity, it is found that they have the same locally-active region and a common stable equilibrium. The mathematical models of the three CCMs are simplified based on the mechanism of neuromorphic behavior, namely, local activity. After the model simplification, the absolute value operation disappears, but the locally-active domain remains unchanged. For the simplified CCM, its small-signal equivalent circuit at the locally-active operating point is established, which is consistent with CCMs before being simplified. Hence, the model simplification does not change the small-signal characteristics of CCMs.&lt;/sec&gt;&lt;sec&gt;To further investigate the application of voltage-controlled locally-active memristor in modeling the neuromorphic behavior of neurons, the simplified CCM model is used to connect a capacitor and an inductor to construct a third-order neuron circuit. By applying theoretical analysis methods such as local activity, edge of chaos, and Lyapunov exponents, we predict the parameter domains where different neuromorphic behaviors are generated. The distribution of neuromorphic behaviors is described on a dynamic map determined by the parameters of applied voltage &lt;i&gt;V&lt;/i&gt;&lt;sub&gt;D&lt;/sub&gt; and external inductance &lt;i&gt;L&lt;/i&gt;. When the memristor is biased in the locally-active region, the system response changes among resting state, periodic spiking oscillation, and chaotic behaviors.&lt;/sec&gt;&lt;sec&gt;Finally, according to the simplified CCM mathematical model, the corresponding emulator circuit is designed by using three operational amplifiers, two multipliers, a current conveyor, and several resistors and capacitors. Based on the presented memristor emulator circuit, the hardware implementation of the neuron circuit is given. The experimental results verify the correctness and feasibility of the simplified CCM emulator circuit, and show that the simplified CCM-based neuron circuit can produce a variety of neuromorphic behaviors, including resting state, periodic spiking, chaotic state, bimodal response, periodic oscillation, all-or-nothing phenomenon, and spike clustering phenomenon. We expect that this work is helpful in further studying the mechanism of neuromorphic behaviors of the neuron circuit and its practical applications.&lt;/sec&gt;

DETERMINATION OF THE PHYSICO-CHEMICAL CHARACTERISTICS OF A MAGNETIC LIQUID IN THE IMPLEMENTATION OF THE METHOD BASED ON AN ELECTROMAGNETIC CONVERTER

A non-contact three-parameter electromagnetic method for measuring magnetic susceptibility κ, electrical conductivity χ, and temperature t of a ferrofluid sample is proposed. Theoretical principles of the operation of the inductive parametric electromagnetic transducer (IPET) with a sample of ferro-fluid are considered. As a result of studies of the universal functions of transformation of the IPET with a sample of the ferro-fluid, the theoretical provisions of the work of the IPET were further developed, which are related to the possibility of estimating the static parameters of the magnetic fluid. Because record of the effect of eddy currents leads to the need to determine three parameters of magnetic fluids with only one IPET, the necessity of using an inductive IPET switching circuit with a ferro-fluid sample, which provides for compensation of interfering external inductance L1 using a compensating capacitance P567 to improve the accuracy of measurements of the physical and chemical parameters of magnetic fluids, has been proved. The operation of the circuit is based on the fact that the eddy EMF excites a magnetic flux in the sample of the magnetic fluid under study, which is added geometrically with the excited magnetic flux from an external source, creating the resulting magnetic flux Ф2t in the sample of the magnetic fluid under study, while the resulting magnetic flux decreases in magnitude and shifts by the phase angle in relation to the excited magnetic flux, all this leads to a change in the components of the signals of the IPET, that is: inductance Lit and resistance Ω2t, which are associated with the physicochemical parameters κ, χ and t of the magnetic fluid sample. In further studies, in order to increase the efficiency of wastewater treatment of a mini-brewery, it is recommended to use a magnetic fluid in complex cleaning methods that involve the use of magnetic fluids in filters for post-treatment of wastewater from food production of acidic and alkaline composition.

A Highly Adaptive and Flipping-Time Optimized Piezoelectric Energy Harvesting Interface IC With Synchronized Triple Bias-Flip

This article presents a piezoelectric energy harvesting interface circuit with high adaptability to external inductors, transducer types, and vibration frequencies. High output power can be obtained with the help of triple bias-flip and optimal flipping time control. The triple bias-flip enables both higher efficiency and the use of an inductor with lower volume compared to conventional bias-flip topologies. Besides, owing to the highly adaptive circuit design and reverse current reduction in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> resonant loop, the proposed interface circuit not only automatically adjusts flipping time according to external inductance and piezoelectric transducer, but also reduces the reverse current of the inductor effectively. Also, an active rectifier that can reduce conduction loss of the diode-based rectifier has been implemented. The prototype integrated circuit has been fabricated in 180-nm CMOS technology and the chip area is 0.646 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The measurement results show that the proposed circuit achieves cold start-up without any external power supply, and can work with high efficiency when the external inductor is varying from 0 to 10 mH, transducer capacitance is changing from 20 to 90 nF, and vibration frequency is ranging from 35 to 200 Hz. The measured maximum output power of the proposed design can achieve as high as 473% enhancement to the full-bridge rectifier.

Variable Saturation Inductor-Based Full Bridge Converter With Wide ZVS Range and Reduced Duty Cycle Loss

A phase-shifted full-bridge (PSFB) converter is widely used in various applications due to its soft-switching characteristics. However, one of the recognized shortcomings of the PSFB converter is that it cannot simultaneously have a wide soft switching range and a small secondary-side duty cycle loss. The shortcoming hinders the high frequency and high efficiency of the converter. In this article, the change of the energy demand of the converter on the external series inductor with input voltage and load is analyzed. On this basis, a variable saturation inductor with controllable energy is proposed to meet the energy demand and solve the problem of core heating. The controllable change characteristics of the inductor energy are studied directly instead of the controllable change of the inductance value. By adjusting the inductor energy, the PSFB can not only achieve soft switching under light loads, but also reduce duty cycle loss under heavy loads. Theoretical analysis and experimental verification are carried out on the soft switching and duty cycle loss of the converter. Since the transformer ratio can be increased due to thesmaller duty cycle loss. The efficiency of the converter can be further improved.

Calculation and analysis of plasma impedance during closing process of laser‐triggered vacuum switch

The plasma characteristics of laser‐triggered vacuum switch (LTVS) have significant effects on the output characteristics of a pulsed power system during closing process. The plasma impedance can link the microscopic properties of plasma and the macroscopic electrical parameters effectively. In this paper, the mathematic representations of plasma impedance are calculated theoretically with the equivalent circuit. External circuit inductance and resistance are calculated by means of ANSYS software and discharge time constant, respectively. Furthermore, the current and voltage experimental waveforms during closing process are analyzed by fitting piecewise linear functions in MATLAB. The plasma impedance can be calculated based on the above conditions. The calculation results show that the plasma resistance reduces with time exponentially, which is caused by an exponential increase in electron density during closing process. In addition, the plasma inductance shows an overall trend of decreasing over time, but there are fluctuations.

A Magnetic Integrated Method Suppressing Power Fluctuation for EV Dynamic Wireless Charging System

This article proposes a magnetic integrated method for the coupler of the electric vehicle dynamic wireless charging system to suppress power fluctuation by transforming the problem into designing a stable equivalent mutual inductance between the receiving coil and transmitting coils on the road. Both primary-side and secondary-side couplers adopt a magnetic integrated design. The primary-side coupler integrates a reverse coil inside the transmitting coil, and the secondary-side coupler integrates a coil in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> resonance compensation inside the receiving coil. Two advantages are unveiled through theoretical analysis of system characteristics: the original single mutual inductance is replaced by the mutual inductance difference between the two reverse series transmitting coils and the receiving coil to determine the power transmission, which suppresses output power fluctuation; the secondary-side integrated inductor coil replaces the external bulky compensation inductor in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> resonance compensation network and additionally realizes better zero-voltage switching conditions. The optimized design process considering the additional couplings is given based on circuit analysis. A prototype is implemented to validate the proposed design. Experimental results show that the output power fluctuation is within ±4% during dynamic charging at a power level of 4.5 kW, and the efficiency reaches 91.6%.

A Giant Dual‐Resonant in Magnetoelectric Composite Based on Electrical and Electromechanical Coupling Towards Enhanced Working Bandwidth and Frequency Tuning

Expanding the resonance bandwidth and achieving tunable frequency are crucial for applying magnetoelectric (ME) composites in variable environments to realize their application, including magnetic and current sensors, tunable microwave devices, energy harvesters, etc. Herein, a dual‐coupling mode of combining electrical and electromechanical to implement wide bandwidth and frequency tuning in a ME laminated composite connected to an external inductor is investigated. Furthermore, this dual‐coupling mode is theoretically and experimentally studied and two resonances based on an equivalent circuit method are predicted. When the ME composite is connected to an inductor of 0.5 mH with an internal resistance of 31.74 Ω, the experimental result shows that the bandwidth increased by 429.32% compared with the original. In contrast, while the ME composite is connected to an inductor of 0.5 mH with an internal resistance of 12.16 Ω, two ME voltage coefficients (αV) are dramatically increased by 302.29% and 356.80% at resonance peaks, and the resonance frequencies are proportionally tuned of 6.84% (Δf1 = 6.24 kHz) and 4.74% (Δf2 = 4.32 kHz), respectively. These experimental results are significantly in agreement with the theoretical analysis. Therefore, the proposed method effectively achieves bandwidth expansion, ME coupling coefficient enhancement, and resonance frequency tuning.

Wetting and Inductivity in the Impedance Behavior of Large Lithium-Ion Cells

The wetting of the porous electrodes and the separator is crucial in the production of lithium-ion cells. Electrochemical impedance spectroscopy is able to measure and characterize the wetting. This paper p resents an equivalent circuit for commercial high-capacity cells and shows a method to analyze the wetting of these cells. The equivalent circuit includes an external inductance, a transmission line model (TLM) for the description of the pore impedance and, additionally, a TLM for the impedance of substrate foil inductance and contact resistance. Based on symmetric and full laboratory cells, the superposition of the impedance is discussed. Furthermore, the method to adjust the impedance and analyze the wetting is demonstrated on hard case cells with a capacity of 22 Ah. It is shown that, in addition to inductance for cables and electrode-external contacts, high-capacity lithium-ion cells build up inductance due to the electrode area in combination with the substrate foil. This inductance, together with the contact resistance, result in a characteristic hook in the Nyquist plot. A TLM describes and explains this behavior quite well. Additionally, the impedance of the cell is adjustable so that it corresponds to a laboratory cell in blocking conditions. Thus, the wetting of the separator and the wetting of the electrode become separately evaluable and calculable.