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In aspects of its simple configuration and tunability, piezoelectric-based metasurface has benefited over its mechanical counterpart in adaptive wavefront manipulation. By tuning the circuitry elements in the shunting circuits properly, the equivalent material properties of the metasurface can be modified to attain a complete 2 π phase shift and to maintain high transmission at desired working frequencies. In this paper, a piezoelectric-based elastic metasurface with hybrid shunting circuits ( NC – LC – NC shunts) are proposed to adaptively control the propagation of flexural waves. Through tuning of negative capacitance and inductance simultaneously, the proposed elastic metasurface can cover a phase shift ranging from 0 − 2 π while having a high transmission ( ≥ 0.7). It is discovered that any similar metasurface structural design with solely single shunting circuit presently available could not achieve the same results as the proposed elastic metasurface. In addition, analytical modeling based on equivalent Young's modulus is developed and a finite element model is built to study the transmission and phase shift of the proposed metasurface. It is demonstrated numerically that the proposed piezoelectric-based elastic metasurface is capable of performing switchable functionalities, such as wave refraction and focusing, at different working frequencies (3500 Hz, 5000 Hz, etc.). Utilization of hybrid shunting circuits in designing a more compact metasurface design. Establish an analytical model based on equivalent Young's modulus to predict effective range of circuitry elements. Build a finite element model to study the transmission and phase shift of the piezoelectric-based metasurface. Cover a full 2 π phase shift and maintain high transmission through tuning negative capacitance and inductance simultaneously. Perform switchable functionalities at different working frequencies. [ABSTRACT FROM AUTHOR]

In the field of high-precision physical field detection, measurements based on magnetic signals are crucial due to their exceptional accuracy, sensitivity, and stability. Superconducting Quantum Interference Devices (SQUIDs), with their ultra-high sensitivity, have become key in detecting minute changes in magnetic flux. However, with increasing demands for higher precision, further enhancing device performance under quantum constraints remains a significant challenge. This study improved the precision of SQUID sensors by optimizing the geometry of microscale washers using the physical response of superconducting films under micromachining technologies and quantum constraints. Our research extensively examined the effects of square, octagonal, and circular washers on the magnetic field response, shielding currents, and inductance. Experimental results showed that, compared to traditional square washers, octagonal washers significantly enhanced sensor sensitivity and efficiency by minimizing edge magnetic flux and optimizing current distribution. Notably, all observed inductance values exceeded predictions based on traditional empirical formulas, with square washers showing the highest average relative error of 80.8%, while circular and octagonal washers had errors of 65.31% and 66.43%, respectively. This breakthrough not only lays a new theoretical foundation for the design of SQUID sensors but also provides robust evidence for enhancing magnetic field detection through microscale technological innovation. [ABSTRACT FROM AUTHOR]

This manuscript examines the output characteristics of a dual three-phase synchronous reluctance motor (DT-SynRM) according to two winding arrangements under normal and half-control modes. In the case of the DT-SynRM, it can operate by using all of the dual three-phase systems (the normal control) or one of the dual three-phase systems (the half control). In this paper, conventional winding function theory (WFT) is applied, because the output characteristic can be predicted by the inductance behavior. According to the WFT, the inductance value can be affected by the winding function, the turn function, and the inverse air gap function. As a result, the rotor barrier shape as well as the winding configuration are the most important factors that have an effect on the performance of the DT-SynRM. Therefore, the effect of the rotor barrier design on the performance is analyzed when the winding configuration and control mode are different. Finally, the validity of the torque characteristic is substantiated through experimental verification. [ABSTRACT FROM AUTHOR]

Coils are designed to have impedance characteristics appropriate for any use of the sensors, analog circuits and so on. The impedance characteristics of a coil depends on the coil shape and used materials, and these factors make coil design difficult. Therefore, we proposed a convenient method to obtain the impedance characteristics of a coil by theoretical calculation of the inductance, resistance, and capacitance. The difference between the calculated and measured values was within 15%, which demonstrated the usefulness of the proposed method. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Abstract Simple and practical methods have been provided for the mutual inductance between rectangular and circular coils with parallel axes. The 2D Integral solution is given for the coils without the axial overlap. To improve the efficacy of the proposed approach for the partial or full axial overlap, the series solution derived by the truncated region eigenfunction expansion (TREE) is provided. Both integral and TREE expressions show very high accuracy through comparison with the finite element method simulation and experiment results. Numerical comparisons reveal that the TREE solution is the most efficient while keeping sufficient accuracy, and it is also applicable to all sorts of coil positions.

A mathematical model is presented for the optimisation of an Electromagnetic Halbach Array (EHA) for wireless power transfer. The mathematical model is based on Biot‐Savart's law of magnetic field in a current‐carrying square loop. The model is validated through static electromagnetic simulations in ANSYS Maxwell and found to be accurate and effective when predicting the magnetic field within the EHA box. To verify the analytical and simulation results, an EHA was fabricated, and experimental verification was carried out. The results show that the mathematical model can be widely used in the analysis and design optimisation of EHAs of any size and with diverse parameters in the case of single‐layer square spiral planar coils. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fe-Si cores with a CoO-SiOx-Co composite coating layer were prepared by sintering Fe-6.5wt.%Si/Co3O4 composite powders. The effects of Co3O4 coating content and structural evolution mechanism on magnetic properties of the Fe-Si cores were systematically studied. The results indicate that the high temperature during hot pressing sintering promotes solid-state interface reactions between Co3O4 coating and Si atoms from the Fe-6.5wt.%Si magnetic powder, resulting in the formation of electrical insulation phase SiOx and ferromagnetic phase Co. The formed CoO-SiOx-Co composite coating layer can effectively weaken the eddy current effect and magnetic dilution effect. When the Co3O4 coating content increases, the saturation magnetization of Fe-Si core decreases but still maintains a high value. And the magnetic loss shows a trend of first decreasing and then increasing. When the Co3O4 coating content is 5.0 wt.%, the Fe-Si core exhibits relatively superior magnetic properties, such as high saturation magnetization (192.9 emu/g), high permeability (98), and low magnetic loss (343.3 kW/m3, 0.02 T/50 kHz). [ABSTRACT FROM AUTHOR]

In this work, a mathematical model of a three-phase nonlinear transformer is suggested. The model enables simulating the transformer operation with allowance for its nonlinearity and covers needs of the relay protection. Our model has been developed on the basis of a mathematical model with phase coordinates, where differential equations are composed by the Kirchhoff's phase-voltage law. Based on this model, we first compose a mathematical model for simulating steady-state operation modes of a transformer, taking into account the asymmetry and nonlinearity of its ferromagnetic core. In this model, the initial values of inductances and mutual inductances of loops are determined from the main phase inductance calculated by the experimentally found no-load current, and their current values are determined from the currents in windings and the magnetic fluxes in legs of the transformer core. The magnetic fluxes are calculated by the nodal-pair method. This improved mathematical model is verified through a comparison between the calculated harmonic components of the phase currents and the experimental results. The harmonic components are calculated with the use of Fourier expansion of the calculated phase currents. Their experimental values are determined with a spectrum analyzer. The calculated and experimental harmonic components of the currents of phase A during no-load and rated-load operation of the transformer are tabulated. The comparison of these results shows that the mathematical model of a three-phase transformer we suggest makes it possible to simulate currents in transformer windings under steady-state operation modes with accuracy acceptable for relay protection. [ABSTRACT FROM AUTHOR]

Simple and practical methods have been provided for the mutual inductance between rectangular and circular coils with parallel axes. The 2D Integral solution is given for the coils without the axial overlap. To improve the efficacy of the proposed approach for the partial or full axial overlap, the series solution derived by the truncated region eigenfunction expansion (TREE) is provided. Both integral and TREE expressions show very high accuracy through comparison with the finite element method simulation and experiment results. Numerical comparisons reveal that the TREE solution is the most efficient while keeping sufficient accuracy, and it is also applicable to all sorts of coil positions. [ABSTRACT FROM AUTHOR]

The performance of the power converter bus bar is not only determined by its normal operational design, but also related to its fault ride-through ability consideration. Conventional busbar design only takes the normal operational performance into account. This article proposes an optimal busbar design method for the modular multilevel converter (MMC) submodule, which takes both the normal and fault ride-through performance into account. The normal operational design is to realize low stray inductance and balanced inductance distribution between parallel capacitor branches. The basic structural design guideline for the MMC submodule is presented. Taking both the stray inductance and manufacturing cost into account, the optimal layout of the busbar is proposed. To balance the capacitor branch currents, the mathematical model of the busbar stray inductance is built. The influence of different busbar structures on the stray inductance is analyzed. The analysis is verified by simulation results. To improve the fault ride-through capability, special consideration is taken into account to reduce the thermal and mechanical stress at the weakest point. Simulation and experimental results verify the efficacy of the proposed approaches. [ABSTRACT FROM AUTHOR]

In this study, the change in input impedance according to the coupling coefficient and self-inductance of the coil of a wireless power transfer system is analyzed. The input impedance is the impedance of the power inverter that plays a decisive role in determining the harmonic current of the coil. When the air gap between the transmitting and receiving coils decreased and the coupling coefficient of the wireless power transfer system increased, the slope of the input impedance decreased, and ultimately, the input impedance in the harmonic component decreased; moreover, the larger the inductance of the transmitting coil, the larger the input impedance of the system. The change in the analyzed input impedance was verified through simulations and experiments. Ultimately, measurements proved that the input impedance changes according to the change in the coupling coefficient and coil self-inductance, which affects the harmonic current. As mathematically analyzed, the larger the coupling coefficient and the smaller the self-inductance of the coil, the lower the input impedance of the harmonic component and the higher the harmonic current flowing in the coil, with a difference of less than 3 % between the simulation and experimental results. [ABSTRACT FROM AUTHOR]

Electrical resistance measurement is central to materials characterization, circuit analysis and resistance-based sensing. Resistance measurement involving the two-probe method (involving two electrical connections) is known to overassess the resistance, due to the electrode-specimen contact resistance. Resistance measurement involving the four-probe method (involving four electrical connections) is advantageous in that it essentially excludes the contact resistance at the connection-specimen interface. Nevertheless, the two-probe method is widely used, because of the simplicity of having only two connections. In the two-probe method, the current passes through the specimen and connections. The connection-related stray inductance is found in this work to cause large additional overassessment of the two-probe resistance when the electrical connection configuration entails current direction changes. The connections pertain to electrical leads and clips. The inductance increase due to a current direction change is in line with Faraday's law. Mere constriction or spreading of the current due to the connections also increases the inductance, but it does not influence the two-probe resistance. The inductance and two-probe resistance increase with the lead length because of the connection-related inductance, not because of the negligible increase in the lead resistance. An inductance increase of ≤ 80% causes a two-probe resistance increase of ≤ 278%. The specimen in this work is aluminum. It does not need to be magnetic. The connections in this work are also not magnetic. This inductance-related source of two-probe resistance overassessment is reported here for the first time. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to present a new Hybrid Analytical Model (HAM) based on Winding Function Theory (WFT) for electromagnetic analysis of the performance of one typical Unbalanced Two-Phase Induction Motor (UTPIM). Difierent indexes of electromagnetic modeling, such as winding distribution, slotting efiect, and magnetic saturation, can be accurately considered by using the proposed HAM. To obtain this new hybrid technique, WFT is reformulated to consider magnetic saturation in addition to the inuence of slotting and winding distribution. The Conformal Mappings (CMs) are used to calculate the slotted air-gap length accurately. The Magnetic Equivalent Circuit (MEC) model is used to consider the Magneto-Motive Force (MMF) drop in stator and rotor cores due to the excitation of one phase-winding. The results obtained from CMs and MEC are then utilized in reformulated WFT to calculate the inductances of the respective phase-winding. Transient analysis is then done to calculate the indexes of performance, such as air-gap magnetic field, phase currents, electromagnetic torque, and rotor speed, by using the lookup table of inductances while considering difierent capacitors in the auxiliary phase. In each step, the accuracy of analytical results is confirmed by comparing with corresponding results obtained from the Finite Element Method (FEM). [ABSTRACT FROM AUTHOR]

The article investigates mathematical modeling of the induction heating element (IHE) at the base of the thermo-anemometric flow meter (TAFM) for measuring the flow of diesel fuel (DF). The consumption of DF is affected by many factors that can affect the accuracy of TAFM, namely fuel temperature, impurities and its viscosity. The heating element in the form of shadows, which was previously studied in the publication [1], is in contact with the fuel medium, which increases the risk of fuel ignition when a large current passes through it. In the induction TAFM, the heating is regulated by turning it on and off cyclically. The very process of heating DF in TAFM is based on the generation of induced electric currents inside the pipeline, which contributes to high efficiency, since heat is generated only where it is necessary and most importantly - does not come into contact with a flammable substance, such as DF. This process is helped by temperature sensors (thermocouple) included in the control system. For this purpose, a selected temperature mode is set for DF and TAFM, after heating the coolant to a certain temperature, it is automatically turned off, and after cooling, it is turned on again. According to a number of criteria, such as TAFM material with an induction heater, length, diameter and wall thickness of the TAFM pipeline, high-speed modes of fuel supply - the amount of energy with the appropriate voltage frequency supplied to two induction heating elements to maintain a constant temperature difference depending on from the volumetric fuel consumption Q. Based on the data of the simulated parameters of the voltage dependence (output signal of the flow meter) and the quantitative fuel consumption through the TAFM, it was determined that the level of the output signal is sufficient for measuring the fuel consumption in a wide range of values.

Problem. The flow of currents in the conductive elements of electrical systems is accompanied by the excitation of electromagnetic fields and the occurrence of induced currents. The excitation of the induced signals, in turn, leads to a change in the parameters of the actual exciting currents. The purpose of the work is to obtain analytical expressions for the quantitative analysis of the results of the mutual influence of the exciting and induced currents and to calculate their ratio depending on the geometric characteristics of the inductor systems. Methodology. The analysis of the processes of mutual influence is carried out on the example of a widespread inductor system, where a flat circular solenoid is placed above the surface of a massive conductor. Analytical expressions for eddy currents excited in a massive conductor and numerical estimates of the effect of induced currents on exciting currents in a solenoid are obtained. Results. It is shown that the influence of the induced current on the current in the solenoid is very significant at small distances between the solenoid and the surface of the massive solenoid. It has been found that an increase in the width of the solenoid winding leads to a significant increase in the influence of the induced current on the excitation current in the solenoid. It is shown that the inductance of the «circular solenoid - massive conductor» system drops with a decrease in the distance between the solenoid and the massive conductor and an increase in the radial dimensions of the solenoid, which requires an increase in the amplitude of the exciting current to maintain a given value of the magnetic flux in the system. Originality. The scientific novelty of this work lies in the proposal of an analytical approach and obtaining numerical estimates of the mutual influence of conductors with exciting and induced currents. Practical value. Estimates of the mutual influence of conductors with currents are of interest for the practice of designing structures of electrical systems for various purposes. Very promising in the direction further research is seen as carrying out experiments with measurements of the quantitative characteristics of the mutual influence of exciting and induced currents in various designs of electrical systems.

In the field of high-precision physical field detection, measurements based on magnetic signals are crucial due to their exceptional accuracy, sensitivity, and stability. Superconducting Quantum Interference Devices (SQUIDs), with their ultra-high sensitivity, have become key in detecting minute changes in magnetic flux. However, with increasing demands for higher precision, further enhancing device performance under quantum constraints remains a significant challenge. This study improved the precision of SQUID sensors by optimizing the geometry of microscale washers using the physical response of superconducting films under micromachining technologies and quantum constraints. Our research extensively examined the effects of square, octagonal, and circular washers on the magnetic field response, shielding currents, and inductance. Experimental results showed that, compared to traditional square washers, octagonal washers significantly enhanced sensor sensitivity and efficiency by minimizing edge magnetic flux and optimizing current distribution. Notably, all observed inductance values exceeded predictions based on traditional empirical formulas, with square washers showing the highest average relative error of 80.8%, while circular and octagonal washers had errors of 65.31% and 66.43%, respectively. This breakthrough not only lays a new theoretical foundation for the design of SQUID sensors but also provides robust evidence for enhancing magnetic field detection through microscale technological innovation.

Electrochemical impedance spectroscopy (EIS) is a powerful tool to characterize and distinguish electrochemical, electrical, and diffusive processes in an electrolysis cell. The EIS response with small impedance (mΩ) depends on components and materials of the cell, but often also on the electrical setup, cables, and connectors, leading to incorrect conclusions about the performance of the electrolysis cells. These parasitic effects are assessed via a short‐circuit measurement and confirmed to be external from the membrane electrode assembly (MEA). In the setup, the inductive characteristic is described by a modified inductive reactance and must be included in the equivalent circuit model (ECM) which is fitting the cell EIS spectra in operation (in situ). If points of the spectra showing inductive characteristic (below x‐axis in Nyquist plot) are excluded from the ECM evaluation, an artificially increased ohmic resistance at high frequencies is obtained. In addition, considerations on other components of the ECM can be misleading and significantly incorrect. The only way to avoid that inductive behavior caused by the external setup is incorrectly assigned to the ECM describing properties of the MEA is to include the inductive effects in the ECM analysis of in situ EIS measurements. [ABSTRACT FROM AUTHOR]

An active inductor (AI) circuit is a widely used component in tuning circuits, filters, oscillators, etc. These circuits offer various advantages over spiral inductors, namely less chip area consumption, high-quality factor (Q-factor), easy tunability, etc., and are also easier to be integrated with an IC. This paper brings together the various grounded AIs constructed using CMOS technology, most of which have been proposed in the last two decades. A detailed analysis has been presented along with the assessment of the various AI designs, with respect to a number of factors, like inductance value and power consumption. Furthermore, these circuits have been exploited to realize a common application such as a band pass filter, and the resulting behaviour of each design has been noted as well to give a fair comparison among all. The simulations have been carried out in Cadence Virtuoso, using 90 nm CMOS technology. To obtain an unbiased comparison, a common supply voltage of 1.2 V is used for simulating all the circuits. [ABSTRACT FROM AUTHOR]

In this paper, two methods Adomian Decomposition Method (ADM) and Laplace Adomian Decomposition Method (LADM) were adopted to solve the telegraph equation. The essence of this research is to establish a relationship between the two analytical methods. It was observed that the two methods were consistent as the results obtained from the numerical examples on the two methods were the same. We also generated the telegraph equation to help provide a solid basis for the application of the telegraph equation. The telegraph equation is one of the nonlinear partial differential equation and it’s application to solving practical problems were suggested for further studies. [ABSTRACT FROM AUTHOR]

Inductive wireless power transfer is a promising technology for powering smart wearable devices. The spiral coil shape is widely used in wireless power transfer applications. Nevertheless, during the coil design process, there are many challenges to overcome considering all the design constraints. The most important is to determine the optimal coil parameters (internal radius, external radius, spacing, wire width, and conductive wire) with the aim of obtaining the highest coil quality factor. Coil modeling is very important for the wireless power transfer system's efficiency. Indeed, it is challenging because it requires a high computational effort and has convergence problems. In this paper, we propose a new approach for the approximation of spiral coils through concentric circular turns to reduce the computational effort. The mathematical model determines the optimal coil parameters to obtain the highest coil quality factor. We have chosen the smart textile as an application. The system operates at a frequency of 100 Khz considering the Q i guidelines. To validate this approach, we compared the approximated circular coil model with the spiral coil model through a finite element method simulation using the COMSOL software. The obtained results show that the proposed approximation reduces the complexity of the coil design process and performs well compared to the model corresponding to the spiral shape, without significantly modifying the coil inductance. For a wire width smaller than 1 mm, the total deviation is around 4% in terms of the coil quality factor in a predetermined domain of its parameters. [ABSTRACT FROM AUTHOR]

Abstract Toroidal inductors are widely used in power electronic systems. With the increasing switching frequency of power devices, the AC losses of high‐frequency inductor windings have become an issue that cannot be ignored in design. A method with low computational time cost and high accuracy is urgently needed by designers. This paper proposes a modified analytical method for winding loss calculation of toroidal inductors based on the one‐dimensional Dowell method and the two‐dimensional Ferreira method, and proposes a compensated analytical model considering the proximity effect of inter‐turn conductors of toroidal windings. The analytical method calculates the non‐linear porosity of toroidal windings, and can accurately solve the AC losses of toroidal inductors with arbitrary porosity winding encapsulation. The analytical results are in good agreement with the finite element method (FEM) and experimental data. The experimental measurement data verifies the validity of the proposed model within 1‐MHz frequency, the calculation error of the modified analytical method is less than 25%, and the calculation error of the compensated analytical model is reduced to 10%.

In this work, a mathematical model of a three-phase nonlinear transformer is suggested. The model enables simulating the transformer operation with allowance for its nonlinearity and covers needs of the relay protection. Our model has been developed on the basis of a mathematical model with phase coordinates, where differential equations are composed by the Kirchhoff’s phase-voltage law. Based on this model, we first compose a mathematical model for simulating steady-state operation modes of a transformer, taking into account the asymmetry and nonlinearity of its ferromagnetic core. In this model, the initial values of inductances and mutual inductances of loops are determined from the main phase inductance calculated by the experimentally found no-load current, and their current values are determined from the currents in windings and the magnetic fluxes in legs of the transformer core. The magnetic fluxes are calculated by the nodal-pair method. This improved mathematical model is verified through a comparison between the calculated harmonic components of the phase currents and the experimental results. The harmonic components are calculated with the use of Fourier expansion of the calculated phase currents. Their experimental values are determined with a spectrum analyzer. The calculated and experimental harmonic components of the currents of phase A during no-load and rated-load operation of the transformer are tabulated. The comparison of these results shows that the mathematical model of a three-phase transformer we suggest makes it possible to simulate currents in transformer windings under steady-state operation modes with accuracy acceptable for relay protection.

Summary: Coils are widely used in magnetorheological dampers, solenoid valves, and electron guns, where a quick response of the magnetic induction to the excitation voltage is needed. To achieve a quick response, the response time of the magnetic induction relative to the current and that of the current relative to the voltage should be shortened as much as possible. The latter is dominant in the total response time and can be shortened by using voltage control with an increased resistance or current control. The current time responses of the Helmholtz coils based on voltage control with an increased resistance and current control are measured. The results indicate that the current response times of the coils based on voltage control with resistances of 23.7 and 162 Ω and current control with a resistance of 23.7 Ω are 235.3, 42.3, and 62.1 μs, respectively. The current time responses of the voltage control are smooth, while those of the current control have large oscillations. Based on Kirchhoff's equilibrium equation, an overshoot voltage waveform design method is proposed to shorten the current response time and eliminate the current oscillations. The experimental results show that the current time response is smooth, and the current response time can be shortened by 91.8%, 54.4%, and 68.9% in comparison with those of the former three control cases. The demonstration experiments of the effect of the different control methods on the electron‐beam scanning path and hot spot distribution show that the scanning path and dwell duration are closer to the expected ones with the proposed method. The proposed method is of great value for improving the damping performance of a magnetorheological damper, the accuracy of the fluid injection of a solenoid valve, and the accuracy of the electron‐beam thermal assessment. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Power Generation Technology is the property of Power Generation Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Toroidal inductors are widely used in power electronic systems. With the increasing switching frequency of power devices, the AC losses of high‐frequency inductor windings have become an issue that cannot be ignored in design. A method with low computational time cost and high accuracy is urgently needed by designers. This paper proposes a modified analytical method for winding loss calculation of toroidal inductors based on the one‐dimensional Dowell method and the two‐dimensional Ferreira method, and proposes a compensated analytical model considering the proximity effect of inter‐turn conductors of toroidal windings. The analytical method calculates the non‐linear porosity of toroidal windings, and can accurately solve the AC losses of toroidal inductors with arbitrary porosity winding encapsulation. The analytical results are in good agreement with the finite element method (FEM) and experimental data. The experimental measurement data verifies the validity of the proposed model within 1‐MHz frequency, the calculation error of the modified analytical method is less than 25%, and the calculation error of the compensated analytical model is reduced to 10%. [ABSTRACT FROM AUTHOR]

Current circuit simulation research on EMU (Electric Multiple Unit) overvoltage has focused on overvoltage amplitude distribution and the oscillation frequency of the operating main circuit breaker overvoltage. However, when studying the suppression method, the overvoltage amplitude and frequency characteristics must be considered simultaneously, and few studies have reported on the overvoltage frequency distribution. In this paper, a new simulation model of train-operational main breaker overvoltage based on the 3D structure of the EMU body was proposed, which provided guidance for the study of overvoltage suppression in operational main circuit breakers. This model simulated the transient overvoltage characteristics and distribution of the vehicle body when the train operated the main circuit breaker. The simulated results showed that the first vehicle had the highest operating overvoltage amplitude, and the fourth vehicle had the lowest. The overvoltage amplitudes of vehicles 1–4 were all above 1 kV, and the main overvoltage oscillation frequencies of each vehicle were at 0.70 MHz and 1.30 MHz. The accuracy of the distribution characteristics and spectral characteristics of the operating main breaker overvoltage was verified by static tests on trains, and the simulation was considered to be in agreement with the test. Aiming at the problem that there was no universal suppression method for the operating main breaker overvoltage, a general suppression method for the overvoltage on the high-voltage side of the EMU was studied, and an overvoltage suppression device based on a grounding inductor was proposed. The inductance parameter requirements of the suppressor were theoretically analyzed, and the validity of the design of the inductance suppressor was experimentally verified. [ABSTRACT FROM AUTHOR]

The surface modification of carbonyl iron powders（CIPs） was carried out by using zirconium butoxide（TBOZ） solution. Zirconium dioxide coated carbonyl iron powders（ZrO2@CIPs） composites with different zirconium content were synthesized by adjusting the amount of TBOZ. The static magnetic properties and insulating properties of CIPs and ZrO2@CIPs composites have been investigated, and it has been shown that ZrO2 can effectively suppress the deterioration of the static magnetic property of CIPs when the temperature is increased to 200 ℃. Meantime, the resistivity of ZrO2@CIPs composites has been greatly improved. Comparing the magnetic loss capacity of CIPs and ZrO2@CIPs composites, it can be found that the magnetic loss capacity and DC bias properties of ZrO2@CIPs composites are improved with increasing the amount of TBOZ. When the amount of TBOZ is 15.57 mL, the μ″ of ZrO2@CIPs composites is only 0.05, quality factor is 116.7, and the rated current is 17.10 A. In addition, compared with CIPs（-0.91 V）, the corrosion potential of ZrO2@CIPs composites is increased to-0.33 V, demonstrating the enhanced corrosion resistance. In general, the results of this work can be served as a reference for the modification of conventional CIPs in the inductance domain.  [ABSTRACT FROM AUTHOR]

The study of the induction periods of hydration and structure formation of cement stone is one of the most urgent problems of modern building materials science. Water and aqueous solutions of inorganic salts are the most widespread forms of mixing liquids for cement systems. The properties of distilled water and aqueous solutions of sodium chloride with different concentrations have been investigated by dielectrometry. It is proposed to consider the structural organization of water and aqueous solutions as a combination of strongly and weakly bound water. The strongly bound water is the result of manifestation of hydrogen bond forces; this type of water specifies the ordered state of the system. Weakly bound water causes fragmentation of the initial water continuum into smaller structural units. The change in the impedance and admittance spectra of cement paste during hardening has been analyzed. Spectra were measured in the frequency range from 20 Hz to 2 MHz using a capacitor measurement cell. Investigations have been performed to find the optimal equivalent electric circuits describing the transformation of the electrical properties of cement paste and the interface phenomena occurring in the near-electrode layer of the measurement cell in dependence of the hardening time. It is found that the equivalent circuit parameters are sensitive to different stages of cement paste hardening. A relationship between the spectra of electrical parameters and the processes of cement stone hardening is demonstrated. [ABSTRACT FROM AUTHOR]

A current sharing method for serially connecting coupled inductors on the secondary side of the interleaved parallel LLC resonant converter is proposed to solve the unbalanced current of each phase caused by inconsistent device parameters. By serializing a fully coupled inductor with a coupling coefficient of -1 on the secondary side of the converter, the two output currents of the converter are reversely coupled, achieving current sharing between the two phases while avoiding the impact of the leakage inductance of the coupled inductor on the resonance of the primary side of the converter. The working principle of coupling inductance for current sharing was analyzed, and an AC equivalent circuit model of a resonant converter based on series coupling inductance was established. The current sharing effect of the improved converter was analyzed, and the proposed method was verified through simulation and experiments. The research results indicate that the influence of coupling inductance on the voltage gain of the converter decreases with the increase of the absolute value of coupling coefficient, and the greater the coupling inductance, the better the current sharing effect of the converter. [ABSTRACT FROM AUTHOR]

Brushless Direct Current (BLDC) motors are a type of permanent magnet synchronous motor with a very high level of efficiency used in wind turbines and other high-speed motor applications. An attempt has been made to design and implement four-quadrant control of a BLDC motor drive by coated conductor winding was tested experimentally. Coating the motor winding made of copper with highly conductive materials such as graphite and silver over the wire using the dip-coating technique was performed. The measurements of resistance, inductance, RPM, and power loss are presented and explained. SEM Image was taken which shows the distribution of graphite particles over a copper surface. Graphite is a low-cost substitute for silver which shows considerable improvement in overall motor efficiency of 2–5% in BLDC motors. [ABSTRACT FROM AUTHOR]

In a sensorless motor speed control system, the motor speed is not directly measured using a speed sensor, but it is estimated using an observer. The sensorless speed control systems are mostly applied to AC motors, while they have not been widely applied to DC motors. Therefore, this paper presents simple observers to estimate the DC motor speed. The observers used were based on the DC motor electric equation. Two methods were used in this research. The first method was the observer estimating the speed based on the resistance inductance values (L-R method), while the second was the observer estimating the motor’s speed only based on the motor’s resistance value (R method). The speed was estimated using armature current (ia) and voltage (va). Therefore, a current and voltage sensor was used. Not only was the observer estimated, but it was also implemented on a real DC motor. An Arduino microcontroller was used to calculate the speed. The LN298 was used as a DC motor drive. Even though the R method is simpler, the test result showed that its speed estimation was less precise than the L-R method. By manual calculation, the motor speed estimation result in the L-R method had an error of 0.14%, while the motor speed estimation results in the R method had an error of 5.03%. The estimation results of motor speed implemented on a real DC motor and microcontroller system in the L-R method had an error of 3.98%, while the result of the estimation of motor speed in the R method had an error of 4.87%.

Abstract A new hybrid analytical model (HAM) based on conformal mapping (CM) method and magnetic equivalent circuit (MEC) model is presented in this paper for electromagnetic modelling of cage rotor induction motors (CRIMs) used in electric submersible pumps (ESPs). For every operating point, the iron parts are modelled with a non‐linear MEC model to calculate the equivalent virtual currents, which represent the influence of magneto motive force (MMF) drops and MMF sources in stator and rotor cores. The effects of the equivalent virtual currents on the air‐gap magnetic field are then considered using the CM method and Hague's solution. This approach for calculating the air‐gap field is also used to prepare a 3‐D lookup table (3‐D LUT) for each element of inductance matrix and derivative of inductance matrix in terms of rotor position. These LUTs are then used for transient modelling and analysis of CRIM under no‐load and loading conditions. The accuracy of proposed HAM is validated by comparing the results obtained through HAM with corresponding results obtained from finite element method and experiment set‐up.

This paper investigates the effect of circuit inductance on pinch-time of plasma focus. The dense plasma focus is a plasma discharge powered by a capacitor bank. The Mather type Dense Plasma Focus is constructed in cylindrical geometry and is made up of coaxial anodes and cathodes with varying radiuses. An insulator sleeve separates the electrodes, and the cathode rode forms circles around the anode tube. Different parameters, such as geometry and structure of the anode bar, and decreasing inductance are involved in the optimization of plasma focus. One way to increase the gain and optimization of pulsed plasma systems is to reduce the inductance of the circuit. For this purpose, we investigate the effect of different values of total circuit inductance on pinch formation time. Experimental and simulation results are compared. the proposed system shows a decent functionality that if the inductance reduces, the efficiency of the system will increase.