Electromagnetic Field Simulation Research Articles

HTS transformers leakage flux and short circuit force mitigation through optimal design of auxiliary windings

Mitigation and control of leakage fluxes and short circuit forces needs much more attention, for a high-temperature superconducting (HTS) transformer, than for a conventional one. Different methods such as the application of auxiliary windings, multi-segment winding, and flux diverter have been presented in the literatures for leakage magnetic field reduction in HTS transformers. In this paper, for the first time, optimal design of auxiliary windings has been performed for a 132/13.8 kV, 50 MVA three phase core type HTS transformer. Genetic algorithm (GA) has been used for the optimization process. Induced current in auxiliary windings which is inversely proportional to the leakage fluxes and short circuit forces has been considered as the objective function. An analytical method has been proposed in this paper which formulates the objective function in terms of the self and mutual inductances of the main and auxiliary windings. Consequently, the optimal parameters of the auxiliary windings have been determined. It is shown that utilizing the optimized auxiliary windings design, the leakage fluxes, the radial and the axial components of the short circuit forces are reduced significantly. Two-dimensional electromagnetic field simulations using finite element method (FEM) by application of COMSOL multiphysics software have verified the theoretical formulations.

Flow field study of radiofrequency ablation of renal sympathetic nerve: Numerical simulation and PIV experiments

ABSTRACT Renal sympathetic denervation (RSD) is a new method for the treatment of resistant hypertension (RH). However, few studies have focused on the effects of RSD on blood flow and the interaction between temperature field and flow field. In this paper, firstly, we designed a numerical simulation of electromagnetic field, flow field and temperature field coupling by finite element method. Secondly, numerical simulation results were verified by particle image velocimetry (PIV) and vitro experiment. From the simulation results, when the flow velocity increases to 0.05 m/s, the turbulence near the electrode disappeared and flow state became uniform laminar flow. With the increases of flow velocity (0 m/s to 0.1 m/s), temperature rise of the renal artery, the electrode tip and blood decreased from 13°C, 24°C and 5.4°C to 9.3°C, 9.7°C and 0.2°C, respectively. From PIV experiment and vitro experiment results, when the flow rate increases to 0.5 L/min, it appeared similar phenomenon with the velocity of 0.05 m/s in simulation. With the increases of flow rate (0 L/min to 0.8 L/min), temperature rise of three points decreased from 11.2°C, 20.5°C and 3.6°C to 7.8°C, 8.5°C, and 0.4°C, respectively. When the blood flow rate exceeds 0.5 L/min, there is no large velocity gradient and reflux area in the flow field, so there will be no hemolysis and thrombosis. Therefore, the temperature field has less influence on the flow field. With the increase of flow rate, the temperature at all three points decreases. Therefore, the flow field has an effect on the temperature field. But the central temperature of renal artery can still reach the treatment target in which temperature rises to be more than 6°C. Therefore, this study preliminarily verified the safety and effectiveness of RSD.

Electrical Circuit Modeling and Validation of Through-Silicon Vias Embedded in a Silicon Microfluidic Pin-Fin Heat Sink Filled With Deionized Water

This article presents the electrical circuit model of signal-ground through-silicon vias (TSVs) in a silicon microfluidic pin-fin heat sink in which the pin-fins are surrounded by deionized water. Such TSVs are asymmetric vertically because the TSVs are partially embedded in cylindrical pin-fins as well as in a rectangular silicon base. In this article, we propose a circuit model that segregates the asymmetric geometry into two symmetric segments: one segment for a silicon base and the other segment for cylindrical silicon pin-fins surrounded by deionized water, which we refer to as “a pin-fin segment.” Specifically, the pin-fin segment is modeled using two-dielectric coaxial-line formulas to represent the double layers of silicon dioxide and silicon that surround the copper vias. Using the developed circuit model, this article quantitatively analyzes the impact of fluidic designs, such as the diameter and height of pin-fins on the electrical characteristics of TSVs. Following circuit model validation using high-frequency electromagnetic field simulations, the modeling results are compared with measured data.

On-Chip Magnetic Probes for Hardware Trojan Prevention and Detection

Security threats due to Hardware Trojans are growing in volume and variety. The miniature size of Trojans coupled with their diversity and their unpredictable effects made them difficult to detect. Researchers have proposed different techniques to either prevent the insertion of Hardware Trojans or detect them at early stages. In this article, a new tamper resilient solution is presented to capture the electromagnetic signature of integrated circuits to ensure their security. In the proposed method, the remaining metal and polysilicon layers are fully utilized as internal magnetic probes to monitor the signature of the device and in the meantime deprive attackers of layout resources to route Hardware Trojans. 3-D full-wave electromagnetic field simulations using high-frequency structural simulator show that tampering with a chip to insert a minimally invasive Trojan of 12 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , the area required to insert an inverter, can be detected through the magnetic signature.

Minimax Robust Landmine Detection Using Forward-Looking Ground-Penetrating Radar

We propose a robust likelihood-ratio test (LRT) to detect landmines and unexploded ordnance using a forward-looking ground-penetrating radar. Instead of modeling the distributions of the target and clutter returns with parametric families, we construct a band of feasible probability densities under each hypothesis. The LRT is then devised based on the least favorable densities within the bands. This detector is designed to maximize the worst-case performance over all feasible density pairs and, hence, does not require strong assumptions about the clutter and noise distributions. The proposed technique is evaluated using electromagnetic field simulation data of shallow-buried targets. We show that, compared to detectors based on parametric models, robust detectors can lead to significantly reduced false alarm rates, particularly in cases where there is a mismatch between the assumed model and the true distributions.

Coherent Enhancement of Dual-Path-Excited Remote SERS.

Combining both localized surface plasmon polaritons (LSPPs) and propagating surface plasmon polaritons, remote surface-enhanced Raman scattering (SERS) emerges as a novel sensing technology in recent years, which could avoid the overlap of incident light and inelastic scattering light in SERS. Compared to traditional SERS, it has novel applications in sensors, plasmon-driven surface-catalyzed reactions, Raman optical activity, etc. However, the weak Raman intensity of remote SERS impedes its further application. In this work, we demonstrated that the remote SERS signals could be enhanced by more than 100% through the subwavelength interference in dual-path-excited Ag-branched nanowire dimer and nanowire-nanoparticle systems. Our experiment has revealed that remote SERS intensities could be modulated by polarization and phase differences of two incident lights illuminating at two separate nanowire terminals. The simulated electromagnetic field distributions through the finite-difference time-domain (FDTD) method indicate that subwavelength interference occurs in Ag nanowires, which causes the Raman intensities collected at a remote site is greatly influenced by the coherent superposition of propagating surface plasmon polaritons (PSPPs). Our work on this coherent enhancement could not only promote the application of remote SERS but also enlarge the research on light manipulating in the subwavelength.

Electromagnetic field simulation of large hollow reactor

The electromagnetic interference problems of large-scale hollow reactor equipment are special and increasingly widespread. In order to thoroughly understand the electromagnetic interference of large hollow reactors on various equipment in a substation, a field test was performed near a SVC in a substation, and the electromagnetic field was explained from three aspects: the main ground network induced circulation, the secondary cable shield current, and the DC system ripple interference. Interference issues. Furthermore, a three-dimensional electromagnetic field simulation model was established for SVC and nearby areas, and the equivalence of the model was verified by comparing it with the spatial magnetic field and induced current on the site. Based on this analysis, the electromagnetic interference improvement and the effect of inductance value changes at different reactor heights were analyzed. The results show that, during normal operation of large hollow reactors, the electromagnetic interference between the nearby grounding system and the DC system has approached or exceeded its rated operating conditions. In the design, attention should be paid to the spatial location of the reactor and the ground network, the control room and the secondary screen cabinet.

Research on Simulation of Electromagnetic Field of DC Motor Based on Finite Element Analysis

With the continuous development of science and technology, the magnetic field distribution of DC motors is analyzed based on the finite element theory. These provide a theoretical basis and reliable basis for analyzing the working principle of DC motors and the further development and application of DC motors, establishing a reasonable non-linear model of DC motors, and applying a finite element analysis software to establish a simulation model of the electromagnetic field of DC motors. The characteristics of the electromagnetic field were analyzed during the start-up process, and the analysis results provided a theoretical basis and basis for the further optimization of the electromagnetic field of the DC motor.

A Computational Study of 2.4 and 3.7 GHz Radiations Deposition Inside Models Made of Human Tissues Placed Nearby a Microstrip Antenna

Abstract The interest for GHz frequency range in present wireless communication devices is high. Therefore, a continuous need to observe peculiarities of electromagnetic power deposition in human tissues, when they are exposed to signals in this range, is obvious. In this paper, by using an electromagnetic field simulation software, we aimed to highlight the differences between specific absorption rates (SAR) of energy absorption and their geometric distribution in four cases: at two different frequencies and in two tissue models (plane and anthropomorphic). First step was to design and analyse the electromagnetic field provided by a microstrip antenna, and second step was to compute SAR averaged over 10 g of tissue in two models: a three-layered planar model of human tissues and a homogeneous human head. Similarities and differences are discussed, together with observations regarding temperature increase due to exposures and its trend in different layers of tissues.

Development of planar microstrip resonators for electron spin resonance spectroscopy

This work focuses on the development of planar microwave resonators for use in electron spin resonance spectroscopic studies. Two half-wavelength microstrip resonators of different geometrical shapes, namely straight ribbon and omega, are fabricated on commercially available microwave laminates. Both resonators have a characteristic impedance of 50 Ω. We have performed electromagnetic field simulations for the resonators and have extracted design parameters that were used for fabrication. The effect of the geometry on the quasi-transverse electromagnetic (quasi-TEM) modes of the resonators is noted from simulation results. The fabrication is done using optical lithography in which laser printed photomasks are used. This prototyping technique allows us to fabricate resonators in a few hours with accuracy up to 6 mils. The resonators are characterized using a Vector Network Analyzer. The fabricated resonators are used in a home built low-temperature continuous wave electron spin resonance (CW-ESR) spectrometer which operates in S-band. It captures the absorption spectrum of the free radical DPPH, at both room temperature and 77 K. The measured g-factor using our resonators is consistent with the values reported in literature. Spin sensitivity of 1015 spins/gauss is achieved at 77 K. The designed resonators will be used in setting up a pulsed electron spin resonance spectrometer by suitably modifying the CW-ESR spectrometer.

The geometric theory of charge conservation in particle-in-cell simulations

In recent years, several gauge-symmetric particle-in-cell (PIC) methods have been developed whose simulations of particles and electromagnetic fields exactly conserve charge. While it is rightly observed that these methods’ gauge symmetry gives rise to their charge conservation, this causal relationship has generally been asserted via ad hoc derivations of the associated conservation laws. In this work, we develop a comprehensive theoretical grounding for charge conservation in gauge-symmetric Lagrangian and Hamiltonian PIC algorithms. For Lagrangian variational PIC methods, we apply Noether’s second theorem to demonstrate that gauge symmetry gives rise to a local charge conservation law as an off-shell identity. For Hamiltonian splitting methods, we show that the momentum map establishes their charge conservation laws. We define a new class of algorithms – gauge-compatible splitting methods – that exactly preserve the momentum map associated with a Hamiltonian system’s gauge symmetry – even after time discretization. This class of algorithms affords splitting schemes a decided advantage over alternative Hamiltonian integrators. We apply this general technique to design a novel, explicit, symplectic, gauge-compatible splitting PIC method, whose momentum map yields an exact local charge conservation law. Our study clarifies the appropriate initial conditions for such schemes and examines their symplectic reduction.

Effect of Electromagnetic Stirrer Position on Mold Metallurgical Behavior in a Continuously Cast Bloom

The multiphase flow, initial solidification and solute diffusion and their interactions in a mold region of 380 × 280 mm2 casting bloom under different installation positions of in-mold electromagnetic stirring (M-EMS) were analyzed and compared by a multi-physical model. The results showed that the simulated electromagnetic field and solute carbon distribution in initial solidified shell are basically consistent with measurements. As the distance from EMS center to the meniscus increases (from 0.32 to 0.62 m), the level fluctuation decrease from 7.2 to 4.5 mm, while the volume of turbulent zone clearly expands. Additionally, the solidified shell thickness at the mold outlets increase from 12.90 to 16.32 mm and from 26.41 to 28.97 mm at outlets of computational domain as EMS center moves down, while the surface temperature decreases. The maximum negative segregation deteriorates from 0.95 to 0.83 at the bloom corner while increasing from 0.84 to 0.92 in the thickness direction, and the difference between the minimum and maximum carbon concentrations at center of computational outlets is only about 0.0029 pct. The EMS should be installed around 0.42 m below the meniscus, by which the disqualified rate of non-metallic inclusions and the level fluctuations are within a low level.

Rayleigh-Schrödinger perturbation analysis of signal propagation modes in inhomogeneous multi-conductor power cables

Locating defects in an underground cable connection can be based on the propagation of transient signals emerging from faults or weaknesses in the insulation. The accuracy depends on the precise knowledge of the propagation characteristics of high-frequency components in the signals. These characteristics are analysed for multi-conductor cables in case of non-perfect rotational symmetry. Deviations can arise from the positioning of the conductors within the cable cross section or from an inhomogeneous distribution of dielectric materials. It is investigated to what extent the signal propagation modes, applicable for a symmetric configuration, remain a suitable representation for signal interpretation when the symmetry is slightly disturbed. This is judged by means of Raleigh-Schrödinger perturbation analysis in comparison to electromagnetic field simulations. Cable designs for the medium-voltage level incorporate measures to confine the electric field in designated regions. Slight asymmetry does not lead to strongly perturbed modes. For low-voltage cables, electric field control is not needed, and the conductors are positioned within short distance of each other. Modes can change significantly upon a relatively small asymmetry. Inhomogeneous heat dissipation, e.g. from a short-circuit current upon a fault, can cause a temporarily asymmetric permittivity distribution over the cable cross section. The feasibility to detect such effect from changing signal velocities of the propagation modes is discussed.

Features of heating technology at induction thermal processing with external electromagnetic field

According to the data of performed calculations and modeling of the hardening process, a design of inductors with magnetic cores for hardening long flat parts has been developed. At the design stage of this type of inductors, it was necessary to find out the degree of influence of the magnetic circuit design on the distribution of the temperature field during heating. To do this, we simulated electromagnetic and temperature fields to assess the concentration of the electromagnetic field at different heights of the “legs” of the inductor. As a result, a significant effect of the length of the “legs” of the magnetic circuit on the intensity of heating and the operability of the system as a whole was established. It is noted that insufficient height of the “leg” leads to a significant decrease in the field concentration, which leads to insufficient heating temperature and uneven distribution of heat zones in the heated part. In turn, an increase in the height of the “legs” leads to a narrowing of the heat release zone in the part compared to the total width of the coil and magnetic circuit. With a significant lengthening of the “legs”, the cooling circuit of the inductor will not be able to remove heat from the magnetic circuit obtained from the part, which will lead to the destruction of the magnetic circuit. The developed design of a two-turn single-circuit inductor and the general methodology made it possible to obtain a high-quality hardened layer with a depth of up to 3 mm with the formation of a martensitic structure of the required hardness on a planar-type flat part without significant energy loss. The part was machined by fixing it on a rigid base to compensate for the effect of temperature changes in linear dimensions. To obtain a uniform gap between the part and the inductor, a special pressure roller was used. The resulting structure of the hardened layer adequately meets the stated requirements for the part. The results of the research were used to develop a flat part of the “guide” type for lifting equipment (for example, a guide for the movement of the traction chain) and were introduced into production.

An Ultra-Wideband Power Combining in Ridge Waveguide for Millimeter Wave

In this article, a novel and efficient ultra-wideband power-combining method over K (18–26 GHz) and Ka (26–40 GHz) band is presented. Ridge waveguide power combiners and contactless transition between ridge waveguide and double microstrip lines will be used in this method. By using this method, a 16-way power combiner system is designed to work in the bandwidth of 18–40 GHz through 3-D electromagnetic field simulation and optimization. A back-to-back configuration of this combiner system is manufactured. The measured power-combining efficiency is higher than 78% within the designed frequency. By using 16 GaAs monolithic-microwave integrated-circuit (MMIC) medium power amplifiers, the active combiner system produces up to a maximum power output of 3.9 W with a power variation of ±1.3 dB within the bandwidth of 18–40 GHz. The measured power added efficiency (PAE) within the operating bandwidth is up to 16%.

Fast extreme ultraviolet lithography mask near-field calculation method based on machine learning.

Near-field calculation for a three-dimensional (3D) mask is a fundamental task in extreme ultraviolet (EUV) lithography simulations. This paper develops a fast 3D mask near-field calculation method based on machine learning for EUV lithography. First, the training libraries of rigorous mask near fields are built based on a set of representative mask samples and reference source points. In the testing stage, the mask under consideration is first segmented into a set of non-overlapped patches. Then the local near field of each patch is calculated based on the non-parametric regression and data fusion techniques. Finally, the entire mask near field is synthesized based on the image stitching and data fitting methods. The proposed method is shown to achieve higher accuracy compared to the traditional domain decomposition method. In addition, the computational efficiency is improved up to an order of magnitude compared to the rigorous electromagnetic field simulator.

Efficiency and Cost Based Multi-optimization and Thermal/Electromagnetic Analyses of 3-Phase Dry-Type Transformer

ABSTRACTDry-type transformers are one of the most significant devices used in the conversion, transmission and management process of the electricity. In practice, the electrical energy conversion entails energy losses such as heat, electromechanical and electromagnetic losses during the transformation. Hence, primary importance is the efficiency of energy conversion for a device that converts AC voltage from one value to another with the same frequency. Therefore, this study offers the best 3-phase dry-type transformer modelling interested in cost and efficiency related to transformer losses and useful energy conversion. Transformer manufacturing industries will produce a low cost and more efficient dry-type transformer by using electromagnetic/thermal analyzing and multi-optimization methods. Firstly, a 250 VA 380/110 V 3-phase cast resin core type transformer is modelled by an electromagnetic field simulator software programme called as ANSYS/Maxwell so the transformer is analyzed in detail in terms of the thermal and electromagnetic. In addition, the cost and efficiency values are optimized based on the current density (s) and C coefficient parameters by the multi-optimization method. Secondly, the transformer model is analyzed as thermal and electromagnetic at the end of the simulation results. Finally, the transformer is tested experimentally so the test results are confirmed by the simulation results considering the measurements. It is hoped that this study will contribute to transformer designers and operators interested in the conversion, transmission and management of the electrical energy.

Flat cutoff probe for real-time electron density measurement in industrial plasma processing

The microwave cutoff probe (CP) is an accurate diagnostic technique to measure absolute electron density even in processing gas plasmas. Because this technique needs the installation of two probe tips and a probe body in the plasma chamber, it may cause plasma perturbation in semiconductor plasma processing; this may increase the uncertainty of the measured value. In this work, a flat CP, which is embedded in the substrate chuck or chamber wall, is proposed to measure electron density without plasma perturbation and to monitor processing plasma in real-time. We first evaluated the performance of various types of flat CPs, such as the point CP, ring CP, and bar cutoff probe (BCP), through electromagnetic (EM) field simulation. The BCP showed better performance with clearer cut-off signal characteristics and minimization of noise signals compared with the other probe types. Therefore, we focused on the characteristics of the BCP through experiments and/or EM simulations and concluded the followings: (i) the measured electron densities of the BCP agree well with those of the conventional CP; (ii) the BCP measures the plasma density near the plasma-sheath boundary layer, which is very closely adjacent to the chamber wall or wafer; (iii) it was demonstrated for the first time that the plasma density can be measured, even though the processing wafers such as un-doped silicon, P type silicon, amorphous carbon, or amorphous carbon/SiO2 patterned wafers were placed on the flat CP; and (iv) we performed real-time measurements of the electron density using the BCP covered with the wafers in plasmas with various process gases, such as Ar, NF3, and O2. These results indicate that the chuck-embed-type or wall-type flat CP can be used as a real-time electron density measurement (monitoring) tool during industrial plasma processing, such as during etching, deposition, sputtering or implantation, and the chuck-embed-type flat CP can measure the plasma density impinging on the wafer in real-time without stopping the processing.

Design and Simulation of A Dual-Frequency Multi-Mode Vortex Microstrip Array Antenna

In order to improve the communication capacity and spectrum utilization, a design scheme of dual-frequency and multi-mode vortex microstrip array antenna is proposed. This antenna is composed of 8 rectangular microstrip patches, and 8 elements with the same structure are distributed at equal intervals on a concentric circle. The optimal structure of the antenna is determined by modeling 3D electromagnetic field simulation software and optimizing patch size. Simulation results show that the antenna has good impedance matching at the resonance point of 1.9 GHz and 2.45 GHz. When different phase excitation is applied to each element, the antenna produces seven effective vortex electromagnetic waves with different modes.

Study on Reliability Improvement of Voltage Transformers by Increasing Voltage Factor

Voltage transformers (VTs) must be highly reliable as they are essential components of the electric power industry. VT failures can cause a significant impact for important facilities such as nuclear power plants. In fact, VTs which passed the international standard, were damaged and sometimes resulted in the shutdown of the nuclear power plants. In order to improve the reliability, VTs with various iron core was studied. The electromagnetic field simulation, a saturation characteristics test, and an overvoltage breakdown test were conducted. The result shows that the magnetic flux density significantly affects the reliability of VTs. To increase the reliability of VTs, it is required to reduce the magnetic flux density by increasing the knee-point and voltage factor. Owing to limited installation space, increasing the size of the iron core is difficult. Instead, VT by decreasing the thickness of the conductor and increasing the number of turns, it was possible to reduce the magnetic flux density without the size change. Therefore, improved VTs were obtained by decreasing the thickness of the conductor and increasing the number of turns, and the improved reliability was verified through a comparison test with existing VTs. The fabricated VTs shows a significantly higher saturation voltage and breakdown time than existing VTs. Thus, by proposed VTs can contribute the stable operation of the nuclear power plant and improve the manufacturer’s quality.