Coil Power Research Articles

Redefining the Channel Bandwidth for Simultaneous Wireless Power and Information Transfer

The ideal simultaneous wireless power and information transfer (SWPIT) system should share the same source and channel bandwidth. However, the requirements of the channel bandwidth between wireless power transfer (WPT) and wireless information transfer are different. In order to alleviate the effect of communications on the WPT, three bandwidths are redefined based on traditional communication systems, namely the modulation bandwidth, channel bandwidth and demodulation bandwidth. A square wave circuit is built to track the frequencies of signals at the receiver power coil, and the harmonic components in the same square wave are used to recreate information source to transmit data. Since the harmonic components can enlarge the deviations of the fundamental component, the needed channel bandwidth is decreased. The transmitter power coil and the receiver power coil still work under the quasi-resonant state with online communications. The communication function shows a strong immunity to various disturbances, such as distances, loads and input voltages. Based on the proposed method, two typical SWPIT systems in near-field and far-field are built, and the experimental data are consistent with the analytical results. The proposed SWPIT achieves a good tradeoff between efficiency and data transfer rate.

Full-Bridge Submodule Development of an MMC-Like Topology for ASDEX Upgrade Toroidal Field Coils Power Supply

The modular multilevel converter (MMC) has become one of the most attractive converters for high-power applications such as high-voltage dc (HVDC) converters, but also fusion devices’ power supplies. This converter, thanks to the discrete-leveled output voltage and its identical submodules (SMs) by which it is composed, represents a promising alternative to replace the flywheel generator (FG) that actually provides electrical power to Axially Symmetric Divertor Experiment (ASDEX) Upgrade device’s toroidal field (TF) coils. Due to the pulsed dc operation of these coils and their high-power needs (up to 150 MW) for each experiment, a small-scale version of MMC is under development with some differences compared with conventional ones: SM’s capacitors have been replaced with supercapacitor (SC) modules to increase the amount of available stored energy, while SMs belonging to different “rows” are interconnected to simplify their control and increase the reliability of the converter. This article shows the development and the operation of a single IGBT full-bridge (FB) SM highlighting advantages of this configuration and challenges of a full-scale converter: a proper power stage filter has been designed to protect SCs from voltage spikes and high-frequency current content generated during IGBT switching events, while SM’s control has been realized, thanks to the EtherCAT protocol, which ensures synchronization in case of SMs’ parallel operation and reliability of the future full-scale converter.

Development of the Magnet Coil Power Supply for Fishtail Divertor on EAST

Fishtail divertor (FTD), a new divertor concept, is a significant research object of Experimental Advanced Superconducting Tokamak (EAST) tokamak divertor system. In order to meet the requirement of sinusoidal current precision and variable frequency, the combination of inductance and capacitance ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> ) series resonance theory and high-frequency pulsewidth modulation (PWM) technology is put forward. A sine wave power supply with multifrequency points (1–3800 Hz) and current up to 8000 A is developed. The FTD power supply (PS) adopts dc switching power technology, sinusoidal PWM (SPWM) technology, and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> series resonance theory. The operating points of output current include 10–20 Hz at 8000 A, 30–110 Hz at 5000 A, and 1300–3800 Hz at 2400 A. The electromagnetic environment in the device is complex and arguable. The output current accuracy can reach 5% by the current feedback and frequency feedback control strategy. The test results demonstrate that the FTD PS can meet the system requirements, and it has strong reference significance, which can provide reference for the design of other divertor PS.

Analysis of coil element distribution and dimension for matrix gradient coils.

The goal of this work is to analyze the influence of the distributions and dimensions of the coil elements and to present a method for improving the performance of the matrix gradient coil. Three typical models (five structures in total) are presented, and a double-layer biplanar matrix gradient coil is used to install coil elements. Two metrics, namely, the role of coil elements and mutual inductance between coil elements, are proposed to assess the performance of coil systems. An optimization approach to design matrix gradient coils is introduced based on analyzing the distributions and dimensions of coil elements. The flexibility of the magnetic field generation of the designed coil structure is demonstrated by generating full third-order spherical harmonic fields and different oblique gradient fields. Matrix gradient coils with suitable distributions are capable of generating target magnetic fields. The role of coil elements quantitatively illustrates that the coil elements have different impacts on generating magnetic fields. Increasing the coil element dimension within a certain range can reduce the mutual inductance between coil elements and improve the performance of the coil system. The designed novel double-layer biplanar matrix gradient coil achieves an acceptable performance in generating different magnetic fields. The proposed metrics can provide theoretical support for designing matrix gradient coils and evaluating their performance. The role of coil elements contributes to analyzing the distributions of coil elements to decrease the number of coil elements and power amplifiers. The mutual inductance between coil elements can be a reference for designing the dimensions of coil elements.

Simulation Study of an Inductively Coupled Plasma Discharge in the Radome Conformal Cavity

In this article, we investigate the influence of external discharge conditions on plasma parameters in the plasma discharge chamber of the radome configuration. We designed a conformal cavity and then used the multiphysics simulation software COMSOL to establish a 2-D axisymmetric model for discharge simulation research. In the study, we found that the changes in coil power and pressure have a noticeable effect on the distribution of plasma parameters. First, the maximum electron density, electric potential, and electron temperature are obtained by changing the power of the coil in a certain pressure argon environment. Then, under the condition of constant coil power, the discharge characteristics of plasma are studied by changing the gas pressure in the cavity. The results show that the change of coil power has a significant impact on the parameter distribution of plasma discharge. The greater the coil power, the greater the electron density, and the more concentrated the distribution. At the same time, the potential induced in the heating zone and the corresponding electron temperature decreased after the reaction stabilized. The increase of gas pressure significantly increases the peak value of electron density and changes the parameter distribution of discharge. However, when the argon pressure exceeds a certain threshold, it will no longer have a significant effect on the distribution of discharge parameters. The general conclusion is that the increase of power and argon pressure plays an essential role in improving the electron density distribution. This conclusion has guiding significance for exploring the law of plasma parameter distribution on electromagnetic scattering characteristics.

Using Overlapped Resonators in Wireless Power Transfer for Uniform Electromagnetic Field and Removing Blank Spots in Free Moving Applications

We propose an induction link based on overlapping arrays to eliminate blank spots on the electromagnetic field for moving object applications. We use two arrays of four aligned coils that have a 50% overlap between the two plates. This mechanism compensates for the internal coil power drop at positions in the boundaries between two adjacent external coils. We showed that if these plates are excited, a uniform electromagnetic field is created in the movement direction of the moving object. This uniform electromagnetic field distribution will result in a constant receiving power at all points in the path of the moving internal coil with the same power consumption of one coil excitation. Power delivery to the moving object tolerance reaches 10% at most, while, in non-overlapped scenarios, it is approximately 50%. In addition, according to the theoretical calculations, printed circuit coils (PCB) for the array are designed for maximum efficiency. We found that the change in distance and dimensions of the receiver coil has a linear effect on power and efficiency. Moreover, a Specific Absorption Rate (SAR) simulation was performed for biocompatibility. In this paper, we investigate and record a 68% electrical power efficiency for the fabricated system. The array consists of eight transmitters coils of the same size and shape and a receiver coil at a distance of 4 cm. Furthermore, the fabricated coil has shown improved efficiency compared to similar studies in the literature and introduces a promising structure for bio-test applications.

Ferrite-Free Closed-Loop 13,56 Mhz Inductively- Coupled Low Mercury Pressure UV Lamp

Electrical and radiation characteristics of inductively-coupled ferrite-free low mercury pressure discharges exited at a frequency of 13.56 MHz and discharge plasma power, Ppl = (5 ? 300) W, in closed-loop quartz tubes of 815 mm in length and of 16.6 mm in diameter were experimentally stud-ied. Discharges were excited and maintained with the help of one-turn induction coil made from litz wire and disposed on the tube wall surface along tube perimeter. Tubes were filled with mercury vapour (~ 10Ц2 Torr) and argon (0.5, 0.7, 1.0, and 2.0) Torr. As discharge plasma power, Ppl, were increased from 130 W to 275 W, coil resonant frequency (RF) voltage grew from (560 ? 700) V up to (840 ? 860) V, RF coil current grew from (1.4 ? 1.8) A up to (2.4 ? 2.6) ј. Coil power losses was highest in the lamp with argon pressure of 0.5 Torr and grew from 30 W (Ppl = 150 W) to 70 W (Ppl = 230 W). UV resonant (254 nm) radiation flux grew with plasma power and was highest in the lamp (pAr = 0.5 Tоrr) while UV radiation generation ef-ficiency of this lamp had maximal value of 34 % at plasma power of 130 W.

A Highly Miniaturized, Chronically Implanted ASIC for Electrical Nerve Stimulation.

We present a wireless, fully implantable device for electrical stimulation of peripheral nerves consisting of a powering coil, a tuning network, a Zener diode, selectable stimulation parameters, and a stimulator IC, all encapsulated in biocompatible silicone. A wireless RF signal at 13.56 MHz powers the implant through the on-chip rectifier. The ASIC, designed in TSMC's 180 nm MS RF G process, occupies an area of less than 1.2 mm2. The IC enables externally selectable current-controlled stimulation through an on-chip read-only memory with a wide range of 32 stimulation parameters (90-750 µA amplitude, 100 µs or 1 ms pulse width, 15 or 50 Hz frequency). The IC generates the constant current waveform using an 8-bit binary weighted DAC and an H-Bridge. At the most power-hungry stimulation parameter, the average power consumption during a stimulus pulse is 2.6 mW with a power transfer efficiency of ∼5.2%. In addition to benchtop and acute testing, we chronically implanted two versions of the device (a design with leads and a leadless design) on two rats' sciatic nerves to verify the long-term efficacy of the IC and the full system. The leadless device had the following dimensions: height of 0.45 cm, major axis of 1.85 cm, and minor axis of 1.34 cm, with similar dimensions for the device with leads. Both devices were implanted and worked for experiments lasting from 21-90 days. To the best of our knowledge, the fabricated IC is the smallest constant-current stimulator that has been tested chronically.

Multi‐objective optimization design of the large‐scale high‐intensity homogeneous magnetic field coil system based on non‐dominated sorting genetic algorithm (NSGA‐II)

With the development of modern tokamak devices, the magnetic interference problem has become increasingly serious. On considering the International Thermonuclear Experimental Reactor (ITER), for example, the stray magnetic field around the tokamak device will be over 200 mT. To ensure the reliable operation of the electrical and electronic equipment installed around the tokamak, the magnetic immunity test becomes a mandatory requirement. Generally, a set of coils is employed to realize the required test field. Since the coil power loss and conductor mass are proportional to the dimension and intensity of the test field, optimization design is of great significance. This paper presents the multi-objective optimization design of a large-scale high-intensity homogeneous magnetic field coil system. The analytical model of the multi-coil system is proposed, and the constrained multi-objective optimization model is established based on the non-dominated sorting genetic algorithm. Taking the ITER test coil as an example, the optimization design is performed and the Pareto-front is figured out. The designed four-coil system enables the magnetic field immunity tests for equipment within 1 m side-length at a highest test level of 275 mT with a magnetic field inhomogeneity of 1.05. The validity of the proposed model is verified by the finite element analysis and experimental tests.

Research on Frequent Failures of Pilot Solenoid Valve of Emergency Diesel Engine in Nuclear Power Plant

The working pressure of the start-up compressed air pilot solenoid valve is 40bar when it starts, it is an important part of the emergency diesel air start system of nuclear power plants. Since the operation of the nuclear power plant, it has been found that the start-up compressed air pilot solenoid valve has more frequent failures, the failure modes are air leaks and jams. The start-up compressed air pilot solenoid valve are all solenoid valves of the same type, the manufacturer is MABO, the model is MV320V DN20 G34 NC. Once the start-up compressed air pilot solenoid valve fails, it will affect the reliability and availability of the diesel engine’s start-up air system, directly cause the diesel engine to fail to start. Through a series of tests, the jamming and air leakage failures in the use of the start-up compressed air pilot solenoid valve are tested and analyzed. The reasons for the frequent air leakage and jamming of the starting compressed air pilot solenoid valve are determined, effective improvement plans are proposed, such as changing to another type of grease, adding the solenoid spool guide ring and return spring, improving the spool structure, increasing the diameter of the pilot valve and coil power, etc.. After analysis and demonstration, it is further clarified that the reasons for the leakage and jamming of the pilot solenoid valve are clear, the improvement plan is effective. The results show that the improved program obtained through research has laid a foundation for solving the problem of frequent leakage and jamming of the pilot solenoid valve.

A numerical tool to optimize voltage waveforms for plasma breakdown and early ramp-up in the presence of constraints

Plasma initiation is an important phase in a tokamak discharge. The main objective of magnetic control in this phase is to first obtain sufficiently high electric field and connection length (implying a low poloidal magnetic field) in the breakdown region, and then, once plasma is formed, to force the plasma current to increase, guaranteeing force balance equilibrium. The problem is dominated by the presence of significant eddy currents induced in the passive structures and by the many constraints due to the coil system and power supplies. The present paper shows how, with minor simplifying hypotheses, the magnetic control design problem can be converted into a Quadratic Programming problem with both linear and quadratic constraints that can be solved with an ad hoc iterative algorithm. On the other hand, the full design problem, including the choice of possible Switching Network resistors, becomes nonlinear and an evolutionary Genetic Algorithm solver is proposed. The algorithms are tested on DEMO breakdown and early ramp-up design which is a quite challenging problem because of the large distance between active coils and vacuum chamber, the presence of shielding passive structures with large time constants, and the active constraints on the CS/PF coil system.

Numerical simulation and experimental study on production of high-speed steel powder by high-frequency induction melting gas atomization

A new method (electrode induction gas atomization, EIGA) of producing high-speed steel powder was preliminarily studied by a combination of numerical simulation and experiment. Based on COMSOL Multiphysics® software, the effect of various parameters including coil angle, output frequency and power of the electrical source on flux density, induced current, temperature field and phase field was simulated. Meanwhile, the experiment was carried out on the EIGA device to produce high-speed steel powder. The results of FEM simulation indicate that when the coil angle is 30°, there is the highest thermal efficiency on the electrode cone, and the induced current and temperature will increase as the output frequency and power of the electrical source increase. In addition, the powder experimentally obtained by the EIGA method exhibits good particle sphericity regardless of the size, with a median diameter (D50) of 71.4 μm and a low oxygen content of 81 μg/g. The phase composition of the powder is mainly composed of γ-Fe and α-Fe structures and MC-type carbides. Due to the faster cooling rate, a solidification microstructure consists of fine cellular crystals and dendrites, and no coarse eutectic carbide network is observed, also confirmed by EDX elemental mapping.

Self-Inductance Calculation of the Archimedean Spiral Coil

In this paper, a new method to calculate the self-inductance of the Archimedean spiral coil is presented. The proposed method is derived by solving Neumann’s integral formula, and the numerical tool is used to calculate the inductance value. The calculation results are verified with several conventional formulas derived from the Wheeler formula or its modified form and 3D finite element analyses. The comparison with simulation results shows that the conventional formula has an error of above 40% compared to the proposed method, which has below 7% when the wire diameter is reduced. To further check the validity, different sizes of the spiral coil are fabricated by changing the geometrical parameters such as the number of turns, turn spacing, inner radius, outer radius, and wire diameter. Litz wire is chosen for making the spiral coil, and bobbins are made using a 3D printer. Finally, the calculation results are compared with the experimental result. The error between them is less than 2%. The comparison with the conventional formulas, simulation, and measurement results shows the accuracy of the proposed method. This method can be used to calculate the self-inductance of wireless power coils, inductors and antenna design.

A fast high current switched resistor used for asymmetric 4-quadrant power supply in HL-2 M tokamak

In order to meet the requirement of diversified plasma configuration and plasma current fast ascending and breakdown segment, the PF7 coil power supply in HL-2 M tokamak has to offer low positive current and high negative voltage at the same time in that segment. The PF7 coil power supply is asymmetric and 4-quadrant, which is consisted of positive group and negative group thyristor converter. However, according to the latest plasma parameter and voltage-current evolution curve, high enough inversion voltage has to been offered by PF7 coil power supply in positive operation. Although it could meet the new requirement if the transformers have been upgraded, it will make deep control of PF7 power supply in most plasma configuration cases. In addition, the ripple will be high which will have a negative effect on plasma control. So, a fast high current switched resistor has been proposed to offer part of negative voltage for the special segment. The fast high current switched resistor is connected with thyristor positive group in series, which is consisted of several IGBTs and resistors. The resistors are connected in parallel so that the total resistance could be changed under different current range for constant voltage. The larger voltage the more resistors working under low current operation. Benefit from the fast high current switched resistor, the parameters of the two converter groups could be relatively low, the difficulty of control could be reduced, and the cost could be cut. The prototype has been made to verify the performance of the fast high current switched resistor. Depending on the experiment, the function is satisfied with the requirement and the theory. The fast high current switched resistor could offer large voltage for the power supply under low current, while the temperature rise of the resistor is low due to 600 s operation interval.

RAMI Analysis for PF Power Supply System of ITER

According to the ITER requirement, the availability of the poloidal field (PF) coil power supply system must be 98.3% during the life cycle of ITER. In order to meet this requirement, Reliability, Availability, Maintainability, and Inspectability (RAMI) analysis has been applied for analyzing the availability and reliability of the PF power supply system. First, the function analyses, which are described using the Integration Definition Function–language Ø or IDEFØ model are performed. Second, the failure mode effect and criticality analyses are used to calculate the risk level, present the potential causes and effects, and provide the risk mitigation actions to reduce the risk level for each failure. Third, the reliability block diagram is built to simulate the availability and reliability of the system. RAMI analysis provides a method that can be followed to improve the availability and reliability of the system, and from the results, the design requirement can be satisfied.

Decomposition and estimation of the pulsed active power of the CPSS in the CFETR tokamak reactor based on the FFT and improved Prony methods

The Chinese Fusion Engineering Test Reactor (CFETR) aims to bridge the gap between the International Thermonuclear Experimental Reactor and the demonstration fusion power plant. Its coil power supply system (CPSS) will be connected to an external high-voltage power grid for producing large pulsed active power and reactive power to feed its superconducting coils. To analyze the impact of its active power on the connected high-voltage grid, the active power signal should be modeled initially. Herein, the characteristics of the active power of the CPSS are analyzed by comparing with the pulsed load, photovoltaic power, and wind power. It is modeled as a combination of periodic and decaying components, which are decomposed by the fast Fourier transform (FFT) and improved Prony methods, respectively. The proposed Prony constraint is diagnosed, and the mode size is changed to avoid exceeding the parameters. Both the calculated signal-to-noise ratio and fitting curves show the high accuracy of the proposed estimation procedure. Numerical results show that the number of selected FFT signals has no distinct influence on the estimation accuracy. The optimum Prony mode size of the decaying component estimation may be half the actual signal size when both the computing time and accuracy are considered.

Modernization of the brake system of unwinding on rope machines

In order to reduce the cost of producing metal cord in the hardware shops of OJSC “BSW” – the Management Company of the Holding “BMC”, work is underway to modernize and select materials for replaceable technological equipment. In the process of twisting the metal cord on the unwinding of the power coils of rope machines, brake devices are used, consisting of a disk and sectors (pads) fixed in a chain. The elements of the unwinding unit are in constant contact, providing the necessary tension force for unwinding a thin wire. The performance of the braking devices affects the manufacturability of the twist, the absence of breaks, the density and geometric arrangement of the wires in the twisted metal cord that meets the requirements of consumers.Due to constant contact friction at high linear speeds, the brake pads wear out, which leads to emergency operation of the equipment. The article considers the test results of the modified thin wire unwinding unit and the impact of modernization on the service life of brake pads.

A Comparison of Force Decay between Coil Spring, Elastomeric Chain and Tie-backs in Various Alcohol Concentrations found in Mouth Rinse: An In-vitro Study

Background: The ability to close space efficiently in Orthodontics is of major clinical importance. Elastomeric power chain, coil spring, and tiebacks are commonly used in Orthodontics to achieve tooth movement during the closure of spaces. Many mouth rinses which are used by the patients to achieve good oral hygiene affect the properties of the material used during treatment resulting in force decay if they contain alcohol.&#x0D; Aim: To know the effect of mouth rinses containing different alcohol Concentrations on the force decay of retraction materials.&#x0D; Materials and Methods: A study was carried out to test the effect of alcohol exposure found in mouth rinses on orthodontic NiTi closing coils, elastomeric chains, and tie-back. A total of 135 specimens were divided into one control group and two test groups submerged in artificial saliva at 37⁰ C. Two test groups each of them exposed to different alcohol-containing mouthwashes (Listerine and Povidone-iodine) for 60 seconds twice a day and the control group were exposed only to deionized (DI) water for 28 days. Force measurements were taken at six-time points (initial, 7 days, 14 days, 21 days, and 28 days) using a digital force gauge.&#x0D; Results: The comparison between the tensile strength was made by digital force gauge and the p-value (≤ 0.05) for tensile strength was derived by ANOVA test, multiple comparisons, and Tukey’s correction. Significant force decay was seen in test groups when compared to the control group.&#x0D; Conclusion: Force degradation of retraction products used during orthodontic treatment was effected by mouth rinses containing alcohol.

Manufacturable 32-Channel Cochlear Electrode Array and Preliminary Assessment of Its Feasibility for Clinical Use.

(1) Background: In this study, we introduce a manufacturable 32-channel cochlear electrode array. In contrast to conventional cochlear electrode arrays manufactured by manual processes that consist of electrode-wire welding, the placement of each electrode, and silicone molding over wired structures, the proposed cochlear electrode array is manufactured by semi-automated laser micro-structuring and a mass-produced layer-by-layer silicone deposition scheme similar to the semiconductor fabrication process. (2) Methods: The proposed 32-channel electrode array has 32 electrode contacts with a length of 24 mm and 0.75 mm spacing between contacts. The width of the electrode array is 0.45 mm at its apex and 0.8 mm at its base, and it has a three-layered arrangement consisting of a 32-channel electrode layer and two 16-lead wire layers. To assess its feasibility, we conducted an electrochemical evaluation, stiffness measurements, and insertion force measurements. (3) Results: The electrochemical impedance and charge storage capacity are 3.11 ± 0.89 kOhm at 1 kHz and 5.09 mC/cm, respectively. The V/H ratio, which indicates how large the vertical stiffness is compared to the horizontal stiffness, is 1.26. The insertion force is 17.4 mN at 8 mm from the round window, and the maximum extraction force is 61.4 mN. (4) Conclusions: The results of the preliminary feasibility assessment of the proposed 32-channel cochlear electrode array are presented. After further assessments are performed, a 32-channel cochlear implant system consisting of the proposed 32-channel electrode array, 32-channel neural stimulation and recording IC, titanium-based hermetic package, and sound processor with wireless power and signal transmission coil will be completed.

Confined DART-MS for Rapid Chemical Analysis of Electronic Cigarette Aerosols and Spiked Drugs.

A confined direct analysis in a real time mass spectrometry (DART-MS) system and method were developed for coupling directly with commercial electronic cigarettes for rapid analysis without sample preparation. The system consisted of a confining heated glass T-junction, DART ionization source, and Vapur interface to assist aerodynamic transport. Suction generated by positioning the electronic cigarette at the junction inlet allowed for direct chemical analysis of aerosolized electronic liquids from both automatic devices powered by drag and manual button-operated devices, which is unachievable with traditional DART-MS. Parametric analyses for the system investigated Vapur suction flow rate, junction heating, puff duration, and coil power levels. Using this method, rapid chemical analyses of electronic cigarette aerosols from electronic liquids, spiked illicit drugs, and polymeric or plasticizer contaminants were performed in <30 s. The confined DART-MS method provides a streamlined tool for rapid screening of illicit and hazardous chemical profiles emitting from electronic cigarettes.