Showing papers on "Solenoid published in 2022"

Metal-as-insulation HTS coils

Abstract: In this article, we summarize what we have learned about metal-as-insulation (MI) winding behavior and technical challenges. High-temperature superconductor (HTS) materials are highly thermally stable. This feature compared to classical low temperature superconductor (LTS) enables the use of MI technology to improve the protection against quenches. We firstly present a review of what has been done worldwide since 2011, which is the first time that a co-winding of a metallic tape without insulation was used in HTS pancake coils. In this review we also focus on the turn-to-turn contact resistivity parameter and the ranges obtained by groups worldwide. Then, we give details of our NOUGAT insert, a LNCMI-CEA-Néel Institute MI HTS insert built in 2018. We describe the specific conception of the magnet including the compact magnetic shielding. The high number of tests performed in high resistive background fields between 2018 and 2021 gives us a unique data set on this technology for ultra-high field (UHF) magnets; even in case of a background field fast drop at 19 T. This magnet is the first REBCO solenoid of this size using this technology, and tested intensively at such high magnetic fields (up to 32.5 T) so far. Finally, we discuss about the self-protection feature of MI coils and we propose a passive protection way for high turn-to-turn resistivity values.

A Three-Stage-Five-Coil IPT System Based on Cylindrical Solenoid Coupler Applied to State Detection Equipment of HV Device

Abstract: A three-stage-five-coil inductive power transfer (IPT) system which is based on cylindrical solenoid coupler (CSC) is proposed in this article. The shape and parameters of the CSC are optimized. The five litz coils compensated by series capacitors are considered to form an IPT system based on equivalent CLC/S/CLC compensation topology with constant voltage characteristics. The mutual inductance between compensation auxiliary coil (CAC) and power transfer coil could be changed by moving the position of CAC, and the freedom of parameter design is enhanced. Mathematical model and loss model of the system are established, and power transfer characteristics of the system are analyzed. The system is considered to be used as a power source for state detection equipment of high-voltage (HV) device to achieve long-distance IPT, the effect of the coupler on the HV electric field is verified. Finally, a prototype with a length of 1.54 m was built. Based on the platform, output voltage and dc–dc power transfer efficiency curves with changed input voltage and load are obtained. The maximum efficiency of the dc–dc system can reach about 60%.

Active magnetic regenerative refrigeration using superconducting solenoid for hydrogen liquefaction

Abstract: A magnetic refrigerator that makes use of the magneto-caloric effect realizes a highly efficient cooling device. Since the cooling power of magnetic refrigerators depends largely on the strength of the magnetic field, the use of a superconducting magnet is essential. Using magnetic refrigeration, achieving a liquefaction efficiency of larger than 50% is theoretically possible, which is twice that of conventional gas expansion refrigerators. In this study, an active magnetic regenerative refrigerator, one of the magnetic refrigerators using a superconducting solenoid, was built and hydrogen liquefaction was successfully demonstrated.

A Free-Rotation Asymmetric Magnetic Coupling Structure of UAV Wireless Charging Platform With Conformal Pickup

Abstract: This article proposes an asymmetric magnetic coupler using the horizontal magnetic field to realize the conformal and lightweight unmanned aerial vehicle (UAV) side pickup mechanism and solve the problems of rotation misalignment and horizontal offset of UAVs. The novel structure uses multiple groups of series circular coils as the transmitting coil to construct a uniform near harness horizontal magnetic field. The solenoid structure covered with flexible magnetic material is used as the receiver, which is attached to the UAV landing gear. A 200-W prototype is produced to validate the proposed structure. The system can maintain smooth mutual inductance with a dc–dc efficiency of 90% under a ±20 mm offset and free-rotation.

A Multiload Wireless Power Transfer System With Concentrated Magnetic Field for AUV Cluster System

Abstract: In this article, a multiload wireless power transfer (WPT) system is proposed for the power supply of autonomous underwater vehicle (AUV) cluster system. The segmented arc solenoid transmitter coil is designed to generate the concentrated magnetic field. The adjacent transmitter coils are reversely wound to form the strengthened magnetic field, which can improve the coupling between the transmitter and the receiver. The proposed coil structure is verified via finite element analysis based on ANSYS Maxwell. The transfer performance is analyzed and it is found that the transfer efficiency can be maximized against the voltage gain under the two-receiver case, which can also be extended to multiple-receiver case. An LCC–LCC compensated multiload WPT prototype was established and the experimental results verified the theoretical analysis and simulations. The output power of each receiver and the system efficiency can reach 500 W and 90% under the different angles between any two receivers.

Thermomagnetic instabilities of Nb3Sn wires inside the superconducting solenoid

Abstract: Thermomagnetic instabilities are widely observed in bulk superconductors and superconducting (SC) films in form of flux jumps and flux avalanches. Recent experiments demonstrate that the frequent flux jumps can also be observed in superconducting coils. These undesirable flux jumps have a significant impact on coils. However, it is much more difficult to simulate the flux jumps in superconducting coils than bulk superconductors because of the unacceptable number of elements for such complex structures with composite materials. In this paper, we develop a possible scheme to numerically simulate the flux jumps inside the superconducting coils with acceptable computation resources, which allows us to qualitatively study the main characteristics of the thermomagnetic instabilities. Furthermore, we explore the sensitivity of flux jumps inside the superconducting solenoid to various electromagnetic and thermal parameters as well as the ramp rate. Our scheme of numerical simulation may pave an appropriate way to further study the thermomagnetic instabilities inside the various superconducting coils with complex structures.

Effect of Local Defects on HTS Fusion Magnets Performance

Abstract: Local defects in the manufacturing of high temperature superconducting cable-in-conduit conductors are known to be present at different stages of the conductor production. The impact of such defects on the performance of one module of the hybrid option of the EU DEMO Central Solenoid is investigated here using the H4C code. For such analysis, the modeling of each strand is needed, since the defect leads to a strong nonuniformity of the current distribution in the conductor cross section, which in turn causes temperature differences in the cross section during the propagation of a quench. The analysis allows to assess the level of damage in strand(s) before inducing a quench. In case a quench is initiated, the model is used to follow its propagation to assess the hotspot temperature. It is also observed that a quench is induced in the low temperature superconducting third layer starting from a quench initiated in the first layer, via interlayer thermal coupling.

Efficient ULF Transmission Utilizing Stacked Magnetic Pendulum Array

Abstract: A novel stacked magnetic pendulum array (MPA) is proposed as an antenna for efficient transmission in ultralow frequencies (ULF). The MPA structure consists of an array of ${m\times n}$ magnets stacked in $n$ rows (m magnets of the same magnetization per row) and a solenoid that encompasses the array. The magnetic flux generated by the solenoid couples to the magnets through a mechanical motion and creates a strong time variant magnetic field at the resonance frequency of the array. The proposed MPA is developed utilizing bearings with extremely small damping which hold the magnets, enable efficient oscillation, and guarantees a high-quality factor ( $Q$ -factor). A comprehensive analysis to study the performance of the MPA and a conventional solenoid will be provided and accordingly, characteristics of an arbitrary ${m\times n}$ array in terms of field strength, resonance frequency, transmission efficiency and inductance are studied. Furthermore, a figure of merit (FOM) is introduced as the ratio of efficiency to the maximum linear dimension of the antenna. The experimental results for a fabricated $5 \times 11$ array show a resonance frequency of 715 Hz and a Q-factor of 94 while the maximum linear dimension of the antenna is just 9 cm. Moreover, measurement results show 24.9 dB improvement in the transmission efficiency of the MPA compared to the efficiency of a single solenoid of the same dimensions. The MPA has the FOM of ${1.26\times 1}{0}^{{4}}$ which is noticeably higher than that of proposed antennas in the literature. To demonstrate broadband transmission with the MPA, a binary frequency shift keying (BFSK) signal is transmitted through the use of direct antenna modulation (DAM) at a rate of 18 bps.

Solenoid-free current drive via ECRH in EXL-50 spherical torus plasmas

Abstract: Abstract As a new spherical tokamak designed to simplify the engineering requirements of a possible future fusion power source, the EXL-50 experiment features a low aspect ratio vacuum vessel (VV), encircling a central post assembly containing the toroidal field coil conductors without a central solenoid. Multiple electron cyclotron resonance heating (ECRH) resonances are located within the VV to improve current drive effectiveness. Copious energetic electrons are produced and measured with hard x-ray detectors, carry the bulk of the plasma current ranging from 50–150 kA, which is maintained for more than 1 s duration. It is observed that over one ampere current can be sustained per watt of ECRH power issued from the 28 GHz gyrotrons. The plasma current reaches I p > 80 kA for high density (>5 × 10 18 m −2 ) discharge with 150 kW ECRH. An analysis was carried out combining reconstructed multi-fluid equilibrium, guiding-center orbits of energetic electrons, and resonant heating mechanisms. It is verified that in EXL-50 a broadly distributed current of energetic electrons creates a smaller closed magnetic-flux surface of low aspect ratio that in turn confines the thermal plasma electrons and ions and participate in maintaining the equilibrium force balance.

Description of a AC Loss Model for the ITER CS Coils

Abstract: AC loss is a major heat load in the pulsed, superconducting ITER coils, and thus a design driver for the cryo-system and superconductor. Given the importance of AC loss, extensive AC loss characterization of the components of the ITER coils, from the superconducting strands, cables, long “coil-like” conductors (so called insert-coils) to the completed coils, were conducted over the past years. Recently the first Central Solenoid (CS) modules were factory tested including AC loss tests representative of the operational conditions. The modelling of the AC loss is critical for the preparation of ITER Tokamak operation and commissioning. The following describes the AC loss models for the ITER CS coils. Such models need to be simple to implement and fast to execute to allow simulation of the long ITER plasma scenarios. The paper explains the simplifications applied and discusses the implications. The status of the validations of the model on experimental data are presented.

Analytical Expressions for Inductances of 3-D Air-Core Inductors for Integrated Power Supply

Abstract: This work presents analytical expressions for the dc inductance of 3-D air-core inductors with circular cross-sectional pillars (CCSPs) and rectangular cross-sectional pillars (RCSPs). We consider the following four types of inductor structures: 1) a toroid with CCSP; 2) a toroid with RCSP; 3) a solenoid with RCSP; and 4) a solenoid with CCSP. For each type, a unique analytical model is developed for obtaining dc inductance. High-frequency (1–100 MHz) effects on inductance are also discussed. The inductance values predicted by the proposed analytical models of the first three types of inductor structures are in an acceptable agreement with numerical finite-element analysis (FEA) solutions, where the maximum difference is 7.3%. Also, our analytical model for the fourth-type inductor reduces the error, when correlated with FEA inductance value, up to $6\times $ compared with previously published models. A comparison of results using the proposed analytical expressions with published measured values as well as our measurement data demonstrates the error ranging from 0.5% to 16.2%, while conventional formulas show errors of up to 143%. The results of the proposed models could serve as a good initial estimate for power supply-on-chip (PwrSoC) and power supply in package (PSiP) applications.

Conceptual Design Studies of an HTS Insert for the DTT Central Solenoid

Abstract: The “Divertor Tokamak Test” (DTT) facility is an experimental fusion reactor being built in Frascati (IT) in the framework of the European Fusion Roadmap. The DTT Central Solenoid comprises six independently energized modules, wound from Nb3Sn Cable-In-Conduit Conductors (CICC). The future addition of a High Temperature Superconductor (HTS) insert would enhance the CS performance, in terms of magnetic flux density and magnetic field produced in the machine and would represent a fundamental technology demonstration toward high-field fusion. Along with the LTS cables, the Central Solenoid complex aims to reach 18 Wb at the pre-magnetization phase, being 16.54 Wb with the LTS CS only. Each LTS module is internally divided into three sub-modules: High Field (HF), Medium Field (MF) and Low Field (LF), each with a dedicated CICC cable optimized for the intense electromagnetic loads during the plasma scenarios. The LTS cables adopt a 316LN steel jacket and a fiberglass-reinforced resin insulation layer. The conceptual design presented here concerns an HTS insert, to be possibly placed inside the CS bore in the machine, employing a Round-In-Square (RIS) configuration of the conductor with either aluminum alloy or steel jackets. The study carried out for the design of the HTS insert and its pre-compression structure, the main electromagnetic and structural analyses and the design solution are presented in this work.

Examination and Characterization of Physical and Mechanical Properties of the ITER Central Solenoid Module Coils

Abstract: The ITER Central Solenoid (CS) consists of a stack of six independent coil packs called modules. It features a total height of 18 m and a diameter of over 4 m. The modules are in an advanced stage of fabrication and testing by the US ITER Project Office (USIPO) and its subcontractor General Atomics (GA). A qualification module mockup at one to one scale but of reduced height was wound and Vacuum Pressure Impregnated (VPI) by GA to validate final manufacturing, using tooling and processes fully representative of a series module. The module was submitted to a thermal cycle down to the temperature of 4.5 K at which the coils will be cooled by supercritical helium. During plasma operation, the CS modules are subjected to a complex combination of static and dynamic forces. The understanding of the mechanical behaviour of the CS module coils is of paramount importance to analyse and predict the overall response of the CS stack. To this purpose, an extensive programme of investigation of the module mockup has been defined and applied. This allowed assessing, through examination and testing of a large number of VPI conductor array samples extracted from the mockup, the soundness of the coil through advanced non-destructive examination techniques including X-ray microtomography, dimensional metrology measurements and micro-optical observations. Moreover, additional testing of physical and mechanical properties carried out at room and cryogenic temperature allowed the behaviour of the conductor stacks to be assessed. The paper summarises the results of these investigations and their interpretation through mechanical analyses based on the individual properties of the coil constituents.

Temperature-Independent Fault Detection of Solenoid-Actuated Proportional Valve

Abstract: Most electrically actuated hydraulic valves utilize solenoids as the actuating element due to their robustness and simplicity. This goes for both on–off and proportional-type valves. However, despite their robustness, solenoid coil malfunction is the largest single failure mode in solenoid actuated valves. An outspoken fault is here solenoid winding short-circuit, i.e., two windings short-circuiting, which may ultimately lead to solenoid failure if more windings short-circuit. Research has therefore also focused on detecting winding short-circuits. Common for the approaches are that they, directly or indirectly, depend on the coil winding temperature, as this directly influences the coil resistance. Alternatively, the approaches are based on injection of high-frequency signals, which is typically a costly solution, which is not a feasible approach for use in hydraulic valves, with the limitations imposed by the control electronics. Therefore, this article focuses on a temperature-independent algorithm to detect coil winding short-circuit, which is easy to implement and only relies on existing position and current sensors. The proposed algorithm is based on an extended Kalman filter, which estimates the coil resistance. As this resistance estimate is indirectly dependent on the coil temperature, a window-based cumulative sum fault detection method is included to detect transient changes in the coil resistance while compensating for the temperature variations. The algorithm is developed based on an experimentally validated model of the valve, and has been tested for several different situations through both simulations and experimentally. Based on the presented results, it is found that the algorithm can consistently detect resistance changes down to 0.11 $\Omega$ for constant input signals and down to 0.17 $\Omega$ for sinusoidal-varying input signals. This while stillbeing robust to parameter variations, such as increased valve friction, spring coefficients, and sensor signal deviations.

Optimal Design of High Density HTS-SMES Step-Shaped Cross- Sectional Solenoid to mechanical stress reduction

Abstract: The high temperature superconducting magnetic energy storage (HTS-SMES) system has an efficient system and is able to storing energy in high density. Therefore, this is an attractive method of energy restore in power system for protection and stability control. In the other hand, one of the most important challenges in HTS-SMES is optimal coil design that have direct relationship with energy stored in unit length of the coil conductor, length of the wire is used, and finally the cost of the winding. In order to resolve design problems, a recent three-objective optimization of the mechanical stress of a coil, uniformity of the magnetic field inside the magnet and coil volume is presented in this paper. Three constraints include energy requirements, the stray field in an around coil, the quench condition and maximum mechanical stress of the HTS-SMES coil are considered. To optimize this three objective optimization design problem, multi objective evolutionary algorithm based on decomposition (MOEA/D) has been used. We optimized step-shaped solenoid coil with maximum mechanical stress and current density constraints. 400 MA/m2 and stresses of about 400 MPa. HTS-SMES solenoid optimal design based on YBCO is considered and the YBCO-coated conductor is employed for the HTS-SMES coil. In this paper, FYSC-SC05 YBCO and FYSC-SC10 tape produced by FUJIKURA superconductor technology company are chosen In this method, in addition to mechanical stress determination, dimension of the HTS-SMES step-shaped cross sectional solenoid is determined. Results show that mechanical stress in FYSC-SC05 and FYSC-SC10 13.5%, 22.3% reduced related to maximum limitation of mechanical stress, respectively.

Digital Control and Power Systems for the Pegasus-III Experiment

Abstract: The PEGASUS-III experiment is a solenoid-free, low aspect ratio spherical tokamak that will serve as a dedicated U.S. platform for comparative nonsolenoidal tokamak plasma startup studies. Approximately 175 megavolt-ampere (MVA) of reconfigured and expanded programmable power systems, 7 MJ of new stored energy, and new digital control and protection systems for the facility are being commissioned to support PEGASUS-III upgrades. These include: increased toroidal field (0.15–0.6 T); new divertor and poloidal field coils; increased pulse length; local and coaxial helicity injectors for solenoid-free plasma initiation; radio frequency (RF) systems for heating and current drive; and a diagnostic neutral beam (DNB). A new real-time digital control system implements 16 proportional-integral differential (PID) feedback controllers with 25 kHz loop rates to control the electromagnets and helicity injectors. The poloidal field coils, helicity injector arc currents, and toroidal field are driven by 36 3.6 MVA (4 kA, 900 V) insulated-gate bipolar transistor (IGBT) buck converters. Helicity injector bias voltage and current will be provided by a set of four 10.8 MVA multi-level buck converters (MLBCs). Each is comprised of an 1800 V integrated gate-commutated thyristor (IGCT) stage and a ±900 V IGBT stage in series, providing controllable $I_{\mathrm {inj}}\le 4$ kA at $V_{\mathrm {inj}}\le 2.7$ kV. A field programmable gate array (FPGA)-based digital fault protection system multiplexes controller commands to individual power semiconductors in these supplies, monitors their operational status, and executes shutdown sequences within $10~\mu \text{s}$ of fault detection. An 80 kV, 4 A zero-voltage-switching (ZVS) resonant converter with < 1% output ripple is under development for the DNB and is being evaluated as a topology to drive RF sources.

Failure Analysis of Linear Electromagnetic Actuators Under Disturbing Magnetic Field

Abstract: Linear electromagnetic actuators (LEAs), operated by electromagnetic action, are widely used in various applications, such as switches and solenoid valves. Since it operates on the principle of electromagnetic attraction, it is very sensitive to magnetic field. LEA may fail under the impact of disturbing magnetic field (DMF), thus threatens the stability of the whole system. As the magnetic field around tokamak is very strong, it is of great importance to evaluate the behavior of LEAs under DMF. This article presents the analysis of two different types of LEAs in DMFs. Based on the finite element method, the influences of DMF on the two LEAs are analyzed, and both the opening and closing processes are considered. Analyses show that the piston-type LEA may fail to act under DMF, while the plate-type LEA may malfunction even it is not energized. Based on the analysis, the failure mechanism is revealed, and the failure thresholds of the two LEAs are also quantified. The experimental verifications are carried out, which are in good agreement with the simulation results. The analysis model and the main conclusions presented in this article are of great significance to guide the antimagnetic field design of LEAs and ensure their reliable operations in tokamakxs.

Optimization of the Coupling Coefficient of the Inductive Link for Wireless Power Transfer to Biomedical Implants

Abstract: This work focuses on the optimization of coupling coefficient (k) of the inductive link for the wireless power transfer (WPT) system to be used in implantable medical devices (IMDs) of centimeter size. The analytic expression of k is presented. Simulations are conducted by using the high-frequency structure simulator (HFSS). Analytic results are verified with simulations. The receiving (Rx) coil is implanted in the body and set as a circular coil with a radius of 5 millimeters for reducing the risk of tissue inflammation. The inductive link under misalignment scenarios is optimized to improve k. When the distance between the transmitting (Tx) and Rx coils is fixed at 20 mm, it is found that, to maximize k, the Tx coil in a planar spiral configuration with an average radius of 20 mm is preferred, and the Rx coil in a solenoid configuration with a wire pitch of 0.7 mm is recommended. Based on these optimization results, an inductive link WPT system is proposed; the coupling coefficient k, the power transfer efficiency (PTE), and the maximum power delivered to the load (MPDL) of the system are obtained with both simulation and experiment. Different media of air, muscle, and bone separating the Tx and Rx coils are tested. For the muscle (bone) medium, PTE is 44.14% (43.07%) and MPDL is 145.38 mW (128.13 mW), respectively.