Double-layer Coil Research Articles

The use of concentric loops and double-layered coils for compact design of wireless charging pads

The use of concentric loops and double-layered coils for compact design of wireless charging pads

Double-Layer Coils Design for 11 kW Wireless Power Transfer

The design of a wireless power transfer system with double rectangular coils for 11 kW power transfer is considered. System modeling and numerical calculation of the system parameters are described. Coils are made from available Litz wire, which has a smaller than necessary diameter for the required power. Thus, a setup with double layer coils was developed, which resulted in a modified design. Starting from a system consisting of coupled coils, as suggested by the standard for wireless power transfer Level 3 in class Z1, different coil and ferrite shield layouts were tested in numerical simulations, and their parameters were calculated. The prototype was constructed based on the simulated model with the best results and properties. Numerical results were verified by laboratory measurements, and a successful power transfer at 11 kW was achieved.

Winding loss analysis of planar spiral coil and its structure optimization technique in wireless power transfer system

Circular planar spiral coils are wildly used for the magnetic coupling system in a high-frequency wireless power transfer system. The loss of the magnetic coupling system usually takes dominance in the whole system. This paper built the calculation model of magnetic field strength and coil loss, the proposed calculation model can effectively consider the mutual influence between the transmitter and receiver coil and accurately calculated the AC loss of WPT coils. Then, the effect of turn spacing on the AC resistance of coil is analyzed. It reveals that the proximity effect loss is greater when the coil is tightly wound, and the AC loss can be optimized by designing the turn spacing. Based on the above analysis, a double-layer coil method is proposed. This method can reduce the AC loss and improve the quality factor (Q) without changing the mutual inductance and footprint of coil at high frequency. The AC resistance of the double-layer coil method can be greatly reduced compared with the general method through simulation and experiment. The work efficiency of WPT system is increased by 4.3%, which verifies the accuracy and flexibility of theoretical analysis.

Analysis of Repetitive Bending on Flexible Wireless Power Transfer (WPT) PCB Coils for Flexible Wearable Devices

In this article, we first designed, measured, and analyzed flexible wireless power transfer (WPT) coils with repetitive bending cycles. To analyze any changes in electrical characteristics through repetitive bending cycles, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\times3$ </tex-math></inline-formula> cm flexible printed circuit board (PCB) coils were fabricated using polyimide substrates. Different coil configurations are designed to find a mechanically robust, flexible PCB coil design. First, we analyzed single-layer and double-layer coils. Generally, via is the mechanically weakest part of the PCB, hence the diameter of the via varies to observe the effect of repetitive bending cycle. Ten thousand bending cycles with a bending radius of 3 mm and a bending cycle frequency of 1 Hz were used to analyze the electrical changes. Moreover, the bending position of the coil is varied to observe the bending effect. The flexible coil’s direct current (dc) resistance is measured during the bending cycle. After the repetitive bending test is completed, the coil impedance is analyzed in a frequency domain. As a result, we conclude that the flexible WPT coil is robust from mechanical stress when the layer of the coil is single a layer, the bending line is applied vertically, and the diameter of the via is small.

A 1-kW and 100-cm Distance Magnetically Coupled Resonant WPT System Achieving 80% Efficiency

For the magnetically coupled resonant wireless power transfer (MCR WPT) applications with high-power level and medium-range distance, the low coupling coefficient brings severe challenges to the system efficiency and reliability, as the coil loss and the voltage/current stress on compensation components are both considerable; meanwhile, the high operating frequency that contributes to improve the power density will result in high switching loss and related electromagnetic interference. In this article, a parameter design methodology for high-power and medium-range-distance MCR WPT applications was proposed to achieve high system efficiency. The accurate time-domain system model was built to obtain the relationship among voltage/current stresses on the compensation components, zero-voltage-switching (ZVS) conditions of power switches and system parameters. The key parameters, including the switching frequency, the coil self-inductance, and the compensation inductance, are designed to realize wide-range ZVS and reduce voltage/current stresses. Double-layer coil configuration was adopted instead of the traditional single-layer coil to reduce coil losses, and the series compensation capacitors in TX and RX coils were split to achieve current sharing between double-layer coils. Meanwhile, the LCCL-TT compensation network was used to achieve the optimal load and maximize the system efficiency. Finally, a 1-kW MCR WPT prototype within 100-cm transmission distance was implemented in the laboratory for experiments, and the system efficiency under the rated condition is 80.62%.

Engineering Design of a Large Aperture 15 T Cable Test Facility Dipole Magnet

The Nb <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{3}$</tex-math></inline-formula> Sn based test facility dipole magnet (TFD), with a rectangular aperture of 100 × 150 mm, and an operation target bore field of 15 T at 1.9 K, is designed to provide a background dipole field for cables and inserts. The design of the magnet is based on four double-layer coils and an aluminum shell-based structure, using key-and-bladder technology, with axial pre-load. The status of the magnet design, and optimization analyses, are here presented. The results of the initial prototyping, initial winding tests, characterization of cable hard-way bend curvature, and layer jump prototype test are also discussed.

Strategies for improving the force performance of a superconducting linear synchronous motor

Combined with superconducting technology, an electrodynamic suspension train can reach a higher traveling speed by taking advantage of the strong magnetic field generated by high-temperature superconducting (HTS) magnets. However, a HTS linear synchronous motor (LSM) in a propulsion system typically uses an air-core structure to reduce the normal force. As a result, excessive propulsive force ripple occurs due to magnetic circuit divergence and a large air gap, which leads to an uncomfortable ride and unexpected mechanical resonance. To reduce this ripple, this study first improves the traditional short-pitch winding structure of the stator. By staggering the double-layer coils of the stator, the ripples of the magnetic flux density generated by the upper and lower coils change from superposition to suppression. Then, the propulsive force of a pair of pole magnets of the HTS-LSM under this structure is analyzed, and its primary ripple frequency is 6 times the fundamental frequency. By installing two pairs of magnets in a bogie and staggering them by a 30° electrical angle, the peak and valley of the propulsive force of the two magnets are staggered so that the total propulsive force waveform of the bogie can be smoothed as much as possible. Concurrently, the AC loss generated by the alternating magnetic field on the HTS magnets can be reduced. Also, this study investigates the influence of the short pitch factor on the propulsive force, and the ripple can be suppressed by reducing the factor.

Коэффициенты взаимной индукции и самоиндукции однослойных и двухслойных катушек

Object and purpose of research. This paper discusses single- and double-layer coils. The purpose of the study was to improve the operation of ship power systems. Materials and methods. The study relied on the methods of mathematical physics and theoretical electric engineering. Main results. The study analyses current methods and recommendations for inductance calculations of single- and double-layer coils. Based on the comparative analysis, the paper suggests the expressions that make it possible to do without the tabular values. Conclusion. The study yielded strict expressions with special functions that entail from the overlapping of a number of idealized representations. As an example for one of them, the paper gives a formula expressing the inductance in terms of spherical Legendre functions with semi-integer index. The comparison of recommended calculation expressions for doublelayer coil inductance has not found any significant deviations.

A Method for Increasing the Bandwidth of Rogowski Coils Without Changing Their Size

According to published papers on Rogowski coils, the sensitivity of Rogowski coils can be increased by using high-density turns and multilayer turns. Low-density turns can increase the bandwidth of the coil but can also reduce the anti-interference ability of the coil. The shielding layer can also increase the anti-interference ability of Rogowski coils. However, for Rogowski coils with high-density turns, using a shielding layer or multilayer turns will reduce their measurement bandwidth. To increase the application flexibility of a Rogowski coil, this article proposes a method capable of increasing the bandwidth without sacrificing size, sensitivity, anti-interference, and measurement accuracy. In this method, coils are segmented without reducing the number of turns, and the induced voltage of the segmented coils is output through the voltage followers and joined together by an adder. Seventeen Rogowski coils are wound by an automatic coil winding machine. These 17 coils consist of single-layer coils, double-layer coils, coils without a shielding layer, and coils with a shielding layer. The method is verified for use with Rogowski coils when measuring the sinusoidal current and the turn-on/off pulse current of an high voltage-insulated gate bipolar transistor (HV-IGBT) collector. The measurement errors of this method and the error compensation method are also explored both theoretically and experimentally.

Differential Coupling Double-Layer Coil for Eddy Current Testing With High Lift-Off

The detection sensitivity and lift-off impaction of the eddy current sensing are the challenges in the field of electromagnetic nondestructive testing. Higher detection sensitivity, larger lift-off capability, and deeper defect detectability remain challenges. This paper presents a double-layer differential planar coil with the discussion of the most sensitive coupling gap. The upper layer contains two symmetrical excitation coils as it can generate symmetrical and opposite magnetic fields. The rectangular structure makes the induced current uniform and symmetrical. The lower layer constructs a differential receiving coil, which can reduce the interference caused by the lift-off impaction as well as the external magnetic field. Different types of surface defects of metallic materials were used for validation. Experimental results show that properly increasing the distance between the excitation and detection layers can effectively improve its sensitivity. Simulation and experimental results confirm that the performance of high sensitivity can be maintained under large lift-off affection.

Design and Analysis of Double-Layer Electromagnetic Field Limiter for Wireless Rechargeable Medical Implants

Human exposure to the electromagnetic field (EMF) has been raising concerns with the fast development of the wireless power transfer (WPT) technology. This article proposes a double-layer coil structure for wireless rechargeable implanted medical equipment, which can effectively strain the power beam into a single direction and limit the EMF emission to other parts of the human body. The system is designed and analyzed based on both the finite-element method (FEM) simulation and practical tests. A prototype of the proposed double-layer receiver with 56 mm diameters has successfully captured 6.84 W power and the EMF emission strength has been effectively reduced by over 20% at the concerning parts of the human body during WPT. The design scheme has been analyzed based on practical considerations and can be embedded into other similar medical implant applications.

Design and Performance Analysis of Magnetic Shape Memory Alloy Actuator With a Compact Electromagnetic Coil Configuration

Magnetic shape memory alloy (MSMA), which has emerged in recent years, has been proven to have great potential for electromagnetic actuators due to the long life cycle, fast response, and relatively large load capacity. Current research on such material mainly focuses on the fundamentals, thermal effect, composition, and magnetic induction strain, but issues involved in its application to the industry are rarely addressed in detail. This article first analyzed the principle of magnetically induced strain and the corresponding constitutive equations, and investigated the magnetomechanical characteristics of the MSMA sample through measurement carried out on a specially designed experimental setup. Taking advantage of good drive performance, MSMA electromagnetic actuator with spring recovery was designed in detail. In order to resolve the contradiction between compactness and high magnetic field strength, a novel configuration with double-layered coils was proposed to achieve the required magnetic flux density. Influences of input current, prepressure, and spring stiffness on the dynamic response characteristics of the actuator excited by step signal and square wave signal input were analyzed by simulation. Finally, the experimental platform is built to verify the feasibility of the configuration and dynamic characteristics of the actuator. The experimental results show that the designed actuator has good output performance with a response time of 25 ms, demonstrating the superiority of MSMA in microdisplacement actuator with high dynamics.

An improved multi-swarm particle swarm optimizer for optimizing the electric field distribution of multichannel transcranial magnetic stimulation.

Multichannel transcranial magnetic stimulation (mTMS) is a therapeutic method to improve psychiatric diseases, which has a flexible working pattern used to different applications. In order to make the electric field distribution in the brain meet the treatment expectations, we have developed a novel multi-swam particle swarm optimizer (NMSPSO) to optimize the current configuration of double layer coil array. To balance the exploration and exploitation abilities, three novel improved strategies are used in NMSPSO based on multi-swarm particle swarm optimizer. Firstly, a novel information exchange strategy is achieved by individual exchanges between sub-swarms. Secondly, a novel leaning strategy is used to control knowledge dissemination in the population, which not only increases the diversity of the particles but also guarantees the convergence. Finally, a novel mutation strategy is introduced, which can help the population jump out of the local optimum for better exploration ability. The method is examined on a set of well-known benchmark functions and the results show that NMSPSO has better performance than many particle swarm optimization variants. And the superior electric field distribution in mTMS can be obtained by NMSPSO to optimize the current configuration of the double layer coil array.

PENINGKATAN SENSITIVITAS SENSOR KOIL DATAR MEMPERGUNAKAN SOFT MAGNETIC VITROVAC

This study reports the design of non-magnetic plate thickness sensors based on Eddy Current principld in the form of flat coils. The principle used in the Eddy Current sensor is a change of mutual coil inductance due to the presence of objects in the magnetic field. The coil is made up of single and double layer coil designed using Corel Draw Software based on printed circuit board (PCB) material with dimensions of 152.4 mm x 101.6 mm, which has a track distance of 0.125 m. Single and double layer coil inductance evaluations are carried out using the EVB LDC 1000 L/V Converter module which converts plate thickness into inductance values. The addition of a 30 mm Vitrovac thin film mounted in the direction of the winding in the 2 mm diameter coil core has been carried out to increase the sensitivity value of the sensor which gives an increase in sensitivity value of S = 0.321 uH / mm or 33.2%. The coil is able to measure plate thickness up to 10mm well.

A Miniature Resonant and Torsional Magnetometer Based on Lorentz Force.

A microelectromechanical system (MEMS) torsional resonant magnetometer based on Lorentz force was investigated, consisting of torsional structures, torsional beams, metal plates, a coil, and a glass substrate. The Lorentz force, introduced by the interaction between the current in the MEMS coil and an external horizontal magnetic field, leads to displacement of the torsional structure. The strength of the magnetic field is proportional to this displacement, and can be detected with two sensing capacitors fabricated on the torsion structure and the substrate. To improve sensor sensitivity, a folded torsional beam and a double-layer excitation coil were introduced. The fabrication processes included lift-off, anodic bonding, chemical mechanical planarization, silicon nitride (SiNx) deposition, plasma-enhanced chemical vapor deposition, and inductively coupled plasma release. The prototype of the magnetometer was finished and packaged. The sensor performance, including its sensitivity and repeatability, was tested in a low-pressure environment. Additionally, the influences of structural parameters were analyzed, including the resistance of the excitation coil, the initial value of the capacitors, the elastic coefficient of the torsional beam, and the number of layers in the excitation coil. The test results demonstrated that this sensor could meet the requirements for attitude determination systems in low earth orbit satellites.

All-Metal Domestic Induction Heating Using Single-Frequency Double-Layer Coils

In the past few decades, induction heating based on near-field magnetic coupling has been actively developed, aiming to improve the efficiency, controllability and safety. For traditional induction heating, the heating coil is energized by an AC power source to generate an alternating magnetic field, which in turn induces the eddy current in the workpiece to produce the heating effect [1]. Nevertheless, the workpiece made of non-ferromagnetic materials like stainless steel, aluminum and copper cannot be properly heated, which dramatically limits its application as compared with traditional open-fire heating. There was an attempt to heat the non-ferromagnetic workpiece using a strong magnetic field provided by superconducting windings [2], but it was not practical for domestic induction heating. By using low-frequency AC (around 20 kHz) to heat the ferromagnetic pan and high-frequency AC (over 70 kHz) to heat the non-ferromagnetic pan, the selective operating frequency technique was developed for all-metal domestic induction heating [3]. However, the corresponding switching and winding losses significantly increased, which inevitably resulted in low heating efficiency. In addition, the frequency selection caused serious electromagnetic interference and increased complexity and cost. Recently, the homogeneity and flexibility of induction heating has been improved by adopting the magnetic resonant coupling (MRC) mechanism [4], [5]. In this paper, a new all-metal domestic heating system is proposed and implemented. The key is to employ double-layer coils and utilizes the MRC mechanism to induce a high current in the resonant coil when heating the non-ferromagnetic pans, thus successfully heating both the ferromagnetic and non-ferromagnetic pans at 30 kHz resonant frequency. Consequently, the advantages of simplicity, high heating efficiency and single operating frequency can be attained for all-metal induction heating.

Optimized Electromagnetic Fields Levitate Bulk Metallic Materials

The bulk metallic electromagnetic levitation technique has a promising application prospect in condensed physics and materials science. In order to resolve the problem of weak levitation force and the small size of samples, an optimized solution based on finite element analysis (FEA) is developed to seek the best electromagnetic field distribution in the levitation zone. The influence of material properties on the distribution of magnetic flux density, surface pressure, and the Lorentz force were studied by the FEA method with various sample sizes of titanium and copper balls. The levitation capability of cylindrical coil system which consists of a single-layer coil with an inner diameter of 30 mm and the levitated object with a diameter of 20 mm was analyzed. To keep a balance between the turn number and increment efficiency of force, the best number of 7 turns is confirmed. Then, two types of optimized coils were predicted by numerical simulations, and the levitation force is improved drastically. The double-layer coil displays an outstanding levitation capability owing to the strong electromagnetic field generated by multilayer turns. In addition, 5 to 50 g aluminum, titanium, copper, and nickel are levitated by the above three kinds of coils and the levitation capacities are validated from the recorded data of the minimum operating current that can levitate the samples. The experimental results show good agreements with the simulation results, and the minimum current for optimized coils is reduced efficiently.

Optimization design of wireless charging system for autonomous robots based on magnetic resonance coupling

Wireless charging is the key technology to realize real autonomy of mobile robots. As the core part of wireless power transfer system, coupling mechanism including coupling coils and compensation topology is analyzed and optimized through simulations, to achieve stable and practical wireless charging suitable for ordinary robots. Multi-layer coil structure, especially double-layer coil is explored and selected to greatly enhance coupling performance, while shape of ferrite shielding goes through distributed optimization to guarantee coil fault tolerance and cost effectiveness. On the basis of optimized coils, primary compensation topology is analyzed to adopt composite LCL compensation, to stabilize operations of the primary side under variations of mutual inductance. Experimental results show the optimized system does make sense for wireless charging application for robots based on magnetic resonance coupling, to realize long-term autonomy of robots.

Cold Powering Tests and Protection Studies of the FRESCA2 100 mm Bore Nb3Sn Block-Coil Magnet

The Nb3Sn block-coil dipole magnet FRESCA2 was developed within the framework of a collaboration between CEA Saclay and CERN, follow up of the European project EuCARD. The magnet is aimed at upgrading the cable test facility at CERN to a bore field of 13 T at 10.6 kA in an aperture of 100 mm as deliverable. The design features four 1.6-m-long double-layer coils wound with a 40 strand, 21-mm-wide Rutherford cable. The first assembly was limited at 12.2 T with a known production defect of the cable close to a splice in one of the coils. Following replacement of this coil, the second assembly reached the target for this run of 13.3 T. In this paper, the performance of the assemblies in terms of training behavior, quench detection, protection, magnetic measurements, and other cold powering tests will be discussed.

A polygonal double-layer coil design for high-efficiency wireless power transfer

In this work, we present a novel coil structure for the design of Wireless Power Transfer (WPT) systems via magnetic resonant coupling. The new coil consists of two layers of flat polygonal windings in square, pentagonal and hexagonal shapes. The double-layer coil can be conveniently fabricated using the print circuit broad (PCB) technology. In our design, we include an angle between the two layers which can be adjusted to change the area of inter-layer overlap. This unique structure is thoroughly investigated with respect to the quality factor Q and the power transfer efficiency (PTE) using the finite element method (FEM). An equivalent circuit is derived and used to explain the properties of the angularly shifted double-layer coil theoretically. Comparative experiments are conducted from which the performance of the new coil is evaluated quantitatively. Our results have shown that an increased shift angle improves the Q-factor, and the optimal PTE is achieved when the angle reaches the maximum. When compared to the pentagonal and hexagonal coils, the square coil achieves the highest PTE due to its lowest parasitic capacitive effects. In summary, our new coil design improves the performance of WPT systems and allows a formal design procedure for optimization in a given application.