Spiral Coil Research Articles

Development of scaling laws for prototyping and heat loss correlations for upward facing cylindrical helical coil and conical spiral coil receivers

A solar receiver is an integral part of any concentrated solar power based plant for energy conversion. An experimental or numerical analysis of a large-scale solar receiver is expensive due to the high infrastructure and computational costs involved. Hence, it becomes necessary to study the effects of scaling on the performance of a solar receiver so that the results of the analysis of small-scale receivers can be extended to large-scale models. Therefore, a scale analysis is carried out in this study to develop constitutional relationships amongst physical and geometrical parameters for upward-facing cylindrical helical coil and conical spiral coil cavity receivers. Similarity parameters are derived from the non-dimensional Navier Stokes equations in the curvilinear coordinate system (s,r,θ). A scaling law is derived based on the identified parameters. A validated numerical model for the cylindrical helical coil receiver and conical spiral coil receiver is used to verify the scaling analysis. Further, Nusselt number correlations for the convective heat losses from the upward-facing cylindrical and conical cavity receivers are proposed. The newly proposed correlations predict the convective losses from the upward-facing cylindrical and conical cavity receivers within the error band of ±20%.

A 4 × 4 array multichannel magnetic stimulation system using submillimeter sized planar square spiral coils: The spatial distribution of electromagnetic field

Multi-coil magnetic stimulation has advantages over single-coil magnetic stimulation, such as more accurate targeting and larger stimulation range. In this paper, a 4 × 4 array multichannel magnetic stimulation system based on a submillimeter planar square spiral coil is proposed. The effects of multiple currents with different directions on the electromagnetic field strength and the focusing zone of the array-structured magnetic stimulation system are studied. The spatial distribution characteristics of the electromagnetic field are discussed. In addition, a method is proposed that can predict the spatial distributions of the electric and magnetic fields when currents in different directions are applied to the array-structured magnetic stimulation system. The study results show that in the section of z = 2 μm, the maximum and average magnetic field strengths of the array-structured magnetic stimulation system are 6.39 mT and 2.68 mT, respectively. The maximum and average electric field strengths are 614.7 mV/m and 122.82 mV/m, respectively, where 84.39% of the measured electric field values are greater than 73 mV/m. The average magnetic field strength of the focusing zone, i.e., the zone in between the two coils, is 3.38 mT with a mean square deviation of 0.18. Therefore, the array-structured multi-channel magnetic stimulation system based on a planar square spiral coil can have a small size of 412 μm × 412 μm × 1.7 μm, which helps improving the spatial distribution of electromagnetic field and increase the effectiveness of magnetic stimulation. The main contribution of this paper is a method for designing multichannel micro-magnetic stimulation devices.

Study and comparison of pulse compression techniques with three types of excitation for high-temperature EMAT detection

To address the low conversion efficiency and high ultrasonic attenuation in the detection of hot castings and forgings, the pulse compression technique (PCT) is an important and efficient method for improving the signal-to-noise ratio (SNR) and range resolution of ultrasonic echoes. A finite element model was established for the process of detection using a spiral coil electromagnetic acoustic transducer (EMAT) with three types of excitation, these being chirp signals, Barkercoded signals and combined Barker-coded signals, and the PCT processions were also provided. The SNR and range resolution of the PCTs with three types of excitation were compared using simulations and verified by experiments. The self-developed and water-cooled EMAT with three PCTs was used to measure a high-temperature forging and the pulse compression effect was also compared. The results indicate that the PCT with Barker-coded excitation has the highest SNR and the PCT with chirp excitation and combined Barker-coded excitation processes a higher range resolution. When the tested forging is at 710°C and compared with the traditional tone-burst excitation, the SNR from the PCT with combined Barker-coded excitation can be improved by 8.5 dB and the ultrasonic echo width can be reduced by 100%.

Inductance Calculation of Single-Layer Planar Spiral Coil

In this paper, an analytical calculation of the inductance of an air-core planar spiral coil is presented. The inner and outer radius of the planar spiral coil is determined from the general equation of the filament of the wire. Using the Neumann integral formula, the expression of inductance is obtained. The double integral of Neumann’s formula is computed numerically to evaluate the inductance. The accuracy of the calculation results is verified by comparing it with the conventional and the simulation results. Different geometry of spiral coils is fabricated to validate it experimentally. Finally, the comparison is performed with the experiment results, which show good agreement. Thus, the accuracy of the calculation result paves the way for designing and optimizing the spiral coil for electromagnetic applications.

Semi-active control for the nonlinear vibration suppression of square-celled sandwich plate with multi-zone MRE filler core

A semi-active controller is designed for the nonlinear vibration suppression of a novel square-celled sandwich plate with a multi-zone magnetorheological elastomers (MRE) filler core that can spontaneously generate a magnetic field using the embedded spiral coil. First, the nonlinear dynamic model of the square-celled sandwich plate with multi-zone MRE filler core is constructed by employing the nonlinear MRE model, the equivalent theory of material mechanics, the sandwich plate theory, the virtual spring technology, the eigenvalue increment method, and the modified Fourier-Ritz method. Next, based on the Newmark-Beta approach, the displacement and acceleration responses of the dynamic system are obtained. Afterwards, the high-order differential equation of the dynamic system is derived based on the relation of input and output of the dynamic system. A reference state of the dynamic response is predefined, and then the transfer function with respect to current can be identified. Furthermore, the verifications of the proposed model and controller are conducted. With the validated model, the optimal design of the semi-active controller is provided, and the feasibility of various control strategies is also discussed in detail.

Wireless Charging of Electric Vehicles Using Dual Spiral Coil Magnetic Resonant Coupling

Abstract: As we get into a new decade in the 21st century, the progress of electric automobiles has been on a significant rise but still flawed with things like range anxiety, limited number of charging stations, high price range etc. But one of the most important flaw is the range anxiety especially in countries like India where we spend half the time stuck in traffic. So, to overcome that we have come up with a project whose technology is still in development and is being tested worldwide. One method to avoid this is by the introduction of Wireless charging into Electric vehicles which is the main focus of this paper.

Simplified Mutual Inductance Calculation of Planar Spiral Coil for Wireless Power Applications.

In this paper, a simplified method for the calculation of a mutual inductance of the planar spiral coil, motivated from the Archimedean spiral, is presented. This method is derived by solving Neumann’s integral formula in a cylindrical coordinate system, and a numerical tool is used to determine the value of mutual inductance. This approach can calculate the mutual inductances accurately at various coaxial and non-coaxial distances for different coil geometries. The calculation result is compared with the 3D finite element analyses to verify its accuracy, which shows good consistency. Furthermore, to confirm it experimentally, Litz wire is used to fabricate the sample spiral coils. Finally, the comparison of a simplified method is also studied relative to the coupling coefficient. The accuracy of the calculation results with the simulation and the measurement results makes it a good candidate to apply it in wireless power applications.

A bi-stable mechanism actuated by patterned permanent magnet and Cu-Ni integrated micro-coil

This paper presents a bi-stable mechanism, which mainly consists of a suspended mass, a spacer and a bottom plate. Electromagnetic actuation is used for switching between two states (i.e. ‘On/Off’ state). The actuation is achieved via permanent magnet (PM) on the suspended mass and micro-coils embedded in the bottom plate. Different from spiral coil and central core in conventional design, micro-coils in this paper integrate Cu and Ni together as a whole, acting as both coil and ferromagnetic core. This integration simplifies the fabrication into one-mask process. Furthermore, chessboard patterned PM is utilized with Cu-Ni integrated micro-coils to generate enhanced force density. The bi-stable mechanism is designed, fabricated and experimentally characterized. Total size of this mechanism is 16 × 14 × 2 mm3. No power is needed for holding either of the state. Switching processes (both ‘On’ to ‘Off’ and ‘Off’ to ‘On’) can be realized with external acceleration of 24 G (gravity) and 37 G, respectively. Furthermore, resetting (i.e. ‘On’ to ‘Off’) can also be accomplished with 1.5 A current input.

Wireless Humidity Sensor for Smart Packaging via One‐step Laser‐Induced Patterning and Nanoparticle Formation on Metallized Paper

AbstractIn this work, a scalable and rapid process is developed for creating a low‐cost humidity sensor for wireless monitoring of moisture levels within packaged goods. The sensor comprises a moisture‐sensitive interdigitated capacitor connected to a planar spiral coil, forming an LC circuit whose resonant frequency is a function of environmental humidity. The sensor is fabricated on a commercially available metallized parchment paper through selective laser ablation of the laminated aluminum (Al) film on the parchment paper substrate. The laser ablation process provides a unique one‐step patterning of the conductive Al layer on the paper while simultaneously creating high surface area Al2O3nanoparticles within the laser‐ablated regions. The intrinsic humidity‐responsive characteristics of the laser‐induced Al2O3nanostructures provide the wireless sensor with a tenfold higher sensitivity to humidity than a similar LC resonant sensor prepared by conventional photolithography‐based processes on FR‐4 substrates. The frequency change of the sensor is observed to be a linear function within the range of 0−85% RH, providing an average sensitivity of −87 kHz RH−1with good repeatability and stable performance. Furthermore, the employment of scalable laser fabrication processes using commercially available inexpensive materials renders these technologies viable for roll‐to‐roll manufacturing of low‐cost wireless sensors for smart packaging applications.

Design of magnetic coupling mechanism for wireless power transmission system based on magnetic flux analysis

Aiming at the wireless charging system that can dynamically change arbitrarily in a three-dimensional space such as a smart robot, this paper proposes a new type of magnetic coupling mechanism that combines a disc coil and a spiral coil. It can not only avoid frequency splitting in the short-distance range, but also effectively enhance the coupling strength in the long-distance range. In addition, it can also effectively improve the position robustness and anti-offset ability of the robot’s wireless charging system. In this paper, the geometric framework of the new magnetic coupling mechanism is first given. Based on the analysis of magnetic flux, it is theoretically confirmed that the magnetic coupling mechanism can reduce the coupling strength in the near range, avoid the frequency splitting phenomenon, and improve the coupling strength of the system and the energy efficiency of the system in the long range. Finally, based on the finite element simulation software COMSOL, it is proved that the proposed magnetic coupling mechanism can achieve high energy efficiency output in a large range, and has strong position robustness and anti-deviation.

Flow characteristics simulation of spiral coil reactor used in the thermochemical energy storage system

According to environmental and energy issues, renewable energy has been vigorously promoted. Now solar power is widely used in many areas but it is limited by the weather conditions and cannot work continuously. Heat storage is a considerable solution for this problem and thermochemical energy storage is the most promising way because of its great energy density and stability. However, this technology is not mature enough to be applied to the industry. The reactor is an important component in the thermochemical energy storage system where the charging and discharging process happens. In this paper, a spiral coil is proposed and used as a reactor in the thermochemical energy storage system. The advantages of the spiral coil include simple structure, small volume, and so on. To investigate the flow characteristics, the simulation was carried out based on energy-minimization multi-scale model (EMMS) and Eulerian two-phase model. CaCO 3 particles were chosen as the reactants. Particle distribution was shown in the results. The gas initial velocity was set to 2 m·s −1 , 3 m·s −1 , and 4 m·s −1 . When the particles flowed in the coil, gravity, centrifugal force and drag force influenced their flow. With the Reynold numbers increasing, centrifugal and drag force got larger. Accumulation phenomenon existed in the coil and results showed with the gas velocity increasing, accumulation moved from the bottom to the outer wall of the coil. Besides, the accumulation phenomenon was stabilized when φ > 720°. Also due to the centrifugal force, a secondary flow formed, which means solid particles moved from the inside wall to the outside wall. This secondary flow could promote turbulence and mixing of particles and gas. In addition, when the particle volume fraction is reduced from 0.2 to 0.1, the accumulation at the bottom of the coil decreases, and the unevenness of the velocity distribution becomes larger.

A 1.7–3.6 GHz 20 MHz-Bandwidth Channel-Selection N-Path Passive-LNA Using a Switched-Capacitor-Transformer Network Achieving 23.5 dBm OB-IIP₃ and 3.4–4.8 dB NF

This article reports a channel-selection N-path passive low-noise amplifier (pLNA) featuring only switches, capacitors, and a step-up transformer (i.e. a SCT network) to build a highly linear, frequency-tunable, and high-Q bandpass response with in-band voltage gain and input-impedance matching. We also reveal the inductive and lowpass properties of the step-up transformer, composed of two vertically coupled spiral coils, for passband centering with the local oscillator (LO) frequency, and harmonic-folding reduction. Prototyped in 28 nm CMOS, a 4-path 20 MHz-bandwidth pLNA scores a 9.8 dB voltage gain and a 3.4–4.8 dB NF over a 1.7–3.6 GHz range. At 3 GHz, the out-of-band (OB)-IIP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> measures +23.5 dBm, and the 3rd-harmonic-folding rejection ratio (HFRR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) is 33 dB. With a blocker applied at the 80 MHz offset, the blocker −1 dB compression point ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{B}_{-1\,\text {dB}}$ </tex-math></inline-formula> ) attains +1.7 dBm, and the blocker NF only raises moderately to 4.7 dB up to a 0 dBm blocker power. The only dynamic power comes from the four-phase 25%-duty-cycle LO generator that consumes 17.8–38.2 mW between 1.7 and 3.6 GHz. The entire pLNA occupies a 0.84 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> die area.

CFD Assessment of Circular and Spiral Recipients in CSP Plants

The primary goal of this research is to create a new billboard-style central spherical solar receiver with varying header and tube diameter, for which two spiral central receiver designs and a new circular central solar receiver with varying pipe radius and varying mass circulation are utilized. The exhaust temperature of the water was determined employing a computational fluid dynamics assessment employing ANSYS Fluent. Following the verification of the standards models, a novel central solar receiver project was made that accomplishes computational fluid dynamics assessment with almost the same boundary condition.The heat export fluid is water, and the spiral coil tube is copper. The mass circulation rate varies among 0.1 LPM, 0.2 LPM, and 0.3 LPM, with the inlet temperature of water being 299K at continuous solar irradiation. The findings demonstrate that at 0.1 LPM, the redesign of the central solar receiver produces a temperature of 383.9 K, which is 28.39 percent higher than the inlet temperature and 7.32 percent higher than the spiral central receiver. As a consequence, the circular central solar recipient to varying pipe radius is suggested and considered in upcoming usages

永久磁石とスパイラルコイルを用いた電磁衝撃力発生装置の最適化

When a momentary large current in opposite directions flows through the two opposing spiral coils, a momentary strong magnetic field in opposite directions is generated in the two coils. The strong magnetic field creates an impact force between the two coils. When a permanent magnet is placed under the spiral coils, the impact force of the actuator is enhanced because of the Lorentz force generated by the static magnetic field. In this paper, we introduce the principle of electromagnetic impact force generation and the calculation method of electromagnetic impact force. The magnetic fields generated by the spiral coil and the permanent magnet are analyzed by the finite element method. Then the electromagnetic impact force is derived from the current waveform and magnetic field. The shape of the spiral coil and permanent magnet is examined to maximize the electromagnet impact force.

Springback control and large skin manufacturing by high-speed vibration using electromagnetic forming

In this paper, a novel method of electromagnetic partitioning forming with elastic cushion is proposed. Its main principle is based on that the parts vibrate at high speed under the action of the electromagnetic force and the rebound force of the elastic pad. The state of the elastic parts inside the workpiece is changed into plastic state, and then, springback is eliminated through vibration. A common spiral coil is used to generate the magnetic field. A finite element model has been developed to analyze the effects of coil structure and coil discharge position on the stress, strain, and surface quality of the parts. It is found that a 1.5-mm bump is generated on the sheet surface, which corresponds to the middle of the coil. This is because this sheet region corresponds to the coil edges moving towards each other in opposite directions. Subsequently, the electromagnetic shielding method is used to isolate half of the spiral coil. Both the simulation and experiment demonstrated that no bulge was produced on the sheet surface. Moreover, the internal stress and springback of the parts are significantly reduced due to that the sheet vibrates at high speed. Large-scale skin was obtained after the coil was discharged multiple times in six different positions. Compared to traditional stretching, the springback of the parts is significantly reduced and the plate surface is smooth after electromagnetic forming. Consequently, the high-speed vibration induced by electromagnetic forming can reduce springback and enables the manufacturing of large size parts with smooth surface.

Geometrical parameter optimization of planner square-shaped printed spiral coil for efficient wireless power transfer system to biomedical implant application

In this paper, the wireless recharging of pacemaker's battery for biomedical implant is considered. Planner square-shaped printed spiral coils (PSCs) are selected as primary (Tx) and secondary (Rx) coil for wireless power transfer (WPT) system. FEM based simulation method is used to optimize the geometrical parameters of square-shaped PSCs. The receiving coil is embedded inside the biomedical implant. The coil track width (w), pitch(s), thickness (t), number of turns(N1,N2) and outer diameter (Dout) of square-shape PCS's are the key parameters for higher coupling coefficient and quality factors. Using magnetic resonance coupling (MRC) based on Series-Parallel (SP) topology; experiments are carried out in an analytical, simulation, and physical environment for four operating frequencies: 300 kHz, 800 kHz, 6.78 MHz, and 13.56 MHz. Efficiency obtained by analytical and simulation method is higher with frequency. The optimum frequency for recharging the pacemaker battery is 6.78 MHz, which provides an efficiency of 85.51% at 100Ω load and is very close to the maximum theoretical efficiency. Voltage gain obtained by physical method is in close approximation with analytical and simulation methods.

Optimal Design of Spiral Coil EMAT for Online and Rapid Detection of High-temperature Forgings

Optimal Design of Spiral Coil EMAT for Online and Rapid Detection of High-temperature Forgings

Compact Hybrid Metasurface-Inspired Resonator With Uniform Magnetic Field Distribution for Wireless Power Transfer

Compact and safe charging platforms have been one of the main goals in wireless power transfer (WPT) research and development. Here, we propose a compact hybrid metasurface-inspired resonator with a uniform magnetic field distribution for WPT. It consists of two orthogonally oriented layers of parallel printed wires with high-permittivity dielectric pads between them. This design allows us to spatially separate electric and magnetic fields, which provide high WPT efficiency and electromagnetic safety simultaneously. The prototype with 28 cm × 28 cm working area with uniform magnetic field was fabricated and experimentally studied. The measured coefficient of variation of the magnetic field in the working area of the resonator is 6.8%. The maximum achievable WPT efficiency reaches 70% over the working area. The numerically assessed specific absorption rate in human tissues placed on the proposed structure is 11 mW/kg, which is 30 times lower than on a conventional planar spiral coil. Our results pave the way to compact and safe WPT platforms for one-to-many charging.

Misalignment Insensitive Wireless Power Transfer System Using a Hybrid Transmitter for Autonomous Underwater Vehicles

Compared to air surroundings, the marine environment is not stable due to the influence of ocean currents and other factors. Misalignments always occur inevitably when autonomous underwater vehicles are charging wirelessly in the docking station. Therefore, misalignment insensitive underwater wireless power transfer system need to be investigated. In this article, a novel hybrid transmitter composed of conical and planar spiral coils is proposed that greatly improves the misalignment tolerance and transfer performance. First, the coil tilt angle theory (CTAT) is presented and verified to determine the optimum tilt angle of conical coil. Then, based on the CTAT, a circular uniform magnetic field zone with a diameter of 30 cm in charging plane can be achieved by flexibly designing the hybrid transmitter. Moreover, a three-dimensional finite-element simulation software is employed to study the eddy current loss under different circumstances. Finally, experimental results show that the proposed transmitter has better performance in output power and power transfer efficiency (PTE) stability within the possible working region compared with conventional transmitters. It has demonstrated that the output power changes only within 5.7&#x0025; and the PTEs maintain at approximately 86&#x0025; in excessive misalignment area with transfer distance of 2 cm.

2線アルキメデス螺旋コイルを用いた完全体内埋込型人工心臓用経皮エネルギー伝送システムへのプッシュプルE級増幅器の適用

2線アルキメデス螺旋コイルを用いた完全体内埋込型人工心臓用経皮エネルギー伝送システムへのプッシュプルE級増幅器の適用