Rectangular Coil Research Articles

Performance Investigation of Multi-Turn Pickup for Circular Fractal Flexible Planar Eddy Current Probe

ABSTRACT This paper aims to compare and analyze the performance differences between a single-coil and multi-coil pickup coil layout in a flexible circular fractal planar eddy current probe. Flexible planar eddy current probes offer flexibility and adaptability, making them widely used in the detection of complex structures. The circular fractal flexible planar eddy current probe is a new type of probe that has a lower miss rate in detecting cracks at specific angles compared to traditional circular and rectangular coil eddy current probes. However, the single-coil structure of the probe’s pickup coil has the drawback of being less sensitive to weak signals. This paper investigates the detection performance of the flexible circular fractal probe by varying the number of turns in the original pickup coil. Experimental comparisons were conducted by preparing and installing single-coil and multi-coil circular fractal planar eddy current probes. The performance differences between single-coil and multi-coil configurations were compared and analyzed under various excitation frequencies, liftoff distances, and internal crack depths. The results showed that, compared to the single-coil probe, the multi-coil probe exhibited significantly improved detection signal values and sensitivity.

Enhancing Magnetic Coupling Using Auxiliary Short-Circuited Coils

The efficiency of Dynamic Inductive Power Transfer (DIPT) depends mainly on the coupling coefficient within the coupler. In order to improve this parameter, a novel approach has been introduced that results in a significant increase of between 25% and 36% at minimal additional cost in the case of juxtaposed rectangular coil configuration on the road. This method involves the incorporation of a passive additional short-circuit coil adjacent to the primary coil for obtaining a higher coupling coefficient, as has been theoretically demonstrated. Simulations carried out on Comsol have optimized the dimensions of this additional coil, not only for cost effectiveness and minimal space utilization, but also for optimal efficiency. Experimental validation was performed at reduced power, using a 2 kW test bench, and confirmed the estimation. The efficiency improvement proposed in this paper is crucial for improving the global DIPT efficiency and then facilitating its social acceptance.

Mutual Inductance Calculation of Rectangular Coils at Arbitrary Position With Bilateral Finite Magnetic Shields in Wireless Power Transfer Systems

Mutual Inductance Calculation of Rectangular Coils at Arbitrary Position With Bilateral Finite Magnetic Shields in Wireless Power Transfer Systems

Induction heating system of massive rings before rolling

The work examines an induction heating system for a large ring in a rectangular coil. The end surface of the workpiece is located horizontally. To form a uniform temperature distribution in the workpiece pushed into the inductor, a rotation mechanism is used. Conducted studies of the distribution of heat generation power and temperature in the workpiece showed the need to reduce the field strength in the hole area. A solution to the problem was found through the use of magnetic cores in the inductor design, displacing currents in the workpiece beyond areas prone to overheating. The obtained results of modeling electromagnetic and thermal fields in the workpiece confirm the correctness of the design solution.

AC Copper Loss Evaluation Method for High-Speed PM Motors with Rectangular Coils

AC Copper Loss Evaluation Method for High-Speed PM Motors with Rectangular Coils

Misalignment‐tolerant coupling cell of 2‐D modular WPT system for charging area simplified extension

Abstract2‐D modular wireless power transfer (WPT) system needs to have stable output when coil misalignment occurs. In order to improve the misalignment tolerance of the system coupling unit, this article proposes a magnetic coupling structure based on the LCC‐S compensation topology by combining a rectangular coil with two sets of mutually orthogonal solenoidal compensation coils. The rectangular coil is used to receive the vertical magnetic flux, and the two sets of compensating coils are used to receive the magnetic flux in the directions of X‐axis and Y‐axis on the horizontal plane, separately. The receiving side of the 2‐D wireless power transmission array cells cascaded half‐bridge rectifiers to connect each group of coils. This arrangement effectively compensates for the voltage drop of the rectangular coil caused by positional offset in any direction, so that the output voltage of the receiving side remains stable. The article firstly establishes the equivalent circuit model of the proposed design and deduces in detail the relationship equations between the output characteristics of the system and each influence factor. Secondly, the magnetic coupling structure is designed by finite element electromagnetic simulation software, and the total equivalent mutual inductance fluctuation of the proposed design is verified to be within 3.9% over the range of 2‐D transmission array cells. Finally, a 150 W experimental platform is built to verify the misaligment‐tolerant of the proposed design in the range of 2‐D transmission array cells. The experimental results show that the output voltage fluctuation of the proposed design within 4.27% at all directional offsets. Moreover, the stable output performance can be obtained in the case of vertical and rotational misalignment.

Design and Experiment of 2D Rectangular Solenoid Transmitting Coil for Novel Gastrointestinal Capsule Robot

Design and Experiment of 2D Rectangular Solenoid Transmitting Coil for Novel Gastrointestinal Capsule Robot

Magnetic Resonance Imaging-Compatible Electromagnetic Actuator: Design and Tests

This paper presents the detailed design, construction and tests of a protype iron-free MRI-compatible electromagnetic actuator. The originality of this proposal lies in the use of the homogeneous static magnetic field B0, present in the MRI bore, to ensure the electromechanical energy conversion. The armature is composed of three rectangular coils in a three-phase arrangement, which makes the actuator very light-weight and compact. The operating principle is that of an AC synchronous motor with a rotating armature. In order to design the actuator, a 3D analytical electromagnetic model is developed to predict the magnetic field produced by the armature winding. Then, a 3D finite element (FE) computation is performed to validate the analytically calculated magnetic field. The developed analytical model is then inserted into an optimization routine based on Genetic Algorithms (GAs) to obtain the prototype dimensions to be realized. Finally, the prototype is constructed and tested inside an MRI research scanner. The results indicate that the reduction in the Signal-to-Noise Ratio (SNR) and the geometrical distortion are less than 5% when the actuator is powered with a current of 10 times the rated one and when it is located very close to the subject to be imaged.

A Novel Folding Wireless Charging Station Design for Drones

Unmanned aerial vehicles (UAV) have been used in many fields nowadays. In long-term applications, batteries need to be constantly changed by someone due to short battery life. This problem is eliminated with wireless power transfer (WPT). A reliable, effective, and autonomous solution is offered using wireless charging. The most suitable wireless charging technique for UAVs is inductive power transfer (IPT). In this paper, a novel foldable coil and charge station design is proposed for the wireless charging of UAVs. IPT is provided by receiver and transmitter coils placed on the drone legs and the charging station, respectively. Receiver coils are placed on both legs of the UAV in a light and balanced manner to avoid creating imbalance and weight on the UAV. Receiver coils are designed as vertical rectangular planar spirals. A transmitter coil consists of three rectangular planar spiral coils with two movable edge windings and a fixed middle winding. The transmitter’s folding windings provide both alignments for the UAV during landing and increase the magnetic coupling. A folding wireless charge system of the UAV is designed for 100 W output power at a 138.1 kHz frequency. The misalignment tolerance of the proposed design in the vertical axis is examined. The design’s magnetic flux density distribution is analysed. As an experimental result of the study, 97.66% efficiency was reached in the aligned condition. Also, over 85.48% efficiency was achieved for up to 10 cm of vertical alignment misalignment.

Simulation and test for the micro-newton electromagnetic calibration force measurement

For micro-Newton (μN) level thrust measurement, achieving highly accurate calibration forces is crucial as an initial step. To provide high-precision and wide-range electromagnetic calibration forces, this study introduces a C-type magnetic circuit structure and a rectangular coil combination method. The magnetic field distribution within the device’s characteristic region was examined using the finite element method, and the impact of the relative positions of the rectangular coil and magnet was explored. Subsequently, calibration experiments were conducted on a specially developed platform. The primary findings are as follows: The electromagnetic force calibration range is from 0.097 to 237.32 μN, with the maximum error between experimental measurement data and simulation results being 1.73%. With a coil current resolution of 10 μA, the measured resolution of the calibration force exceeds 0.1 μN. Within the characteristic region, the magnetic field distribution exhibits high uniformity, with a maximum deviation rate of only 0.7%. This research establishes a technique for micro-Newton level thrust measurement.

Analytical method of mutual inductance for T-R rectangular coils perpendicular to the planar medium

Some studies indicate that for specific defect detection in eddy current testing (ECT), the transmitter-receiver (T-R) probe models with tangential rectangular transmitter coil exhibit effective detection performance. In this context, mutual inductance being a crucial parameter. The calculation of mutual inductance for vertically oriented T-R coils is more intricate compared to that of parallel T-R coils, which is currently predominantly focused on circular mutual inductance analysis. This paper presents a closed-form formula for the mutual inductance of rectangular T-R coils oriented vertically to the conductor based on the method of the second-order vector potential approach. In this model, a form function concerning the coil's position and shape is defined, allowing convenient extension to T-R coils of arbitrary shapes and positions. Simultaneously, the validity of the theory is tested against experimental measurements on different positions and frequencies of coil systems above an aluminum plate. The results indicate good agreement between theoretical and experimental results within the 100 Hz to 100 kHz range. Consequently, this model can offer guidance for the calculation of mutual inductance for vertically oriented rectangular T-R coils in ECT.

Measurement of Knee Extensor Torque During Repetitive Peripheral Magnetic Stimulation: Comparison of the Forces Induced by Different Stimulators.

To investigate the factors that induce strong contractions during repetitive peripheral magnetic stimulation (rPMS) and compare the muscle torque induced by two stimulators (Stim A and Stim B) with different coil properties. rPMS was applied to the right vastus lateralis of 30 healthy young adults. Stim A contained a 10.1 cm2 rectangular iron core coil, while Stim B contained a 191 cm2 round coil. The knee extensor torque (KET) induced by rPMS at 30 Hz was measured isometrically and divided by the maximum voluntary contraction (MVC) to obtain a relative value of MVC (%MVC). KET at 100% intensity of Stim A (A100%, 1.08 T) was compared to those at 100% or 70% intensity of Stim B (B100%, 1.47 T vs. B70%, 1.07 T). Additionally, we conducted a comprehensive literature search for studies that measured the KET during rPMS. Both the mean values of %MVC using B100% and B70% were significantly greater than that using A100%. Furthermore, the KET induced by Stim B was found to be larger than that described in previous reports, unless booster units were used to directly stimulate the main trunk of the femoral nerve. Stim B induced a stronger muscle contraction force than Stim A did. This may be because the larger the coil area, the wider the area that can be stimulated. Additionally, a circular coil allows for deeper stimulation.

High-Sensitivity Detection of Carbon Fiber-Reinforced Polymer Delamination Using a Novel Eddy Current Probe

The demand for non-destructive testing of carbon fiber-reinforced polymer (CFRP) is becoming increasingly pressing to ensure its safety and reliability across different fields of use. However, the complex structural characteristics and anisotropic bulk conductivity of CFRP make achieving high sensitivity in detecting internal defects such as delamination extremely challenging. To address this issue, a novel triple rectangular coil probe with high sensitivity developed for detecting delamination in CFRP is presented in this paper. A finite element model using COMSOL Multiphysics was developed for CFRP delamination eddy current testing with the designed probe. Based on this model, the probe parameters were determined through orthogonal experiments. By analyzing the eddy current distribution in CFRP samples, the scanning mode was defined. Following this, the detection voltage was evaluated for various delamination parameters, and the sensitivity of different probes was compared. Results indicate that, under the same excitation coil parameters, for a 5 mm delamination lateral dimension change, the single pancake and single rectangular coil probes exhibit sensitivities of 88.24% and 72.55%, respectively, compared with the designed probe. For a 0.5 mm delamination thickness change, their sensitivities are 49.04% and 56.69% of those of the designed probe. The designed probe meets the demand for high-sensitivity detection.

A Flexible Rectangular PCB Coil to Excite Uniform Magnetic Field in Nuclear Magnetic Resonance Spectroscopy: Design, Optimization and Implementation

A Flexible Rectangular PCB Coil to Excite Uniform Magnetic Field in Nuclear Magnetic Resonance Spectroscopy: Design, Optimization and Implementation

Design of continuous repeater power transmission coil for wireless power transfer system for EVs with consideration of vehicle deviation

In recent years, EVs have become increasingly popular around the world, and research on wireless power supply technology for EV driving has progressed accordingly. In order to realize this wireless power transfer system for EVs on a real scale, it is necessary to lengthen the power transfer section per power transfer unit and to secure a sufficient power transfer section with a small number of power transfer units as a whole. To solve this problem, the single coil method, in which one coil is lengthened, has been proposed. However, as the coil length increases, resistance loss increases and efficiency decreases. Therefore, a repeater coil system has been proposed. In this in-transit power-feeding system, it is necessary to consider transient phenomena when the EV to be fed deviates from the feeding lane. Therefore, we propose a new repeater coil configuration on the transmission side that assumes a no-load condition. In this study, a new repeater coil system combining rectangular coils and orthogonal coils is proposed, which enables stable feeding of power to EVs by rectangular coils and response to transient phenomena. A comparison was also made with the single coil method that has been studied previously.

Optimization of magnetic coupling mechanism of dynamic wireless power transfer based on NSGA-II algorithm

Optimization of magnetic coupling mechanism is an important way to improve the performance of a dynamic wireless power transfer system. Inspired by the common radial magnetic core for circular coils, a new radial magnetic core for rectangular coils is adopt. Through simulation and experimental results comparison, which has higher coupling coefficient with the same core area. Combined with the magnetic circuit analysis, the magnetic flux leakage and conduction regions are divided into magnetic fluxes with different shapes, which magnetic resistances are calculated respectively. Based on the simulation results, parameter distributions of fluxes under different conditions are obtained. Therefore, the expressions of the coupling coefficient k of the adopt magnetic cores and coils and the design parameters of coils and cores are obtained. Taking the maximum k and the minimum rate of change of coupling coefficient with 100 mm displacement as the optimization objectives, a multi-objective optimization solution is carried out by using NSGA-II algorithm. The coil optimization scheme is obtained and verified by experiments. k and Δk are 0.442 and 6.8% respectively, and the errors are less than 5%. In the optimization process, there is no simulation model constructed. The optimization modeling combined of magnetic field segmentation method and parameter fitting has lower complexity and calculation time of optimization.

A Novel Antenna Design of Compact HF and UHF Passive RFID Tags with Interconnected Structure for Energy Harvesting and Tracking Systems

We propose a new dual-band passive RFID tag antenna design by combining a rectangular spiral coil and patch-meander-line dipole with an interconnected structure. This design enables operation in high-frequency (HF) and ultra-high-frequency (UHF) RFID systems, suitable for energy harvesting and tracking applications. The simulations by the CST full-wave software demonstrate conjugate impedance matching between the tag antenna and two RFID tag chips. At 13.56 MHz (HF), the tag antenna exhibits an inductive reactance of 422.79 Ω, while at 922.5 MHz (UHF), it presents an impedance of 9.41+j174.96 Ω. The antenna generates a maximum magnetic field intensity of 0.5 A/m and omnidirectional electromagnetic fields with an antenna realized gain of -4.26 dBi at 922.5 MHz. We also analyze the impact of the tag antenna combination using numerical software. Furthermore, we fabricate a prototype tag antenna and validate its performance with RFID readers. The proposed tag antenna achieves the maximum read ranges of 11 cm and 6.9 m for the HF (13.56 MHz) and UHF (920-925 MHz) bands, respectively, accompanied by the energy harvesting of 1.48 volts at the HF band by the coupling magnetic field received by the HF antenna to the chip ST25DV04K at the output voltage pin.

Comparative the effect of distribution transformer coil shape on electromagnetic forces and their distribution using the FEM

Abstract During the normal life of the transformers, they are subjected to different electromagnetic stresses. One of these stresses is the electromagnetic forces resulting from the passage of short-circuit current in the transformer coils due to internal or external faults and may lead to the failure of the transformer when this electromagnetic force exceeds the threshold level. This work deals with the computation and analysis of leakage magnetic flux and electromagnetic forces when the worst-case fault (symmetrical short-circuit current) occurs in distribution transformer (DT) coils using the finite element method (FEM). The three types of DTs that were adopted in this work are similar in capacity and voltage transformation ratio (250 kVA and 11,000/416 V), but they are different in the shape of coils (oval, cylindrical, and rectangular coils). ANSYS software was used to build two-dimensional models of the three transformers, which were different in coil shapes and in the type of iron core. The objective of this work is to compare the effect of coil shape on the distribution of electromagnetic forces and their value, in order to find out which coil shape is the best to withstand electromagnetic forces when short-circuit current is passed in the coils. The results of the simulation of the finite element models were approximately equivalent to the results of the design calculations that depend on the classical method (the analytical method), but the FEM is more accurate, due to the accuracy of calculating the magnetic flux and its distribution, which cannot be calculated using the classical method. One of the most important contributions of this research is the analysis and calculation of electromagnetic forces for three types of DTs with different coils by applying the same design parameters to all the transformers. The research also contributed to determining the best coil shape by comparing simulation results, and it was found that transformers with cylindrical coils are the best to withstand electromagnetic forces due to the homogeneity of the cylindrical coil structure from all sides.

Investigations on eddy current sensors regarding inline-capability of zinc coating monitoring using a model-based estimator

This work deals with preliminary investigations for the reliable thickness determination of a conductive, nonmagnetic metal coating on ferromagnetic steels. For this purpose, an eddy current sensor system is used. Different analytical coil models are compared: a normal solenoid, a differential coil and a rectangular coil. Thus, a sensitivity analysis regarding interfering influences, e.g., liftoff fluctuations, is done. Based on this, the advantages and disadvantages of the analyzed coil geometries are discussed. Finally, an model-based estimator is used to determine the coating thickness from simulation data at different operating points.

Stretching the Limits of MRI-Stretchable and Modular Coil Array Using Conductive Thread Technology.

We propose a modular stretchable coil design using conductive threads and commercially available embroidery machines. The coil design increases customizability of coil arrays for individual patients and each body part. Eight rectangular coils were constructed with custom-fabricated stretchable tinsel copper threads incorporated onto textile. Tune, match, and detune circuits were incorporated on the coil. A hook-and-loop mechanism was used to attach and decouple the modular coils. Phantom and in vivo scans at various anatomical flexion angles were acquired to highlight performance, and a temperature test was performed to verify safety. In vivo MRI experiments demonstrate high sensitivity and coverage of each anatomy. As the coils are stretched, the sensitive volume increases at a rate of 10.93 mL/cm2. The SNR reduction of a single coil was greater during compression than when stretched, but this did not affect image quality for the array. The modularity of the array allows for adaptability for any anatomy with simple on-demand adjustment to the number and position of coil elements. The images demonstrated high sensitivity and coverage of the stretchable array for various anatomies and flexion angles. Stretching the coils increases the sensitive volume, allowing for a larger region to be effectively imaged. The resonance shift and SNR decrease during stretch and compression support further investigation of methods to reduce frequency shift in stretchable coils. The proposed array design allows for highly stretchable, flexible, modular, and conformal patient-centered coils that allow for increased imaging quality, greater comfort, and rapid production.