Rectangular Coil Research Articles

Recognizing Multitype Misalignments in Wireless EV Chargers With Orientation-Sensitive Coils: A Data-Driven Strategy Using Improved ResNet

In wireless electric vehicle charging systems, misalignments between ground-assembled transmitter and vehicle-assembled receiver are undesirable but inevitable, which may cause efficiency deterioration and even thermal risks. The recognition of horizontal misalignment, including that in the longitudinal and lateral direction, has been made gradual progress by previous works. While yaw angle, with rare attention, can also degrade the charging performance, especially for those employing non-centrosymmetric coupling coils, such as rectangular coils. In this paper, a data-driven strategy based on improved ResNet is proposed to recognize the above multi-type misalignments simultaneously, which is accurate, reliable, and of practical and general value. Large-scale data is sampled using the proposed detection coils by double-group cooperation, which features high sensitivity to the misalignments of all kinds, especially yaw angle. Benefit to the compression technique in the pre-processing phase, the number of training data and labels can be successfully reduced by 3/4. As the core algorithm of the overall strategy, the adaptive channel parameter recalibration ResNet (ACPR-ResNet) can effectively perceive slight differences among similar input samples and map them to proper labels. This is achieved by an adaptive operation of nonlinear transformation and recalibrated importance of channel features during the training process. The effectiveness of the proposed strategy is verified experimentally using a 6.6-kW prototype. Within the 24×24 cm range, 95.2% of the test cases have an error of less than 1.7 cm when recognizing horizontal misalignment, and 91.7% of the test cases have an error of less than 1.5° when recognizing yaw angle.

Mutual Inductance Calculation Method of Rectangular Coils with Bilateral Bounded Single-hole Type Magnetic Medium in Wireless Power Transfer Systems

Mutual Inductance Calculation Method of Rectangular Coils with Bilateral Bounded Single-hole Type Magnetic Medium in Wireless Power Transfer Systems

Research on optimization technology of excitation coil in downhole annular flow electromagnetic measurement system

External interference and non-uniform velocity distribution influence the downhole annular flow electromagnetic measurement, reducing detection accuracy. Optimizing the structure of the excitation coil can effectively enhance the uniformity of magnetic field distribution, constituting an essential approach for improving measurement accuracy. Aiming at the excitation coil optimization technology of annular flow electromagnetic measurement system, the study first analyzes and obtains the magnetic field model of the excitation coil based on the principle of annular flow electromagnetic measurement, combined with the theory of vector weight function and puts forward the optimization theory of annular excitation coil. Secondly, the simulation models of rectangular and saddle exciting coils are established using finite element software to analyze the magnetic field distribution of annular flow under different coil and core sizes. The optimal structural parameters of the exciting coils in the annular flow electromagnetic measurement system are determined through evaluation indexes for the magnetic field. Finally, an experimental platform was established for optimizing the electromagnetic measurement of annular flow, and this platform was used to conduct comparative experiments. The experimental results show that the maximum reduction of the optimized system is 3.192%, 1.289%, and 1.813% for the single verification relative value error, single-point verification relative value error, and repeatability compared with the rectangular excitation coil annular flow electromagnetic measurement system. In the flow measurement interval of 25–100 m3 h−1, the single-point verification of the optimized system has a maximum relative display value error of 0.378%, and the measurement accuracy reaches 1.0 level and meets the consistency of the transmission of quantity and value. The research findings hold significant guidance for enhancing the measurement accuracy of the downhole annular flow electromagnetic measurement system.

DDD coil design for wireless charging of unmanned aerial vehicles

AbstractThe utilization of unmanned aerial vehicles (UAV) has become prevalent nowadays. UAVs are autonomous devices, except for self‐charging. Wireless power transfer (WPT) technologies eliminate human intervention in UAV charging and enable independent charging. The factors making WPT systems popular are autonomizing charging, eliminating cable complexity, and avoiding difficulties caused by environmental conditions. WPT of the UAV in the near field is provided by inductive coupling. In this paper, two vertical rectangular coils and horizontal DDD (triple rectangle) coils were placed in the receiver and the transmitter for UAV wireless charging, respectively. The design of the coils was made in ANSYS Maxwell 3D. A wireless charger of the UAV was designed for 100 W output power at 140 kHz frequency. The misalignment tolerance of the proposed design concerning the x‐ and y‐axis was examined. In addition, the magnetic flux density and magnetic field distributions of the WPT system were investigated. The study found that the proposed design can transfer energy wirelessly with 94% efficiency up to 10.3 cm horizontal and 1.7 cm vertical misalignment.

Design and analysis of a coupling coil structure for high‐efficiency wireless charging system for consumer electronics

SummaryThis paper introduces a novel type of coupling coil structure that can be used for wireless charging of consumer electronics. The coupling loop configuration includes an eight‐shaped transceiver coil and dual rectangular coils integrated on the printed circuit board (PCB). Moreover, when numerous transmitting coils of this structure are staged in parallel, it can sustain a consistent mutual inductance even when the receiver coil is not aligned, which can efficiently stabilize output power during charging. The article first models three different coil structures based on circuit theory and simulates their electromagnetic fields in commercial software and then performs a comparison among the three types of coils. Finally, it verifies the anti‐offset capability of the modified structure through a 25 W wireless power transmission experimental platform. The experimental outcomes are in accordance with the simulation and theoretical analysis, and compared with traditional dual‐transmitting coil structures, better overall power transmission efficiency has been achieved.

Mutual inductance calculation for rectangular and circular coils with parallel axes

Mutual inductance calculation for rectangular and circular coils with parallel axes

Dry-Type Phantom Emulating Quadrupole-Like Magnetic Field Distribution for Evaluation of Magnetoneurography

This study proposes a dry-type phantom for evaluating the accuracy of magnetoneurography (MNG). The phantom emulates the quadrupole-like pattern of the typical magnetic field distribution observed in MNG. It is composed of a printed circuit board patterned with long rectangular coils, whose short and long edges measure 5 and 360 mm, respectively. The magnetic field distribution from the dry-type phantom was obtained using a 132-ch MNG system equipped with an array of vector-type superconducting quantum interference device (SQUID) flux sensors, and it showed a clear quadrupole-like pattern. The dry-type phantom is easier to handle, and provides comparable or higher accuracy than that of the previously developed wet-type phantom in terms of goodness-of-fit.

Numerical signal calculation and detection capability of magnetic resonance antenna with high rectangular coefficient

Magnetic resonance technology is widely used for groundwater detection due to its direct and quantitative advantages, typically employing square antennas. However, in narrow environments such as mine roadways, canyons, and dams, rectangular antennas with varying dimensions are more practical than square ones. The existing literature lacks comprehensive discussion about the response characteristics of magnetic resonance signals of rectangular antennas, particularly those with high rectangular coefficients. This paper addresses the challenges encountered in a particular application scenario by computing the magnetic resonance excitation magnetic field generated by a rectangular antenna. In addition, it determines the response characteristics of the magnetic resonance signal of rectangular multi-turn coils. We propose coefficient indices of magnetic resonance antennas with different rectangular coefficients, in conjunction with the receiving antenna's matching system to evaluate the actual detection capabilities of various rectangular antennas. Field testing validates the proposed method's effectiveness, providing a robust foundation for assessing the actual detection capability of magnetic resonance antennas and selecting appropriate antennas for specific scenarios.

Conceptual design of narrow annular channel heater with rectangular wire coil for the simulator of solid-fuel thorium molten salt reactor

To heat the simulator core of a solid-fuel thorium molten salt reactor, the narrow annular channel heater with rectangular wire coil separating from the tube wall is proposed. Three-dimensional numerical models are developed, and the simulated result shows that negative axial, radial and tangential velocities in the enhanced narrow annular channel heater are generated compared to the smooth narrow annular channel heater. As the wire width increases and helical pitch decreases, the Nusselt number and friction factor increase. The maximum Nusselt number for enhanced narrow annular channel heater is 5.6 times that for smooth narrow annular channel heater. The overall performance of enhanced narrow annular channel heater is evaluated at a constant pumping power, the value of which is in the range of 1.21–1.85. The best enhanced narrow annular channel heater for the simulator of solid-fuel thorium molten salt reactor is determined based on the overall performance. The maximum outer wall and fluid temperatures of enhanced narrow annular channel heater for the simulator of solid-fuel thorium molten salt reactor are 937.94 K and 931.01 K, which are within the safety limit values of 1143.15 K and 977.15 K, respectively. This design will provide a new method to heat molten salt.

Magnetic shielding simulation for particle detection

Cherenkov-type particle detectors or scintillators use as a fundamental element photomultiplier tubes, whose efficiency decreases when subjected to the Earth’s magnetic field. This work develops a geomagnetic field compensation system based on coils for large scale cylindrical detectors. The effect of different parameters such as the size of the detector, the distance between coils or the magnetic field strength on the compensation using a basic coil system composed of circular and rectangular coils is studied. The addition of coils of very specific geometry and position to the basic configuration is proposed in order to address the compensation in the areas of the detector where it is more difficult to influence, in order to minimize the loss of efficiency. With such improvement, in the considered simulated system, more than 99.5% of the photomultiplier tubes in the detector experience an efficiency loss of less than 1% due to the effect of the magnetic fields.

Coupling coefficient calculation and optimization of positive rectangular series coils in wireless power transfer systems

In wireless power transfer (WPT) systems using magnetic coupling resonance, when there is a registration deviation between the transmitting and receiving coils, there will be significant fluctuations in the coupling coefficient, output power, and transmission efficiency, which will seriously affect the stability of the WPT system. The coupling coefficient is related to the length and width of the rectangular coil, number of turns, mutual geometric position, and space magnetic medium, making it difficult to maintain a constant value when the coil is offset. A single-emitter two-receiver positive-series rectangular coils structure and a method of calculating the structure are proposed. Then an optimization method for mutual inductance was proposed, and the structural parameters that met the design requirements were obtained using the proposed optimization method. The calculation formula for coupling coefficient was verified through simulation and experiments. The results showed that when the offset distance of the receiving coil along the Y-axis (driving direction) and X-axis reaches half of the length of the transmitting coil and 10 cm, the coupling coefficient, transmission efficiency, and output power remain almost unchanged.

Zero-Pole Optimization of a Novel High-Quality-Factor Planar Helical Resonator

A novel micro-solenoid resonator has been designed, simulated, and measured. The solenoid core consisted of a DuroidTM circuit board with a relative permittivity of 2.2. The resonator design incorporated four embedded copper vias with a radius of 125 µm and three surface conductors to form a rectangular coil. A pitch size of 250 µm was used for a 3.02 mm thick substrate. To enhance the resonator’s performance at higher frequencies, a capacitance was introduced in series through the via. This additional capacitor effectively couples the inductance, resistance, and stray capacitance. The optimization of the quality factor was investigated through pole transfer analysis, resulting in an increased resonance frequency of 12.25 GHz and an elevated Q-factor of 306. Moreover, besides its very high Q-factor, this resonator offers a simplified design and easy integration. An analytical lumped circuit model was employed to investigate the design, and the measured S-parameters closely matched the analytical model and electromagnetic simulation results. The tuned resonator exhibited a superior quality factor compared to other micro-resonators.

Open-Source Magnetometer for Characterizing Magnetic Fields in Ultracold Experiments

We demonstrate a fully automated open-source magnetometer designed primarily for characterization of magnetic fields produced by coils, permanent magnets or by parasitic sources. It is based on an Arduino Mega microcontroller and a three-axis Hall sensor with a measurement range of ±8 G per axis and the RMS of the field readout below 0.3 mG. For all practical purposes, the sensor displacement during data acquisition is virtually unlimited, which can be particularly useful for characterizing large or extended coils like Helmholtz cages or Zeeman slowers. All components needed for the construction are cheap and widely available off-the-shelf elements or are 3D-printed. The operation of the magnetometer is controlled via a graphical user interface (GUI), which manages all essential functionalities, like data acquisition and plotting. The GUI also incorporates additional features, like data averaging, calibration of the displacement of the Hall sensor or real-time readout of the magnetic field, useful for monitoring magnetic field changes. We have used a pair of rectangular coils constructed for a potassium–cesium 2D magneto-optical trap to benchmark the performance of the magnetometer. We have obtained good agreement with both simulations and measurements acquired with a commercial gaussmeter.

Verification and validation of multi-physics numerical analysis of thermomechanical fatigue test conditions under induction heating and forced convection

This paper presents the validation and verification of thermomechanical fatigue multi-physics numerical analysis. To determine the local thermomechanical stress–strain state and displacement fields, an algorithm for the multi-physics numerical calculations is developed and implemented incorporating the Maxwell 3D, Fluent, and Transient Structural modules of ANSYS 2021R1. Single-edge-notch tension specimen heating is modelled using a rectangular induction coil. The temperature distribution in the specimen under forced and natural convection is considered. The nonlinear solid mechanics are analysed considering the temperature nonuniformity under in-phase and out-of-phase loading cycles with a triangular waveform and temperature range of 400–650 °C. Sensitivity analysis is performed to explore the effects of the mesh density. To complement the multi-physics computations, crack-opening displacement and infrared thermography temperature distribution measurements are employed for the thermomechanical fatigue test control in a single-edge-notch tension specimen produced from a nickel-based alloy XH73M. Based on the interconnected verification and validation of coupled numerical analysis, recommended ranges of numerical model parameters have been found to provide a stable solution.

LitzImp: A Fast Impedance Extraction Algorithm for Litz Wire Coil

Litz wire coil (LWC) is an electronic component commonly used in wireless power transfer (WPT) and heating applications. However, due to its complex twisting structure with turns, existing calculation methods such as analytical methods and finite element method (FEM) cannot extract the impedance of LWC efficiently. This paper proposes an efficient numerical calculation algorithm named LitzImp for fast impedance extraction of LWC. LitzImp provides different simplification schemes for different coil structures, reducing the resource consumption in the repeated calculation for the same structures and improving efficiency while maintaining high accuracy. Experiments with nine manufactured coils, including circular coils (CC) and rectangular coils (RC), from simple to complex, are adopted to verify the performance of LitzImp. The comparative verification compared with FEM and the analytical method shows the advantages of LitzImp in terms of efficiency and accuracy. Through the analysis of the time consumption, the proposed method is 45 times faster than the similar numerical method for a given coil structure. For highly complex coils (500 strands), the impedance is obtained in less than 5.5 hours with good agreement with the measurement. LitzImp will be a powerful tool for the optimal design of LWC due to its high efficiency.

Simulation and experimental research on local continuous induction heating of inner corrugated section

The inner corrugated pressure-resistant shell has superior pressure resistance and can be formed by continuous rolling with corrugated rolls. However, there is a problem of excessive temperature drop during the rolling process. Meanwhile, lower rolling temperature leads to larger deformation resistance which affects plastic forming and increases the load of the rolling mill, which makes the size and shape control of the inner corrugated section more unstable. There is thickness variation in the inner corrugated section. The local supplementation and continuous induction heating of the inner corrugated section to complete the energy supplementation during the rolling of the inner corrugated section is an issue worthy of investigation. In this paper, Rectangular, profiling and anti-profiling coils were designed for the structure of the inner corrugated section, and continuous induction heating is carried out through the induction coil at the local position of the inner corrugated section. Based on the comparison of the simulation results, the heating efficiencies of rectangular coil, profiling coil, and anti-profiling coil were 46.39%, 75.07%, and 41.16%, respectively. The induction heating of the profiling coil is more efficient and uniform. Moreover, by optimizing the process parameters of profiling coil induction heating, the effects, caused by current, frequency, and air gap, on the induction heating results of the inner corrugated section were studied and analyzed, and the optimal profiling coil induction heating process parameters were obtained. Finally, an experimental platform for induction heating of the inner corrugated section was built. The induction heating experiment of the inner corrugated section was carried out by rectangular, profiling, and anti-profiling coil respectively. The experimental results were compared and analyzed, the heating efficiencies of rectangular coil, profiling coil, and anti-profiling coil were 47.88%, 84.14%, and 50.27%, respectively. The profiling coil had high heating efficiency and good uniformity.

Rotating uniform eddy current probe using four rectangular excitation coils with ferrite cores for cracks detection in conductive materials

In this study, we introduce a new rotating uniform eddy current (RUEC) probe designed to identify artificial cracks in conductive materials. The RUEC probe comprises four rectangular coils, divided into two sets of diagonally positioned coils. By providing two alternating current sources with a 90° phase difference to the two sets of coils, a RUEC distribution with uniform amplitude in all directions can be produced on the surface of the test specimen. Furthermore, ferrite cores are integrated into the four coils to enhance the crack detection ability. To confirm that the RUEC probe model produces RUECs with uniform amplitude in all directions on the test specimen surface, we conducted finite element method (FEM) simulations. We then conducted experiments with the RUEC probe to identify artificial cracks of varying sizes on the test specimen. The experimental results demonstrate that the RUEC distribution on the test specimen surface enabled successful detection of cracks in all directions with the probe.

Investigation of HTS Coil Structure Robustness Against Misalignment Between Coils in a Wireless Power Transmission System for Railway Vehicles

A wireless power transmission (WPT) system using high-temperature superconducting (HTS) coils has been investigated. However, it is difficult to precisely match the positions of the primary and secondary coils. Thus, the HTS coil structure with high misalignment tolerance is required. In this paper, we investigated the non-circular HTS coil structure with a high quality factor for the WPT system, such as a rectangular coil and a racetrack coil. Also, we evaluated the power transmission characteristics of the WPT system using the non-circular HTS coils. As a result, the quality factor of the non-circular HTS coils was maximum when the radial gap between turns was almost the same as the HTS wire width, and increased with increasing coil length in a rail longitudinal direction. Also, the receiving power and the system efficiency using the non-circular HTS coils were more robust against misalignment between coils than those using the circular HTS coils. On the other hand, the receiving power decreased with increasing the coil length of the non-circular HTS coils in the rail longitudinal direction due to thermal radiation from normal temperature. From the above, the receiving power of the WPT system with small lateral misalignments can be improved by using the rectangular coils with a short coil length in the rail longitudinal direction in parallel. Moreover, the system efficiency of the WPT system with large lateral misalignments can be improved by using the rectangular coils or the racetrack coils with a long coil length in the rail longitudinal direction.

A Novel Three-Phase Omnidirectional Wireless Power Transfer System With Zero-Switching-Loss Inverter and Cylindrical Transmitter Coil

Aiming at the problems of large switching loss and large output power fluctuation in the existing omnidirectional wireless power transfer (OWPT) system, a novel OWPT system with zero-switching-loss inverter and cylindrical transmitter coil is proposed. By introducing an auxiliary resonant network with simple structure and low-loss on each phase arm of the three-phase inverter, zero-voltage switching (ZVS) turn-ON and zero-current switching (ZCS) turn-OFF within the full power range can be acquired. The switching loss in the main circuit of inverter is reliably eliminated. The transmitter coil is a cylindrical coil composed of the three curved rectangular coils, whose excitation current amplitude is equal and the phase difference is 120°. It can arise a spatial rotating magnetic field around the transmitter coil and provide an omnidirectional energy transmission channel. The operating principle of soft-switching is analyzed in detail, and the design rules of soft-switching in full power range and the parameter design method of coupler to reduce the fluctuation of output power are given. Ultimately, an experimental prototype is used to verify the feasibility of the proposed OWPT system. The experimental results indicate that the system output power is retained at 93.4W∼104.7W and transfer efficiency is retained at 71.2%∼78.1% under arbitrary angular misalignment of receiver.

The influence of excitation coil size on the eddy electric field and on overcoming slurry noise in electromagnetic flowmeter

When the electromagnetic flowmeter (EMF) measures the slurry flow, the sensor signal of EMF will be disturbed by the intense slurry noise. How to use the eddy electric field more effectively to overcome the slurry noise is a problem worthy of further investigation. In this paper, the influence of the size change of the excitation coil in the conventional sensor of EMF on the overcoming of slurry noise by the eddy electric field was researched. Firstly, the strength of the eddy electric field in different sizes of rectangles was discussed by using the rectangular excitation coil model. The result of the analysis was that the eddy electric field intensity increases with the increase in coil size. Finally, the effect of the size change of the excitation coil on the slurry flow signal was researched. The experimental results show that the effect of overcoming slurry noise becomes better as the size of the excitation coil increases.