Single-layer Coil Research Articles

Thermal Simulation and Analysis of Dry-Type Air-Core Reactors Based on Multi-Physics Coupling

A reactor is an important piece of equipment used for reactive power compensation in power system and has a significant impact on the safe operation of power system. Thermal behavior is one of the main causes of reactor failures. For an accurate analysis of the thermal behavior of reactors, electromagnetic–thermal–fluid multi-physics coupling modeling is chosen. However, there is a huge difference in size between the overall structure of the reactor and its insulating material, which makes it difficult to perform mesh generation, resulting in dense mesh and significantly increased solution degrees of freedom, thus making the solution of the reactor’s multi-physics field model very time-consuming. To address this, this paper proposes a simplified processing method to accelerate the solution calculation of the reactor’s multi-physics model. This method calculates the equivalent turns of each encapsulate with parallel coils in the reactor, simplifying the encapsulate into a single-layer coil, thereby greatly reducing the division and solution degrees of freedom of the multi-physics model, and thus accelerating the simulation calculation. Taking a BKDCKL-20000/35 dry-type air-core shunt reactor as an example, the outer diameter of the coil is nearly 12,000 times bigger than the coil insulation, which is a huge size difference. Both refined models and simplified models are established. Compared to the simulation results of the detailed model, the simplified model demonstrates good accuracy; the maximum relative error of temperature is just 2.19%. Meanwhile, the computational time of the simplified model is reduced by 35.7%, which shows promising effectiveness and significant potential for applying the optimization design and operation prediction of dry-type air-core shunt reactors for enhanced thermal performance.

Phenomenon of Standing Waves on Uniform Single Layer Coils - Revisited and Extended

Accurate knowledge of the natural frequencies and shapes of corresponding standing waves are essential for gaining deeper insight into the nature of response of coils to impulse excitations. Most of the previous analytical studies on coils assumed shape of standing waves as sinusoidal but numerical circuit analysis and measurements suggest otherwise. Hence, this paper revisits the classical standing wave phenomenon in coils to ascertain reasons for this discrepancy and thereafter extends it by analytically deriving the exact mode shape of standing waves for both neutral open/short conditions. For this, the coil is modeled as a distributed network of elemental inductances and capacitances while spatial variation of mutual inductance between turns is described by an exponential function. Initially, an elegant derivation of the governing partial differential equation for surge distribution is presented which is then analytically solved, perhaps for the first time, by the variable-separable method to find the complete solution (sum of time and spatial terms). Hyperbolic terms in spatial part of solution have always been neglected but are included here, thus, yielding the exact mode shapes. Voltage standing waves gotten from analytical solution are plotted and compared with simulation results on a 100-section ladder network. The same is measured on a large-sized single layer coil. So, it emerges that, even in single layer coils, shape of standing waves deviates considerably from being sinusoidal and this deviation depends on spatial variation of mutual inductance, capacitive coupling, and order of standing waves.

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%.

Индуктивности и силы сжатия в двухслойных катушках

Expressions for calculating the self-induction coefficients of two-layer and single-layer coils are considered, and related comparisons are carried out. Examples of calculating the induction coefficients for known design versions of coils are given. An expression for calculating axial compression forces in two-layer coils is presented. The axial compression forces in coils as part of three-phase load devices designed for testing generator sets of autonomous power plants have been calculated. The expressions obtained for calculating the inductances and axial compression forces in two-layer coils are quite concise and can be recommended for practical use. These expressions include only the coil design parameters: the number of turns in the layers, layer radii, winding pitches, and layer lengths. The article is illustrated with particular examples of calculating the coil inductance and compression forces.

Performance Analysis of Multilayer Coil Based MI Waveguide Communication System

In the non-conventional media like underwater and underground, the Radio Frequency (RF) communication technique does not perform well due to large antenna size requirement and high path loss. In such media, magnetic induction (MI) communication technique is very promising due to small coil size and constant channel behavior. Unlike the RF technique, the communication range in MI technique is relatively less. To enhance this range, a waveguide technique is already brought in practice. This technique employs single layer coils to enhance the performance of MI waveguide. To further enhance the system functioning, in this paper, we investigated the performance of multi-layer coil (MLC) antenna based MI waveguide communication system in terms of transmission range, path loss, bit error rate (BER) and bandwidth. Besides, the system performance is quantitatively evaluated in three different non-conventional media viz., dry soil, fresh water and wet soil. As compared with the single layer counterpart, the MLC system shows a significant improvement in transmission range, BER even in loosely coupled scenarios and shows a corresponding reduction in path loss. However, the bandwidth is observed to be low (< 1 KHz). In this analysis, the eddy current effects and parasitic capacitance are compared for single and multi-layer coils. It is observed that the proposed system performs better in dry soil medium due to less medium conductivity.

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.

Design of double-layer parallel printed spiral coil for wireless power transfer applied to rotating equipment

Wireless power transfer (WPT) is a promising technology for remotely powering a wide variety of applications in rotating electronic devices. Although this method was introduced a long time ago, it still faces several challenges. The main challenge is that the traditional Litz coil cannot be fixed in high-speed rotating equipment, and the existing single-layer printed spiral coil has low quality factor. Therefore, to increase the coils’ quality factor and improve the transmission efficiency and output power of the system, a novel double-layer parallel coil model is proposed and compared with a conventional single-layer coil. Through experimental validations and simulation analysis, this study shows that, when the system frequency is 100 kHz and a double-layer parallel coil is employed, the quality factor of the coil is enhanced by 57.4 % compared to a single-layer coil. In the case of an input voltage of 8 V and a transmission distance of 10 mm, the output power of the double-double coil is increased by 1.65 W compared with the single-single coil, and the transmission efficiency is increased by 22.5 %, thereby realizing efficient WPT and providing reliable power transmission for sensors on rotating machinery such as helicopters and aero engines.

Modeling of Stacked Single-Layer Coils Wound with Bi2223 Tapes Using a Lumped Constant Circuit

Modeling of Stacked Single-Layer Coils Wound with Bi2223 Tapes Using a Lumped Constant Circuit

Optimization of the Emitting Coil of a Hardware-Software Complex for Study of Low-Frequency Electromagnetic Radiation’s Shielding Effectiveness

Optimization of the radiation coil of the hardware-software complex for studying the effectiveness of shielding of low-frequency electromagnetic radiation will make it possible to assess the effectiveness of shielding coatings at a higher level. This fact will make it possible to develop coatings with improved characteristics. The purpose of this work was to determine the optimal characteristics of the emitting coil which will ensure its stable operation and magnetic field strength in the frequency range up to 100 kHz.The parameters of the manufactured samples, such as inductance (L), active (R) and total resistance (Z), were obtained using an MNIPI E7-20 emittance meter. In practice, the coils with the optimal parameters calculated theoretically were connected to a current source and amplifier. To detect electromagnetic radiation, a multilayer inductor connected to a UTB-TREND 722-050-5 oscilloscope was used as a signal receiver.The results of measurements showed that the resistance of multilayer coils is approximately 1000 times higher than that of single-layer coils. Also, for multilayer coils, an avalanche-like increase in total resistance is observed starting from a frequency of 10 kHz, while for single-layer coils there is a uniform increase in total resistance over the entire frequency range up to 100 kHz.The paper presents results of research on the correlation of the performance of single-layer and multilayer inductors depending on their parameters in the frequency range from 20 Hz to 100 kHz. Values of the voltage required to provide the magnetic field strength of 1, 5, 20 Oe at 25 Hz and 100 kHz have been calculated. After analyzing the data obtained, the optimal parameters of the inductor were found which ensure stable performance in the frequency range up to 100 kHz.

Experimental Comparison of Designed Inductance Coils for Wireless Power Transfer

Abstract The paper is devoted to the comparison of different types and different values of coils for inductive power transfer in the classical circuit. This topic is relevant with the growing demand and interest in wireless chargers and the diversity of inductance coils for wireless power transfer. The main geometric parameters affecting the coil efficiency are determined. For experimental verification the classical scheme for wireless power transfer is used based on a full-bridge inverter. Different coils at different distance between them, lateral misalignment and load resistance changed are tested. It is determined that single-layer coils have better transmit-receive efficiency than double-layer ones, especially with series-series compensation topology. The application of two-layer coils is recommended in case of high input current. The investigated samples have efficiency at the level of industrial standards. The design approach can be used for any level of power and application, including wireless charging of electric vehicle batteries.

Measurement of Equivalent Conductivity and Permeability of Liquid-Solid Mixture Based on Single-Layer Coil

Coil-based non-contact testing is widely used for the measurement of conductivity and permeability of bulk metal. However, there is a lack of researches on the application of this method to liquid-solid mixture with lower conductivity and permeability. In this article, a model for simultaneously predicting the conductivity and permeability of liquid-solid mixture based on coil impedance and equivalent circuit analysis is proposed and verified by numerical simulation. The parameters of the model are determined by the experiments of the solutions with and without magnetic granule. With the proposed model, the prediction errors of the conductivity and permeability of the liquid-solid mixture used in this article are less than 5.0% and 3.4%, respectively.

Effect of Frequency on the Linearity of Double-Layer and Single-Layer Rogowski Coils

The Rogowski coils are usually used to measure high frequency currents due to their air core. The higher the turn number, the higher the mutual inductance between Rogowski coil and the primary conductor. Performance of Rogowski coil with a high turn number is very difficult to figure out by simulation software. This paper presents an improved lumped parameter model of Rogowski coils. According to the model, the influence of parasitic turn-turn capacitance, turns self-inductance, turn-turn inductance, turn-shielding capacitance, turns resistor, sample resistor and others on the linearity of Rogowski coil with a high turns number at several different frequency ranges are explored. The model is applicable to both double and single layer coils. Three high-turn-number coils of double and single layer are studied and compared in this paper. The improved lumped parameter model is verified by experiments. Five main influence factors on the linearity of the Rogowski coil at a certain frequency range are studied both theoretically and experimentally. The five influence factors include sampling resistors, turns density, shielding layer, positions of the primary conductor, and turns nonuniformity. The numerical and experimental results analyze the influence of the factors on the linearity of the output voltage of the coils at different frequencies quantitatively and qualitatively. The principle of the improved model can be used for multi-layer coils. The model can be a useful guidance in designing coils with suitable structure for special applications at different frequencies.

Application of inductive coupling for wireless power transfer

Considering the massive development that took place in the past two decades, wireless power transfer has yet to show the applicability to be used due to several factors. This work focuses on determining the main parameters like, mutual inductance, and coupling coefficient for a pair of helical coils for wireless power transfer applications. These parameters are important in designing and analyzing a wireless power transfer system based on the phenomenon of inductive/ resonant inductive coupling. Here presents a simple approach based on fundamental laws of physics for determining the coupled coil parameters for single layered helical coils. The results conducted by computer simulation which is MATLAB. Furthermore, this analysis is used to study the effect of change in coil diameter, mutual inductance coefficient and change in distance between coils on parameters like self and mutual inductance of coupled coils which is of great importance in Wireless Power Transfer applications. The research yielded promising results to show that wireless power transfer has huge possibility to solve many existing industrial problems.

Experiment, Optimization, and Design of Electromagnetic Track Brake for High-Speed Railways System

To enhance braking force and control convenience of high-speed railway systems, this paper proposes a new electromagnetic track brake, and the corresponding design, optimization, and experimental test are implemented. The proposed track brake is longitudinal-axis magnetic circuits excited by multiple coils electromagnets, and the pole shoes are extending outward. A preliminary design of an electromagnetic track brake is developed, including iron core height, iron core width, iron core gap, excitation ampere-turn, coil arrangement form, coil thickness, and preliminary height of single-layer coil. The electromagnet number and pole shoe gap are optimized through three-dimensional electromagnetic simulation comparisons. The final design of the electromagnetic track brake is determined, including iron core length, copper wire diameter, coil turn, and final height of single-layer coil. Experimental verification of electromagnetic attractive force is performed through prototype tests, and the newly developed electromagnetic track brake can enhance electromagnetic braking deceleration by 39%.

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.

Single-Layer Transmitter Array Coil Pattern Evaluation toward a Uniform Vertical Magnetic Field Distribution

A uniform magnetic field distribution is a critical aspect in the transmitter array coil design process for achieving a homogenous vertical magnetic field distribution. The free position and orientation features can thus be implemented in the wireless power charging system. This paper presents vertical magnetic field distribution generated by a single-layer circular flat spiral air core transmitter array coil model analysis and evaluation using a numerical analysis method. This method is developed based on the off-symmetry axis magnetic field distribution due to a circular current loop derived from the Biot-Savart law. The proposed evaluation criteria are used to obtain the vertical magnetic field distribution characteristic of the evaluated array coil model. The vertical magnetic field distribution of several circular flat spiral air core coils, in both single and array coil models with different coil geometries were investigated to obtain the relation between the coil parameters and the distance between the adjoining coil centers to generate uniform vertical magnetic field distribution. A case study was also conducted to analyze and evaluate several array coil model patterns (1 × 2 array coil, 1 × 3 array coil, 2 × 2 array coil, 2 × 3 array coil) to meet uniform vertical magnetic field distribution. The array coil model is composed of an identical single circular flat spiral air-core coil. Every single coil has inner coil diameter (Di), outer coil diameter (Do), wire diameter (W), pitch (P) and a number of turns (N) at 25 mm, 47.8 mm, 0.643 mm, 0.03 mm, 17 respectively. The study and evaluation of several array coil pattern models show that the distance between the adjoining coil centers should be defined close to the half of coil outer diameter (1/2Do) to generate close to uniform vertical magnetic field distribution. The vertical magnetic field distribution average and magnetic field effective transmitting areas array coil model with the given coil parameters changing as the effect in variation in distances between the adjoining coil centers.

Field of a Multilayer and Multiturn Coil with Analytically Set Laws of Variations in the Distances between Layers and Turns

Design formulas for three-dimensional magnetic fields generated with a complex system of circular currents, which compose a multilayer and multiturn coil are derived. The distribution of a vector field in any spatial domain can be obtained by setting the analytic function that establishes the distances between turns and/or layers. It is revealed that under uniform winding and equal densities of surface currents, the magnetic fluxes of a single-layer coil and equidimensional axial magnetized cylinder are identical. The magnetic flux of the cylinder is calculated by the demagnetizing factor.

Оn the structure of the device for measuring residual stresses

Тhe article deals with a relevant problem – improvement of the accuracy of measurement of residual stresses in the elements of machines and structures with the use of attachable transducers.Analysis of flexible current-vortex transducers designed in the form of a single-layer coil has been performed. To solve the problem, the method of eddy currents is proposed, which can be used to set the calibration value of the magnetic resistance of the air gap between the transducer and the object.This method implementation based on the scheme of the oscillator with a reactive circuit has been demonstrated. The design of the residual stress measurement unit in the form of «capacitive three-point» self-excited oscillator has been substantiated. The structure of the device for measuring stresses has been proposed. The core element of the calibration value setting unit is a self-excited oscillator with a reactive frequency oscillating circuit, the inductance thereof been the excitation coil of the current-vortex transducer.Magnetic resistance of the gap is measured by moving the transducer vertically versus the surface of the object in the measurement area. The circuit of the proposed device consists of a block for setting the gap magnetic resistance, eddy-current transducer, electron-counting frequency meter, and residual stress measuring unit.

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.

Influence of 3-D Effects on Field Quality in the Straight Part of Accelerator Magnets for the High-Luminosity Large Hadron Collider

A dedicated D1 beam separation dipole is currently being developed at KEK for the large hadron collider luminosity upgrade (HL-LHC). Four 150-mm aperture, 5.6-T magnetic field, and 6.7-m-long Nb–Ti magnets will replace resistive D1 dipoles. The development includes fabrication and testing of 2.2-m model magnets. The dipole has a single-layer coil and thin spacers between coil and iron, giving a nonnegligible impact of saturation on field quality at nominal field. The magnetic design of the straight section coil cross section is based on two-dimensional (2-D) optimization and a separate optimization concerns the coil ends. However, magnetic measurements of the short model showed a large difference (tens of units) between the sextupole harmonic in the straight part and the 2-D calculation. This difference is correctly modeled only by a 3-D analysis: 3-D calculations show that the magnetic field quality in the straight part is influenced by the coil ends, even for the 6.7-m-long magnets. The effect is even more remarkable in the short model. We investigate similar 3-D effects for other magnets, namely the 11-T dipole for HL-LHC. We also consider the case of the 4.5-T recombination magnets for HL-LHC (D2), where the larger space between coil and iron makes this effect less important, but still visible. We conclude the paper by outlining the different classes of accelerator magnets, where this coupling between 3-D effects and iron saturation can be relevant.