Variation Of Coupling Factor Research Articles

Design and Simulation of a High-Efficiency Micro-Transformer for Photovoltaic Application

This paper presents the design and analysis of a micro-transformer model aimed at achieving high efficiency in photovoltaic applications. The proposed micro-transformer structure consists of two circular planar coils made of copper mounted on PCB (FR4) and Si substrates. The Mohan formula is employed to calculate the micro-transformer’s geometric parameters, ensuring alignment with flyback converter specifications. Consequently, the inductance, quality factors, and coupling factor variation parameters versus frequency, and the impact of the gap between the coils (500, 750, and 1000 µm) on them were analyzed. The simulation findings unequivocally demonstrated that a judicious reduction in gap thickness to 500 µm resulted in a remarkable enhancement of the coupling factor by an impressive 91%. Moreover, finite element-based software was used to analyze the thermal, magnetic, and electric performance of the micro-transformer across varying gap sizes. The investigation led to the determination of the optimal gap thickness that achieves adequate temperature, current, and magnetic flux distribution in the micro-transformer. Finally, the simulation circuit of a photovoltaic system that incorporates a flyback converter including the proposed micro-transformer was performed. Overall, the results revealed that the proposed micro-transformer model with its circular planar coil design offers high efficiency in PV applications.

Design and Optimization of Wireless Charging Drawer Coil for Smart Garments

In this letter, wireless charging chests suitable for smart garments are analyzed and optimized. The coil structure is optimized to generate a uniform magnetic field in a variety of drawer sizes. With the hybrid Helmholtz–solenoid coil structure, the variation of coupling factor is reduced from 78.2% to 26.4% as compared with solenoidal coil. Two design approaches for multidrawer chest are examined. In the first approach, the coils are optimized for individual drawers. In the second approach, the coils are optimized by considering the entire drawer chest. The measurement results show that the second approach further reduces the variation of charging current of receiver coils placed at different locations.

A Position-Insensitive Wireless Power Transfer System Employing Coupled Nonlinear Resonators

Conventional magnetically coupled resonant wireless power transfer (WPT) systems suffer from a significant performance degradation as the coupling factor between transmit and receive coils changes from its optimum value. In this article, a new WPT circuit that consists of two passive nonlinear resonators in both the transmitter and receiver is proposed. The circuit can adapt well to a wide range of coupling factor variations to provide constant output power without using any active control circuitry, frequency tuning, or complicated coil configurations. Both analytical and numerical simulations for the WPT circuit are provided. A 60-W nonlinear WPT prototype circuit operating at 1.5 MHz is designed, fabricated, and measured. The results show that the WPT system based on the proposed circuit is capable of maintaining almost a constant output power, while the distance between the coils varies up to 15 cm, a significant performance improvement compared to the linear WPT circuit tested under the same conditions.

Design Guidelines of Inductive Coils Using a Polymer Bonded Magnetic Composite for Inductive Power Transfer Systems in Electric Vehicles

This article studies design guidelines to optimize the inductive coils for electric vehicles by replacing the standard compact ferrite core with a compound of polymers, nanoparticles, and tile-links of ferrite and by reviewing different aspects of the winding to improve mechanical behavior and efficiency. A system composed of the studied vehicle assembly and ground assembly from the society of automotive engineers’ recommended practice is defined. Fast three-dimensional (3-D) finite element simulations are performed by evaluating different geometric aspects of the vehicle assembly. In doing so, the variation of coupling factor and inductance related to the geometry can be observed and compared in order to analyze the performance when the amount of compact ferrite is reduced. The polymer bonded magnetic is, then, incorporated to improve the decreased magnetic behavior due to the reduction in ferrite. In previous works, the modeling of the litz-wire and polymer bonded magnetic were developed to accelerate the simulations. In this article, we include the modeling of the compact ferrite tile-links to further reduce the time consumption of these simulations. Moreover, simple two-dimensional simulations are described to study the windings’ parasitic capacitances. The design guidelines, based on fast 3-D simulations, are detailed and validated with particular prototypes.

Position-Insensitive Wireless Power Transfer Based on Nonlinear Resonant Circuits

Near-field resonant-based wireless power transfer (WPT) technology has a significant impact in many applications ranging from charging of biomedical implants to electric vehicles (EVs). The design of robust WPT systems is challenging due to its position-dependent power transfer efficiency (PTE). In this paper, a new approach is presented to address WPT's strong sensitivity to the coupling factor variation between the transmit and receive coils. The introduced technique relies on harnessing the unique properties of a specific class of nonlinear resonant circuits to design position-insensitive WPT systems that maintain a high PTE over large transmission distances and misalignments without tuning the source's operating frequency or employing tunable matching networks, as well as any active feedback/control circuitry. A nonlinear-resonant-based WPT circuit capable of transmitting 60 W at 2.25 MHz is designed and fabricated. The circuit maintains a high PTE of 86% over a transmission distance variation of 20 cm. Furthermore, transmit power and PTE are maintained over a large lateral misalignment up to ±50% of the coil diameter and angular misalignment up to ±75°. The new design approach enhances the performance of WPT systems by significantly extending the range of coupling factors over which both load power and high PTE are maintained.

Grain orientation dependence of ΔE effect and magnetomechanical coupling factor in polycrystalline Galfenol alloy

The ΔE effect of Galfenol single crystal is anisotropic and symmetric. The magnetomechanical behavior of polycrystalline Fe-Ga alloy was found to be dependent on the grain distribution. An energy-based model was used to simulate the effect of grain distribution on ΔE effect and coupling factor of the polycrystalline Galfenol alloy. Seven types of textured Fe84Ga16 alloys each with 95, 75 and 50 vol% textured grains were designed by the MTEX toolbox. The alloys having the same <uvw> preferred orientation show a similar ΔE effect and coupling factor variation with the stress and magnetic field. Different <uvw> preferred oriented alloys have great difference in the ΔE effect and coupling factor variation. The effect of texture intensity on the ΔE effect and coupling factor depends on the texture types. The 〈100〉 oriented alloys with fiber texture, Goss texture and cube texture respectively have a similar large ΔE effect. The texture intensity has a relatively small effect on the ΔE effect and coupling factor k of 〈100〉 oriented alloys. Compared with 〈100〉 oriented alloys, the 〈110〉 and 〈112〉 oriented alloys have much smaller ΔE effect and coupling factor. The ΔE effect and coupling factor variation with stress and magnetic field of those two kinds of textured alloys is much more complex than that of 〈100〉 textured alloys.

A Dual-Side-Detuned Series–Series Compensated Resonant Converter for Wide Charging Region in a Wireless Power Transfer System

Wireless power transfer (WPT) system usually suffers from wide range of coupling condition. This causes deep impact on the transferred power level, which further limits the mobility of receiver. In this paper, a dual-side-detuned series-series (SS) compensation method is proposed to provide stable power transfer over wide geometric area. The primary and secondary tuning methods are classified into three categories, respectively, namely fully tuned, inductively tuned, and capacitively tuned. Then, the general power transfer characteristic against coupling factor is identified and it is found that the primary inductively and secondary capacitively tuned (PISC) system is advantageous over other candidates in performance, especially the resistance to variation of coupling factor. Compared to conventional fully tuned SS system, the PISC-type WPT system provides much wider stable power transfer region, which enables higher mobility for the receiver side. The design consideration and principle of the detuned resonant tank is developed, based on which the iteration approach is proposed to guide parameter design procedure. Finally, the validity of the proposed dual-side-detuned SS topology is experimentally verified. Under coupling variation from 0.08 to 0.2, the power transfer is maintained above 80% of its nominal power level with agreeable efficiency.

Design Optimization of Multiple-Layer PSCs With Minimal Losses for Efficient and Robust Inductive Wireless Power Transfer

Inductive wireless Power Transfer (IPT) is a promising technology for remote powering of a wide variety of applications of electronic devices. To design IPT systems with the highest power transfer efficiency and the maximal robustness to coupling factor variations between transmitter and receiver of printed spiral coils (PSCs), high quality factors ( Q-Factor ) of the utilized PSCs are required. Designing PSCs with high Q-Factor is limited by the eddy current, the proximity effect, and parasitic losses. In this paper, PSC parasitic losses are carefully analyzed and specific design solutions are proposed. Genetic algorithm optimizations are developed to accommodate the proposed design solutions in minimizing losses. Single and multiple layer variable width PSCs are optimally designed with eddy current and proximity effect losses minimized. The designed PSCs are fabricated and experimental measurements are performed. The validity of the proposed approach to largely improve both IPT efficiency and robustness are confirmed. Using multiple coil layers, the robustness to axial and lateral coupling variations between coils is highly improved. For a triple-layer PSC design case, up to 3.5-fold improved robustness are obtained in reference to conventional IPT systems. Compared with the previous state of the art IPT topologies, the highest Figure-of-Merit value is obtained using the proposed design solutions.

An LCC-Compensated Resonant Converter Optimized for Robust Reaction to Large Coupling Variation in Dynamic Wireless Power Transfer

In this paper, a reformed compensation network based on traditional LCL topology is proposed to realize robust reaction to large coupling variation that is common in dynamic wireless charging application. From the perspective of smoothing, the power characteristic against coupling factor and to achieve high efficiency simultaneously, extra reactive element is inserted into the resonant tank to provide higher degree of design freedom, forming the improved LCC type compensated inductive power transfer (IPT) system that features with distinct parameter design approach. Comparing to existing compensation topologies, the optimized LCC compensation topology shows more robust power characteristic against variation of coupling factor and, thus, minimizes the need for complex control which is usually undesired in dynamic charging scheme, thereby helping maintain effective power transfer in dynamic charging application and largely enhancing the systematic controllability. Finally, the effectiveness of the proposed method is experimentally verified. The power transfer profile is smooth against coupling factor to realize high tolerance to position as the power drop is no more than 20% within almost 200% of coupling factor variation.

A Dual-Side Controlled Inductive Power Transfer System Optimized for Large Coupling Factor Variations and Partial Load

In this study, a 3-kW inductive power transfer system is investigated, specifically intended for contactless vehicle charging. A series-series-compensated topology with dual-side power control and a corresponding control strategy is proposed to significantly increase the overall efficiency, especially for systems with large coupling factor variations and in partial load mode. The topology, which is closely related to the dual-active bridge converter, enables the dual-side power control without adding additional dc/dc converters to the system, and thus keeping the additional hardware effort minimal. A detailed analysis of the proposed topology is provided, and the benefits of the dual-side control are demonstrated both theoretically and experimentally. A hardware prototype is built and a peak dc-to-dc efficiency of 95.8% at 100 mm air gap and a minimal efficiency of 92.1% at 170 mm air gap is measured, including the power electronic components. The partial load efficiency at 500 W output power is still as high as 90.6% at 135 mm air gap. Overall, the proposed topology provides a practical method to overcome the main drawback of most single-side controlled inductive power transfer systems, which is a significant efficiency drop outside the nominal operating point.

Inductive Power Transfer System With Self-Calibrated Primary Resonant Frequency

Inductive power transfer (IPT) is a commonly employed technique for wirelessly supplying power to implantable medical devices. A major limit of this approach is the sensitivity of the inductive link to coupling factor variations between transmitting and receiving coils. We propose in this paper a new method for compensating these variations and improving the inductive link efficiency. The proposed technique is based on a mechatronic module that dynamically tunes the primary resonant capacitor value in order to maintain the resonance state of the IPT system. The module is able to maintain resonance state for apparent primary inductance range at least from 0.5 to 5 $\mu {\rm H}$ using a high capacitance resolution of 0.032 pF. Experimentations conducted on a 13.56-MHz IPT system showed a $65\%$ higher power transfer compared to a traditional IPT system.

Power Transfer With an Inductive Link and Wireless Tuning

This paper presents the analysis of two air-coupled coils used to transfer energy to charge a battery. This battery is used to power an electronic device designed to monitor variables such as impact strength, range of temperature, and humidity associated with the transport of fruits. The device is inside a sealed enclosure that cannot be opened for recharging the battery. The study shows that the coupled coils need to work with a resonance capacitor, at least on the secondary coil. However, the resonance frequency also depends on the coupling factor <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> . Therefore, this work proposes a monitoring system with a closed loop for fine-tuning the resonance frequency of the secondary coil circuit. Before starting charging the battery, the system scans the resonance frequency on the primary coil and measures the output power on the secondary coil looking for the optimal point. This procedure reduces problems of coupling factor variations with positioning of the coils during the battery charging.

Switchable and tunable strontium titanate electrostrictive bulk acoustic wave resonator integrated with a Bragg mirror

The realization and the radio-frequency characterization of a tunable strontium titanate (STO) electrostrictive solidly mounted acoustic resonator (SMR) bulk acoustic wave are reported. For a 430nm thick strontium titanate layer, the resonance frequency at 2.2GHz can be switched on with a bias voltage of 6V and tuned ±0.85% with a bias voltage between 6 and 30V. No hysteresis is observed. The SMR tunability is found to be affected by (i) the variation of coupling factor versus bias which is the dominant effect and (ii) the variation of SrTiO3 stiffness at constant electric displacement.

Dielectric and piezoelectric properties of Mn‐doped (K,Na)0.96Sr0.02NbO3 ceramics

AbstractDense, lead‐free ceramics with composition of (K0.5Na0.5)0.96Sr0.02Nb1–x Mnx O3 (x = 0, 0.01, 0.02, 0.03, 0.04) were successfully prepared by a conventional mixed‐oxide method. The X‐ray diffraction patterns revealed pure peroveskite structure after Mn doping as compared to the original composition. This was attributed to the inhibition of K+ volatility during the sintering process. A dielectric anomaly was observed and explained by a multiple‐cell structure resulting from Mn‐induced lattice distortion. Low loss tangent and relatively high planar electromechanical coupling factor were obtained at x = 0.02. The main parameters for the composition of x = 0.02 are: ε T 33/ε0 = 479, d 33 = 121 pC/N, K p = 41%, Q m = 298, tan δ = 1.6%, T c = 391 °C. The rates of resonant frequency variation, α , and planar coupling factor variation, α , with a temperature of 80 °C are –1.85% and +1.19%, respectively. This material may be suitable for applica‐ tions in ultrasonic transducers. (© 2006 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

DIELECTRIC AND PIEZOELECTRIC PROPERTIES OF Mn DOPED (K, Na)0.96Sr0.02NbO3 CERAMICS

ABSTRACT Dense lead free ceramics with composition of (K0.5Na0.5)0.96Sr0.02Nb1-x MnxO3 (x = 0,0.01,0.02,0.03,0.04) were successfully prepared by conventional mixed oxide method, and their dielectric and piezoelectric properties have been investigated. The X-ray diffraction patterns indicated phase transition from peroveskite structure with orthorhombic symmetry to pseudo-tetragonal symmetry with increasing Mn content. Low loss tangent and relative high planar electromechanical coupling factor were obtained at x = 0.02 by the introduction of Sr and Mnion. The main parameters for the composition of x = 0.02 are: ϵ33 T/ϵ0 = 479, d33 = 121 kp = 41%, Qm = 298, tanδ = 1.6%, Tc = 391°C. The rates of resonant frequency variation, αfr, and planar coupling factor variation, αkp, with temperature 80°C are −1.85% and +1.19%, respectively. This material may be suitable for applications in ultrasonic transducers.

Design of a Variable Directional Coupler in Rectangular Waveguide

A design theory of a three-aperture rectangular waveguide coupler with adjustable directivity and coupling factor achieved by introducing a very thin slice of an anisotropically conducting material like Pyrolytic Graphite (P.G.) in the central aperture is discussed. By suitable adjustment of the orientation angle of the anisotropically conducting aperture, the directivity can be maintained at very high value over a bandwidth given by 0.5 ⩽ λλgo/λg ⩽ 1.5. The corresponding variation of coupling factor withλλgo/λg has been presented and variation of coupling factor and directivity with orientation angle at the design frequency has been studied.