Coil Dimensions Research Articles

Multi-Objective Optimization of 50 kW/85 kHz IPT System for Public Transport

Inductive power transfer (IPT) is an attractive solution for the automated battery charging of public transport electric vehicles (EVs) with low maintenance requirements. This paper presents the design of a 50 kW/85 kHz contactless EV charger, with a focus on the IPT transmitter and receiver coils. The multi-objective magnetics optimization reveals the Pareto tradeoffs and performance limitations in terms of high efficiency, high power density, and low stray field for high-power IPT systems without moving mechanical parts. A full-scale hardware prototype is realized and experimentally investigated. The dc-dc conversion efficiency, including all the power electronics stages, is measured as 95.8% at 50 kW power transfer across an air gap of 160 mm (coil dimensions $410\times 760\times 60$ mm3). With 150 mm coil misalignment in the worst case direction, the dc-dc efficiency drops to 92%. The measurements of the magnetic stray field show compliance with ICNIRP 2010 at 800 mm distance from the IPT coil center.

Comprehensive Evaluation of Rectangular and Double-D Coil Geometry for 50 kW/85 kHz IPT System

In this paper, the influence of the inductive power transfer (IPT) coil geometry on the performance factors efficiency, power density, and stray field is studied for a public transport electric vehicle battery charging system. IPT coil geometries with rectangular winding and with double-D winding are compared based on the Pareto fronts obtained from a multi-objective optimization. In order to study the effect of the winding layout experimentally, two full-scale 50 kW/85 kHz hardware prototypes with the same outer coil dimensions ( $410\times 760\times 60$ mm3) and ferrite core structure are constructed. For both the prototypes, the measured dc–dc efficiency is approximately 95.5% at 50 kW with a 160 mm air gap and ideally positioned coils, which confirms the calculations. The positioning tolerance of the double-D prototype is inferior, because with coil misalignment the efficiency decays faster than for the rectangular winding prototype. Flux density measurements show that both the prototypes fulfill the ICNIRP 2010 standard at 800 mm lateral distance from the coil center. However, the measured magnetic stray field is a factor of two lower for the double-D prototype, which is a key advantage in high-power applications.

Lumped Track Layout Design for Dynamic Wireless Charging of Electric Vehicles

Dynamic wireless charging (DWC) of electric vehicles (EVs) is an emerging technology that could lead to the breakthrough of EVs. The technology is based on the inductive coupling between an electrified track deployed under the road surface and a pickup coil fitted in EV. This paper refers to a lumped track made of DD coils and is concerned with the design of the track layout, namely coil dimension in the motion direction and track coil distance for a given energy requirement. This paper starts by comparing the coupling characteristics of DD coils with different dimensions by a finite-element method (FEM) analysis. Afterward, an analytical procedure is developed to establish the track coil distance able to transfer to a moving EV the propulsion energy required per unit of traveled space. The procedure utilizes the DD-coil coupling characteristics to calculate the power and, from it, the energy transferred from the track coils to the pickup coil along the track. Instrumental in the calculation is the definition of a parameter, denoted as track flux coverage, which gives the ratio between the dimension of the track coils in the motion direction and the coil distance; such a parameter corresponds to the percentage of road populated with track coils so that it is a cost index of the DWC system implementation. Effects of a lateral displacement of the EV motion from the line joining the track coil centers are also analyzed. Design findings are checked against the results obtained with a computer-assisted analysis.

The influence of temperature, sucrose and lactose on dilute solution properties of basil (Ocimumbasilicum) seed gum

Hydrocolloid interactions with solvent/cosolutes play a vital role in the resolution of their functional properties. Basil seed gum (BSG) is a plant-derived hydrocolloid which has been found many applications in food formulations as stabilizer, emulsifier, thickener and gelling agents. Sucrose and lactose are the most effective sugars in textural and sensorial properties of bakery and dairy products which adding them to solutions containing hydrocolloids can be helpful to approach a proper formula. In this paper, the effect of temperature (25–65°C), sucrose (10, 20, 30 and 40%) and lactose (5, 10 and 15%) were investigated through some molecular parameters of BSG. Results revealed high flexible chain (665.35), intrinsic viscosity (11.38 dl/g) and hydrogel content (73%) of BSG, which may be attributed to some extent by its high molecular weight (1.73×106Da). The density and intrinsic viscosity of BSG were diminished by growing temperature from 25 to 55°C. Among five models, which were applied to estimate intrinsic viscosity, Higiro-2 was the most suitable model at varying temperatures and cosolutes concentrations. The sugars showed a significant effect on the molecular parameters of BSG such as swollen specific volume, shape function, hydration parameter, and coil dimensions. The sugars showed more impact on the [η] of BSG and its molecular parameters than that of temperature. However, lactose had a more prominent effect on the BSG dimensions than that of sucrose, which can be related to its molecular conformation and spatial orientation. It is feasible to make a proper formula by BSG and explain some phenomena in its applications in food and pharmaceutical systems.

Effect of Different Low‐Molar Mass Electrolytes on the Viscometric Behaviour of Sodium Polystyrenesulfonate in Methanol–Water Mixed Solvent Media

SummaryPrecise measurements on the viscosities of sodium polystyrenesulfonate (NaPSS) in water as well as in methanol–water mixed solvent media have been reported in presence of NaCl, KCl, NaBr and KBr having concentrations of 0.1 and 0.5 mol.L−1 at 308.15 K with the polyelectrolyte concentrations in the range ∼ 0.001 to ∼ 0.012 eqv L−1. The reduced viscosities of the polyelectrolyte solutions vary linearly with polymer concentration for all the systems investigated which enabled us to determine the intrinsic viscosities of sodium polystyrenesulfonate in methanol–water mixtures using the Huggins equation. The coiling of the polyion chains are found to increase in the order: NaPSS‐NaCl < NaPSS‐NaBr < NaPSS‐KCl < NaPSS‐KBr. The solvodynamic dimensions of the polyion coils are found to be reduced as the relative permittivity of the medium decreases. The present study also indicates that the polyion structures become more compact with increasing salt concentration in the medium.

Polyelectrolyte behavior of copolymers of 2-deoxy-2-methacrylamido-d-glucose with cationic comonomers in water and dimethylsulfoxide solutions

Copolymers of 2-deoxy-2-methacrylamido-d-glucose with N,N-dimethyl aminoethyl methacrylate were synthesized. Triple copolymers containing N,N-dimethyl-N-dodecyl-N-methacryloyl oxyethyl ammonium iodide units were obtained by alkylation of tertiary amino groups. These copolymers were studied by hydrodynamic and optical methods in various solvents. It was revealed that polyelectrolyte effect in salt-free aqueous solutions is far less pronounced than that in dimethyl sulfoxide (DMSO) solutions. The values of equilibrium rigidity A of alkylated macromolecules in salt-free solutions obtained from viscosimetry data is equal to ∼ (150±50)Å in aqueous solutions and to (750±250)Å in DMSO solutions. Change in intrinsic anisotropy of alkylated macromolecules in DMSO solutions demonstrated that in the concentration range from 2.5 to 0.5g/dL, electrostatic interactions lead to isotropic increase in dimensions of macromolecular coils. In the concentration range from 0.5 to 0.02g/dL, increase in equilibrium rigidity by almost a factor of 4 is observed. It was established that in water-salt solutions of copolymers which contain more than 10mol.% of dodecyl groups, compact structure is formed; in this structure, intramolecular fragments of polymer chain are hindered. In dimethylsulfoxide solution, in the presence of a salt, the value of intrinsic viscosity [η] increases by more than a factor of 6–8 as compared to that in water-salt solutions. The observed differences in conformation, optical and relaxation properties of the triple copolymers in aqueous and DMSO solutions are related to hydrophobic interactions between alkyl substituents. These interactions lead to the formation of hydrophobic “core” and shielding the charged quaternary ammonium groups (N+) in aqua solutions.

Mathematical model to determine the dimensions of superconducting cylindrical coils with a given central field – the case study for MgB2 conductors with isotropic Ic(B) characteristic

In this work, we present a mathematical model which enables to design cylindrical coils with a given central field, made of the superconducting conductor with isotropic Ic(B) characteristic. The model results in a computer code that enables to find out the coil dimensions, and to calculate the coil parameters such as critical current, maximum field in the winding and field non-uniformity on the coil axis. The Ic(B) characteristic of the conductor is represented by the set of data measured in discrete points. This approach allows us to express the Ic(B) as a function linearized in parts. Then, it is possible to involve the central field of the coil, coil dimensions, and parameters of the conductor, including its Ic(B) characteristic, in one equation which can be solved using ordinary numerical non-linear methods. Since the coil dimensions and conductor parameters are mutually linked in one equation with respect to a given coil central field, it is possible to analyze an influence of one parameter on the other one. The model was applied to three commercially available MgB2/Ni/Cu conductors produced by Columbus Superconductors. The results of simulations with the Ic(B) data at 20K illustrate that there exists a set of winding geometries that generate a required central field, changing from a disc shape to long thin solenoid. Further, we analyze how the thickness of stabilizing copper influences the coil dimensions, overall conductor length, coil critical current, maximum field in the winding. An influence of the safety coefficient in operating current on coil dimensions and other above mentioned parameters is studied as well. Finally, we compare the coil dimensions, overall conductor length as well as coil critical current and maximum field in the winding if the value of required central field changes between 1 and 3 T.

The Fast-Pulsed Superconducting Dipole Prototype Magnet of HIAF at IMP

The High-Intensity Heavy-Ion Accelerator Facility is a new major engineering project in the Institute of Modern Physics. The dipole magnets of the booster ring are conceived as fast-cycled superconducting magnets with a high magnetic field and a large gap, the warm iron and superconducting coil structure (superferric) is adopted. The coil is wound with a Nuclotron-type superconducting cable to reduce the ac loss. The magnet with a large operation current and a low inductance assures the fast-pulsed operation. Based on the superconducting cable with large operation current, the design of a superconducting coil prototype is shown in this paper. The magnetic field analysis based on 3-D-OPERA is carried out to obtain the basic dimension of coils. Then, the design of the Nuclotron-type superconducting cable, the coil, and coil case are described in detail. In addition, fabrication of the superconducting cable, the coil winding, and other components are also introduced in this paper.

Design of Nb3Sn Wiggler Magnets for the Compact Linear Collider and Manufacturing of a Five-Coil Prototype

To achieve the luminosity requirements of the Compact Linear Collider (CLIC) at the collision point, damping rings (DRs) equipped with superconducting wiggler magnets should be used to produce ultralow emittance with high bunch charge. Although Nb-Ti wigglers meet the specifications for CLIC DRs, the more challenging Nb3Sn technology could be used to increase the magnetic flux density amplitude in the gap and reduce the total length of wigglers in the DRs. To test the Nb3Sn technology, a small wiggler prototype is under design and will be built and tested at CERN. Magnetic calculations concerning the selection of the main wiggler's parameters are presented in this paper, which include the optimization of the main coil dimensions and the period length, in order to fulfill the normalized emittance and intrabeam scattering effect constraints, while decreasing the amount of wigglers in the DRs. Another advantage of using Nb3Sn, instead of Nb-Ti, as superconducting material is the possibility of increasing the working margin. Several scenarios well suited for CLIC damping wigglers, in which the working point is less than 80% of the magnet's current limit, are addressed in this work. In addition, the description of the manufacturing process and the current status of the Nb3Sn prototype fabrication are presented.

Influence of piston and magnetic coils on the field-dependent damping performance of a mixed-mode magnetorheological damper

This work presents a 2D simulation study of a mixed-mode magnetorheological (MR) damper in which the influence of the geometric elements of the piston and magnetic coil on the MR damper’s performance is investigated by using the Ansoft Maxwell software tool. Four results of the simulation, which are magnetic flux density (B), MR fluid yield stress (τ0), and are used to compare the performance of the MR damper. Multiplication of the yield stress by the active operating mode length represents the variable portion of the active (on-state) damping force of the flow mode motion, while the value of represents the active damping force of the shear mode motion. The contribution of each operating mode (shear and flow) is related to the mixed-mode geometry and piston velocity. Therefore, each operating mode is evaluated separately. In this work, a total of 154 simulations are done in which 74, 20 and 60 simulations are conducted to analyse the effect of the piston radius, coil dimensions (width and length) and coil boundary lengths, respectively, on the performance of the MR damper. The simulation results show that increasing the piston radius can increase the value and reduce the value. For a given area of magnetic coil housing, a greater housing length in the axial direction of the piston can increase the achieved yield stress of the MR fluid and hence consequently the performance of the MR damper. A minimum boundary length is needed around the magnetic coil in order to attain a supreme magnetic field distribution. However, there is an optimised value for axial coil boundary lengths, which are the lengths of the upper and lower mixed-mode areas.

Analysis of Subsea Inductive Power Transfer Performances Using Planar Coils

AbstractSubsea inductive power transfer is one of the reliable and efficient methods for limited electric power transfer between closely located subsea systems. A planar coiled system is modeled using the electromagnetic finite element analysis software MagNet, and the simulation results are compared with those of a developed prototype; it is found that 75‐125 kHz is the optimum frequency for electrical power transfer in sea water conditions. The power transfer performance for various water gaps and offsets is identified. The results indicate that the power transfer efficiencies vary from 63.4% to 0.9% for water gaps ranging from 50 to 500 mm at an operating frequency of 125 kHz. The model is also extrapolated to flux concentrated designs, and the coil dimensions required for higher power transfer applications are identified.

Intensity correction for multichannel hyperpolarized 13C imaging of the heart.

Develop and test an analytic correction method to correct the signal intensity variation caused by the inhomogeneous reception profile of an eight-channel phased array for hyperpolarized (13) C imaging. Fiducial markers visible in anatomical images were attached to the individual coils to provide three dimensional localization of the receive hardware with respect to the image frame of reference. The coil locations and dimensions were used to numerically model the reception profile using the Biot-Savart Law. The accuracy of the coil sensitivity estimation was validated with images derived from a homogenous (13) C phantom. Numerical coil sensitivity estimates were used to perform intensity correction of in vivo hyperpolarized (13) C cardiac images in pigs. In comparison to the conventional sum-of-squares reconstruction, improved signal uniformity was observed in the corrected images. The analytical intensity correction scheme was shown to improve the uniformity of multichannel image reconstruction in hyperpolarized [1-(13) C]pyruvate and (13) C-bicarbonate cardiac MRI. The method is independent of the pulse sequence used for (13) C data acquisition, simple to implement and does not require additional scan time, making it an attractive technique for multichannel hyperpolarized (13) C MRI.

Modeling and design of Galfenol unimorph energy harvesters

This article investigates the modeling and design of vibration energy harvesters that utilize iron-gallium (Galfenol) as a magnetoelastic transducer. Galfenol unimorphs are of particular interest; however, advanced models and design tools are lacking for these devices. Experimental measurements are presented for various unimorph beam geometries. A maximum average power density of 24.4 and peak power density of 63.6 are observed. A modeling framework with fully coupled magnetoelastic dynamics, formulated as a 2D finite element model, and lumped-parameter electrical dynamics is presented and validated. A comprehensive parametric study considering pickup coil dimensions, beam thickness ratio, tip mass, bias magnet location, and remanent flux density (supplied by bias magnets) is developed for a 200 Hz, 9.8 amplitude harmonic base excitation. For the set of optimal parameters, the maximum average power density and peak power density computed by the model are 28.1 and 97.6 respectively.

Silicon MEMS bistable electromagnetic vibration energy harvester using double-layer micro-coils

This work reports the development of a MEMS bistable electromagnetic vibrational energy harvester (EMVEH) consisting of a silicon-on-insulator (SOI) spiral spring, double layer micro-coils and miniaturized NdFeB magnets. Furthermore, with respect to the spiral silicon spring based VEH, four different square micro-coil topologies with different copper track width and number of turns have been investigated to determine the optimal coil dimensions. The micro-generator with the optimal micro-coil generated 0.68 micro-watt load power over an optimum resistive load at 0.1g acceleration, leading to normalized power density of 3.5 kg.s/m3. At higher accelerations the load power increased, and the vibrating magnet collides with the planar micro-coil producing wider bandwidth. Simulation results show that a substantially wider bandwidth could be achieved in the same device by introducing bistable nonlinearity through a repulsive configuration between the moving and fixed permanent magnets.

Design Considerations to Reduce Gap Variation and Misalignment Effects for the Inductive Power Transfer System

An inductive power transfer (IPT) system usually consists of four parts: an ac–dc power factor correction (PFC) converter, a high-frequency dc–ac inverter, a compensation network comprising a loosely coupled transformer (LCT) and the resonant capacitors, and a rectification output circuit. Due to the relatively large air gap, the magnetic coupling coefficient of the IPT system is significantly lower than that with tightly coupled transformer. As a result, the efficiency of the IPT system is always a main concern for applications with possible gap variation or misalignment condition. To ensure high power transfer efficiency, these IPT systems should have high tolerance for different gap variation and horizontal misalignment conditions. In this paper, the effect of coupling coefficient deviation to compensation network efficiency is analyzed, and design considerations to reduce gap and misalignment effects for the IPT system are proposed. By using finite-element analysis simulation method, the performance of different transmitter and receiver coil dimensions is compared. In order to validate the performance of the proposed design considerations, a 100-W hardware prototype with two sets of LCT is built and the corresponding experiments are carried out. As compared to the symmetrical LCT architecture, the proposed asymmetrical LCT prototype improves the coupling coefficient reduction from 68% to 28% when the gap varies from 6 to 20 mm and from 89% to 31% when the misalignment ranges from 0 to 50 mm. Therefore, the efficiency deviation for the asymmetrical LCT is maintained within 3.5% over the entire tested gap variation and misalignment ranges.

Compliance Testing Methodology for Wireless Power Transfer Systems

Wireless power transfer (WPT) systems have become popular, with applications in charging portable electronics via inductive coupling between a transmit and receive coil. Accurate estimation of the induced exposure is required as the incident magnetic fields near the coils often exceed the reference levels. Standardized procedures do not yet exist for the demonstration of compliance of these products with electromagnetic guidelines for human exposure. For this purpose, we propose a conservative methodology using simplified homogeneous phantoms. An approximation for the minimum compliance distance for user exposure is developed based on the theoretical evaluation of the induced fields and simulations of detailed anatomical models. The simulation results are experimentally validated for a practical WPT application at 6.78 MHz. Criteria for exclusion of WPT systems from compliance evaluation are presented as a function of coil dimensions, operating current and frequency.

Comparison of three formulations for eddy-current and skin and proximity problems in a meander coil electromagnetic acoustic transducer

Three differential equations based on different definitions of current density are compared. Formulation I is based on an incomplete equation for total current density (TCD). Formulations II and III are based on incomplete and complete equations for source current density (SCD), respectively. Using the weak form of Finite Element Method (FEM), the three formulations were applied in a meander coil Electromagnetic Acoustic Transducer (EMAT) example to solve magnetic vector potential (MVP). The FEM results from frequency domain and time domain models are in excellent agreement with previously published works. Results show that the errors for Formulations I and II vary with coil dimensions, coil spacing, lift-off distance and external excitation frequency, for the existence of eddy-current and skin and proximity effects. And the current distribution across the coil conductors also follows the same trend. It is better to choose Formulation I instead of Formulation III to solve MVP when the coil height or width are less than twice the skin depth, due to the low cost and high efficiency of Formulation I.

Structural and dynamic characteristics of thermo- and pH-sensitive copolymers of 2-(diethylamino)ethyl methacrylate and 2-deoxy-2-methacrylamido-d-glucose

Polarized luminescence and flow birefringence methods were used in the studies of structural and dynamic characteristics of 2-(diethylamino)ethyl methacrylate and 2-deoxy-2-methacrylamido-d-glucose copolymers with varied content of cationic monomer units while changing temperature, pH and ionic strength of solutions. It was demonstrated that with increasing temperature, nanosecond relaxation times τIMM (which characterize intramolecular mobility of fragments of copolymer chain in solution) increase over a relatively narrow temperature range. Increase in relaxation times indicates strengthening intramolecular interactions and the formation of intramolecular hydrophobic domains. From the obtained flow birefringence data, it follows that in the vicinity of the lower critical solution temperature (LCST) we have molecular dispersed diluted copolymer solutions. The influence of temperature and ionic strength of solutions on the transition temperature were also studied. The observed changes in intramolecular interactions are accompanied by insignificant changes in root-mean-square dimensions of macromolecular coils; however, coils retain their asymmetry.

Phase stability and dynamics of entangled polymer-nanoparticle composites.

Nanoparticle–polymer composites, or polymer–nanoparticle composites (PNCs), exhibit unusual mechanical and dynamical features when the particle size approaches the random coil dimensions of the host polymer. Here, we harness favourable enthalpic interactions between particle-tethered and free, host polymer chains to create model PNCs, in which spherical nanoparticles are uniformly dispersed in high molecular weight entangled polymers. Investigation of the mechanical properties of these model PNCs reveals that the nanoparticles have profound effects on the host polymer motions on all timescales. On short timescales, nanoparticles slow-down local dynamics of the host polymer segments and lower the glass transition temperature. On intermediate timescales, where polymer chain motion is typically constrained by entanglements with surrounding molecules, nanoparticles provide additional constraints, which lead to an early onset of entangled polymer dynamics. Finally, on long timescales, nanoparticles produce an apparent speeding up of relaxation of their polymer host.

Accelerated dynamic cardiac MRI exploiting sparse-Kalman-smoother self-calibration and reconstruction (k − t SPARKS)

Accelerated dynamic MRI, which exploits spatiotemporal redundancies in k − t space and coil dimension, has been widely used to reduce the number of signal encoding and thus increase imaging efficiency with minimal loss of image quality. Nonetheless, particularly in cardiac MRI it still suffers from artifacts and amplified noise in the presence of time-drifting coil sensitivity due to relative motion between coil and subject (e.g. free breathing). Furthermore, a substantial number of additional calibrating signals is to be acquired to warrant accurate calibration of coil sensitivity. In this work, we propose a novel, accelerated dynamic cardiac MRI with sparse-Kalman-smoother self-calibration and reconstruction (k − t SPARKS), which is robust to time-varying coil sensitivity even with a small number of calibrating signals. The proposed k − t SPARKS incorporates Kalman-smoother self-calibration in k − t space and sparse signal recovery in x − f space into a single optimization problem, leading to iterative, joint estimation of time-varying convolution kernels and missing signals in k − t space. In the Kalman-smoother calibration, motion-induced uncertainties over the entire time frames were included in modeling state transition while a coil-dependent noise statistic in describing measurement process. The sparse signal recovery iteratively alternates with the self-calibration to tackle the ill-conditioning problem potentially resulting from insufficient calibrating signals. Simulations and experiments were performed using both the proposed and conventional methods for comparison, revealing that the proposed k − t SPARKS yields higher signal-to-error ratio and superior temporal fidelity in both breath-hold and free-breathing cardiac applications over all reduction factors.