Inductor Geometry Research Articles

Analysis on Variable Inductances of Planar Coils Sandwiched by Soft Magnetic Layers

Filmed planar coils have obvious advantages for miniaturization, micro-fabrication, and circuit integration. Amorphous and nanocrystalline films exhibit extremely large permeabilities and are extensively used to film planar coils for inductance enhancement. In this paper, we analyze aspects in designing a soft magnetic film/planar coil multilayer structure. It is pointed out that when the inductance of a filmed coil varies with the film permeability, it may get saturated before the permeability reaches its maximum. The saturation and variable tendency are closely related to the filmed inductor geometry. It is the ratios of the film dimensions and gap to the coil conductor width that determine the variation rate and saturated value. In addition, the film aspect ratio must be considered to produce suitable effective permeability as the inductance actually responds to the effective permeability instead of the nominal material permeability. Experimental and simulation data demonstrate the validity of the analysis.

Origami Inductors: Rapid Folding of 3-D Coils on a Laser Cutter

Origami manufacturing, the use of folding to create 3-D shapes using 2-D fabrication tools and techniques, is a promising avenue for creating low cost parts. In this letter, we demonstrate the hands-free cutting and folding of 3-D inductor geometries from blank metal foil using only a 2-D laser cutter. Laser forming, localized laser heating to create thermal stresses to deform a workpiece, is used to fold traces out of plane without manual handling. The laser forming of thin copper foil is first characterized, followed by cutting and folding of two 3-D inductors: a three-turn planar coil with folded overpass and a twelve-turn toroid. The planar coil was found to have inductance 199 nH and peak quality factor of 99.7 at 54.7 MHz, while the toroid had inductance 159 nH with peak quality factor 64.9 at 86.7 MHz. With laser cutters, one of the most widely available machine tools, this technology allows custom, high performance electrical passives to be rapidly fabricated without specialized equipment.

Design and Characterization of Inductors for Self-Powered IoT Edge Devices

This paper discusses the design, fabrication, and characterization of packaged planar inductors with magnetic material [nickel zinc (NiZn) ferrite]. Inductors are designed specifically for Internet of Things (IoT) applications based on power loss in an IoT architecture. Different spiral inductor geometries are demonstrated on a printed wiring board with varying thicknesses using a stencil printing process. The magnetic material can be applied to one or both sides of the inductor and, therefore, provides size reduction. This paper examines the role of varying dimensions on inductor performance along with model-to-hardware correlation. The fabrication process demonstrates inductance increase through a very simple procedure for applying a magnetic material on both sides of the inductor, while having flexibility to customize the geometry for minimal power loss in an IoT architecture. With NiZn ferrite material added to both sides of the inductor, the inductance increases between approximately 60% and 80% for the two substrate thicknesses studied, as compared to air-core inductors.

Methodology to improve the model of series inductance in cmos integrated inductors

Abstract This paper presents a systematic optimization methodology to achieve an accurate estimation of series inductance of inductors implemented in standard CMOS technologies. Proposed method is based on an optimization procedure which aims to obtain adjustment factors associated to main physical inductor characteristics, allowing to estimate more accurate series inductance values that can be used in design stage. Experimental measurements of diverse square inductor geometries are shown and compared with previous approaches in order to demonstrate and validate presented approach

Analysis of the impact of modification of cold crucible design on the efficiency of the cold crucible induction furnace

The article includes numerical simulation results for two induction furnace with cold crucible (IFCC). Induction furnaces differ in cold crucible design, while the inductor geometry was preserved for both variants. Numerical simulations were conducted as three dimensional one, with coupled analysis of electromagnetic, thermal and fluid dynamics fields. During the experiment, six calculation variants, differ in amount of molten titanium (three different weights of titanium for each type of cold crucible) were considered. Main parameters controlled during the calculations were: electrical efficiency of the IFCC and the meniscus shape of liquid metal.

ANALYSIS OF ELECTROMAGNETIC PROCESSES IN THE SYSTEM «CYLINDRICAL SOLENOID – MASSIVE CONDUCTOR»

Purpose. Defining the key parameters of the inductor geometry, as a long multi-turn solenoid, that influence on the current amplitude induced excited in a massive conductor with a flat boundary surface. Methodology. Performing a mathematical analysis of the electrodynamic problem solution for an area with variable structure by integrating Maxwell's equation within the given boundary and initial conditions and also physical assumptions simplifying the process of solving but not distorting the result and carrying out an experiment that confirms not only the correctly construction considered but also the acceptability of the chosen assumption the opacity applying of the metal blank for these operating fields frequencies. Results. Functional dependencies of the current induced parameters on the metal surface of the heating object have been obtained, along which numerical estimates of the electrodynamic process have been performed, and key parameters influencing the heating efficiency have been determined. The correctness of the solutions obtained was confirmed experimentally. The final form of the solution function of the physical-mathematical problem was shown to be acceptable for performing further engineering and research calculations. Originality. The functional connection of the measured values of the induced surface current and the parameters of the measuring system is determined, the experimental confirmation of which indicates the satisfactory calculation model of the induction heating system and the entire solution as a whole. Practical value. Based on the calculations performed, working samples of inductive systems for induction heating that meet the specified heating rate and area requirements can be constructed. The obtained analytical expressions were transformed and simplified for their further using for engineering calculations with a minimum error value.

Control of nanoparticle agglomeration through variation of the time-temperature profile in chemical vapor synthesis

The influence of the time-temperature history on the characteristics of nanoparticles such as size, degree of agglomeration, or crystallinity is investigated for chemical vapor synthesis (CVS). A simple reaction-coagulation-sintering model is used to describe the CVS process, and the results of the model are compared to experimental data. Nanocrystalline titania is used as model material. Titania nanoparticles are generated from titanium-tetraisopropoxide (TTIP) in a hot-wall reactor. Pure anatase particles and mixtures of anatase, rutile (up to 11 vol.%), and brookite (up to 29 vol.%) with primary particle sizes from 1.7 nm to 10.5 nm and agglomerate particle sizes from 24.3 nm to 55.6 nm are formed depending on the particle time-temperature history. An inductively heated furnace with variable inductor geometry is used as a novel system to control the time-temperature profile in the reactor externally covering a large wall temperature range from 873 K to 2023 K. An appropriate choice of inductor geometry, i.e. time-temperature profile, can significantly reduce the degree of agglomeration. Other particle characteristics such as crystallinity are also substantially influenced by the time-temperature profile.

Modeling Intracochlear Magnetic Stimulation: A Finite-Element Analysis.

This study models induced electric fields, and their gradient, produced by pulsatile current stimulation of submillimeter inductors for cochlear implantation. Using finite-element analysis, the lower chamber of the cochlea, scala tympani, is modeled as a cylindrical structure filled with perilymph bounded by tissue, bone, and cochlear neural elements. Single inductors as well as an array of inductors are modeled. The coil strength (~100 nH) and excitation parameters (peak current of 1-5 A, voltages of 16-20 V) are based on a formative feasibility study conducted by our group. In that study, intracochlear micromagnetic stimulation achieved auditory activation as measured through the auditory brainstem response in a feline model. With respect to the finite element simulations, axial symmetry of the inductor geometry is exploited to improve computation time. It is verified that the inductor coil orientation greatly affects the strength of the induced electric field and thereby the ability to affect the transmembrane potential of nearby neural elements. Furthermore, upon comparing an array of micro-inductors with a typical multi-site electrode array, magnetically excited arrays retain greater focus in terms of the gradient of induced electric fields. Once combined with further in vivo analysis, this modeling study may enable further exploration of the mechanism of magnetically induced, and focused neural stimulation.

STRAIGHTENING TOOL «INDUCTOR SYSTEM WITH AN ATTRACTING SCREEN» AND LENGTHY SOLENOID

The article presents the analysis of electrodynamic processes in the «inductor system with an attracting screen». Its design is presented by a cylindrical multi-turn solenoid at the end of which various thin-walled sheet metals are attached. Estimates of excitation efficiency of electrodynamic attracting forces are presented. The adequacy of Physics and mathematical model is provided by taking into account the inductor geometry, its location and diffusion effects

Shaping inductor geometry for casting functionally graded composites

Purpose – The attractiveness of functionally graded composites lies in the possibility of a gradual spatial change of their properties such as hardness, strength and wear resistance. The purpose of this paper is to discuss the use of electromagnetic buoyancy to separate the reinforcement particles during the casting process of such a composite. Design/methodology/approach – The basic problem encountered in the process of casting composites is to obtain electromagnetic buoyancy and simultaneously to avoid a flow of the liquid metal which destroys the desired composite structure. In this paper the authors present the methodology of numerical optimization of inductor geometry in order to homogenize the electromagnetic force field distribution. Findings – The optimization method based on searching the solution subspace created by applying knowledge of the modelled process physics proved better than the universal local optimization methods. These results were probably caused by the complex shape of the criterion function hypersurface characterized by the presence of local minima. Practical implications – Due to their characteristics, functionally graded composites are of great interest to the automotive, aerospace and defense industries. In the case of metal matrix composites casting techniques (as the presented one) are the most effective methods of producing functionally graded materials. Originality/value – The paper presents the optimization of a new process of casting functionally graded composites in a low-frequency alternating electromagnetic field. The process involves problems that did not occur previously in the area of electromagnetic processing of materials. The paper proposes the use of special design of inductors to homogenize the electromagnetic force field.

Self-Capacitance of Coupled Toroidal Inductors for EMI Filters

This paper presents a derivation of an expression for the self-capacitance of single-layer coupled toroidal inductors, which are commonly used in EMI filters and other applications. A physics-based geometrical method is used in the derivation. This method requires information about the inductor geometry and material properties, such as dimensions of core, technique of winding, as well as diameter, thickness, and permittivity of winding wire isolation. The geometrical method is very useful because it saves time and does not require an impedance analyzer. However, all information about material properties has to be known. The theoretical results are validated by experimental results. The agreement between the calculated and measured results was very good.

Inductor Geometry With Improved Energy Density

The “constant-flux” concept is leveraged to achieve high magnetic-energy density, leading to inductor geometries with height significantly lower than that of conventional products. Techniques to shape the core and to distribute the winding turns to shape a desirable field profile are described for the two basic classes of magnetic geometries: those with the winding enclosed by the core and those with the core enclosed by the winding. A relatively constant flux distribution is advantageous not only from the density standpoint, but also from the thermal standpoint via the reduction of hot spots, and from the reliability standpoint via the suppression of flux crowding. In this journal paper on a constant-flux inductor (CFI) with enclosed winding, the foci are operating principle, dc analysis, and basic design procedure. Prototype cores and windings were routed from powder-iron disks and copper sheets, respectively. The design of CFI was validated by the assembled inductor prototype.

Modelling and Optimization of Induction Cooking by the Use of Magneto-Thermal Finite Element Analysis and Neural Network

The main advantage of induction cooking is the pan heating without thermal inertia.However to obtain best efficiency, it is essential to have an inductor geometry that gives ahomogeneous temperature on the pan bottom. In this paper, we will first model the magnetothermal phenomena of the system by a finite element method (FEM) in order to determine thedistribution of temperature on the pan bottom taking into consideration the nonlinearity of thesystem. This study shows that the temperature is not homogeneously distributed. Then, in the aim tohave homogeneous temperature distribution in the pan bottom, we propose an inductor structurewith four throats containing the coils and we will use Neural Networks to determine the optimalthroats distribution and their dimensions. The optimized structure permits us to achieve our goal.

Mitigating Time Interval Error (TIE) in High-Speed Baseband Digital Transports: Design for Delay Compensation at Baseband Infrastructure of Smart-Phones Using Fractal Dispersive Delay-Lines

A major concern in modern smart-phones and hand-held devices is a way of mitigating the time interval error (TIE) perceived at high-speed digital transits along the traces of the circuit-board (rigid and or flexible) used in baseband infrastructures. Indicated here is a way of adopting a planar fractal inductor configuration to improvise the necessary time-delay in the transits of digital signal phase jitter and reduce the TIE. This paper addresses systematic design considerations on fractal inductor geometry commensurate with practical aspects of its implementation as delaylines in the high-speed digital transports at the baseband operations of smart-phone infrastructures. Experimental results obtained from a test module are presented to illustrate the efficacy of the design and acceptable delay performance of the test structure commensurate with the digital transports of interest.

Constant‐flux inductor with enclosed winding for high‐density energy storage

The ‘constant-flux’ concept has been described in a recent Letter as a way to utilise space more efficiently for inductor geometry with the core enclosed by winding. While the concept can conceptually be extended to the companion case of the inductor with winding enclosed by the core, structural synthesis is complicated by the absence of circular symmetry. Thus, this Letter delineates a procedure to shape the core and distribute winding turns to realise a magnetic field profile that is advantageous not only from the density standpoint, but also from the thermal standpoint via the reduction of hot spots, and from the reliability standpoint via the suppression of flux crowding. Design and fabrication results are delineated for a constant-flux inductor with the same specifications as a commercial counterpart, but the total height of the inductor is reduced by a factor of two.

Microfabrication of air core power inductors with metal-encapsulated polymer vias

This paper reports three-dimensional (3-D) microfabricated toroidal inductors intended for power electronics applications. A key fabrication advance is the exploitation of thick metal encapsulation of polymer pillars to form a vertical via interconnections. The radial conductors of the toroidal inductor are formed by conventional plating-through-mold techniques, while the vertical windings (up to 650 µm in height) are formed by polymer cores with metal plated on their external surfaces. This encapsulated polymer approach not only significantly reduces the required plating time but also exploits the relative ease of fabricating high-aspect-ratio SU-8 pillars. To form the top radial conductors, non-photopatternable SU-8 is introduced as a thick sacrificial layer. Two toroidal inductor geometries were fabricated and tested. The first inductor had an inner diameter of 2 mm, an outer diameter of 6 mm, 25 turns and a vertical via height of 650 µm. The second inductor had an inner diameter of 4 mm, an outer diameter of 8 mm, 50 turns and a vertical via height of 650 µm. Both inductor geometries were successfully fabricated and characterized in the frequency range of 0.1−100 MHz. Characterization results of the 25- and 50-turn inductors showed an average inductance of 76 and 200 nH, a low frequency (0.1 MHz) resistance of 0.2 and 1 Ω and a quality factor of 35 and 24 at 100 MHz, respectively. Finite-element simulations of the inductors were performed and agreed with the measured results to within 8%. The turn-to-turn breakdown voltage was measured to be in excess of 800 V and currents as high as 0.5 A could be successfully carried by the inductor windings.

Robust and Postless Air-Suspended High Q Integrated Inductors on Silicon

In this paper, integrated air-suspended inductors were newly developed on silicon substrate for on-chip radio frequency (RF) circuit and system applications. For the improvement of Q-factors and self-resonant frequencies of the integrated inductors, they were designed and fabricated by using air-suspended spiral conductor lines, photoresist sacrificial layer, and electroplating technique. For forming the air-suspended conductor lines without selectively etching the substrate and using any metal or insulating posts, the conductor lines were designed to have a shape of `U' at the center of each conductor line. In comparison of the fabricated conventional planar and air-suspended inductors, an increase of 25% in the Q-factor was achieved for the air-suspended inductors. The self-resonant frequency was also increased about 10 to 15% compared with the planar ones. The proposed inductor geometry and fabrication processes were developed for integrating with metal-insulator-metal (MIM) RF capacitors.

Embedded Ferrite LTCC Inductors

This paper presents for the first time one realization of simple planar inductor realized inside the stack of ferrite LTCC (Low Temperature Co-fired Ceramic) tapes. Presented inductor is one layer square spiral fabricated in the LTCC technology. In order to point out benefits of implementation of ferrite material on inductor inductance, the same inductor geometry was fabricated between two dielectric LTCC tapes. Commercially available LTCC material (both ferrite and dielectric) were implemented for the realization of proposed inductors. Designed structures were characterized and obtained experimental results show that even implementation of a very thin layer of ferrite material around inductor lines drastically increases its inductance. For the same inductor design that occupies the same chip area the inductance enhancement over 11 times is achieved. In addition this enhancement is followed with maintenance of good performance of the inductor.

Performance of High-$Q$ Inductors in LTCC Using FTTF Techniques

Inductors have been produced in low-temperature co-fired ceramic in a manner that increases the cross-sectional area of the conductor. This geometry helps to compensate for high-frequency non-idealities, such as skin effect, current crowding and proximity effect. An array of various inductor geometries and probing structures has been fabricated and characterized. $Q{\rm s}$ of over 80 were confirmed, with $Q{\rm s}$ of over 100 believed to be possible. Accurate measurements of such values require careful consideration of error sources and the use of rigorous measurement techniques that are discussed. Finally, a filter has been fabricated to demonstrate the usefulness of these inductors in real-world applications.

Magnetic Field Synthesis in the Design of Inductors for Magnetic Fluid Hyperthermia

A magnetic fluid hyperthermia (MFH) inductor design using multiobjective evolution strategy techniques is proposed. Uniformity of the magnetic field and solution sensitivity are the objective functions chosen for the selection of the inductor geometry. After a 3-D finite-element analysis (FEA) of the thermal field, the coupled-field response of the synthesized inductor has been assessed.