Commercial Inductors Research Articles

Analysis and Determination of Self-Inductance through Direct and Indirect Measurements Methods

Practicum is an activity that helps students to understand an abstract concept. One of the concepts in physics that requires practicum is the concept of electricity. Inductance is an electrical quantity studied in high and vocational high schools. This study aims to determine the inductor's inductance value using several methods and analyze the most suitable method for determining the inductor inductance value. The inductor used is a commercial inductor with a color band code with an inductance value of 2.7 mH and a tolerance of 10%. Inductor inductance measurements were carried out using a benchtop LCR meter, handheld LCR meter, series RLC method, and LC resonance method. Each measuring instrument requires a frequency setting: refer to the manual for benchtop and handheld LCR meters, the resonant frequency for the serial RLC method, and adjusting the AFG (arbitrary function generator) frequency. Hence, a clear oscillation pattern is visible on the oscilloscope. The results of this study indicate that measurements using benchtop LCR meters, handheld LCR meters, and LC resonance methods produce inductance values within the inductance tolerance limits.

Self-Heating Induced Instability of a Non-Linear Inductor in a SMPS: a Case Study

This paper proposes a case study to show that the non-linear operation of a power inductor in a SMPS can induce instability of the control system leading to overheating of the inductor beyond its allowable temperature and to an excessive peak of the maximum current. The case study is performed by a commercial ferrite inductor employed in a synchronous boost converter encompassing a control system to adjust the duty cycle, assuring a constant output voltage. The thermal transient is described by the time domain waveforms and thermal images.

Observation of anisotropic magneto-inductance effect

We have discovered a new phenomenon that inductance oscillates as a function of the angle between an in-plane magnetic field and an electric current direction in permalloy films, which we have named “the anisotropic magneto-inductance (AML) effect.” We have investigated the dependences of the AML effect on the size and voltage. The length, frequency, and amplitude dependences suggest that the AML effect should be evaluated in terms of “inductivity.” Inductors based on this AML effect have the potential to be variable, on-chip, and one billion times smaller than the small commercial inductor.

Matrix Coupled All-in-One Magnetics for PWM Power Conversion

This article investigates the matrix coupled “all-in-one” magnetic structure that combines both series coupling and parallel coupling for pulse-width modulated (PWM) power conversion. A systematic analysis of the current ripple reduction mechanism is performed. Current ripple steering among asymmetric series coupled windings is discussed. The transient performance of the matrix coupled inductor is demystified, providing insights for analyzing converter dynamics and its large- or small-signal modeling. To quantify the benefits of matrix coupling, a figure of merit is defined by comparing the current ripple of a matrix coupled inductor to that of a discrete inductor given the same transient speed. The comparison results indicate that a higher number of phases and a stronger matrix coupling coefficient amplify the benefits of matrix coupling. A 1 V-to-5 V input, 1 V-to-5 V output, four-phase matrix coupled synchronous SEPIC converter with planar PCB integrated magnetics is built and tested. The matrix coupled SEPIC prototype can support load current up to 185 A at 5 V-to-1 V voltage conversion with a maximum power density over 470 W/in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\text{3}$</tex-math></inline-formula> . Compared to commercial discrete inductors, the matrix coupled inductor has a 5.6 times smaller size and 8.5 times faster transient speed with similar current ripple and current rating. The experimental results validate the matrix coupling concept and the theoretical analysis, opening the possibilities toward wide adoption of ‘‘all-in-one-magnetics” in PWM topologies.

Inductor Design for Nonisolated Critical Soft Switching Converters Using Solid and Litz PCB and Wire Windings Leveraging Neural Network Model

High frequency and high efficiency inductor design method is proposed for the application of critical soft switching with large current ripple to improve the power density and efficiency of electrified energy conversion systems. Firstly for the theoretical design section, the core/coil size, number of turns, airgap, inductance are optimized to minimize the inductor losses. Secondly for the structural design section of coil, a 3D routing method of litz PCB winding is developed to reduce the AC copper losses. The strand number, trace width, thickness and layout of litz PCB are analyzed in detail. Different types of coil, including solid/litz types of PCB/wire windings, are compared and analyzed based on the high frequency copper loss reduction and space utilization. For the structural design section of core, E and I cores are optimized to reduce the volume and core losses. Specifically, E-E, E-I, I-I and E-Air types of core structures are designed and compared considering the core loss, volume reduction and airgap limitation for the stack of turns. Ten derived prototypes are built to benchmark with the commercial inductors. Power losses, temperature rise and cost are reduced by a factor of 10, 2.5 and 3 with the proposed core and coil structures.

Non-Linear Inductors Characterization in Real Operating Conditions for Power Density Optimization in SMPS

The exploitation of power inductors outside their linear region in switching converters can be achieved by raising the current until a decrease in the inductance can be noticed. This allows using a smaller magnetic core, increasing the power density of the converter. On the other hand, a detailed description of the magnetization curve including the temperature is required. Since this information is often not included in the inductor’s datasheets, this paper shows how to identify the behavior of an inductor when it is operated up to saturation and its temperature rises. In order to characterize the inductor in real operating conditions, a dedicated measurement rig was developed. It consists of a switching converter that encompasses the inductor under test and is controlled by a virtual instrument developed in LabVIEW. The characterization system was tested by retrieving the inductance and the magnetization curves vs. current for two commercial inductors at core temperatures up to 105 °C. The magnetic core was then characterized by the saturation current vs. inductance, obtaining an expression for the whole family of inductors sharing the same core. Finally, we experimentally analyzed the thermal transient of the inductors in operating conditions, confirming the fundamental role of the temperature in changing the current profiles and the core saturation condition.

Micron-sized iron oxide particles for both MRI cell tracking and magnetic fluid hyperthermia treatment

Iron oxide particles (IOP) are commonly used for Cellular Magnetic Resonance Imaging (MRI) and in combination with several treatments, like Magnetic Fluid Hyperthermia (MFH), due to the rise in temperature they provoke under an Alternating Magnetic Field (AMF). Micrometric IOP have a high sensitivity of detection. Nevertheless, little is known about their internalization processes or their potential heat power. Two micrometric commercial IOP (from Bangs Laboratories and Chemicell) were characterized by Transmission Electron Microscopy (TEM) and their endocytic pathways into glioma cells were analyzed. Their Specific Absorption Rate (SAR) and cytotoxicity were evaluated using a commercial AMF inductor. T2-weighted imaging was used to monitor tumor growth in vivo after MFH treatment in mice. The two micron-sized IOP had similar structures and r2 relaxivities (100 mM−1 s−1) but involved different endocytic pathways. Only ScreenMAG particles generated a significant rise in temperature following AMF (SAR = 113 W g−1 Fe). After 1 h of AMF exposure, 60% of ScreenMAG-labeled cells died. Translated to a glioma model, 89% of mice responded to the treatment with smaller tumor volume 42 days post-implantation. Micrometric particles were investigated from their characterization to their intracellular internalization pathways and applied in one in vivo cancer treatment, i.e. MFH.

99% Efficient 2.5-kW Four-Level Flying Capacitor Multilevel GaN Totem-Pole PFC

In this article, a high-efficiency and high-density 2.5 kW four-level flying capacitor multilevel (FCML) totem-pole bridgeless power-factor-correction (PFC) rectifier with 200 V GaN devices is analyzed, designed, and tested. This 2.5 kW four-level continuous conduction mode (CCM) GaN totem pole PFC operates with 360 kHz current ripple frequency which significantly reduces the inductor size while keeping a very low switching loss. This article compares the device loss of the four-level and two-level CCM GaN totem-pole PFC with the same ripple frequency (360 kHz) and shows that the four-level CCM GaN PFC has much less device loss. In addition, this article introduces the detailed design of a compact and low-profile matrix inductor based on the commercial composite inductors. This article also introduces the design of a high-density and low-loss flying capacitor. A 2.5 kW four-level FCML GaN totem-pole PFC prototype with 120 kHz switching frequency (360 kHz current ripple frequency) is developed and tested in this article. The tested peak efficiency is 99.25%. The PFC system power density is 104 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , without a heatsink and with forced air cooling.

Emergent electromagnetic induction in a helical-spin magnet.

An inductor, one of the most fundamental circuit elements in modern electronic devices, generates a voltage proportional to the time derivative of the input current1. Conventional inductors typically consist of a helical coil and induce a voltage as a counteraction to time-varying magnetic flux penetrating the coil, following Faraday's law of electromagnetic induction. The magnitude of this conventional inductance is proportional to the volume of the inductor's coil, which hinders the miniaturization of inductors2. Here, we demonstrate an inductance of quantum-mechanical origin3, generated by the emergent electric field induced by current-driven dynamics of spin helices in a magnet. In microscale rectangular magnetic devices with nanoscale spin helices, we observe a typical inductance as large as -400nanohenry, comparable in magnitude to that of a commercial inductor, but in a volume about a million times smaller. The observed inductance is enhanced by nonlinearity in current and shows non-monotonous frequency dependence, both of which result from the current-driven dynamics of the spin-helix structures. The magnitude of the inductance rapidly increases with decreasing device cross-section, in contrast to conventional inductors. Our findings may pave the way to microscale, simple-shaped inductors based on emergent electromagnetism related to the quantum-mechanical Berry phase.

Magnetic Sensor Based on Giant Magneto-Impedance in Commercial Inductors

Magnetic sensors have various applications in navigation, power distribution, robotics, factory automation, and medical diagnosis. The development of highly sensitive magnetic sensors usually requires complicated and costly fabrication process. Herein, we report giant magneto-impedance of 41036% in the commercially available ferrite core inductors. A magnetic field detection limit of 10 nT at 1 Hz has been obtained by directly measuring the impedance of the as-obtained inductor without any optimization. With a 100 pF capacitor in series connection with the inductor where lower impedance facilitates the measurement process, a limit of detection of 625 pT at 1 Hz has been obtained in the series <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RLC</i> resonator. These results can be understood in terms of the magnetic field-dependent self-resonance in the inductors which act as lumped <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RLC</i> resonators. Compared with the traditional electromagnetic induction sensing mode, the magneto-impedance sensing mode shows 5000 folds improvement in the magnetic field detection capability.

Design Methodology of a One-Turn Inductor With Significant DC and AC Fluxes—Demonstration in a Resonant Cross-Commutated Buck Converter

One-turn inductors must cope with high dc flux in conventional hard-switched point-of-load converters. These inductors need to handle both high dc and ac fluxes in soft-switched converters with high current ripple, for example, resonant cross-commutated buck (rccBuck) converters. In order to understand the losses associated with those fluxes, the winding loss in megahertz range is modeled in this paper through calculating the fringing field in the window area. The dc-biased core loss for resonant waveforms is modeled by the equivalent elliptical loop (EEL) method. According to the loss models, winding and core dimensions are designed systemically to minimize the total loss within a volume smaller than that of a commercial product. Four 1-turn inductors were fabricated for a 12 to 1.2 V rccBuck converter switched at 2 and 2.5 MHz. The designed one-turn inductors demonstrated 2.1% higher efficiency at 20 A output and 50% lower total magnetic volume than commercial inductors with similar inductances, on the same rccBuck converter.

A Power-Loss-Dependent Inductance Model for Ferrite-Core Power Inductors in Switch-Mode Power Supplies

This paper proposes a new modeling approach for ferrite-core (FC) power inductors used in switch-mode power supplies (SMPSs). In particular, a novel power-loss-dependent inductance behavioral model is proposed, whose parameters can be identified through a limited set of proper experimental measurements of inductor current and voltage. Unlike conventional thermal modeling approaches, which require information on core temperature, the proposed behavioral model relies only on easily measurable quantities. The model is also suitable for being implemented in circuit simulators. By comparing PSIM simulations and experimental measurements on a buck converter for commercial FC inductors, we show that the model allows a reliable prediction of the steady-state inductor current, under different SMPS working conditions.

Note: Development of a multichannel magnetic probe array for magnetohydrodynamic activity studies in Sino-United Spherical Tokamak.

A 30-channel movable magnetic probe radial array measuring the poloidal magnetic field's time derivative Ḃθ has been developed and installed on the Sino-United Spherical Tokamak to investigate the magnetohydrodynamic (MHD) activities in ohmic discharges. The probe array consists of thirty identical commercial chip inductors mounted on a slim printed circuit board and shielded by a customized quartz tube of 14 mm in outer diameter. With the application of instrumentation amplifiers, the system exhibits a good signal to noise ratio and the measured vertical field spatial distribution agrees well with the simulation result. The measured spatial and temporal distribution of Ḃθ during the MHD activities exhibits a clear phase reversal layer, which is a direct proof of tearing mode and provides a reliable indication of the magnetic island chain position.

Modeling and analysis of fractional order DC-DC converter

Due to the non-idealities of commercial inductors, the demand for a better model that accurately describe their dynamic response is elevated. So, the fractional order models of Buck, Boost and Buck-Boost DC-DC converters are presented in this paper. The detailed analysis is made for the two most common modes of converter operation: Continuous Conduction Mode (CCM) and Discontinuous Conduction Mode (DCM). Closed form time domain expressions are derived for inductor currents, voltage gain, average current, conduction time and power efficiency where the effect of the fractional order inductor is found to be strongly present. For example, the peak inductor current at steady state increases with decreasing the inductor order. Advanced Design Systems (ADS) circuit simulations are used to verify the derived formulas, where the fractional order inductor is simulated using Valsa Constant Phase Element (CPE) approximation and Generalized Impedance Converter (GIC). Different simulation results are introduced with good matching to the theoretical formulas for the three DC-DC converter topologies under different fractional orders. A comprehensive comparison with the recently published literature is presented to show the advantages and disadvantages of each approach.

Design and Implementation of a Test-Bench for Efficiency Measurement of Domestic Induction Heating Appliances

The operation of a domestic induction cooktop is based on the wireless energy transfer from the inductor to the pot. In such systems, the induction efficiency is defined as the ratio between the power delivered to the pot and the consumed power from the supplying converter. The non-transferred power is dissipated in the inductor, raising its temperature. Most efficiency-measuring methods are based on measuring the effective power (pot) and the total power (converter output). While the converter output power is directly measurable, the measurement of the power dissipation in the pot is usually a cause of inaccuracy. In this work, an alternative method to measure the system’s efficiency is proposed and implemented. The method is based on a pot with a reversible base to which the inductor is attached. In the standard configuration, the inductor is placed below the pot in such a way that the delivered power is used to boil water, and the power losses are dissipated to the air. When the pot base is flipped, the inductor is immersed into the water. In this case the losses in the inductor also contribute to heating up and boiling the water. The induction efficiency is calculated from the boiling rates in both configurations. A commercial inductor was tested under real working conditions with consistent results.

SIM.EM-K3 Key comparison of 10 mH inductance standards at 1 kHz

A key comparison of 10 mH inductance standards at 1 kHz has been carried out with the participation of seven National Metrology Institutes of the Inter-American Metrology System, within the frame of the International Committee for Weights and Measures Mutual Recognition Arrangement (MRA), which was piloted by CENAM, Mexico. Three previously characterized commercial inductors, contained in individual enclosures with controlled temperature were used as traveling standards. This document presents the results and technical details of the comparison.Main textTo reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Alternative control of Chalara paradoxa, causal agent of black rot of pineapple by plant extract of Mormodica charantia

Black rot of pineapple caused by the fungus Chalara paradoxa is considered an aggressive and difficult disease to control. The use of natural products has been studied with the goal to incorporate them into integrated pest management and reduce the use of agrochemicals. Plant extracts have shown satisfactory results in controlling postharvest diseases by providing fungitoxic action and inducing plant resistance. The aim of this study was to evaluate C. paradoxa severity by the application of plant extract of Mormodica charantia, determinate effect of the plant extract on post-harvest quality, and induction of enzymes linked to host resistance induction. The following treatments were studied: plant extract of bitter melon at concentrations of 10, 100, 500 and 1000 ppm, the commercial products acibenzolar-S–Methyl and fungicide (thiabendazole) in the dosages recommended by the manufacturers, and distilled water as the control, with five replications and two plants per plot. The extract of M. charantia reduced the severity of black rot caused by C. paradoxa, compared to the control treatment, showing similar efficacy to the treatments with commercial inductor Acibenzolar-S-methyl and the fungicide. The enzymatic analysis showed increase of the peroxidase by the use of the bitter melon extract along the evaluation period. The enzymes polyphenol oxidase and phenylalanine ammonia lyase showed greater activity by treatment with M. charantia extract at 500 ppm. It was observed that the plant extract did not affect most of the variables analyzed related to postharvest quality of treated fruits. The use of the extract reduced the fruit weight loss, being a positive aspect under the studied conditions.

Design and calibration of high-frequency magnetic probes for the SUNIST spherical tokamak.

A new high-frequency magnetic diagnostic system is designed, installed, and calibrated in the Sino-United Spherical Tokamak (SUNIST) to investigate Alfvén waves (AWs). The system consists of a fixed toroidal array and a movable radial array of high-frequency magnetic probes (HFMPs) with 21 and 60 probes, respectively. Based on the method of vacuum enameled wire wound on ceramic bobbins, the fixed toroidal array is located as near as possible to the plasma and carefully shielded to reduce the attenuation of high-frequency magnetic field. Meanwhile, by using the technology of commercial chip inductors mounted on printed circuit boards, the movable radial array is inserted into a thin quartz tube that allows positioning along radial direction. A Helmholtz coil is utilized to calibrate the effective areas as well as the frequency response of each HFMP. The calibration results are consistent with the calculated results of an equivalent probe-and-cable circuit model. High-frequency magnetic signals related to AW are detected with these HFMPs. These HFMPs are expected to play a key role in analyzing Alfvén eigenmodes excited by AW antenna in the SUNIST.

Magnetic diagnostic suite of the C-2 field-reversed configuration experiment confinement vessel

Magnetic measurements are a fundamental part of determining the size and shape of field-reversed configuration (FRC) plasmas in the C-2 device. The magnetic probe suite consists of 44 in-vessel and ex-vessel probes constructed using various technologies: ultra-high vacuum compatible mineral-insulated cable, nested triple axis coils hand-wound on ceramic bobbins, and commercial chip inductors mounted on printed circuit boards. Together, these probes measure the three-dimensional excluded flux profile of the FRC, which approximates the shape of the separatrix between the confined plasma volume and the scrape-off layer. High accuracy is achieved by using the extensive probe measurements to compensate for non-ideal effects such as flux leakage through the vacuum vessel and bulk motion of the FRC towards the wall. A subset of the probes is also used as a set of Mirnov arrays that provide sensitive detection of perturbations and oscillations of the FRC.

Improving Light and Intermediate Load Efficiencies of Buck Converters With Planar Nonlinear Inductors and Variable On Time Control

It has been addressed that light and intermediate load efficiencies of high-frequency buck converters in portable electronic devices are very important for extending lifetime of batteries. This paper proposes to utilize wide range, gradually changeable nonlinear inductors with variable on time control to improve light and intermediate load efficiencies. Integrated multipermeability magnetic cores are advanced to realize the nonlinear inductors. And based on the nonlinear inductors, variable on-time control scheme is proposed to reduce the frequency-dependent loss. The theoretical loss reduction is demonstrated by comparing loss of a converter employing conventional constant on-time control scheme and employing the proposed control scheme. A two-permeability nonlinear inductor prototype is fabricated. Its inductance could vary from 0.13 μH at full load to 0.66 μH at no load. The nonlinear inductor is employed in a 12 V input, 1.6 V output buck converter to evaluate its performance. With the purpose of comparison, other two commercial chip inductors are also tested in the converter. The results show the nonlinear inductor with variable on time control could effectively improve efficiencies of light and intermediate load conditions as theoretical analysis does.