Core Inductor Research Articles

Improved Method for Measuring Power Losses in the Inductor Core

This article considers the problem of measuring power losses in the ferrite core contained in the inductor. The new method of measuring these losses is proposed. This method uses thermal properties of the ferrite core. The concept of the developed measuring method and the measurement setup that enables implementation of this method are described. The advantage of the proposed method is a simple setup which does not require expensive instruments. Factors affecting the measurement standard uncertainty of the new method are discussed. Dependence of power losses in a selected ferrite core is measured using the new method and the classic literature method. The obtained results of measurements are compared and discussed. The way of estimating values of parameters occurring in the Steinmetz model based on the obtained measurement results is also indicated.

Effects of Current Distortion on DC Link Inductor and Capacitor Lifetime in Variable Frequency Drive Connected to Grid With Active Harmonic Filter

In this research article, new investigation and comprehensive analysis is done on the current distortion effects of dc link inductor and capacitor in variable frequency drive (VFD). Shunt active filter (SAF) is the most prominent solution for harmonic mitigation at the point of common coupling in the power distribution system. However, SAF connectivity reduces the grid impedance ( ZTH ) seen at the input of six pulse diode bridge rectifier in VFD. Commutation behavior of the diode rectifier is changed due to this grid impedance variation resulting in increased harmonic current distortion (THD i ) at the input of the rectifier bridge. This effect increases the ripple current of dc capacitor, dc link inductor losses, and diode rectifier conduction losses. This study investigates the drive dc link inductor and capacitor lifetime reduction with and without SAF, under various grid operating conditions of 3% voltage unbalance and 8% predistortion. Moreover, the high frequency (2–9 kHz) impact on dc link inductor core and copper losses is detailed. A 250 kW VFD with SAF of 180 A capacity is used for test measurement under various operating conditions. Current distortion effects are analyzed, and test results are compared with MATLAB simulation. Grid impedance variation due to SAF and its effect on the reliability of the VFD front-end components were not covered in detail in any of the earlier research. Lifetime estimation of dc link inductor and capacitor due to grid impedance variation is one among the significant outcomes of this investigation.

Low Phase Noise and Wide-Range Class-C VCO Using Auto-Adaptive Bias Technique

This paper proposes a new structure of 24-GHz class-C voltage-controlled oscillator (VCO) using an auto-adaptive bias technique. The VCO in this paper uses a digitally controlled circuit to eliminate the possibility of start-up failure that a class-C structure can have and has low phase noise and a wide frequency range. To expand the frequency tuning range, a 3-bit cap-bank is used and a triple-coupled transformer is used as the core inductor. The proposed class-C VCO implements a 65-nm RF CMOS process. It has a phase noise performance of −105 dBc/Hz or less at 1-MHz offset frequency and the output frequency range is from 22.8 GHz to 27.3 GHz, which consumes 8.3–10.6 mW of power. The figure-of-merit with tuning range (FoMT) of this design reached 191.1 dBc/Hz.

Magnetic Comparison Between Experimental Flake Powder and Spherical Powder for Inductor Cores at High Frequency

This article is the first work to carefully investigate the characteristics of iron loss per weight and relative permeability between the flake and spherical powders with a sinusoidal excitation up to a high frequency of 3.5 MHz in experiments using three separate measurement systems. The composition of the considered powder samples contains 0.001 wt% C, 0.012 wt% Si, 0.09 wt% Mn, 0.0004 wt% P, 0.008 wt% S, and 0.06 wt% O. The flake particle has the preferred orientation that the easy axes are normal to the platelet face, and the water atomized iron powder was processed with ball milling with the lubrication. Key objectives of the utilization of the three independent measurement systems with different specialized equipment and probes are to cross-check and overcome unexpected measurement errors of the related devices in use for validating measured results thoroughly. Experimental results demonstrate the much better performances on the iron loss per weight and relative permeability of the flake powder than that of the spherical powder at high frequencies. Physics-based explanations for the measured results are also presented. Furthermore, two estimation functions based on a six-parameter Steinmetz equation for the measured iron loss of the powders are developed by using MATLAB.

Detection and Identification of Power Switch Failures Using Discrete Fourier Transform for DC–DC Flying Capacitor Buck Converters

Prompt detection of power switch failure is crucial for fault-tolerant operation of multilevel converters. This article presents a new technique of detecting, identifying, and locating a device fault in a multilevel dc-dc flying capacitor (FC) buck converter (FCBC). This is realized by continuously analyzing the magnetic component (inductor or transformer) voltage harmonics for failure detection and subsequently identifying failure type and location with a look up table method. The harmonics analysis is performed by the existing FPGA controller using discrete Fourier transform (DFT). This new approach uses an auxiliary winding in the existing inductor core without adding any new hardware and can identify the location and fault type with good accuracy and speed. The experimental results validate the proposed concept on a three-level GaN-based FCBC prototype.

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.

Fuzzy FDI System for Flyback Converters

In this article, the design of a fault detection and isolation (FDI) system for a flyback converter, based on a fuzzy unknown input observer, is presented. The proposed FDI system aims to detect the saturation in the inductor core as a fault, considering the current increment can cause an avalanche effect provoking a failure in the system. A Takagi–Sugeno model of the flyback converter is used. The observer's convergence and the stability of the fault diagnosis system are guaranteed by Lyapunov's theory and the estimation error used to determine the necessary LMIs. A comparison of different FDI methods applied in fuzzy systems is performed in order to select the most robust system, capable of estimating the current in the system even in the presence of external disturbances. The system validation is performed in both, simulation and online implementation, using experimental data.

Determination of the roll-off value in the air-gapped inductor of a DC-DC boost converter circuit with FEA parametric simulations

The electromagnetic behavior of the inductors used as passive circuit elements directly affects the electrical and mechanical performance of the power electronics circuits. In general, when using inductor core structures with or without airgap in the classical design process, the dynamic effects of the inductance value are not considered in the design stage. However, the inductance value may change during the operation of the circuit due to electrical and magnetic parameters of the inductor, and this change is called roll-off value of the inductance. In this study, the roll-off value has been measured graphically and numerically based on mechanical parameters (such as air-gap length) and electrical parameters (such as winding turns and DC current amplitude) for an air-gapped ferrite E core designed with FEA software. Thus, not only the inductance value calculated in the design stage but also the roll-off value during the operation of the circuit has been reported with the parametric simulation studies.

A Nonlinear Behavioral Ferrite-Core Inductance Model Able to Reproduce Thermal Transients in Switch-Mode Power Supplies

More compact Switch-Mode Power Supplies (SMPSs) satisfying typical design specifications can be obtained by exploiting ferrite core inductors working in partial saturation. In this case, the inductance is no longer a constant parameter, since it exhibits a sharp drop as the inductor current increases. A behavioral model was recently proposed, which provides the inductance at steady state as a function of easy-to-measure quantities. Here, a generalization of this model is presented, in order to capture the inductance behavior also during thermal transients. The model fitting to experimental measurements relies on an iterative optimization procedure grounding on accurate SMPS simulations based on shooting analysis. The model validation exploits the envelope analysis method, particularly suitable for slow-fast systems. The obtained fitting results show a good agreement with experimental data both in transient conditions (after sudden variation of the SMPS operating condition) and at steady state. Finally, by partially re-identifying the model based on data measured when the inductor is cooled with a fan, we still obtain a good matching between model and experimental data.

Effect of magnetic field environment on the performance of 3/2 solenoid valve

• 3/2 solenoid valve functionality has been checked under external magnetic field environment. • External magnetic field limit has been defined below which 3/2 solenoid valve functions well. • Magnetic shielding of the 3/2 solenoid valve has been proposed. ITER, an experimental fusion reactor uses solenoid valves to close cryogenic control valves instantly in case of any incidental event in the ITER cryogenic system takes place. Many of these solenoid valves are functioning with the magnetic field environment of the order of ∼25 m T. Since a solenoid valves is an electrically activated valve, presence of the environment magnetic field can lead to partial or non-closing of the valve. In this paper, the effect of magnetic field environment on the performance of 3/2 solenoid valves through simulation and experiment is studied. The variable external magnetic field is generated by supplying variable power from Switched Mode Power Supply (SMPS) to the magnetic coil and magnetic field readings are recorded with a tesla meter. The validation of the magnetic field profile of the magnetic coil is done by comparing the E-mag analysis simulation performed on ANSYS® platform and the experimental results. An experiment setup, inside ITER-India cryogenic laboratory, has been assembled to see the functionality of the 3/2 solenoid valve in the presence of an external magnetic field. A 3/2 solenoid valve is placed in the external magnetic field which has been generated with the help of an air core inductor magnetic coil. The external magnetic field from the coil is varied from 10 m T to 35 m T with the help of a variable power supply and checked the functionality of the solenoid valve in different orientation and different external magnetic fields strengths. The outcome of the study shows that the 3/2 solenoid valve stopped functioning over the external magnetic field strength of 14.29 m T. The paper also concludes the requirement of the magnetic shielding and correct orientation of the solenoid valves to be installed in order to nullify the effect of external magnetic field on the functionality of the 3/2 solenoid valves.

Investigation of physical properties of synthesized Zr doped Ni–Zn ferrites

The samples of Ni0.5-0.5xZn0.5ZrxFe2–xO4 (x = 0.0–0.4, step 0.1) have been prepared by co-precipitation method and then sintered at 1000 °C. The respective characterization has been performed by using XRD, FT-IR and Raman spectroscopy. In particular, the agglomeration and homogeneity of the samples have been investigated by SEM, EDX and element mapping images. The Rietveld refined XRD results of the samples carried out by using MAUD software, have revealed the existence of a cubic spinel ferrite phase beside two other phases ZnZrO3 and ZnO which have growing volume fraction with increasing Zr4+ content. The variation of lattice constant of the ferrite samples has been discussed according to the site preference of the cations and cation distribution CD. The results obtained from the FT-IR spectra and M−H hysteresis loops confirm the validity of the suggested CD which based on Rietveld refined XRD results. The S-shaped of the M−H curves of the samples with high Ms and low Mr and Hc values, in addition to the enhancement of the dielectric properties σʹac, εʹ and tanδ, make these ferrites suitable for soft magnetic devises used in high frequency applications such as an inductor core in switching mode power supply.

Matrix Inductor With DC-Bias Effect Reduction Capability for GaN-Based DC-DC Boost Converter

In this brief, a 400-W Gallium Nitride device based DC-DC boost converter with a four phase matrix inductor is proposed. It is well-known that there is a significant influence of the DC bias on inductor core losses and the simplest solution is to employ multiphase structures. However, the size of the converter will also increase as the number of phases increases. Therefore, in order to achieve both high efficiency and high power density, a matrix inductor is proposed for four phases boost converter. The proposed matrix inductor retains the flux sharing advantages of conventional inductors with E-cores and thus greatly increases the power density and utilization rate, by integrating the inductors through flux cancellation. Therefore, both the size and the core loss are reduced when compared with four conventional inductors. Moreover, since the four phases are operated in parallel, the phase error, which is a critical problem in the interleaved structure, may not affect the proposed converter, removing the current balance issue. Critical operation mode is utilized to achieve zero-voltage switching (ZVS) for all switches. Finally, the proposed four phase DC-DC boost converter and matrix inductor is built and tested to verify its feasibility. The peak and CEC efficiency is tested to be 99.3% and 99.1%, respectively.

Nanoscale structural evaluation of 0-3 magnetic nanocomposites fabricated by electro-infiltration

Magnetic nanocomposites with 0-3 connectivity, whereby a 0D magnetic nanoparticle phase is embedded into a 3D magnetic metal matrix phase, have gained increased interest for use in applications ranging from integrated power inductor cores to exchange-spring magnets. The electro-infiltration process, in which a metal phase is electroplated through a nanoparticle film phase, is an inexpensive approach compatible with semiconductor fabrication methods for the formation of these nanocomposites. Past demonstrations of electro-infiltrated nanocomposites have relied on scanning electron microscopy and energy dispersive x-ray spectroscopy to evaluate the 0-3 composite structure. However, a detailed investigation of the boundary between the particle and metal matrix phases cannot be performed with these tools, and it is unknown whether the particle/matrix interfaces are dense and void-free. This detail is critical, as the presence of even nanoscale voids would affect any potential magnetic exchange coupling and hence the overall electromagnetic properties of the material. This work seeks to explore the phase boundary of 0-3 magnetic nanocomposite fabricated by electro-infiltration by using scanning transmission electron microscopy and energy-dispersive x-ray spectroscopy to analyze the nanostructure of two different composites—a nickel/iron-oxide composite and a permalloy/iron-oxide composite. High-resolution imaging indicates that the interface between the particle phase and matrix phase is dense and void-free. These results will help guide future studies on the design and implementation of these magnetic nanocomposites for end applications.

Grain boundary engineering of power inductor cores for MHz applications

In this article we present the latest trends in processing, composition, theory, and utility of spinel ferrites for use as power inductor cores for a wide range of applications including power generation, conversion, and conditioning at MHz frequencies. Furthermore, it is a principle goal of this article to examine state of the art approaches and innovative methodologies to engineer grain boundary regions in composition, structure, and electrical and magnetic properties that allow spinel ferrites to operate at frequencies well above the state of technology (i.e., f > 1 MHz) with low core power loss while concomitantly maintaining high efficiency, high permeability and saturation induction.

Magnetic properties of hydrothermally synthesized Ba1–xSrxFe12O19 (x = 0.0–0.8) nanomaterials

Barium strontium hexaferrite (BSFO) nanomaterial compositions were prepared using hydrothermal technique. The phase identification of BSFO revealed the hexagonal structure. The field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM) techniques were used to study the surface morphology of BSFO nanostructures. TEM study showed the presence of distorted spheres like nanostructures of size 7–28 nm. Furthermore, the presence of metal oxides (Ba–O, Sr–O, and Fe–O) and functional groups were detected using Fourier transform infrared spectra (FTIR). Subsequently, magnetic nature of BSFO was confirmed using magnetization–magnetic field (M–H) and magnetic permeability–temperature (μi–T) plots. The μi–T plots suggested the enhancement of Tc from 703 K–753 K as a function of Sr-content (x). In addition, the variation of μi, magnetic loss (μ″) as well as relative magnetic loss factor (rlf: tanδ/μi) with respect to the frequency was performed for probable transformer and inductor core device applications.

Automated tool for 3D planar magnetic temperature modelling: application to EE and E/PLT core‐based components

Thermal performance of power converters is a key issue for the power integration. Temperatures inside the active and passive devices can be determined using thermal models. Modelling the temperature distribution of high-frequency magnetic components is quite complex due to the diversity of their geometries and used materials. This study presents a thermal modelling method based on lumped elements thermal network model, applied to planar magnetic components made of double planar E shaped cores (EE) and planar E core combined with plate one (E/PLT). The 3D model is automatically generated from the component's geometry. The computation enables to obtain 3D temperature distribution inside windings and core of planar transformers or inductors, in steady state or in transient case. This study details the proposed modelling method as well as the automated tool including the problem definition and the solving process. The obtained temperature distributions are compared with finite-element simulation results and measurements on different planar transformers.

Ripple reduction of DC current sources in three-level CE-CSI circuits using single core inductors

Current source inverter operates producing a predetermine ac current from dc current inputs. In practical, ac current waveform will have harmonic contents appeared in the frequency spectrum. Some factors may affect these harmonics contents such as voltage drops occurred in the power devices of controlled power switches, and voltage drops caused by the resistances of power inductor and conductor. The dc current sources usually generated by using power inductors connected to dc power source. Another factor that can escalate the harmonics is the current ripples of dc current sources. To regulate the dc current sources flowing in the inductor, controlled switches and current controller are required. This paper proposed a novel strategy to minimized current ripple of inductors by applying single core inductors. Some test results of computer simulation were presented in the paper.

Study on a Three-Phase Inductor Based on Equal Magnetic Flux Path

Owing to a uniform air-gap distribution of the magnetic powder materials, it is found that the conventional structure of a three-phase inductor made of magnetic powder cores will cause the three-phase magnetic flux paths to be unequal, thereby making the three-phase input voltages of a pulsewidth modulation (PWM) rectifier imbalanced. This paper presents a novel magnetic powder core structure applicable to a three-phase inductor for PWM rectifier. An equal magnetic flux path for the inductor core is designed to solve the imbalance problem of three-phase voltages. The proposed design is based on measuring the maximum flux density and the inductance values, modeled with electromagnetic simulation of a three-dimensional finite-element method. Simulation and experimental results of the proposed design show that it reduces the three-phase voltage imbalance to less than 3%. Furthermore, the unit volume of the three-phase inductor is reduced by 34% and 23%, and the efficiency is increased by 1.2% and 0.9%, compared to those of a conventional three-phase silicon-steel core inductor and three single-phase inductors, respectively.

Current Ripple Analysis of Three-Phase Vienna Rectifier Considering Inductance Variation of Powder Core Inductor

Three-phase three-level Vienna rectifier using powder core inductors has been widely used for power conversion. Inductor current ripple analysis of rectifier is essential for pulsewidth modulation method optimization, loss estimation, filter inductor design, etc. However, it is hard to analyze the current ripple of Vienna rectifier. Moreover, the inductance of powder core inductor varies with sinusoidal input current, which makes it even more complicated. In this article, a current ripple analysis method for three-phase Vienna rectifier considering the inductance variation of the powder core inductor is presented. The current ripple distribution of Vienna rectifier with constant inductance is studied based on the space vector approach. To determine the current ripple of Vienna rectifier with powder core inductors, an inductor voltage calculation method considering inductance variation is proposed. The compensation voltage is introduced to compensate for the effect of inductance variation on current ripple. Then, the analytical expression of the peak-to-peak current ripple with powder core inductor is derived. In addition, a design method of powder core inductor is proposed based on the analytical expression. At last, the correctness of the analytical result is verified by both simulation and experiment.

Magnetic Properties of Manganese-Zinc Soft Ferrite Ceramic for High Frequency Applications.

A soft magnetic MnZn-type ferrite is considered for high frequency applications. First, the morphological, structural, and chemical composition of the material are presented and discussed. Subsequently, by using a vibrating sample magnetometer (VSM), the hysteresis loops are recorded. The open magnetic circuit measurements are corrected by employing demagnetization factors, and by taking into consideration the local magnetic susceptibility. Finally, the hysteresis losses are estimated by the Steinmetz approach, and the results are compared with available commercial information provided by selected MnZn ferrite manufacturers. Such materials are representative in planar inductor and transformer cores due to their typically low losses at high frequency, i.e., up to several MHz, in low-to-medium power applications and providing high efficiency of up to 97%–99%.