Showing papers on "Magnetic core published in 2013"

Coil Design and Shielding Methods for a Magnetic Resonant Wireless Power Transfer System

Abstract: In this paper, we introduce the basic principles of wireless power transfer using magnetic field resonance and describe techniques for the design of a resonant magnetic coil, the formation of a magnetic field distribution, and electromagnetic field (EMF) noise suppression methods. The experimental results of wireless power transfer systems in consumer electronics applications are discussed in terms of issues related to their efficiency and EMF noise. Furthermore, we present a passive shielding method and a magnetic field cancellation method using a reactive resonant current loop and the utilization of these methods in an online electric vehicle (OLEV) system, in which an OLEV green transportation bus system absorbs wireless power from power cables underneath the road surface with only a minimal battery capacity.

Robust antiferromagnetic coupling in hard-soft bi-magnetic core/shell nanoparticles

Abstract: The growing miniaturization demand of magnetic devices is fuelling the recent interest in bi-magnetic nanoparticles as ultimate small components. One of the main goals has been to reproduce practical magnetic properties observed so far in layered systems. In this context, although useful effects such as exchange bias or spring magnets have been demonstrated in core/shell nanoparticles, other interesting key properties for devices remain elusive. Here we show a robust antiferromagnetic (AFM) coupling in core/shell nanoparticles which, in turn, leads to the foremost elucidation of positive exchange bias in bi-magnetic hard-soft systems and the remarkable regulation of the resonance field and amplitude. The AFM coupling in iron oxide-manganese oxide based, soft/hard and hard/soft, core/shell nanoparticles is demonstrated by magnetometry, ferromagnetic resonance and X-ray magnetic circular dichroism. Monte Carlo simulations prove the consistency of the AFM coupling. This unique coupling could give rise to more advanced applications of bi-magnetic core/shell nanoparticles.

A 2.5D Integrated Voltage Regulator Using Coupled-Magnetic-Core Inductors on Silicon Interposer

Abstract: An integrated voltage regulator (IVR) is presented that uses custom fabricated thin-film magnetic power inductors. The inductors are fabricated on a silicon interposer and integrated with a multi-phase buck converter IC by 2.5D chip stacking. Several inductor design variations have been fabricated and tested. The best performance has been achieved with a set of eight coupled inductors that each occupies 0.245 mm2 and provides 12.5 nH with 270 mΩ DC. With early inductor prototypes, the IVR efficiency for a 1.8 V:1.0 V conversion ratio peaks at 71% with FEOL current density of 10.8 A/mm2 and inductor current density of 1.53 A/mm2. At maximum load current, 69% conversion efficiency and 1.8 V:1.2 V conversion ratio the FEOL current density reaches 22.6 A/mm2 and inductor current density reaches 3.21 A/mm2.

Method For Making Magnetic Components With M-Phase Coupling, And Related Inductor Structures

Abstract: Methods and structures for constructing a magnetic core of a coupled inductor. The method provides for constructing N-phase coupled inductors as both single and scalable magnetic structures, where N is an integer greater than 1. The method additionally describes how such a construction of the magnetic core may enhance the benefits of using the scalable N-phase coupled inductor. The first and second magnetic cores may be formed into shapes that, when coupled together, may form a single scalable magnetic core. For example, the cores can be fashioned into shapes such as a U, an I, an H, a ring, a rectangle, and a comb, that cooperatively form the single magnetic core.

Integrating Magnetics for On-Chip Power: A Perspective

Abstract: Integration of efficient power converters requires technology for efficient, high-power on-chip inductors and transformers. Increases in switching frequency, facilitated by advances in circuit designs and silicon or wide-bandgap semiconductors, can enable miniaturization, but only if the magnetics technology works well at the higher frequencies. Technologies, geometries, and scaling of air-core and magnetic-core inductors and transformers are examined, and their potential for integration is discussed. Air-core inductors can use simpler fabrication, and increasing frequency can always be used to decrease their size, but magnetic cores can decrease the required thickness without requiring as high a frequency.

CCTT-Core Split-Winding Integrated Magnetic for High-Power DC–DC Converters

Abstract: A novel CCTT-core split-winding integrated magnetic (IM) structure is presented in this paper. The IM device is optimized for use in high-power dc–dc converters. The IM structure uses a split-winding configuration which allows for the reduction of external leakage inductance, which is a problem for many IM designs. Magnetic poles are incorporated to help shape and contain the leakage flux within the core window. Low-cost and low-power loss ferrite is used which results in a very efficient design. An IM reluctance model is developed which uses fringing equations to develop a more accurate design. An IM design algorithm is developed and implemented in Mathematica for design and optimization. FEA and experimental results from a 72 kW, (155-V dc, 465-A dc input, and 420-V dc output) prototype validate the new IM concept. The 72 kW CCTT- core IM was shown to be 99.7% efficient at full load.

Planar coil element

Abstract: In a planar coil element, the quantitative ratio of inclined particles to total particles of a first metal magnetic powder contained in a metal magnetic powder-containing resin provided in a through hole of a coil unit is higher than the quantitative ratio of inclined particles to total particles of the first metal magnetic powder contained in the metal magnetic powder-containing resin provided in other than the through hole, and many of particles of the first metal magnetic powder in the magnetic core are inclined particles whose major axes are inclined with respect to the thickness direction and the planar direction of a substrate. Therefore, the planar coil element has improved strength as compared to a planar coil element shown in FIG. 9A and has improved magnetic permeability as compared to a planar coil element shown in FIG. 9B.

Magnetic head, magnetic recording method and apparatus for controlling magnetic head with spin torque oscillator in a disk drive

Abstract: A microwave assisted magnetic recording head includes a recording magnetic pole unit that produces a recording field for writing to a perpendicular magnetic recording medium, and a high-frequency magnetic field oscillator that produces a high-frequency magnetic field. The recording magnetic pole unit includes a magnetic core with a write gap portion at which a main recording field component is concentrated, and the high-frequency magnetic field oscillator is disposed in the write gap.

Experimental Analysis of the Magnetic Flux Characteristics of Saturated Core Fault Current Limiters

Abstract: A fault current limiter (FCL) is a device that is designed to reduce the impact of fault currents on electricity networks and increase the availability of such networks to consumers. One particular FCL technology that is currently attracting worldwide attention, from both researchers and commercial engineering companies, is the saturated core FCL. This device utilizes the change in permeability between the saturated and unsaturated states of a magnetic core to provide both low steady state losses and effective fault current limiting. Typically the core is saturated using an electromagnetic coil, which can be either superconducting or non-superconducting. Although there have been several studies on the electrical characteristics of this device, the transient magnetic behavior has been largely overlooked. In this paper the magnetic flux characteristics of saturated core FCLs are experimentally analyzed. The study includes the magnetic behavior during both the initial biasing of the cores and during transient fault conditions. The influence of FCL topology and alternative low-cost core materials, on the flux characteristics and overall device performance, is also discussed.

High Frequency Magnetic Core Loss Study

Abstract: The core used to build power inductors and transformers are soft magnetic materials. When there is alternating external field, the magnetic moments rotate and consume energy, which is the core loss. The core loss depends on the AC flux frequency, amplitude, waveform, DC bias and temperature. These dependences are nonlinear and difficult to predict. How to measure, model and analyze the core loss is a challenge for decades. In this dissertation, two new core loss measurement methods are introduced first. These two methods use the reactive cancellation concept to reduce the sensitivity to phase discrepancy, which will destroy the accuracy in classic two-winding method for high frequency high quality factor sample measurements. By using the new measurement techniques the accuracy can be improved by several orders. The first is for sinusoidal waveforms, and the second is for non-sinusoidal wave. The new methods enable high frequency core loss characterization capability, which will help scientists and engineers on material research and inductor/transformer design. Measurement examples, considerations and error analysis are demonstrated and discussed in detail. With the measurement techniques, the core loss under rectangular AC voltage and DC bias current are investigated. A new core loss model named rectangular extension Steinmetz equation (RESE) is proposed based on the measurement results. The new iii model is shown to be more accurate than the existing core loss models. Several commercially available MnZn ferrites are characterized and modeled. Other than conventional MnZn ferrite materials, three commercial LTCC ferrite materials are characterized for integrated power supply applications. Based on characterized properties of these LTCCs, a group of new LTCC ferrites are fabricated and tested. The new LTCC is fabricated by laminating commercial LTCC tapes and co-firing. The new LTCC is demonstrated to have over 50% more inductance over the commercial LTCC materials. This work indicates that the power electronics engineers should work with material engineers to get the optimum material for a given application. In the last part, the core loss of the partially saturated lateral flux planar inductor is analyzed. The challenge of the analysis is the complexity of the distribution of bias field and flux density in a highly biased planar inductor. Each point in the core is working at different excitation and bias condition, and the core loss density is very non-uniform. The proposed method combines the characterization tested in previous chapters and the commercial finite element tool. Experiments verified that the calculation errors are within about 10%. In conclusion, the research in this dissertation proposed a complete solution to measure, model and analyze the high frequency core loss. This solution will not only facilitate fundamental research on physics understanding and material innovation, but also development of power electronics and RF applications.

Microfabricated V-Groove Power Inductors Using Multilayer Co–Zr–O Thin Films for Very-High-Frequency DC–DC Converters

Abstract: V-groove microinductors are designed, fabricated, and tested for operation above 10 MHz. Multilayer nanogranular Co-Zr-O/ZrO2 magnetic thin films are used as the core material of these inductors, to improve the magnetic performance of the films deposited on the sidewalls of V-grooves and to control eddy-current loss in the core. Prototype V-groove inductors are fabricated in a Si substrate based on optimization results for 7 to 3.3-V, 1-A dc-dc buck converters. The inductors exhibit an inductance of 3.4 nH from 10 to 100 MHz, a dc resistance of 3.83 mΩ, and a quality factor of up to at least 50. The prototype inductors are a promising candidate for high-power-density high-efficiency dc-dc converters. The measured inductor performance indicates that they could be used to make a 7 to 3.3-V, 1-A converter exhibiting a power density of 2.5 W/mm2 and an efficiency of 86% at 100 MHz; or a power density of 0.36 W/mm2 and an efficiency of 91% at 11 MHz.

High-Bandwidth Low-Insertion Loss Solenoid Transformers Using FeCoB Multilayers

Abstract: High-bandwidth low-insertion loss solenoid transformers using a multilayered FeCoB magnetic core have been designed, modeled, fabricated, and characterized for high-frequency power conversion. Various transformer designs are compared in terms of inductance, resistance, quality factor, mutual coupling, and insertion loss. A mutual coupling coefficient of 0.9 up to 50 MHz is achieved for intertwined solenoid transformers with a patterned magnetic core.

Finite Element Analysis of Inductor Core Loss Under DC Bias Conditions

Abstract: Finite element analysis is a popular way to analyze magnetic core loss in complex core structures. However, accurate calculation of the inductor core loss under dc bias conditions is still a challenge, as magnetic properties such as permeability and core-loss density change when a dc premagnetization is present, especially for saturable cores. This paper proposes a method that can accurately calculate the inductor's loss when it works under dc bias current conditions. The method utilizes an effective and simple material model built by curve-fitting the measurement data. To prove the accuracy of this approach, planar inductors built with low-temperature co-fired ceramic ferrite are simulated, and the calculated core losses are experimentally verified.

Plasma reactor and plasma ignition method using same

Abstract: One aspect of the present invention relates to a plasma reactor and a plasma ignition method using the same. The plasma reactor of the present invention comprises: a magnetic core having a primary winding of a transformer; an alternative current power supply source for supplying alternative current power to the primary winding of the transformer wound around a magnetic core; a plasma chamber body provided with the magnetic core and enables induction of electromotive force by directly inducing a voltage through the magnetic core; and a floating chamber connected to the plasma chamber body through an insulating region and receiving the induced electromotive force, and a large voltage difference is generated between the plasma chamber body and the floating chamber according to a phase change of the alternative current power supplied from the alternative current power supply source so as to enable easy plasma ignition and to supply the plasma to a process chamber. The plasma reactor and the plasma ignition method using the same of the present invention can separate a floating region and a region provided with a magnetic core, and enable the plasma discharge using a low voltage in comparison with a voltage necessary for an existing ignition using a large voltage difference according to a potential difference of the alternative current power. Thus, the re-ignition due to the failure of the plasma ignition is not required and the damage of the plasma reactor due to arc discharge can be minimized. In addition, the ignition for the plasma discharge can be easily implemented in a low-pressure state of a gas flow when supplying the same voltage in comparison with known devices. Furthermore, the ignition for the plasma discharge can be easily implemented at a low temperature when supplying the same voltage in comparison with known devices.

Prototyping a Ferrofluid-Cooled Transformer

Abstract: This paper presents the work conducted on prototyping a step-up/step-down, single-phased, low-power, and medium-voltage electrical transformer cooled by a fluid with colloidal magnetic nanoparticles. The magnetic and fluid dynamic properties and the heat capacities of the ferrofluid (magnetic nanofluid) and that of the regular coolant (UTR-40 transformer oil) were experimentally determined and comparatively evaluated. Mathematical models for the electromagnetic field and the heat transfer were defined and numerically solved to assess the capacity of the transformer to sustain the working conditions. The simulation results were utilized to improve the design of a prototype, where the UTR-40 regular coolant is replaced by ferrofluid. The numerical simulation results and the experiments evidence the superior performance of the prototype.

A Power Supply of Self-Powered Online Monitoring Systems for Power Cords

Abstract: This paper presents a power supply of self-powered online monitoring systems for power cords The proposed power supply obtains energy from the magnetic field induced by wire-carrying currents using a specially designed coil-based magnetic energy harvester (CMEH) The CMEH reduces the influence of the magnetic flux leakage and can harvest enough energy, especially when the wire-carrying current is small The magnetic core of the CMEH contains two special C-cores and all end faces are tooth profile The relationship between the magnetic flux leakage and the number of teeth has been analyzed The design details of the power supply circuit including the unit for power management and overvoltage protection are given in this paper Test results show that the overvoltage protective unit can protect the supercapacitor from over its max operating voltage With the low dropout regulator unit function, the power supply is capable of providing a stable output voltage

Mitigation of the magnetic field generated by a wireless power transfer (WPT) system without reducing the WPT efficiency

Abstract: This paper deals with the magnetic shielding of the field generated by a wireless power transfer (WPT) system in air at the frequency of 20 kHz. Different shielding techniques are considered and the results obtained by the use of conductive shields, magnetic shields and passive coils are compared. The analysis is carried out by a hybrid technique based on the coupling between electrical circuits and quasi-static electromagnetic fields.

Experimental Investigation of DC-Bias Related Core Losses in a Boost Inductor

Abstract: Soft magnetic components in electronic systems are often subjected to dc bias-flux conditions. These dc bias conditions result in distorted hysteresis loops, increased core losses, and have been shown to be independent of core material. The physical origin of these increased losses is not well understood and there is no simple model that can predict these losses without extensive measurements. Absence of a widely accepted model coupled with the complete lack of dc loss attributes on core manufacturers' data sheets result in a requirement to empirically determine loss values for specific design applications. These deficiencies have motivated our efforts to investigate dc bias dependent loss phenomenon in a Fe-based Metglas core inductor operating in a dc-dc boost converter. Since dc flux levels in the core are proportional to the controllable converter load currents, this topology is ideal to study dc-related losses. Inductor core B - H hysteresis loop characterization was accomplished as a function of switching frequency, input voltage, and load current operating conditions and parameters. In this paper, the core loss results were presented as a function of the dc bias conditions, and the results showed that the core losses increased with the pre-magnetized (Bde) fields. As a result of our observations, we have proposed a modification to the conventional Steinmetz loss equation to include the effects of dc pre-magnetization flux in the core.

Leakage inductance calculation for planar transformers with a magnetic shunt

Abstract: The magnetic shunt is generally inserted in a planar transformer to increase the leakage inductance which can be utilized as the series inductor in resonant circuits such as the LLC resonant converter. This paper presents a calculation methodology for the leakage inductance of the transformer with a magnetic shunt by means of the stored magnetic energy in the primary and secondary sides of the transformer using the magnetomotive force (MMF) variation method, as well as the stored energy in the shunt based on the reluctance model. The detailed calculation method is described. Both the FEA simulation and the experimental results have proven the validity of the proposed calculation method for leakage inductance.

High frequency integrated Point of Load (POL) module with PCB embedded inductor substrate

Abstract: In this paper, a novel alloy flake composite material is used to demonstrate the PCB integrated magnetic component with low temperature fabrication process. The most important benefit of the alloy flake composite core is easy to be patterned into any desired shape for integration. Compared with the traditional flake composite, the permeability and core loss of the new flake composite are improved prominently, by doing some lateral alignment of the flake and increasing the volume ratio of the alloy. The layerwise magnetic core is sandwiched into multilayer PCB using conventional PCB laminating technique. It has been proved that the manufacturing process, such as laminating, cutting and drilling, has very little impact on the magnetic properties of the flake core. Based on a simple 4-layer PCB substrate with embedded core, the megahertz 3D integrated Point of Load (POL) modules are built, which achieve more than 700 W/in3 power density. The PCB modules survive after hundreds of thermal variation cycles, validating the reliability and compatibility of the alloy flake composite material with PCB integration. In addition, the application of standard PCB process reduces the cost for manufacturing such integrated modules due to the easy automation and low temperature process.

An Improved Calculation of Copper Losses in Integrated Power Inductors on Silicon

Abstract: Thin-film Si-integrated inductors with closed cores have different magnetic field distributions in the winding window space compared to the inductors with unclosed cores. One-dimensional methods are no longer applicable for these inductors to calculate the ac resistance. Based on the analysis of the magnetic field distribution of the devices, a 2-D field solution was developed, which leads to an improved 2-D method to calculate the ac resistance of the device. High accuracy of this new approach has been verified by finite-element analysis, while 1-D methods can lead to significant errors.

A Global Study of a Contactless Energy Transfer System: Analytical Design, Virtual Prototyping, and Experimental Validation

Abstract: This paper presents a design methodology dedicated to a two-winding transformer with large air gap and magnetic cores. To design this kind of components, it is necessary to consider the influence of inductive parameters on electrical magnitudes and the converter, which supplies this magnetic device. Indeed, this kind of a magnetic device has a large leakage inductance and a small magnetizing inductance. Therefore, to transfer the desired power, the transformer needs important reactive energy to magnetize magnetic core and to provide leakage flux. Like inductive parameters can be determined only when geometry is known, sizing has to be iterative. Moreover, resonant converters can be used to compensate inductive behavior, but modify electrical constraints of the transformer. A robust algorithm of design and all necessary tools are presented in order to make it easier to size such components. After the analytical design, 3-D FEM simulations and experimental measurements have been carried out in order to validate the theoretical study. Moreover, the power electronics converter has been optimized in order to improve the efficiency of power transfer. A prototype of 1.6 kW 100 kHz with an air gap of 6 mm has been realized with its converter. The global efficiency is 93.3%.

A Coreless Electric Current Sensor With Circular Conductor Positioning Calibration

Abstract: This paper presents a novel coreless current sensor unit for measuring electrical current of circular conductors. The proposed sensor unit consists of three magnetic field sensors and a microcontroller unit (MCU). The new sensor unit does not need a bulky magnetic core necessary for magnetic field concentration, and can be used in the same way as conventional current transformers (CTs). An algorithm is developed to calibrate the outputs of the magnetic field sensors (e.g., Hall effect integrated circuits (ICs) with respect to the relative position of the current-carrying circular conductor. The algorithm can be implemented on a low-cost MCU for automatic real-time operation. Unlike other coreless magnetic field sensors that need to be fixed onto the conductor for accurate current measurement, the proposed sensor unit affords a more flexible installation option. A hardware prototype is constructed for the proposed coreless current sensor unit. The performance evaluation results show that the accuracy of the proposed sensor unit is comparable to the conventional magnetic core CTs.

Autonomous Underwater Biorobots: A Wireless System for Power Transfer

Abstract: This article describes a new design for wireless power transfer in autonomous underwater robots. The aim is to propose a solution for battery charging by taking into account the morphological and dimensional constraints of robots requiring small and low-weight internal modules. An innovative design is presented for inductive power transfer suitable for a wide range of applications. The system is conceptually equivalent to a transformer in which the core can be separated into two parts during operation, one for each coil. Inductive power transfer is selected to have a system to easily and reliably charge different kinds of underwater robots. The secondary coil and its magnetic core are designed to be placed inside a bioinspired robot; the weight, dimensions, and power output for battery charging are optimized. The shape of the secondary magnetic core section is hollow to house the control electronics and sensors. The primary coil is the power inductor, which is placed in a docking unit outside the robot. Experimental results are also reported.

Modeling and Computation of Losses in Conductors and Magnetic Cores of a Large Air Gap Transformer Dedicated to Contactless Energy Transfer

Abstract: This paper focuses on the study of the losses in conductors and magnetic cores of a large air gap transformer dedicated to contactless energy transfer. It is composed of two E -shaped cores and two windings. In order to estimate the losses, homogenization method and three-dimensional finite-element method (3D-FEM) have been used. Indeed, the equivalent complex properties of the windings composed of Litz wire, and magnetic core in ferrite have been calculated from homogenization method. Then, they have been implemented in 3D-FEM simulations to compute copper and iron losses with accuracy and by considering working condition of the magnetic component. Theoretical approach is validated by experimental results for a prototype of 1.6 kW-100 kHz.

Magnetic properties of soft magnetic powder composites at higher frequencies in comparison with electrical steels

Abstract: To ensure a fair comparison of magnetic properties between electrical steels and SMC the measurements should be done on samples with a similar geometry. At a certain transition point of frequency the specific core losses of SMC become lower then those of electrical steels. Thus, the application of SMC instead of electrical steels in electrical machines operating at elevated frequencies can improve their efficiency.

Analysis of the temperature dependence of losses in electrical machines

Abstract: In electrical machines, the current heat losses increase with rising motor temperature, while the iron core losses decrease. These effects will be described in this paper both theoretically and experimentally for synchronous and induction machines. The result is the existence of an energy optimal motor temperature. The losses in a non-optimal temperature condition can be significantly higher than in an optimal thermal condition. An energy optimal temperature control could be used to reduce losses in embedded powertrain systems for Battery Electric Vehicles.

Multipermeability Inductors for Increasing the Inductance and Improving the Efficiency of High-Frequency DC/DC Converters

Abstract: Distributed air-gap inductors such as iron powder chip inductors and low-temperature cofired ceramic (LTCC) inductors have the advantage of low-fringing effect loss However, the flux density nonuniformly distributes in the magnetic cores, which results in the magnetic material closer to the conductor becoming saturated while the magnetic material further away from the conductor is still not fully utilized This paper proposes a multipermeability distributed air-gap inductor structure to increase inductance without the necessity of increasing the inductor volume The best discrete permeability value is investigated Based on the best discrete permeability value, inductance as well as the inductance density trends is calculated by varying the number of permeability layers under the condition that thickness for each layer is constant Also, the inductance variations versus the number of permeability layers are also obtained under the condition that the inductor thickness is constant A three-permeability inductor and a single-permeability inductor are fabricated to evaluate the proposed method The measured results show that the three-permeability inductor has a much higher inductance than the single-permeability inductor for the entire load range Both inductors are tested in a 5-V input, 3-V output dc/dc converter to compare their performances The results show that the three-permeability inductor can further improve the efficiency of high-frequency dc/dc converters

A Fiber Bragg Grating RMS Current Transducer Based on the Magnetostriction Effect Using a Terfenol-D Toroidal-Shaped Modulator

Abstract: A new approach to the fabrication of robust and low-cost fiber Bragg gratings optical current transducers using a Terfenol-D magnetostrictive material is presented. Electro-erosion is used to manufacture a magnetic core in a toroidal shape, which results in a single piece robust mechanical design. By applying mechanical compression to the toroidal sensor and making its response very close to a quadratic function, it is possible to calculate the rms value of the current directly from the output of the sensor and eliminate the dc biasing magnetic field used in all previous techniques. A new electronic interrogation circuit technique, which allows for the measurement of ac signals and keeps the dc operation point of the fiber Bragg grating, is developed and successfully used in the prototype. Experimental results measured in the developed optical current transducer show that an error of ±0.6% is achieved for currents over the 320-900 A range. When tested over the temperature range of 25°C -45°C, a maximum error of ±2% is observed. The developed system presents a fast transient response, and needs only 34 ms to reach the steady state after a 150% amplitude step increase is applied to current being measured.