Showing papers on "Magnetic core published in 2008"

High-Frequency Modeling of Power Transformers for Use in Frequency Response Analysis (FRA)

Abstract: This paper presents an advanced model of the frequency response of a three-phase power transformer for use in conjunction with diagnostic measurements by the method of frequency response analysis (FRA). The model includes high- frequency behavior of the laminated core and the insulation through taking into account the frequency dependencies of the complex permittivity of insulation materials (paper, pressboard, and oil) and of the anisotropic complex permeability of magnetic core and conductors. A lumped parameter circuit model is used to simulate the frequency response of open-circuit impedance, short-circuit impedance, and impedance between primary and secondary windings, in which the characteristics of circuit elements are calculated by means of the finite-element method. The effect of correct representation of each circuit element on the FRA response is analyzed and discussed in comparison to measurement results on a real transformer.

Fabrication and Analysis of High-Performance Integrated Solenoid Inductor With Magnetic Core

Abstract: Integrated solenoid inductors with magnetic core were fabricated and analyzed. An inductance above 70 nH was achieved while keeping the coil resistance below 1 Omega and the device area below 1 mm2 using a solenoid design with a single magnetic layer. The inductance of the magnetic inductor was more than 30 times that of the air core inductor of the identical geometry, and the quality factor of the magnetic inductor was >5. Novel inductor designs and the scalability were also examined, and an inductance density higher than 200 nH/mm2 was obtained. The measured device properties and engineering tradeoffs were well explained by analytical models we developed.

Integrated on-chip inductors using magnetic material (invited)

Abstract: On-chip inductors with magnetic material are integrated into both advanced 130 and 90 nm complementary metal-oxide semiconductor processes. The inductors use aluminum or copper metallization and amorphous CoZrTa magnetic material. Increases in inductance of up to 28 times corresponding to inductance densities of up to 1.3 μ H / mm 2 were obtained, significantly greater than prior values for on-chip inductors. With such improvements, the effects of eddy currents, skin effect, and proximity effect become clearly visible at higher frequencies. The CoZrTa was chosen for its good combination of high permeability, good high-temperature stability ( > 250 ° C ) , high saturation magnetization, low magnetostriction, high resistivity, minimal hysteretic loss, and compatibility with silicon technology. The CoZrTa alloy can operate at frequencies up to 9.8 GHz , but trade-offs exist between frequency, inductance, and quality factor. The effects of increasing the magnetic thickness on the permeability spectra were measured and modeled. The inductors use magnetic vias and elongated structures to take advantage of the uniaxial magnetic anisotropy. Techniques are presented to extract a sheet inductance and examine the effects of magnetic vias on the inductors. The inductors with thick copper and thicker magnetic films have resistances as low as 0.04 Ω , and quality factors up to 8 at frequencies as low as 40 MHz.

Evaluation of magnetic materials for very high frequency power applications

Abstract: This paper investigates the loss characteristics of several commercial rf magnetic materials forpower conversion applications in the 10 MHz to 100 MHz range. A measurement method is proposed that provides a direct measurement of inductor quality factor QL as a function of inductor current at rf frequencies, and enables indirect calculation of core loss as a function of flux density. Possible sources of error in measurement and calculation are evaluated and addressed. The proposed method is used to identify loss characteristics of different commercial rf magnetic core materials. The loss characteristics of these materials, which have not previously been available, are illustrated and compared in tables and figures. The results of this paper are thus useful for design of magnetic components for very high frequency applications.

Coupled Input-Series and Output-Parallel Dual Interleaved Flyback Converter for High Input Voltage Application

Abstract: This paper proposes an integrated magnetic dc-dc converter suitable for high input voltage application. The converter is based on a coupled input-series and output-parallel dual interleaved Flyback converter concept. All the center and outer legs are gapped, and the transformers are integrated into one magnetic core with not so tight coupling. The gap is beneficial for suppressing current spike caused by the voltage mismatch between the windings. The two transformers are inversely coupled, and current ripple reduction can be achieved with suitable coupling design. A prototype with 350-450-V input and 24-V/4-A output is built. Experimental results verify the performance of the new topology.

Derating of Asymmetric Three-Phase Transformers Serving Unbalanced Nonlinear Loads

Abstract: A new analysis into the steady-state operation and derating of three-phase transformers under nonsinusoidal and asymmetric operating conditions is proposed. The combined effects of transformer core and load asymmetry, nonlinearity, and harmonics, as well as nonsinusoidal input excitation are examined. A time-domain nonlinear model for three-phase three-leg transformers is implemented. Transformer derating is estimated by modeling additional power losses due to harmonics generated by the iron core, nonsinusoidal excitation, and nonlinear (rectifier and electric drive) loading. Laboratory tests are performed to verify simulated waveforms. The contribution of this paper is a nonlinear transformer modeling technique for steady-state operation under unbalanced, asymmetric, and nonsinusoidal operation, capable of computing derating factors.

Magnetic field coupling type antenna, magnetic field coupling type antenna module, magnetic field coupling type antenna device,and their manufacturing methods

Abstract: Disclosed is a magnetic field coupling type antenna comprising an insulating layer (110) and a magnetic core (112) embedded in the insulating layer (110). A coil having a coil axis parallel to the upper surface of the insulating layer is formed by an upper conductor (116) formed on the upper surface of the insulating layer (110), a lower conductor (118) formed on the lower surface of the insulating layer (110), a lateral conductor (120) for electrically connecting the upper conductor (116) and the lower conductor (118), and a via (122). This magnetic field coupling type antenna can be manufactured by a simple process and has high antenna sensitivity without deteriorating impact resistance.

[Mn6] under Pressure: A Combined Crystallographic and Magnetic Study†

Abstract: Folding under pressure: Crystallographic studies on a Mn6 single-molecule magnet under high pressure conditions show the drastic structural changes of the magnetic core (see picture, Mn purple, O red, N blue), which impact on the magnetic properties of ferromagnetic exchange between the metal atoms will be in booster weaker, and under extremely high pressure, a transition to antiferromagnetic behavior.

Improved Wireless, Transcutaneous Power Transmission for In Vivo Applications

Abstract: Electric power, sufficient for many in vivo applications, can be transmitted wirelessly from a small external solenoid (filled with a soft magnetic core), to a novel, magnetoelectric (ME) receiver a few centimeter (cm) inside the body. The ME receiver is a sandwich of electroactive (e.g., piezoelectric) material bonded between two magnetostrictive layers. The electroactive layer may be poled in its plane so that it can function in the stronger g33 mode (induced voltage parallel to the direction of principal magnetostrictive stress). Preliminary experimental results indicate that a 7 cm long ferrite-filled solenoid (NI ap 122 Amp-turns) producing an RMS magnetic field of order 1600 A/m (20 Oe) at the ME receiver (of volume 0.1 cm3) 3 cm from the field source, generates in the ME receiver a power of 200 mW (2 W/cm3). The receiver, in turn, generates a power of 160 mW.

Permanent-magnet brushless DC motor

Abstract: The invention relates to a permanent-magnetic brushless direct current motor which comprises a shell, a front end cover, a rear end cover, a stator, a rotor, and a position sensor, wherein the stator comprises a stator iron core and a winding, the inner side of the stator iron core is provided with a plurality of tooth grooves, the winding passes through the tooth grooves; the rotor comprises a rotating shaft, a rotor iron core and at least one pair of magnetic steels, the rotor iron core is sleeved on the rotating shaft, the magnetic steels are arranged at the periphery of the rotor iron core; and the position sensor comprises a circuit board and a Hall element connected with the circuit board, wherein magnetic conduction inlaid strips used for magnetic conduction are arranged in the tooth grooves of the stator iron core, the cross sections of the magnetic steels of the rotor have an arc shape the thickness at the middle part of which is more than those at both sides, and the Hall element of the position sensor is close to end parts of the magnetic steels of the rotor and takes the magnetic leakage of the magnetic steels of the rotor as a running signal of the Hall element. The permanent-magnetic brushless direct current motor can effectively save production cost and improve the working performance of the motor.

Capacitor failure detection

Abstract: The inventive technique includes methods, devices and computer-readable media for monitoring a magnetic device One such device includes a magnetic core for generating a magnetic field, a power supply and a capacitor bank that is charged by the power supply and is for pulsing the magnetic core The device also includes a processor that measures a charging response of the capacitor bank during charging and determines whether the measured charging response is within a predetermined tolerance of a predetermined charging response

Comprehensive Dynamic Loss Model of Electrical Steel Applied to FE Simulation of Electrical Machines

Abstract: This paper presents a dynamic loss model of electrical steel that can be used with the transient finite-element simulation of electrical machines. The model is used to compute the iron losses in a 37-kW induction machine fed from a sinusoidal and frequency converter voltage supply at different frequencies and loads. The computed losses are compared with results from conventional iron loss computation method based on harmonic analysis as well as with measured losses. The presented dynamic model is based on the investigation of different measurement results as well as on phenomenological backgrounds and analogies. The model is tuned to account for the rotational losses and thus can be used with arbitrary wave form or loci of the magnetic flux density vector (as is the case in the iron core of electrical machines). The parameters of the model are identified from measurements and can be stress dependent to account for the effect of mechanical stresses on the losses in magnetic materials. The presented model differs from previously presented ones in a way that the losses can be calculated at any time and not as an average over a period of the magnetic flux density.

A novel permanent magnet flux-switching linear motor

Abstract: A novel permanent magnet flux-switching linear motor is investigated in this paper. It is cost-effective, since the magnets and coils are both set in the mover, while the long stator is only made of laminated iron core. This simple motor structure costs much lower than other conventional types. Finite element analysis (FEA) shows that, with proper design, the performance can be rather good.

Twisted inductors for low coupling mixed-signal and RF applications

Abstract: Parasitic magnetic coupling is a major design challenge for integrated circuit designers. Fundamentally, it originates in conventional spiral inductors because the magnetic field is not localized, extending far beyond the perimeter. This paper introduces a twisted winding scheme for inductors that increases the localization of the magnetic field, reducing parasitic magnetic coupling by as much as 3100X and the edge-to-edge spacing of inductors by 10X. These results are validated in a 0.18 mum CMOS process.

Mutual inductances comparison in Rogowski coil with circular and rectangular cross-sections and its improvement

Abstract: Rogowski coils are increasingly used to measure AC, high amplitude and transient currents in power industry. One of the most important applications of them is current measurement of industrial electronic devices. Since they have no iron core, they are not saturable. However, due to this phenomenon, their mutual inductance varies by changing their structures. In this paper, the effects of two kinds of cross-sections in Rogowski coils, named Circular and Rectangular, on mutual inductance of coils are compared and their mutual inductance variations are investigated. Also, the methods for increasing mutual inductance are presented. Finally, the method to obtain an optimum mutual inductance in Rogowski coil is suggested. Simulation results are also presented.

Design and fabrication of integrated solenoid inductors with magnetic cores

Abstract: Integrated solenoid inductors with magnetic core were designed and fabricated. An inductance above 70 nH was achieved while keeping the coil resistance below 1 Omega and the device area below 1 mm2. The inductance of the magnetic inductor was more than 30 times that of the air core inductor of the identical geometry, and the inductance density reached above 200 nH/mm2. Comparison with the planar spiral inductor shows that the solenoid inductor is significantly more efficient when the magnetic core is used. Our results indicate that integrated magnetic inductors suitable for mobile power conversion and RF system-on-chip circuits can be reliably designed and fabricated.

Soft magnetic ribbon, magnetic core, magnetic part and process for producing soft magnetic ribbon

Abstract: A soft magnetic ribbon that especially in a relatively low magnetic field region of 500 A/m or less, is high in the squareness of magnetic flux density-magnetization curve. There is disclosed a soft magnetic ribbon of 100 μm or less thickness comprising a parent phase structure in which by volume ratio, 30% or more of crystal grains of 60 nm or less (not including 0) crystal grain diameter are dispersed in an amorphous phase and comprising an amorphous layer disposed on the surface side of the parent phase structure. Preferably, the soft magnetic ribbon is represented by the composition formula Fe100-x-yCuxXy (wherein X is at least one element selected from among B, Si, S, C, P, Al, Ge, Ga and Be), in which the atomic percents (%) satisfy the relationships 0

Magnetic material for high frequency wave, and method for production thereof

Abstract: Disclosed is a magnetic material for a high frequency wave which has high magnetic permeability and small eddy-current loss, particularly a magnetic material for a high frequency wave which can be used suitably in an information device which works in a high frequency field of 1 GHz or higher. Specifically disclosed is a composite magnetic material for a high frequency wave, which comprises a (rare earth element)-(iron)-(nitrogen)-based magnetic material and a (rare earth element)-(iron)-(nitrogen)-based magnetic material whose surface is coated with a ferrite magnetic material.

Single-phase transformer model including magnetic hysteresis and eddy currents

Abstract: In this paper, a single-phase core-type and shell-type transformer model is proposed on the level of state equations. The magnetic hysteresis and the eddy currents effects are successfully included based on the analytical description of the magnetic core topology. Predicted values from simulations are in very good agreement with published measurements and hence, the developed transformer model is a powerful tool for transient and steady-state studies.

Magnetic and relaxometric properties of Mn ferrites

Abstract: We present the magnetic properties and the 1H nuclear magnetic resonance dispersion profiles of Mn-ferrites-based compounds, as possible novel contrast agents (CAs) for magnetic resonance imaging (MRI). The samples consist of nanoparticles (NPs) with the magnetic core made of Mn1+xFe2−xO4, obtained by the rapid decomposition of metalcarbonyl into a hot solvent containing an oxidizer and a coordinating surfactant; by this procedure, monodisperse capped NPs with different sizes have been obtained. We have performed structural and morphological investigation by x-ray powder diffraction and transmission electron microscopy techniques and SQUID magnetometry experiments to investigate the magnetic behaviour of the samples. As required for MRI applications using negative CAs, the samples are superparamagnetic at room temperature, having blocking temperatures in the range 14–80 K. The longitudinal r1 and transverse r2 nuclear relaxivities appear to vary strongly with the magnetic core size, their values being comparable to commercial compounds in the high-frequency range ν > 100 MHz. The experimental results suggest that our samples are suitable for high-frequency MRI imagers in general and in particular for the 3 T clinical imager, as indeed suggested by a recent report (Tromsdorf et al 2007 Nanoletters 7 2422).

HTS dc bias coil for 35 kV/90 MVA saturated iron-core fault current limiter

Abstract: A superconductive coil with 141,000 ampere-turns designed magnetizing power, made of 17,600 meters of BSCCO 2223 HTS tapes, was fabricated and tested. This coil was built for a 35 kV/90 MVA saturated iron-core fault current limiter. Computer simulations on the performance of the coil were carried out using ANSYS. The critical current of the superconducting coil and the dc resistance of the coil, including the non-superconducting joints, were investigated. Spatial distribution of the magnetic field was measured and compared with the simulation results. In this paper, we will report the configuration and the key parameters of the coil as well as the experimental and simulation results.

Magnetic material comparisons for high-current gapped and gapless foil wound inductors in high frequency dc-dc converters

Abstract: The inductor often drives the dc-dc converter size. Thus, the inductor optimization process is required for the most effective design. The paper presents inductor analysis only. The material properties are essential for the design size. In this paper, various magnetic materials are analysed and investigated for use in a practical design. The investigation is concerned with the magnetic material selection for a dc-dc power inductor in the medium (20 kHz) to high (150 kHz) frequency range. The materials under investigation are iron-based amorphous metal, silicon steel, nanocrystalline, ferrite, and gap-less powder materials. A lumped parameter algorithm is derived which includes such effects as the foil ac copper loss effects, the gap core loss, and the cooling path. The algorithm is implemented in EXCEL and generates material comparisons over a range of frequencies, ripple ratios, cooling paths. The results show that the core power loss limited inductor tends to be oversized while the minimum size is achieved for the design which is at the sweet-spot where the size is driven by the core power loss, winding power loss and core saturation limit. A 1.25 kW half-bridge dc-dc converter is built in order to proof the algorithm feasibility at the interest frequency range.

Amorphous nano crystal soft magnet alloy strip with surface insulation coating and its preparation method

Abstract: The utility model puts forward a soft magnetic alloy belt material and production method; wherein, the surface of the belt material has a coating layer with good electrical insulation properties. The soft magnetic alloy belt material is dip-coated in the treating liquid confected through the selection of at least one type of the inorganic matter suspension, the inorganic solution and organic solution with the soft magnetic alloy belt material being dip-coated for 60 to 600 seconds in the treating liquid; then the soft magnetic alloy belt material is baked under the temperature of 90 to 250 DEG C for 60 to 1200 seconds, which makes the thickness of the coating layer up to 0.5 to 15 Mum; the soft magnetic alloy belt material is wound to a magnetic core of corresponding size and then processed by annealing heat treatment to become a soft magnetic alloy belt material with an electrical insulation coated layer. The utility model has the outstanding advantages that the breakdown voltages of the electrical insulation layer per Mum of the soft magnetic alloy belt material are all above 20V and the loss is reduced about 25%; the electrical insulation layer can guarantee the outstanding insulation between the belt material layers; meanwhile, the belt material has the excellent medium high frequency soft magnetism, and the coating material can endure the high temperature above 500 DEG C; thus, the outstanding electric insulation properties and performance can be achieved.

Multi-layer folded high-frequency toroidal inductor windings

Abstract: Multi-layer windings can effectively decrease losses in inductors and transformers in many applications. We introduce a simple way to achieve lower losses in both air-core and magnetic-core inductors or transformers by incorporating multiple layers, with proper interchange of layer positions to ensure the same flux and current in each layer. We have applied this technique to toroidal inductors, but it can be applied to other winding geometries like windings on E cores or U-U cores. Experimental measurement of an inductor constructed using this approach match predicted performance.

Variable flux permanent magnet synchronous motor

Abstract: A variable flux permanent magnet synchronous motor relates to a motor, in particular to a variable flux permanent magnet synchronous motor with easy magnetic field regulating, high efficiency and board speed range. In the motor, a stator consists of an iron core (1) and an armature winding (2), and a rotator consists of an NeFeB permanent magnet (3), an AlNiCo permanent magnet (4), a soft iron (5), a non-magnetic interlayer (6) and a non-magnetic rotating shaft (7), etc. Each electrode of the permanent magnet is formed by the superposition of two different magnets and tangentially magnetized. The permanent magnet near to the rotating shaft is the AlNiCo permanent magnet with a trapezoidal shape; the permanent magnet near to an air gap is the NeFeB permanent magnet with a rectangular shape. The non-magnetic interlayer in the rotator is triangular, the part of which close to the rotating shaft is connected with the permanent magnets. The entire rotator is sealed by a cylinder staggered by a magnetic conductor and a non-magnetic conductor. By applying stator direct axis pulse current id, the magnetization state of the AlNiCo permanent magnet is changed, the effective regulation of the air gap magnetic field of the motor is realized.

Transformer and transformer assembly

Abstract: The transformer has a bobbin, a coil assembly and a magnetic core assembly The bobbin is mounted in the magnetic core assembly and has multiple connecting pins being formed on at least one side of a bottom surface of the bobbin Each connecting pin has a top surface as a soldering surface that corresponds to a solder pad on a back of a circuit board At least one fastener is further formed on the bottom surface of the circuit board Therefore, when the transformer is mounted through the circuit board, the connecting pins are soldered on the back of the circuit board to reduce the total thickness of the combination of the transformer and the circuit board

Lead frame-based discrete power inductor

Abstract: A lead frame-based discrete power inductor is disclosed. The power inductor includes top and bottom lead frames, the leads of which form a coil around a single closed-loop magnetic core. The coil includes interconnections between inner and outer contact sections of the top and bottom lead frames, the magnetic core being sandwiched between the top and bottom lead frames. Ones of the leads of the top and bottom lead frames have a generally non-linear, stepped configuration such that the leads of the top lead frame couple adjacent leads of the bottom lead frame about the magnetic core to form the coil.

Gradient waveform synthesis for magnetic propulsion using MRI gradient coils.

Abstract: Navigating an untethered micro device in a living subject is of great interest for both diagnostic and therapeutic applications. Magnetic propulsion of an untethered device carrying a magnetic core in it is one of the promising methods to navigate the device. MRI gradients coils are thought to be suitable for navigating the device since they are capable of magnetic propulsion in any direction while providing magnetic resonance images. For precise navigation of the device, especially in the peripheral region of the gradient coils, the concomitant gradient fields, as well as the linear gradient fields in the main magnetic field direction, should be considered in driving the gradient coils. For simple gradient coil configurations, the Maxwell coil in the z-direction and the Golay coil in the x- and y-directions, we have calculated the magnetic force fields, which are not necessarily the same as the conventional linear gradient fields of MRI. Using the calculated magnetic force fields, we have synthesized gradient waveforms to navigate the device along a desired path.

Multiple coupling and non-coupling inductor

Abstract: A multi-coupling and non-coupling inductor at least comprises an iron core coating piece and a plurality of conductors; the iron core coating piece is composed of an upper magnetic conductor and a lower magnetic conductor which are corresponding to each other; grooved channels in the directions of axes X and Y are respectively horizontally arranged in the upper magnetic conductor and the lower magnetic conductor; corresponding grooved ditches are arranged on the lower magnetic conductor; the grooved channels serve for the conductors which are respectively threaded and arranged inside the channels and are folded upward to the bottoms of the conductors along the grooved ditches; the conductors enable mutual inductance long the directions of axes X and Y and enable no mutual inductance between the directions of axes X and Y, so that an iron core component can have multiple multi-directional magnetic fields.

Method of manufacturing an encapsulated package for a magnetic device

Abstract: A method of manufacturing an encapsulated package for a magnetic device on a substrate. In one embodiment, the method includes providing a magnetic core on the substrate and placing a shielding structure over the magnetic core to create a chamber thereabout. The method also includes depositing an encapsulant about a portion of the magnetic core within the chamber. The shielding structure limits the encapsulant entering the chamber.