Showing papers on "Magnetic core published in 2002"

Atom Transfer Radical Polymerization Synthesis and Magnetic Characterization of MnFe2O4/Polystyrene Core/Shell Nanoparticles

Abstract: An atom transfer radical polymerization route is developed for the coating of MnFe2O4 nanoparticles with polystyrene yielding the core−shell nanoparticles with size <15 nm. Magnetic studies show a decrease in coercivity after the formation of polystyrene shell, which is considered due to the reduction of magnetic surface anisotropy upon polymer coating. The MnFe2O4 nanoparticles as the magnetic core were separately prepared by a reverse micelle microemulsion method. Polymerization initiators are chemically attached onto the surface of nanoparticles. The modified nanoparticles are then used as macro-initiators in the subsequent polymerization reaction. This approach provides great flexibility in the selection of magnetic core. Consequently, magnetic tunability is able to be introduced into these core/shell nanoparticulate systems to achieve the desired superparamagnetic response.

Multi-layered magnetic pigments and foils

Abstract: Multilayered magnetic pigment flakes and foils are provided. The pigment flakes can be a symmetrical coating structure on opposing sides of a magnetic core, or can be formed with the encapsulating coatings around the magnetic core. The magnetic core can be a magnetic layer between reflector or dielectric layers, a dielectric layer between magnetic layers, or only a magnetic layer. Some embodiments of the pigment flakes and foils exhibit a discrete color shift so as to have distinct colors at differing angles of incident light or viewing. The pigment flakes can be interspersed into liquid media such as paints or inks to produce colorant compositions for subsequent application to objects or papers. The foils can be laminated to various objects or can be formed on a carrier substrate.

Synthesis and Magnetic Characterization of Zinc Ferrite Nanoparticles with Different Environments: Powder, Colloidal Solution, and Zinc Ferrite−Silica Core−Shell Nanoparticles

Abstract: Synthesis of nanoparticles under restricted environments offered by water-in-oil microemulsions provides excellent control over particle size and shape and interparticle spacing These environments have been used in the synthesis of silica nanoparticles with a ZnFe2O4 magnetic core First, aqueous magnetic fluids constituted of zinc ferrite nanoparticles with a size ranging between 4 and 6 nm have been synthesized using a soft chemical approach Chemical analysis has shown that the zinc ferrite nanoparticles are nonstoichiometric with the estimated formula Zn087Fe209X004O4 (X represents vacancies) The obtained silica nanoparticles (40−60 nm) with a zinc ferrite magnetic core (4−6 nm) have been characterized by X-ray diffraction, electron microscopy, and magnetization measurements Preliminary magnetic measurements have inferred that the magnetic properties of these nanoparticles at low temperature are essentially governed by the interface particle−habitat

Iron-core coils for transcranial magnetic stimulation.

Abstract: Transcranial magnetic stimulation requires a great deal of power, which mandates bulky power supplies and produces rapid coil heating. The authors describe the construction, modeling, and testing of an iron-core TMS coil that reduces power requirements and heat generation substantially, while improving the penetration of the magnetic field. Experimental measurements and numeric boundary element analysis show that the iron-core stimulation coil induces much stronger electrical fields, allows greater charge recovery, and generates less heat than air-core counterparts when excited on a constant-energy basis. These advantages are magnified in constant-effect comparisons. Examples are given in which the iron-core coil allows more effective operation in research and clinical applications.

Integrated circuit inductors

Abstract: The invention relates to an inductor comprising a plurality of interconnected conductive segments interwoven with a substrate. The inductance of the inductor is increased through the use of coatings and films of ferromagnetic materials such as magnetic metals, alloys, and oxides. The inductor is compatible with integrated circuit manufacturing techniques and eliminates the need in many systems and circuits for large off chip inductors. A sense and measurement coil, which is fabricated on the same substrate as the inductor, provides the capability to measure the magnetic field or flux produced by the inductor. This on chip measurement capability supplies information that permits circuit engineers to design and fabricate on chip inductors to very tight tolerances.

A megahertz switching DC/DC converter using FeBN thin film inductor

Abstract: A dual spiral sandwiched thin film inductor with a dimension of 5 mm /spl times/ 5 mm was fabricated by a LIGA-like micromachined process. FeBN magnetic films were used as a core material. The inductance and quality factor value of the inductor were measured approximately 1 /spl mu/H and 4 up to 5 MHz, respectively. Using the FeBN film inductor, a hybrid dc/dc converter (15 mm /spl times/ 12 mm /spl times/ 1.5 mm) was designed and fabricated. The circuit topology of the converter was a zero voltage switching clamp voltage (ZVS-CV) buck converter. An input of 3.6 V was bucked to 2.7 V at a switching frequency of 1.8 MHz. The maximum power was 1.5 W. The measured efficiency of the buck converter reached a maximum value of 80% and kept stable up to 300 mA of load currents at 1.8 MHz.

RF equivalent circuit modeling of ferrite-core inductors and characterization of core materials

Abstract: Ferrite-core inductors play an important role in electromagnetic noise suppression The radio-frequency (RF) equivalent circuit modeling of the inductor is very useful for characterizing the inductor and for noise filtering studies A technique is proposed for extracting the equivalent circuit parameters of the inductor and determining the frequency-dependent effective rod permeability as well as the intrinsic permeability of the ferrite-core material The equivalent series resistance, inductance, and the lumped shunt parasitic capacitance have been calculated versus frequency for a slug-type inductor and a toroidal-type inductor The effective rod permeability of the ferrite rod used in the slug-type inductor and the intrinsic permeability of the ferrite core used in the toroidal-type inductor have also been estimated as a function of frequency The calculated intrinsic permeability of the toroidal core agrees very well with that measured by the HP4291A RF Material Analyzer The proposed method is simple and accurate In addition, it provides an alternative way for characterizing ferrite cores at radio frequencies

Shift actuator for a transmission

Abstract: A shift actuator (5) for a transmission, which actuates, in a direction of shift, a shift lever (34) for operating a synchronizing device of the transmission, the shift actuator (5) comprising a first electromagnetic solenoid (6) and a second electromagnetic solenoid (7) for actuating an operation member (50) coupled to the shift lever (34) in the directions opposite to each other Each of the first electromagnetic solenoid (6) and the second electromagnetic solenoid (7) comprises a casing (61, 71), a fixed iron core (62, 72) disposed in the casing (61, 71), a moving iron core (64, 74) arranged to be allowed to approach and separate away from the fixed iron core (62, 72), an operation rod (63, 73) mounted on the moving iron core (64, 74) to engage with the operation member (50), and an electromagnetic coil (66, 76) arranged between the casing (61, 71) and the fixed iron core (62, 72) as well as the moving iron core (64, 74)

Integrated magnetic converter circuit and method with improved filtering

Abstract: A converter and rectifier circuit comprises a magnetic core, a first secondary winding, a second secondary winding, a third secondary winding, a first rectifier, a second rectifier and an output capacitor. The first, second and third secondary windings are wound around the magnetic core and are connected to each other. The first rectifier is connected to the first secondary winding and the second rectifier is connected to the second secondary winding. The output capacitor is connected to the first and second rectifiers and is connected in series with the third secondary winding.

Ultra-miniature magnetic device

Abstract: An ultra-miniature magnetic device generally comprises a conductive winding and a magnetic core. The conductive winding includes an upper conductor and a lower conductor. The magnetic core is of an elongate rectangular or oval shape having two elongate sections and two short sections. The lower conductor is preferably positioned below the elongate sections of the magnetic core while the upper conductor is preferably positioned above the elongate sections of the magnetic core. The lower and upper conductors are electrically connected by conducting via structures that are formed in sequential steps using semiconductor processing technology. The result is a coil winding around the elongate sections, with the short sections being preferably free of windings. The process provides an advantage of avoiding shorting between the via structures and the magnetic core caused by overetching when etching the via holes.

Stator iron core of electric motor, manufacturing method thereof, electric motor, and compressor

Abstract: The present invention aims to provide a stator iron core of an electric motor which can eliminate the reduction of efficiency, vibration or noise of the electric motor by decreasing stress generated at a bottom portion of a slot on manufacturing or integrating the electric motor. Plural magnetic pole segments, each having a back yoke portion and a teeth portion projected from the back yoke portion, are connected so as to be bendable via a connection portion provided to the back yoke portion. After winding the coil wire, a stator iron core of the electric motor is circularly formed by bending the connection portion of the plural magnetic pole segments. In the stator iron core, the bottom portion of the slot constituted by the back yoke portion and the teeth portion is made to have a curved line after the stator iron core is circularly formed.

Magnetic tunnel element and its manufacturing method, thin-film magnetic head, magnetic memory and magnetic sensor

Abstract: A magnetic tunnel element ( 1 ) including a plurality of ferromagnetic films ( 5, 9 ) laminated across an insulating film ( 11 ) formed of metal oxide films ( 6, 7, 8 ) and in which asymmetric tunnel barriers are formed along the direction in which the ferromagnetic films ( 5, 9 ) are laminated by this insulating film ( 11 ) ( 6, 7, 8 ). There are also constructed a thin-film magnetic head, a magnetic memory and a magnetic sensor, each of which includes the magnetic tunnel element ( 1 ). Since a magnetoresistive ratio can be suppressed from being lowered by decreasing a bias voltage dependency, there are provided a highly-reliable magnetic tunnel element which can obtain a high output when the magnetic tunnel element is applied to a thin-film magnetic head and the like and a method of manufacturing such a magnetic tunnel element. When a magnetic head, a magnetic memory and a magnetic sensor include this magnetic tunnel element, they become highly reliable and also become able to obtain a high output.

High frequency electric motor or generator including magnetic cores formed from thin film soft magnetic material

Abstract: A device such as an electric motor, an electric generator, or a regenerative electric motor includes at least one stator arrangement having a plurality of electromagnetic assemblies with each electromagnetic assembly including at least a portion of a magnetic core that is formed from thin film soft magnetic material. The electromagnetic assemblies define a plurality of stator poles. The device also includes at least one rotor arrangement supported for rotation about a given rotational axis at a certain range of normal operating rotational speeds. The rotor arrangement has a plurality of rotor poles for magnetically interacting with the stator poles. The rotor poles are supported for rotation about the rotational axis along a circular path. A switching arrangement for controlling the electromagnetic assemblies is configured such that the switching arrangement is able to cause the stator poles of the electromagnetic assemblies to magnetically interact with the rotor poles of the rotor arrangement within a certain range of frequencies. The number of rotor poles is selected to be a number such that the switching arrangement causes the stator poles of the electromagnetic assemblies to magnetically interact with the rotor poles of the rotor arrangement in a way which causes the ratio of the frequency of the device in cycles per second relative to the revolutions per minute of the device to be greater than 1 to 4 during the operation of the device.

Ferromagnetic RF inductors and transformers for standard CMOS/BiCMOS

Abstract: Integrated solenoidal radio-frequency (RF) inductors and transformers with a ferromagnetic core are demonstrated by using a fully IC-compatible fabrication process. For a 500-nm-thick Ni/sub 80/Fe/sub 20/ film, a cut-off frequency of over 7.5 GHz for a 2.5-nH inductor is realized. Optimum inductor design based on tailored inductance, quality factor, and cut-off frequency is discussed. RF transformers realized have a coupling factor of /spl sim/70% up to 200 MHz.

Single magnetic push-pull forward converter featuring built-in input filter and coupled-inductor current doubler for 48 V VRM

Abstract: This paper proposes an improved push-pull forward converter with a single EI or EE core for all the magnetic components including the input inductor, the stepdown transformer and the output inductors. This topology is essentially the modified push-pull converter with the built-in input filter and the coupled-inductor current doubler rectifier. The proposed integrated magnetics features minimized leakage inductance and an air gap in only the center leg; its winding and core losses are both lower than those of conventional integrated magnetic structures.

Analysis of laminated cores through a directly coupled 2-D/1-D electromagnetic field formulation

Abstract: Summary form only given. One of the most critical aspect in the modelling of laminated cores is the capability to evaluate the influence of the skin effect in the lamination depth on the magnetic flux distribution in the sheet plane. On this subject, the authors have already presented a computational procedure, based on a standard vector potential 2D magnetic field solution, which accounts for the effects of eddy currents flowing along the rolling plane both for unidirectional and for rotational fluxes. The proposed procedure handles the diffusion phenomena in the lamination depth by means of a dynamic magnetic model, consisting of the solution of 1D electromagnetic field problems defined in the sheet thickness. The linkage between the 2D (xy-plane) and 1D (z-axis) electromagnetic problems requires the use of two nested iterative Fixed Point (FP) schemes. Here an alternative approach is proposed, by directly coupling the equations governing the 2D and 1D electromagnetic field problems, to reduce the computational burden of the entire algorithm, without affecting the result accuracy.

Switching power converter circuits providing main and auxiliary output voltages

Abstract: A converter circuit includes a magnetic core, a primary winding, a secondary winding, a main rectification circuit, and an auxiliary rectification circuit. The primary winding and the secondary winding are wound around the magnetic core. The main rectification circuit and the auxiliary rectification circuit are both connected to the secondary winding and produce output voltages having different magnitudes. The auxiliary voltage powers the control and drive circuits for both the primary switches and the synchronous rectifiers used for the main rectification circuit.

Method of manufacturing an ultra-miniature magnetic device

Abstract: An ultra-miniature magnetic device generally comprises a conductive winding and a magnetic core. The conductive winding includes an upper conductor and a lower conductor. The magnetic core is of an elongate rectangular or oval shape having two elongate sections and two short sections. The lower conductor is preferably positioned below the elongate sections of the magnetic core while the upper conductor is preferably positioned above the elongate sections of the magnetic core. The lower and upper conductors are electrically connected by conducting via structures that are formed in sequential steps using semiconductor processing technology. The result is a coil winding around the elongate sections, with the short sections being preferably free of windings. The process provides an advantage of avoiding shorting between the via structures and the magnetic core caused by overetching when etching the via holes.

Low-profile transformer and method of manufacturing the transformer

Abstract: A low-profile transformer for switching power supply, wherein insulating paper (13) having at least one of pressure sensitive adhesive and adhesive agent on both surfaces is inserted between low-profile coil layers at at least one position to form a multi-layer coil, and magnetic cores (15) are assembled from the upper and lower sides of the multi-layer coil, whereby a variation in distances between upper and lower coils (11) and coils (12) and distances between the coils (11) and (12) and the magnetic core (15) can be suppressed.

A test case for validation of magnetic field analysis with vector hysteresis

Abstract: An experimental setup, made up of a three-limbed ferromagnetic core fitted with pickup coils, has been designed and built to be used as test bench for validation of magnetic field analysis with hysteresis. Unidirectional or rotational flux patterns and distorted waveforms can be generated by modifying the supply conditions of the coils. A detailed description of the structure with its supply and pickup coils is given. The analysis has been developed under different operating conditions. The experimental results of local and integral quantities are presented and compared with finite-element methods simulations.

Materials system for low cost, non wire-wound, miniature, multilayer magnetic circuit components

Abstract: This invention describes materials system and processing conditions for manufacturing magnetic circuit components such as induction coils and transformers that are non wire-wound, miniature in size and, have a low manufacturing cost The materials system of this invention is comprised of: (1) Low Temperature Cofire Ceramic (LTCC) tapes or thick film pastes of ferromagnetic ceramics with a 20 to 750 range of magnetic permeability to form the magnetic core of the components, (2) Thick film buried silver conductor paste to form the planar induction coils on individual magnetic layers, (3) Thick film via-fill silver conductor paste to interconnect two or more of the planar induction coils through the thickness of the magnetic layers, (4) Thick film silver solderable top layer conductor paste compatible with the ferrite and, (5) Thick film dielectric paste with low magnetic permeability to redirect the magnetic flux for enhancing the magnetic coupling coefficient and to insulate the silver conductors for enhancing the dielectric breakdown voltage The key characteristics of the materials system of this invention that facilitate manufacture of low cost non wire-wound, miniature magnetic circuit components are: (1) Mutual compatibility essential for either of the techniques, the cofire technique or the sequential technique, used for manufacturing multilayer hybrid microelectronic components, (2) Complementary thermo-physical properties such as shrinkage and thermal expansion coefficient essential for manufacturing flat multilayer magnetic components, (3) Magnetic components with magnetic coupling coefficients greater than 095 under optimal processing conditions and, (4) Magnetic components with dielectric breakdown voltage greater than 500V/mil under optimal processing conditions

An all-solid-state pulsed power generator using a high-speed gate-turn-off thyristor and a saturable transformer

Abstract: Recently, high-repetition-rate pulsed power generators using a magnetic pulse compression circuit (MPC) and semiconductor switches have been developed. We have developed a new all-solid-state pulsed power generator for use with a high-repetition-rate excimer laser and in an ozonizer. The all-solid-state generator consists of a semiconductor switch and an MPC with saturable inductors (SI) and a saturable transformer (ST). The semiconductor switch is a high-speed gate-turn-off (GTO) thyristor. The switching speed of the GTO thyristor was improved, decreasing the switching loss. The ST with an Fe-based nanocrystalline magnetic core has two functions, those of step-up transformer and magnetic switch. The high-speed GTO thyristor and the new MPC can be used to realize a high-performance, simple all-solid-state pulsed power generator. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(4): 17–26, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.2006

Iron core exhibiting excellent insulating property at end face, and method for coating end face of iron core

Abstract: An iron core having an insulating coating film on the end face thereof which comprises a dried coating film of a pure silicon polymer, a modified silicon polymer and/or a mixed silicon polymer, the silicon polymers being defined in the specification, has an average film thickness of 0.5 μm or more, and exhibits a withstand voltage of 30 V or more and a heat resistance temperature in air of 400˚C or higher; and a method for producing the iron core, which comprises forming an iron core and then subjecting the core to an immersion or spraying treatment using one or more of a pure silicon polymer, a modified silicon polymer and a mixed silicon polymer. The iron core is greatly excellent in insulating characteristics, corrosion resistance, adhesion of a coating to base iron, heat resistance, the effect to improve magnetic characteristics, and the like, and the method allows the practice of an insulating treatment for the iron core with no pre-treatment such as degreasing, annealing or the like at a low temperature in a short time.

Design of a 100 kVA high temperature superconducting demonstration synchronous generator

Abstract: The paper presents the main features of a 100 kVA high temperature superconducting (HTS) demonstrator generator, which is designed and being built at the University of Southampton The generator is a 2-pole synchronous machine with a conventional 3-phase stator and a HTS rotor operating in the temperature range 57–77 K using either liquid nitrogen down to 65 K or liquid air down to 57 K Liquid air has not been used before in the refrigeration of HTS devices but has recently been commercialised by BOC as a safe alternative to nitrogen for use in freezing of food The generator will use an existing stator with a bore of 330 mm The rotor is designed with a magnetic core (invar) to reduce the magnetising current and the field in the coils For ease of manufacture, a hybrid salient pole construction is used, and the superconducting winding consists of twelve 50-turn identical flat coils Magnetic invar rings will be used between adjacent HTS coils of the winding to divert the normal component of the magnetic field away from the Bi2223 superconducting tapes To avoid excessive eddy-current losses in the rotor pole faces, a cold copper screen will be placed around the rotor core to exclude ac magnetic fields

ELF magnetic field mitigation by active shielding

Abstract: The reduction of extremely low frequency (ELF) magnetic field in an area excited by power frequency currents is investigated by active shielding techniques. The magnetic field inside a shielded area is measured in simple test configurations. The performances of the proposed field-controlled active shield are showed.

Improved design of a novel PM disc motor by using soft magnetic composite material

Abstract: Summary form only given. We present some aspects of soft magnetic composite (SMC) material application in electrical machines. The object applied in the research is an inverter fed double sided axial field permanent magnet disc motor having two stators with 36 slots each and a centred rotor with 8 skewed neodium-iron-boron permanent magnets. Although the SMC materials have low permeability and high iron loss at low frequencies they are still very attractive for manufacturing the stator cores of permanent magnet motors in general. We present not only the construction procedure improvement of the permanent magnet disc motor (PMDM), but also an improvement of the PMDM parameters, magnetic field and magnetic characteristics when SMC material is used as a magnetic material for the stator construction. The complex analysis of the electromagnetic characteristics will also be performed.

Linear motor including cooling system

Abstract: Disclosed is an iron core type linear motor, and more particularly an iron core type linear motor with an improved cooling system for an easy manufacture thereof while having a high cooling efficiency. The iron core type linear motor includes a moving part including a core, a coil, and an upper plate, and a stator including magnets, and a magnet fixing plate. The iron core type linear motor according to the present invention is characterized by a cooling system including a lower cooling conduit, a thermal insulating plate, and an upper cooling conduit laminated over one another in this order between the core and the upper plate.

Magnetic core and magnetic core-use adhesive resin composition

Abstract: The present invention provides a magnetic core whose outer surface has been coated without handling brittle ribbon to thereby impart insulating properties and shape retention properties to the magnetic core after annealing heat treatment, and further provides an adhesive resin composition for a magnetic core, which is useful for efficiently producing the above-mentioned magnetic core without using any organic solvent and which per se is stable to heat and elapse of time. By forming a coating film having a certain thickness or more on an outer surface using a composition containing a resin of specific properties, there can be obtained a magnetic core whose outer surface has been coated without handling brittle ribbon to thereby impart insulating properties and shape retention properties to the magnetic core after annealing heat treatment. The adhesive resin composition containing particles of a resin having specific properties is useful for efficiently producing the above-mentioned excellent magnetic core without using any organic solvent, and this composition is stable to heat and elapse of time.