Showing papers on "Magnetic core published in 2001"

Improved calculation of core loss with nonsinusoidal waveforms

Abstract: An extension to the Steinmetz equation is proposed, to enable estimation of hysteresis losses in magnetic core materials with nonsinusoidal flux waveforms The new formulation is shown to avoid anomalies present in previous modified-Steinmetz-equation calculations of loss with nonsinusoidal waveforms Comparison with experimental measurements in MnZn ferrite shows improved accuracy The result may be optionally formulated in terms of an effective frequency and an effective amplitude, and options for defining these are discussed

Analysis of eddy-current losses over conductive substrates with applications to monolithic inductors and transformers

Abstract: In this paper, a closed-form integral representation for the eddy-current losses over a conductive substrate is presented. The results are applicable to monolithic inductors and transformers, especially when such structures are realized over an epitaxial CMOS substrate. The technique is verified against measured results from 100 MHz to 14 GHz for spiral inductors.

Miniature resonating marker assembly

Abstract: A miniature resonating marker assembly that includes, in one embodiment, a ferromagnetic core, a wire coil disposed around the core, and a capacitor connected to the wire coil adjacent to the magnetic core. The core, coil, and capacitor form a signal element that, when energized, generates a magnetic field at a selected resonant frequency. The magnetic field has a magnetic center point positioned along at least one axis of the signal element. An inert encapsulation member encapsulates the signal element therein and defines a geometric shape of the resonating marker assembly. The geometric shape has a geometric center point substantially coincident with the magnetic center point along at least a first axis of the signal element. The shape and configuration of the assembly also provides for a miniature signal element specifically tuned to resonate at a selected frequency with a high quality factor.

Electric motor or generator

Abstract: A device such as an electric motor, an electric generator, or a regenerative electric motor includes a rotor arrangement and a stator arrangement. The stator arrangement has a dielectric electromagnet housing and at least one energizable electromagnet assembly including an overall amorphous metal magnetic core. The overall amorphous metal magnetic core is made up of a plurality of individually formed amorphous metal core pieces. The dielectric electromagnet housing has core piece openings formed into the electromagnet housing for holding the individually formed amorphous metal core pieces in positions adjacent to one another so as to form the overall amorphous metal magnetic core. The device further includes a control arrangement that is able to variably control the activation and deactivation of the electromagnet using any combination of a plurality of activation and deactivation parameters in order to control the speed, efficiency, torque, and power of the device.

Composite magnetic body, and magnetic element and method of manufacturing the same

Abstract: The present invention provides a composite magnetic body containing metallic magnetic powder and thermosetting resin and having a packing ratio of the metallic magnetic powder of 65 vol % to 90 vol % and an electrical resistivity of at least 104 Ω·cm. When a coil is embedded in this composite magnetic body, a miniature magnetic element can be obtained that has a high inductance value and is excellent in DC bias characteristics.

On-chip eddy current sensor for proximity sensing and crack detection

Abstract: In this paper, we present a new integrated eddy current sensor for proximity sensing and for the detection of microcracks on the surface of metals. The device consists of two stacked planar coils fabricated onto a glass substrate and encapsulated on one side by a Ni/Fe permalloy magnetic core. Fabrication of the device is achieved by a UV–LIGA thick photoresist lithography process, which involves the lithographic patterning of 15–25 μm thick molds using AZ-4000 series photoresist. The introduction of the permalloy core coupled with the thick conductor lines produces a high inductance, low resistance device capable of generating large magnetic fields at low driving currents. The device has been tested in the frequency range of 10–500 kHz and has been shown to work as both a proximity sensor and crack detector at input powers of 30 mW or less. When used as a proximity sensor, the unamplified output voltage on the sensing coil changes by as much as 75 mV with an aluminum target placed at a distance of 400 μm from the coil. The device has also shown the capability of clearly detecting cracks with depths of as little as 8 mil (200 μm) in both aluminum and titanium. Results show an extremely linear relation between crack depth and output signal voltage with an unamplified signal strength of several millivolts.

Losses in three-phase induction machines fed by PWM converter

Abstract: The paper deals with the analysis and evaluation of test results of PWM converter-fed induction motors. The test results presented point out the dependency of the harmonic losses on the pulse frequency. The measured values were obtained by means of a novel high precision power-analyzer capable of measuring the harmonics of voltage, current and power. Following a detailed investigation regarding the sources of the harmonic losses the paper describes new methods for determining the harmonic losses by both calculation and measurement. The calculation is based on a new equivalent circuit comprising specific impedances for imaging the eddy-current circuits within the iron core derived from the fundamental equations of the three-phase asynchronous machine. These impedances permit the calculation of the harmonic iron losses under the influence of the eddy-currents in all sections of the magnetic circuit caused by the harmonics. Measured and calculated losses were found to correspond satisfactorily for the various voltage harmonics.

Hysteresis and eddy currents compensation in current transformers

Abstract: In the paper a digital technique for improving the accuracy of instrument current transformers is presented. Since the exciting current can be considered as the main error source, its evaluation can allow the compensation of its detrimental effects to be obtained. The exciting current required by the transformer in every kind of steady state operation can be determined by simply acquiring the secondary current, provided that the examined CT has been preliminarily identified. A simple scalar model for the CTs magnetic core, taking into account saturation as well as hysteresis and eddy currents phenomena, has been implemented in a software compensation routine. This allows us to improve the accuracy in the reproduction of the primary current, in the case of both sinusoidal and distorted current waveforms (provided that DC components are not present). Many experimental tests, under different practical situations, have been performed. The results clearly show that the proposed technique is able to significantly reduce, in comparison with traditional methods, the errors introduced by current transformers.

Multiple lamp lcd backlight driver with coupled magnetic components

Abstract: In this invention an inverter for driving multiple lamps has a first circuit for driving a first lamp. The first circuit is made up of a first inductor in series with a first output transformer to drive the first lamp. A second circuit drives a second lamp. The second circuit is made up of a second inductor in series with a second output transformer which drives a second lamp. The first and second transformers are coupled together by a first single magnetic core such that magnetic flux from said first and second transformers is cancelled in the magnetic core to reduce core losses while improving current matching. In a second embodiment the inverter described in the first embodiment further includes a second magnetic core coupling the first and second inductors with minimized leakage inductance. The number of magnetic components for a 2 lamp backlight is then reduced to two.

Small-angle neutron scattering investigations of magnetic nanostructures and interfaces using polarized neutrons

Abstract: Using polarized neutrons, the relative contrasts for small-angle scattering are strongly modi"ed which allows a precise evaluation of magnetization, density and composition pro"les at surfaces and interfaces of nanoscaled materials. In Co ferro#uids, the magnetic core behaves as a non-interacting single domain. The core is encapsulated by a shell of surfactant molecules which was found to be impenetrable for the solvent. In soft magnetic Fe}Si}B}(Nb,Cu) and Fe}Nb}B alloys, the presence of a weak magnetic interface between ferromagnetic nanocrystals and amorphous matrix has been demonstrated which breaks the exchange interactions. 2001 Elsevier Science B.V. All rights reserved.

Repetitive power pulse generator with fast rising pulse

Abstract: A solid-state pulse generator using a split magnetic core transformer is described. In one embodiment, the solid-state drive circuit uses MOSFETs switching a blumlein to produce a desired input pulses in a primary winding of the split magnetic core. The pulse length is determined primarily by the characteristics of the blumlein and the split core transformer. The “on” time of the solid-state devices can exceed the output pulse length, thereby reducing the chance of damaging voltage spikes. The use of a split magnetic core allows several solid-state drive circuits to be used in parallel to produce a single output pulse. In one embodiment, each solid-state drive circuit drives a separate single-turn primary winding of a split magnetic core transformer. In one embodiment, each core of the split core transformer has one primary winding. The separate cores of the split core transformer are provided with a single secondary winding that couples all of the cores to produce a relatively high-voltage output pulse with relatively few turns in the secondary winding.

Motionless electromagnetic generator

Abstract: An electromagnetic generator without moving parts includes a permanent magnet and a magnetic core including first and second magnetic paths. A first input coil and a first output coil extend around portions of the first magnetic path, while a second input coil and a second output coil extend around portions of the second magnetic path. The input coils are alternatively pulsed to provide induced current pulses in the output coils. Driving electrical current through each of the input coils reduces a level of flux from the permanent magnet within the magnet path around which the input coil extends. In an alternative embodiment of an electromagnetic generator, the magnetic core includes annular spaced-apart plates, with posts and permanent magnets extending in an alternating fashion between the plates. An output coil extends around each of these posts. Input coils extending around portions of the plates are pulsed to cause the induction of current within the output coils.

Dc/dc power processor with distributed rectifier stage

Abstract: A technique, which substantially reduces the number of power-stage and control circuit components in an isolated DC/DC converter with parallel current-doubler rectifier stages, includes on the primary side transformers with serially connected primary windings each having a corresponding secondary winding coupled to one of the voltage-doubler stages. In one embodiment, the primary and secondary windings and filter inductors of the current-doubler rectifier stages are provided on an integrated magnetic core. The filter inductors in each current-doubler rectifier stage can be provided as coupled inductors. In one embodiment, an X-shaped magnetic core is provided to achieve coupled or uncoupled filter inductors.

High frequency (GHz) and low resistance integrated inductors using magnetic materials

Abstract: Integrated microinductors, using magnetic materials were fabricated with cutoff frequencies over 3 GHz. Magnetic materials are typically not used in high-frequency inductors because their frequency range has been limited to <100 MHz. The high-frequency magnetic film, an amorphous CoZrTa, was integrated into standard silicon process technology. Inductors consume large amounts of chip area, but with magnetic materials, the inductors can be made smaller thereby reducing their capacitance and resistance. A novel 3-dimensional structure for reducing the inductor's resistance by an order of magnitude was also developed. Simulations of inductors with magnetics and measurements are presented.

Planar inductive element

Abstract: A storage magnetic element, which minimizes the power loss in the planar winding due to the fringe magnetic field associated with a discrete air gap, is presented. The invention describes a construction technique wherein the magnetic core is formed by an E section made of high permeability magnetic material and an I section made by a material capable to store energy due to its distributed gap structure. The I section of the magnetic core in one of the embodiments is covered by an electrically conductive shied to force the magnetic flux into the I section and to minimize the component of the fringe magnetic field perpendicular on the planar winding. In another embodiment of this invention the electrically conductive shield is replaced by a high magnetic permeability material to accomplished the same goal of reducing the magnetic field component perpendicular on the planar winding. In a prefer embodiment of this invention the I section of the magnetic core has a cavity which will accommodate the middle leg of the E section. This construction will force the fringe magnetic field at the edge of the gap to be parallel with the planar winding of the storage magnetic element. In another embodiment of this invention a flat I section is used with the addition of another high permeability magnetic material placed on the I section on top of the winding. This construction will force the fringe magnetic field around the edge of the gap to be parallel with the planar winding. The embodiments of this invention are aimed at reducing the fringe magnetic field perpendicular on the planar winding, lowering the eddy current induced by this field.

Method and apparatus for transmitting a signal through a power magnetic structure

Abstract: A method and apparatus for transmitting a signal through a power magnetic structure. A power magnetic core has one or more windings for transmitting power, and two windings for transmitting a signal or auxiliary power. The signal or auxiliary power windings are looped around features of the core so as to cancel the effect of magnetic flux circulating in the core as a result of currents flowing through the one or more power windings.

Direct current converter with integrated transformer windings and output voltage filtering coils on the same magnetic core

Abstract: Chopper-type direct-current converter comprising a magnetic core (M), which comprises a first and a second side leg (MS 1 , MS 2 ), the ends of which are connected to each other with pieces, and a center leg provided with an air gap and connected to the end pieces between the first and the second side legs. According to the invention, the secondary side filter coil is wound around the center leg. The primary and secondary windings are wound around the side legs so that the magnetic flux produced by them flows in the same direction as the magnetic flux of the filter coil.

Stator for rotary machine and method of manufacturing the stator

Abstract: A stator for a rotary machine includes a rotor 7 and a stator 8 having a stator iron core 15 disposed oppositely around the outer circumference of the rotor 7 and a stator coil 16 fitted around the iron core 15, wherein the iron core 15 has a laminated iron core 150 with plural axially extending slots 15 a formed circumferentially at predetermined pitches, an insulating resin 100 is coated on an axial end face 15 f of the iron core 15 and an inner wall face of a slot 15 a in the laminated iron core 150 to provide insulation between the iron core 15 and the stator coil 16, and the iron core is cylindrically shaped by bringing both circumferential end portions 15 g of the laminated iron core 150 into contact to bend the laminated iron core 150 so that an opening face 15 b of the slot 15 a is directed inside

Multiphase induction device

Abstract: An induction device, such as a transformer or reactor, comprises windings (53) of different phases arranged around magnetic core limbs (52) The magnetic core limbs are connected by at least one body (51) formed from magnetic particles in a matrix of a dielectric material In alternative embodiments the device is substantially spherical or cylindrical Regulating windings mounted on inner and outer magnetic core parts may be transferable therebetween

Inductor with magnetic material layers

Abstract: A spiral inductor fabricated above a semiconductor substrate provides a large inductance while occupying only a small surface area. Including a layer of magnetic material above and below the inductor increases the inductance of the inductor. The magnetic material also acts as barrier that confines electronic noise generated in the spiral inductor to the area occupied by the spiral inductor. Inductance in a pair of stacked spiral inductors is increased by including a layer of magnetic material between the stacked spiral inductors.

Electromagnetic device and high-voltage generating device and method of producing electromagnetic device

Abstract: An electromagnetic device and a high-voltage generating device which are thin and have excellent performances, wherein a magnetic core (3) is formed into a columnar shape by using a large-resistivity ferrite material. Winding is formed by winding a rectangular conductor (2) edge-wise directly around the magnetic core (3) across the almost entire length thereof. Since there is no need of an insulation material such as a coil bobbin between the magnetic core (3) and the conductor (2), the outer shape of the winding can be formed small and thin to thereby make the electromagnetic device thin. The conductor (2) directly wound around the magnetic core (3) can shorten the entire length of the winding and reduce a winding resistance. The absence of a clearance between the core (3) and the winding can reduce self-inductance compared with those required by devices of, for example, the same size and the same number of turns.

Coreless superthin PCB transformer and non-contact battery charger using the same

Abstract: A super-thin PCB (Printed Circuit Board) transformer is manufactured by installing windings on a common PCB without using a magnetic core. A non-contact battery charger using the PCB transformer includes a converter for converting a supply voltage into a high frequency square wave and then applying the converted square wave into a first winding of the PCB transformer; and a charger for converting an electromotive force to a DC voltage to apply the converted DC voltage to a charge circuit, the electromotive force being induced to a second winding of the PCB transformer by a magnetic wave which is generated by the square wave induced in the first winding of the PCB transformer. The non-contact battery charger can be applied to portable information communication and calculation devices such as a mobile telephone, a PDA (Personal Digital Assistant Device), a palm-top, an interetphone, etc.

The influence of air gap size and winding position on the proximity losses in high frequency transformers

Abstract: The proximity losses in high-frequency transformers strongly depend on size and position of the air gaps as well as on the position of the turns inside the winding area. This paper demonstrates the analytical calculation of the two-dimensional field distribution, which is needed for the accurate calculation of these losses.

Compensation of nonlinearities in a current transformer for the reconstruction of the primary current

Abstract: The measurement of the current in industrial electrical devices is often carried out by current transformers. The reliability of these devices is compromised when the measured current is higher than the nominal value, due to the saturation and hysteresis effects of the magnetic core. In this paper, a nonlinear model of the current transformer is identified by means of a separable least squares technique. This model is successfully employed for the estimation of the primary current starting from experimental measurements of the distorted secondary current. In this way, a fair estimate of the primary current is obtained even when its maximum intensity reaches up to 60 times (or more) its nominal value. Some sensible experimental trials are reported in order to demonstrate the effectiveness of the technique developed.

Compact low cost current sensor and current transformer core having improved dynamic range

Abstract: A current sensor and current transformer for monitoring electrical current is provided with a magnetic core having a mixture of magnetic materials to provide a low cost design in a compact configuration with an expanded dynamic range. The mixed material core can be fabricated either from stamped laminations or from coil stock and may include an air gap for activating a magnetic flux sensor. Multiple core configurations, including Figure-O, Figure-C, and Figure-8, having mixed material construction are disclosed and offer advantages over non-mixed material cores where dynamic range and frequency response characteristics are a consideration.

The effect of flux diverters on AC losses of a 10 kVA high temperature superconducting demonstrator transformer

Abstract: In this paper the design, construction and characterization of a 50 Hz single phase high temperature superconducting (HTS) transformer is presented. The transformer is designed to deliver 10 kVA at 77.4 K and 20 kVA at 65 K. The transformer is made of two windings positioned at the middle limb of a three-limb iron core. The secondary winding is made of nine double pancake superconducting coils, using silver sheathed BPSCCO-2223 multifilamentary tapes with nominal critical current of 20 A (at 77.4 K and self field). The primary winding is made of copper to reduce the cost of HTS material. Utilizing a superinsulated nonmetallic doughnut shaped cryostat with low background heat leak, the AC losses in the superconducting winding have been measured by calorimetric method. Two powdered iron flux diverters have been used inside the cryostat at both ends of the superconducting winding in order to reduce the radial component of leakage flux density in the HTS tapes. The use of these flux diverters is shown to be very effective in reducing the AC losses by 40% at the nominal current.

Inductive component and method for the production thereof

Abstract: The invention relates to an inductive component (10) whose soft magnetic core (11) is produced by pouring a casting resin into a mold (1a) filled with a soft magnetic alloy powder and by subsequently hardening the casting resin with the alloy powder in order to form a solid soft magnetic core. Contrary to conventional injection molding methods, this technique prevents the surface insulation of the alloy particles from becoming damaged so that the formation of bulk eddy currents in the resulting soft magnetic cores can be prevented to a large extent. This enables a distinct reduction in the electric loss of the inductive component.

Integrated plasma chamber and inductively-coupled toroidal plasma source

Abstract: A material processing apparatus having an integrated toroidal plasma source is described. The material processing apparatus includes a plasma chamber that comprises a portion of an outer surface of a process chamber. A transformer having a magnetic core surrounds a portion of the plasma chamber. The transformer has a primary winding. A solid state AC switching power supply comprising one or more switching semiconductor devices is coupled to a voltage supply and has an output that is coupled to the primary winding. The solid state AC switching power supply drives an AC current in the primary winding that induces an AC potential inside the chamber that directly forms a toroidal plasma that completes a secondary circuit of the transformer and dissociates the gas.

Axial gap electrical machine

Abstract: An axial gap electrical machine employs unique architecture to (1) overcome critical limits in the air gap at high speeds, while maintaining high torque performance at low speeds, while synergistically providing a geometry that withstands meets critical force concentration within these machines, (2) provides arrangements for cooling said machines using either a Pelletier effect or air fins, (3) “windings” that are produced as ribbon or stampings or laminates, that may be in some cases be arranged to optimize conductor and magnetic core density within the machine. Arrangements are also proposed for mounting the machines as wheels of a vehicle, to provide ease of removing and installing said motor.