Showing papers on "Magnetic core published in 2010"

An Improved Magnetic Equivalent Circuit Model for Iron-Core Linear Permanent-Magnet Synchronous Motors

Abstract: The aim of this work is to establish an accurate yet simple method for predicting flux density distribution and iron losses in linear permanent-magnet synchronous motors (LPMSMs) for iterative design procedures. For this purpose, an improved magnetic equivalent circuit for calculation of the teeth and yoke flux densities in the LPMSMs is presented. The magnetic saturation of iron core is considered by nonlinear elements and an iterative procedure is used to update these elements. The armature reaction is also taken into account in the modeling by flux sources located on the teeth of motors. These sources are time dependent and can model every winding configuration. The relative motion between the motor primary and secondary is considered by wisely designing air gap elements simplifying the permeance network construction and preventing permeance matrix distortion during primary motion. Flux densities in different load conditions are calculated by means of the proposed model. The effects of saturation and armature reaction on the flux density distribution are shown in detail. Using these flux densities, iron losses in the motor are examined and its variations versus motor parameters are then studied. All results obtained by proposed model are verified by finite-element method based on an extensive analysis.

Power transfer apparatus

Abstract: A power transfer apparatus includes: a magnetic resonance coil for transferring magnetic energy by magnetically resonating with an external coil; a power receiving unit for picking up, as electrical power, the magnetic energy that the magnetic resonance coil receives from the external coil; and a magnetic body arranged on a side of the magnetic resonance coil opposite a transfer side of the magnetic energy of the magnetic resonance coil.

New core loss measurement method for high frequency magnetic materials

Abstract: Magnetic core loss is an emerging concern for integrated POL converters. As switching frequency increases, core loss is comparable to or even higher than winding loss. Accurate measurement of core loss is important for magnetic design and converter loss estimation. And exploring new high frequency magnetic materials need a reliable method to evaluate their losses. However, conventional method is limited to low frequency due to sensitivity to phase discrepancy. In this paper, a new method is proposed for high frequency (1MHz∼50MHz) core loss measurement. The new method reduces the phase induced error from over 100% to <5%. So with the proposed methods, the core loss can be accurately measured.

Magnetic components and methods of manufacturing the same

Abstract: Magnetic component assemblies and core structures including coil coupling arrangements, that are advantageously utilized in providing surface mount magnetic components such as inductors and transformers.

Influence of Compressive Stress on Magnetic Properties of Laminated Electrical Steel Sheets

Abstract: In a practical motor, the compressive stress of more than 100 MPa is sometimes impressed by a shrink fitting etc, as a result, the magnetic properties of iron core deteriorate. Therefore, it is necessary to measure magnetic properties under the compressive stress. However, the measurement under the compressive stress of more than 100 MPa is difficult if a single sheet tester is used, because of the buckling of a single sheet specimen. Then, we measured the magnetic properties under the compressive stress up to 150 MPa without buckling by using a laminated specimen. It is shown that the permeability rapidly decreases even by small stress in both cases of rolling and transverse directions. The iron loss is increased by the stress, but it almost does not increase when the stress is larger than about 50 MPa. Furthermore, the permeability and iron losses of the rolling direction and transverse direction become the same values, and the anisotropy disappears when the stress is larger than about 50 MPa.

Impact of balanced and unbalanced direct current bias on harmonic distortion generated by asymmetric three-phase three-leg transformers

Abstract: The impacts of dc bias and (un)balanced operation including tank effects on harmonic distortions generated by three-phase three-leg transformers are studied Phase imbalances in power networks can arise from unbalanced loads, imperfections in the transposition of long transmission lines and asymmetry in the structure of transformer cores When coupled with dc biases, such as those generated by geomagnetically induced currents, the current harmonic distortion in three-phase three-leg transformers can increase significantly A detailed theoretical study based on electromagnetic theory is performed to explain this phenomenon A time-domain model of a non-linear three-phase three-leg transformer considering magnetic coupling and core structure asymmetry under (un)balanced dc bias is implemented Theoretical predictions are confirmed by simulation results which are further supported by experimental tests The main contribution of this study is a new analysis explaining the link between dc bias and (un)balanced operation on the generation of harmonic distortion in three-phase three-leg transformers

Zero-voltage switching phase shift full-bridge step-up converter with integrated magnetic structure

Abstract: A zero-voltage switching (ZVS) phase shift full-bridge (PSFB) step-up converter with integrated magnetic structure is proposed. In order to improve ZVS ranges, an external inductor is imposed. Especially, to save the volume of the magnetic core of external inductor, the external inductor and transformer are integrated into one magnetic core and then the coupling is formed. Furthermore, coupling coefficients are analysed and can be adjusted by the gaps in the three legs of magnetic core. Besides, the fluxes and the maximum flux density in the three legs of magnetic core are also analysed. Finally, a 100 W prototype converter is made and the experimental results are given to verify the analysis.

Experimental Determination of Equivalent-Circuit Parameters of a Tubular Switched Reluctance Machine With Solid-Steel Magnetic Core

Abstract: The model-based analysis of a switched reluctance machine, which has significant losses in the iron core, requires the machine to be represented by parameters that account for nonlinearities caused by both the magnetic saturation and the iron losses. This paper describes the methodology for determining the parameters of the equivalent electric circuit that includes the representation of iron losses. The parameters are derived from measurements performed under static conditions. The methodology is verified by comparing the dynamically measured results for the pull-out force against the results predicted by the model that is based on the equivalent circuit.

Rotor of permanent magnet embedded motor, compressor, and refrigeration and air conditioning device

Abstract: A rotor of a permanent magnet embedded motor according to this invention includes: a rotor iron core formed by stacking a predetermined number of electromagnetic steel plates perforated in a predetermined shape; a plurality of permanent magnet insertion holes formed along an outer circumferential section of the rotor iron core; permanent magnet end gaps provided at both ends of the permanent magnet insertion hole; a permanent magnet inserted in the permanent magnet insertion hole; and a plurality of slits formed in an iron core section on the outer side of the permanent magnet insertion hole. The width in the radial direction of a slit thin section of each of the slits between the slit and the rotor iron core outer circumference gradually increases from an inter-electrode side toward a magnetic pole center and changes in a sine wave shape having a peak in the magnetic pole center.

Current-controlled variable inductor

Abstract: A variable inductor comprises one or more magnetic cores providing magnetic flux paths. An inductor coil is wound around one or more inductor sections of the one or more magnetic cores. An inductor magnetic flux flows through one or more closed flux paths along the inductor sections of the magnetic core. A control coil is wound around one or more control sections of the one or more magnetic cores. A control magnetic flux flows through one or more closed flux paths along the control sections of the magnetic core. Under this arrangement, the inductor magnetic flux substantially does not flow through the control sections of the magnetic core and the control magnetic flux substantially does not flow through the inductor sections of the magnetic core. The closed flux paths associated with the inductor magnetic flux and the closed flux paths associated with the control magnetic flux share one or more common sections of the magnetic core not including the control sections and inductor sections. The inductance of said variable inductor is varied by varying said control magnetic flux.

Applications of ferro-nanofluid on a micro-transformer.

Abstract: An on-chip transformer with a ferrofluid magnetic core has been developed and tested. The transformer consists of solenoid-type coil and a magnetic core of ferrofluid, with the former fabricated by MEMS technology and the latter by a chemical co-precipitation method. The performance of the MEMS transformer with a ferrofluid magnetic core was measured and simulated with frequencies ranging from 100 kHz to 100 MHz. Experimental results reveal that the presence of the ferrofluid increases the inductance of coils and the coupling coefficient of transformer; however, it also increases the resistance owing to the lag between the external magnetic field and the magnetization of the material.

Bifunctional Nanocomposites with Magnetic and Luminescence Properties

Abstract: Many applications require nanoparticles that exhibit high magnetic moment and luminescence. Compounds exhibiting this combination of properties do not exist. However, this combination of properties may be obtained by nanocomposites. There are two possible configurations for these composites: the core-shell design, leading to the smallest composite particles, and agglomerates containing separated particles with the properties in question. The magnetic core is, in most cases, maghemite or magnetite, whereas the luminescence carrier is either an organic molecule or an inorganic quantum dot. One of the basic problems in designing such composites, to be overcome by the appropriate layout choice, is the potential incompatibility between the magnetic core and the lumophore. Experimentally realized solutions of these problems are presented.

A new formulation of anisotropic equivalent conductivity in laminations

Abstract: A new and simple formulation of equivalent conductivity in the direction normal to the laminations is derived by analyzing and comparing the electromagnetic fields and the eddy current losses in a laminated iron core and a single lamination. Then the anisotropic conductivity tensor is updated. The conductivity formulation can make it easier to calculate numerically three-dimensional eddy current fields in laminations with good accuracy. The validity of the formulation is verified by comparing the eddy current losses, computed with the finite element method using the proposed conductivity formulation and the long known formula, in an analyzed model.

Efficiency optimization of high power density Dual Active Bridge DC-DC converter

Abstract: A DC-DC converter based on the Dual Active Bridge topology is designed, having high power density as main design target. To that aim, a simple structure has been proposed for the transformer with embedded inductor, allowing high frequency operation with low losses and requiring only readily available magnetic core shapes. Simple phase-shift control has been used, and the switching frequency is varied in order to minimize the peak transformer current, thus achieving high conversion efficiency. A fully operational prototype has been built and tested, demonstrating a power density figure of 7.1 kW/Liter with forced air cooling, and a peak efficiency at rated 4 kW load equal to 96.6 %.

Position indicator, circuit component and input device

Abstract: A position indicator includes a tubular core member, a first coil, a second coil, a substantially bar-like rod, a pen-pressure detecting element, at least one capacitor, and a switch. The tubular core member is formed by a substantially bar-like first magnetic core and a substantially bar-like second magnetic core, which are combined in a transversal direction thereof to form a through-hole therebetween. At least one of the first and second magnetic cores may include a recessed portion formed therein extending in the axial direction thereof. The first coil is wound around the tubular core member, and the second coil is wound around the second magnetic core. The rod is inserted into the through-hole of the tubular core member. The pen-pressure detecting element detects a pressure applied to an end of the rod (i.e., the pen tip). The capacitor is connected to the first coil to form a resonant circuit. The switch controls "on" and "off' states of the second coil for the purpose of calculating a rotation angle of the position indicator about its axis.

Low-ripple power source device

Abstract: The utility model discloses a low-ripple power source device, which comprises a direct current input unit, a semi-bridge switch unit, a switch driving circuit, a magnetic core inductor, a current detection unit, an output filter wave capacitor, a first voltage output end and a control chip. An output end of the direct current input unit is connected with the semi-bridge switch unit and the control chip, the semi-bridge switch unit is connected with the control chip through the switch driving circuit, an output end of the semi-bridge switch unit is sequentially connected in series with the magnetic core inductor, the current detection unit and the output filter wave capacitor prior to being connected with the first voltage output end, and an output end of the current detection unit is connected with the control chip. The low-ripple power source device can ensure extremely low ripple of direct current voltage, avoids surge and noise, further avoids electromagnetic interference, ensures steadiness and reliability of power supply, and can meet the high requirements of wireless communication products.

Magnetostriction Measurement by Using Dual Heterodyne Laser Interferometers

Abstract: Electrical machines and transformers have a core built out of laminations of ferromagnetic materials. A portion of the vibrations and noise of these devices is due to magnetic forces and magnetostriction arising from the magnetic core. Magnetic forces are well known, and analytical methods are extensively used to calculate them. Magnetostriction can be defined as the deformation of the ferromagnetic material in the presence of a magnetic field. Unlike magnetic forces, magnetostriction shows a rather complex behavior. It varies for every material, and it depends on the applied magnetic field and external pressure. Therefore, magnetostrictive behavior of every material needs to be determined experimentally by means of strain measurements. Strain gauge measurement techniques have been used before at the Electrical Energy Laboratory (EELAB), Ghent University, Ghent, Belgium. In this paper, a new measurement method using dual heterodyne laser interferometers is proposed to overcome the drawbacks of the old method. The proposed measurement setup and the working principles are explained. The possibility to apply both techniques on one and the same sample can also reveal some interesting results about the quality of both techniques.

Analysis of Integrated Solenoid Inductor With Closed Magnetic Core

Abstract: The effect of a closed magnetic core structure on an integrated inductor was investigated by winding two series connected inductors around a stretched hexagonal ring of CoTaZr. The 8.5 and 17.5 turn inductors were fabricated using standard silicon process, and simulations were performed using Ansoft HFSS software. The resulting inductance of the device showed no improvement over two inductors without the closed magnetic cores, indicating that the closed core structure was insufficient to enhance the mutual inductance between the two devices. This was attributed to the uniaxial anisotropy of the magnetic film, which prevented the film from routing the generated flux circularly around the core. Therefore, while the physical shape of the magnetic film was closed, the effective magnetic shape maintained an air gap.

Improved Frequency Response of On-Chip Inductors With Patterned Magnetic Dots

Abstract: Single-turn spiral inductors with magnetic material to enhance inductance are fabricated. Using double-layered Permalloy dots above and below the inductor metal, inductance improves and remains constant beyond 10 GHz with a Q factor around 11 and a peak frequency around 9 GHz. By employing single-turn small-sized inductors, the self-resonance frequency of the inductors is shifted to very high frequencies. It is illustrated that the superior frequency response is mainly attributed to the significant reduction in mutual inductive coupling between a magnetic layer and inductor metal wires.

Contribution of magnetostriction to transformer noise

Abstract: An important source of transformer noise is magnetostrictive vibration of the magnetic core. This paper outlines some important effects of mechanical building stress on magnetostriction. Harmonic analysis of magnetostriction is necessary to quantify its influence on acoustic noise but it implied here that the most important magnetostrictive parameter has not yet been identified. A route is proposed for obtaining a definite, quantified relationship between defined magnetostrictive characteristics of core laminations and noise by systematically assessing noise and vibration modes of simple, small transformer cores.

Current sensor and method for manufacturing sensor module for use in current sensor

Abstract: A current sensor for outputting a detection signal corresponding to a current flowing through a bus bar. The current sensor includes a magnetic core that concentrates and amplifies magnetic flux generated by the current near a detection portion of the bus bar. A magnetic detection element detects the magnetic flux concentrated by the magnetic core and outputs an electrical signal corresponding to the detected magnetic flux. A signal processing circuit includes electronic components and processes the electrical signal output from the magnetic detection element to generate the detection signal. A lead frame holds the magnetic detection element and the electronic components. The magnetic detection element, electronic components, and lead frame are combined to form a single sensor module. The current sensor detects the current flowing through the bus bar with the sensor module and outputs the detection signal.

Temperature rise analytical method for predicting temperature of permanent magnet in permanent magnet synchronous motor

Abstract: The invention relates to a temperature rise analytical method for predicting temperature of a permanent magnet in a permanent magnet synchronous motor (PMSM), belonging to the application electrical engineering design field; the method is characterized in that: distributed heat source of a motor is analyzed by a filed-circuit compact coupling method, comprising eddy current loss in the permanent magnet, iron loss in an iron core and copper loss in armature; on the consideration of precision requirements, the coupling analysis of a magnetic field and a temperature filed can be realized by single-way coupling mode A thermal model of the permanent magnet synchronous motor is built based on a mixing method of a novel equivalent heat network and a finite element, heat parameters are rationally selected by adopting a combining mode of experimental measurement and empirical formula, the heat transferring coefficient and cooling condition of the motor are described completely, a stator and a rotor can be systematically combined by adopting air gap joints in the heat network, the stator and rotor unified temperature rise model is formed, the difficulty of measuring air gap temperature is avoided, material parameters are adopted at the practical working temperature, so as to lead the analysis to be rational; the accurate and optical method for predicting the temperature of the permanent magnet is realized by special correction processing in experimental links; in addition, the design method is used to give suggestions for model selection of the permanent magnet material in the motor

Optimization of a Switched Reluctance Motor Made of Permendur

Abstract: A switched reluctance (SR) motor has a doubly salient pole structure. A stator has concentrated windings on each pole, while a rotor is only made of iron core. Therefore, the SR motor is expected as a low cost, extremely robust, variable speed motor. The performance of the SR motor greatly depends on magnetic properties of core material since it consists of only laminated-core and windings. This paper investigates the performance of an SR motor made of permendur which has extremely high saturation flux density and very low core loss. Motor torque, iron loss, and efficiency of the SR motor are estimated by finite element method (FEM). Furthermore, a suitable structure for the SR motor made of permendur is examined based on the design of experiments.

An electromechanical generator for converting mechanical vibrational energy into electrical energy

Abstract: An electromechanical generator for converting mechanical vibrational energy into electrical energy, the electromechanical generator comprising a housing, an electrically conductive coil assembly fixedly mounted in the housing, a magnetic core assembly movably mounted in the housing for linear vibrational motion along an axis, a first biasing device, mounted between the housing and the magnetic core assembly, adapted to apply a centering force acting to oppose movement of the magnetic core assembly away from a central position on the linear axis and a second magnetic biasing device adapted to provide a compensating force to compensate for variations in the centering force of the first biasing device due to temperature.

A single-sided linear synchronous motor with a high temperature superconducting coil as the excitation system

Abstract: Thrust measurements were performed on a coil made of a YBa2Cu3O7 − δ coated conductor acting as the excitation system of a single-sided linear synchronous motor. The superconducting coil was a single pancake in the shape of a racetrack with 100 turns, the width and effective lengths were 42 mm and 84 mm, respectively. The stator was made of conventional copper wire. At 77 K and a gap of 10 mm, with an operating direct current of IDC = 30 A for the superconducting coil and alternating current of IAC = 9 A for the stator coils, a thrust of 24 N was achieved. With addition of an iron core, thrust was increased by 49%. With addition of an iron back-plate, thrust was increased by 70%.

Stability Analysis of Three-Phase PWM Converter with LCL Filter by Means of Nonlinear Model

Abstract: In this paper the stability problem of the three phase PWM converters with LCL filter without additional passive or active damping is analyzed. The system with the converter current feedback is considered where the stability problem is more acute. The analysis is performed using two theoretical methods, the discrete z-domain root locus technique and the nonlinear model simulation. The system with two different LCL filters is considered, one with the iron core inductors and the other with the air core inductors. In that way the influence of the iron losses on the system stability is investigated. It is shown that the stability margins obtained by means of the nonlinear model simulation are somewhat wider than the ones obtained by the root locus technique. The theoretical results are validated by the measurements performed on a 40 kW laboratory setup.

Composite magnetic core assembly, magnetic element and fabricating method thereof

Abstract: A composite magnetic core assembly includes an inner magnetic core and an outer magnetic core. The inner magnetic core is made of a high saturation flux density and low permeability material. The outer magnetic core is made of a low saturation flux density and high permeability material. The outer magnetic core includes a ring-shaped wall and a receptacle. The inner magnetic core is accommodated within the receptacle.

Ultra slim power supply device and power acquisition device for electric vehicle

Abstract: An ultra slim power supply device for supplying power to an electric vehicle in a contactless manner includes at least one power supply track buried in a road. Each power supply track includes a plate-shaped magnetic core extending along the road, a plate or strip shaped magnetic field generator arranged above the magnetic core through which an alternating current is supplied to generate a magnetic field, a plate or strip shaped insulating body positioned between the magnetic core and the magnetic field generator to isolate them from each other, and a housing for enclosing the magnetic core, the magnetic field generator and the insulating body.

Experimental Evaluation of AC Losses of a DC Restive SFCL Prototype

Abstract: A DC resistive SFCL consists of an inductance and a quenching superconducting resistance embedded in diode bridge. The superconductor operates in nearly DC current conditions. This regime of operation drastically reduces the AC losses and makes it possible to implement the device by means of present state of the art superconductors. In this paper the AC losses of a laboratory scale prototype of DC resistive SFCL (a 200 V/60 A) are experimentally investigated. The prototype consists of a non inductive Bi2223 winding series connected with a conventional iron core inductor and embedded in a diode rectifier which is connected to the protected circuit. The AC losses are measured and compared with those occurring in pure AC operation at the same current.