Showing papers on "Magnetic circuit published in 2002"

Magnetic micro encoder and micro motor

Abstract: A magnetic micro encoder (1), comprising a magnetic disk (4) magnetized in axial direction, a first back yoke (5) installed on the magnetic disk (4), two magnetic sensors (6) installed on the sensor mounting part of a flexible printed circuit board (7) so as to be disposed opposedly to the magnetic disk (4) through a gap in the axial direction of the magnetic disk (4) and so that the longitudinal direction thereof is generally parallel with the band-like wiring part of the flexible printed circuit board (7), a second back yoke (8) installed on the rear surfaces of the magnetic sensors (6) through the flexible printed circuit board (7) and forming a magnetic circuit in combination with the first back yoke (5) and the magnetic disk (4), and a housing (3) for storing the first back yoke (5), the magnetic disk (4), the magnetic sensor (6), and the second back yoke (8).

Coupled-inductor design optimization for fast-response low-voltage DC-DC converters

Abstract: Multiphase voltage regulator modules (VRMs) for microprocessor power delivery with coupled output inductors are discussed. Strong coupling is shown to be feasible and effective at reducing ripple if the correct magnetic topology is used. For more than two phases, this can be a "ladder" core with windings around each rung. Typical ripple reduction is better than a factor of six with no effect on response time. One can also chose to improve response time while still significantly reducing ripple. A simultaneous numerical optimization of the magnetics and the circuit is used to minimize loss in a fast-response 100 A design.

Nanocomputing by field-coupled nanomagnets

Abstract: Demonstrates through simulations the feasibility of using magnetically coupled nanometer-scale ferromagnetic dots for digital information processing. Microelectronic circuits provide the input and output of the magnetic nanostructure, but the signal is processed via magnetic dot-dot interactions. Logic functions can be defined by the proper placements of dots. We introduce a SPICE macromodel of interacting nanomagnets and use this tool to design and simulate the proposed nanomagnet logic units. This SPICE model allows us to simulate such magnetic information processing devices within the same framework as conventional electronic circuits.

IPM Synchronous Machine Drive Response to Symmetrical and Asynunetrical Short Circuit Faults

Abstract: A closed-form solution is presented for the steady-state response of interior permanent magnet (IPM) synchronous machines to symmetrical short circuits including the effects of q-axis magnetic saturation. Machine response to single-phase asymmetrical short circuits is also investigated. Experimental data are presented to verify predicted behavior for both types of short circuits. It is shown that single-phase asymmetrical short circuit faults produce more severe fault responses with high pulsating torque and a significant threat of rotor demagnetization. A control strategy that purposely transitions such faults into symmetrical three-phase short circuits can minimize the fault severity and associated demagnetization risks. Implications for the design of IPM machines with improved fault tolerance are discussed.

Radial force and torque of a bearingless switched reluctance motor operating in a region of magnetic saturation

Abstract: Bearingless switched reluctance motors, which can control rotor radial positions with magnetic force, have been proposed These motors are characterized by integration of switched reluctance motors and magnetic bearings It is essential for a control system to consider magnetic saturation in real time in order to realize stable operation at a full torque load Thus, this paper proposes a method for fast calculation of radial force and torque of a bearingless switched reluctance motor operating in a region of magnetic saturation It is shown experimentally that the proposed method is effective in calculating the radial force and the torque under conditions of magnetic saturation

Geomagnetically induced current effects on transformers

Abstract: Geomagnetically induced currents (GICs) can cause saturation of the magnetic circuit of transformers in a power system. This saturation can increase the MVAr absorption of the transformers, leading to voltage-control problems, generating significant harmonic currents, and cause heating of the internal components of the transformer itself, leading to gas relay alarm/operation as well as possible damage. This paper sets out the methods used to examine these effects using a mathematical model explicitly incorporating the electric and magnetic circuits, including the shunting effect of the tank to predict the current and flux waveforms. The model has been used to predict GIC effects for a variety of winding connections for single-, three-, and five-limb core-type transformers connected to the National Grid Company plc transmission system in England and Wales. The size and form of the return limbs along with the tank shunting effect determine the magnitude and the often complex shape of the waveforms resulting from GIC. Field and factory DC injection tests on various types of transformers have been conducted to validate the model and gain an insight into the magnetic behavior of transformers. With the aid of finite-element analysis (FEA) techniques and a consideration of the various constructional arrangements of the core and coils in the tank, it is possible to evaluate the power losses and accompanying temperature rises of the core, structural components, windings, and tank. Some guidance on the acceptable GIC current levels for various transformer types is given.

A saturating lumped-parameter model for an interior PM synchronous machine

Abstract: This paper presents a lumped-parameter magnetic model for an interior permanent-magnet synchronous machine. The model accounts for the effects of saturation through a nonlinear reluctance-element network used to estimate the q-axis inductance. The magnetic model is used to calculate inductance and torque in the presence of saturation. Furthermore, these calculations are compared to those from finite-element analysis with good agreement.

Design of a High-Efficiency Magnetorheological Valve:

Abstract: A high efficiency design was explored for meso-scale magnetorheological (MR) valves (< 25 mm OD with an annular gap < I mm). The objective of this paper is to miniaturize the MR valve while maintaining the maximum performance of the MR effect in the valve. The main design issues in the MR valve involve the magnetic circuit and nonlinear fluid mechanics. The performance of the MR valve is limited by saturation phenomenon in the magnetic circuit and by the finite yield stress of the MR fluid. When field is applied to the magnetic circuit in the MR valve, a semisolid plug (as a result of particle chain formation) forms perpendicular to the flow direction through the valve, and a finite yield stress is developed as a function of field. The resulting plug thickness is used to control flow rate through, and pressure drop across, the MR valve. The nondimensional plug thickness is evaluated as a basis for evaluating valve efficiency. Design parameters of the MR valve are studied and an optimal performance was designed using steel (Permalloy) material in the magnetic circuit. A maximum magnetic flux density at the gap was achieved in the optimized valve design based on a constraint on the outer diameter limitation. Valve performance was verified with simulation. A flow mode bypass damper system was fabricated and was used to experimentally validate valve performance.

Permanent magnet type reluctance rotary electric machine

Abstract: PROBLEM TO BE SOLVED: To provide a permanent magnet type reluctance electric machine which is compact, high in output and is able to operate at a wide range of variable speed. SOLUTION: In the permanent magnet type reluctance dynamo electric machine of this invention, the permanent magnet 6 placed in a cavity 5 formed along a magnetic pole axis is magnetized in a direction almost intersecting the magnetic pole axis at right angles, so a magnetic flux entered from a space between magnetic poles is repelled, and in addition since the specific permeability of the permanent magnet is almost one (1), the magnetic resistance in a permanent magnet direction is made higher. Thus, the magnetic flux of an armature coil 2 is distributed so that it may pass through an iron core of the magnetic pole without almost passing through between the magnetic poles. As a result, an unevenness is formed in the distribution of the magnetic flux in the void space to generate a higher reluctance torque due to a change in the magnetic energy. Moreover, the magnetic flux of the permanent magnet arranged at a second cavity formed along the outer periphery between the magnetic poles generates torque by crossing the armature coil. Thus the resultant of these torques generates a high torque.

Nonlinear magnetic circuit analysis for a novel stator-doubly-fed doubly-salient machine

Abstract: Summary form only given. The doubly-salient permanent-magnet (DSPM) machine takes the advantages of high power density and high efficiency, but still suffers from limited constant-power speed range and high PM material cost. We propose a novel topology, namely the stator-doubly-fed doubly-salient (SDFDS) machine, which not only solves the problems of the DSPM machine, but also offers the flexibility to on-line optimize the efficiency. In order to effectively analyze and efficiently optimize the proposed machine, a new nonlinear magnetic circuit (NMC) analysis approach is also proposed.

Method and apparatus for providing three axis magnetic bearing having permanent magnets mounted on radial pole stack

Abstract: An improved magnetic bearing that uses permanent magnets to provide the bias flux. The magnetic circuits generating the control flux and bias fluxes are substantially non-coincident but share the same path over some portions that include radial and axial airgaps allowing for a low reluctance and an efficient path for the electromagnetic flux. The flux paths of the permanent magnets are completely defined with minimized airgaps for achieving higher forces and efficiency and very low control currents that produce extremely large forces. A single coil and amplifier for the axial force control and two coils with one associated amplifier for each radial axis of control provides simplicity and cost effectiveness. A single thrust disk is provided that is reacted against for both radial and the axial displacement. The permanent magnets used in the present invention are first fabricated and axially magnetized as segments or as continuous rings prior to being mounted on the sides of the rotor pole, providing an effective and inexpensive technique of manufacturing magnetic bearings.

Magnetic Field Generator

Abstract: A permanent magnet type magnetic field generator (10) which can generate a ferro magnetic field of 3T or above in a field generation space (12). The magnetic field generator (10) has the field generation space (12) located at a central part in the axial direction thereof and comprises a first Haar-Bach type magnetic circuit (14) formed in the center on the outer circumference, and a second magnetic circuit (16) formed to surround the field generation space (12) on the inside of the first magnetic circuit (14). The first magnetic circuit (14) comprises permanent magnets (20a)-(20f), and the central part (A) of permanent magnets (22a)-(22f). The second magnetic circuit (16) comprises a pair of pole pieces (24a, 24b) having saturation magnetization of 1.6T or above, and the central part (B) of permanent magnets (26a)-(26d) for coupling the pair of pole pieces (24a, 24b) magnetically.

Electrically isolated power and data coupling system suitable for portable and other equipment

Abstract: An electrically isolated combined power and signal coupler is usable for a portable medical monitoring device attachable to a patient in a medical environment. A power coupling system transfers power between a power source and a powered device separated by a physical and electrical isolation barrier. The system comprises a power coupler including in a first device, a first section of a magnetic circuit including a first core section of magnetically permeable material of cross-sectional area substantially larger at an isolation barrier interface than within a first winding located on the first core section. The first section of magnetic circuit being suitable, in a docking mode, for positioning adjacent to a second section of magnetic circuit in a second device to form a completed magnetic circuit used to transfer power between said first and second device. The second section of magnetic circuit including a second core section with a second winding magnetically coupling with the first winding via the completed magnetic circuit in the docking mode for the power transfer. The first core section comprises at least one substantially planar core section at the isolation barrier interface for positioning adjacent to a corresponding substantially planar core section of said second section of magnetic circuit at the isolation barrier interface to form the completed magnetic circuit without a device containing the second section of magnetic circuit enveloping a significant portion of the substantially planar core section.

New structures of polyphase claw-pole machines

Abstract: New structures of motor magnetic circuits can be realized by use of the soft magnetic composites. This paper presents new claw-pole motors with a polyphase winding and a standard cylindrical rotor which use these isotropic materials. A division of the stator magnetic circuit into three parts and the use of a centralized-concentrated winding with a small number of coils simplify the production process, the mechanical assembly, and the winding realization. With these special stator geometries, the electromagnetic, mechanical and thermal functions are integrated into the same stator parts. This integration is much better than in a classical two-dimensional (2-D) structure using a laminated material. There is no end winding and the copper volume can be minimized. The size of the additional parts which are necessary for the bearing housings and the mechanical fixation of the rotor are reduced. These structures can be equipped with an integrated cooling system, with efficient air convection or water circulation. This paper describes the design approach of these original structures. It demonstrates that such three-dimensional (3-D) structures can be derived from their equivalent 2-D structures with a concentrated winding. The concept and the design approach are validated by the realization and the comparative experimental tests of two prototypes with a 3-D and its equivalent 2-D structure.

A coil for an electroacoustic transducer

Abstract: An electroacoustic transducer comprising a magnetic circuit of a magnetically conductive material with a pair of opposed surfaces defining a gap therebetween, the magnetic circuit comprising a magnet inducing a magnetic field in the gap, the magnet having a surface constituting one of the opposed surfaces. The magnetic circuit further comprises a diaphragm and a coil having electrically conducting paths secured to the diaphragm. The coil has portions of its paths situated in the gap.

Transient analysis of a new outer-rotor permanent-magnet brushless DC drive using circuit-field-torque coupled time-stepping finite-element method

Abstract: In this paper, a new outer-rotor permanent magnet (PM) brushless DC drive is designed and analyzed. To enable this drive to be applied to electric vehicles, its transient performances at both normal and flux-weakening operations are particularly focused. The distinct feature in design is due to the new motor configuration including the outer-rotor topology, the multipole magnetic circuit and the full slot-pitch coil span arrangement. The distinct feature in analysis is due to the development of the circuit-field-torque coupled time-stepping finite-element method. The proposed PM brushless DC drive is prototyped. The analysis results are verified by experimental measurement.

An improved two-dimensional numerical modeling method for E-core transformers

Abstract: A new 2D modeling method for E-core transformers adds an extended flux return path to the model of the section perpendicular to the core. Averaged with a section parallel to the core modified to have the same reluctance as the 3D model, the finite-element simulation results for total magnetic energy and magnetic energy in the windings are within 0.2-5.6% error relative to the 3D model in fifteen of sixteen cases, a large improvement over existing methods. A refinement of fringing-flux calculations for gapped core legs is also presented.

Magnetic saturation effects on the control of a synchronous reluctance machine

Abstract: Experimental results on the magnetic saturation effects on the control of a small synchronous reluctance machine (600 W) are presented in this paper. A new model of the machine, including saturation effects and cross magnetization is first developed. An approach based on total and mutual inductances is followed instead of the traditional approach through magnetizing and leakage inductances. All of the electrical and mechanical parameters measurements required for the simulations are given. A rotor-oriented vector control of the synchronous reluctance machine is achieved with a digital-signal-processor (DSP) board (TMS320C31) and experimental results are presented. When the magnetic circuit is saturated, the simulation with the developed model shows good, accurate results when compared to the experimental ones.

Flux feedback control system

Abstract: An electrical machine includes a rotor, a stator operably coupled with the rotor, at least one phase winding operably coupled with the rotor and stator and arranged to establish flux in a magnetic circuit in the machine, and a flux observer adapted to produce a signal indicative of flux-causing voltage across the at least one phase winding. A flux control system includes a flux controller adapted to receive a flux command as an input and to provide a phase coil energization signal as an output. The system also includes an electromagnetic system adapted to receive the phase coil energization signal, the electromagnetic system including at least one phase coil, and a flux observer adapted to provide a feedback signal to the flux controller. The feedback signal corresponds to flux in the electromagnetic system, and the phase coil energization signal provided by the flux controller energizes the electromagnetic system such that flux in the electromagnetic system follows the flux command.

Magnetic circuit arrangement for a transducer

Abstract: The magnetic circuit arrangement, which is preferably used in a fluid-measuring transducer, comprises at least one coil which is traversed in operation by a current. It further comprises two armatures that are fixed to two flow tubes vibrating in phase opposition. The coil is float-mounted by means of a holder to a double flow tube configuration formed by the flow tubes. The armatures are shaped and aligned relative to each other in such a manner that magnetic fields produced by means of the magnetic circuit arrangement are essentially concentrated within the magnetic circuit arrangement, whereby the latter is also largely insensitive to extraneous magnetic fields. The magnetic circuit arrangement is marked by a long service life and, particularly if the transducer is used for fluids with high and/or varying temperatures, by constantly high accuracy in operation.

Circuits and circuit elements for high efficiency power conversion

Abstract: Several novel zero voltage switching (ZVS) cells and a ZVS dc to dc transformer circuit are revealed. A U core transformer structure for use with the dc to dc transformer circuit is also revealed. An optimal gate drive circuit that achieves optimal switch timing for ZVS switches is revealed. The optimal gate drive circuit achieves optimal timing for the case in which there is sufficient energy available to drive a zero voltage transition and also for the case in which there is insufficient energy to drive a zero voltage transition providing turn on current to the switch at the minimum drain voltage of the switch. A magnetically coupled multi-phase converter cell structure is revealed which achieves reduced switch ripple current and fast transient response for multi-phase systems with three or more cells. A ZVS active reset switch drive scheme is revealed for providing zero voltage switching in bi-directional power flow converters for both directions of power flow using a single active reset circuit. A primary switching network that applies only one quarter of the input dc source voltage to a winding network connected to the switching network is revealed. The primary switching network is useful for planar magnetic circuit elements which benefit from lower applied voltages and suffer from windings with high number of turns.

Calibrated, low-profile magnetic sensor

Abstract: A calibrated, low profile magnetic sensor and method for forming such a sensor are described herein. Generally, a magnetic sensing device is formed within a housing (120), wherein the magnetic sensing device comprises at least one magnet (126). The magnetic sensor includes a compact integrated circuit package (124) such as, for example, a small outline integrated circuit package (SOIL). A magnetic sensing element (126) is generally mounted to the compact integrated circuit package (124). The magnetic sensing device (134) can be configured to additionally incorporate a printed circuit board (128) (PCB) having a hole (125) formed therein such that the compact integrated circuit package (124) can be surface mounted off-center on the printed circuit board (128), so that the hole (125) can be located within the printed circuit board (128) to match a shape of the magnet, allowing the magnet to pass through the circuit board adjacent to the SOIC to complete the magnetic circuit.

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.

Generation of remote homogeneous magnetic fields

Abstract: This paper presents a magnetic efficiency model for comparing efficiencies of various magnets for magnetic resonance imaging. It demonstrates that monohedral magnets, magnets with sources on one side, can generate remote saddle points in the field profile relatively efficiently. These magnets may be modeled by a minimum of two magnetic dipoles. The paper examines the field profile and magnetic dipole efficiency for the two-dipole model in detail, and develops some fundamental properties of homogeneous magnetic fields.

Actuator for optical pickup

Abstract: An actuator for an optical pickup includes a magnetic circuit having a structure in which coils to drive an objective lens in one direction selected from a focusing, tilting, or tracking directions, and magnets to drive the objective lens in the other directions. The coils and magnets are installed on the bobbin. The actuator for an optical pickup reduces the number of wires required for 6-axis direction driving, thereby making assembly easy. The actuator includes magnets, yokes, and coils in the bobbin, thereby reducing the mass of the bobbin, improving sensitivity, and increasing the efficiency of magnetic force.

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

Magnetically influenced current or voltage regulator and a magnetically influenced converter

Abstract: A magnetically influenced current or voltage regulator includes a body of an anistropic magnetisable material that provides a closed, magnetic circuit. A first electrical conductor is wound around the body along at least a part of the closed circuit for at least one turn which forms a first main winding. At least one second electrical conductor is wound around the body along at least a part of the closed circuit for at least one turn which forms a control winding. The winding axis for the main winding is at right angles to the winding axis for the control winding. Orthogonal magnetic fields are generated in the body when the first main winding and the control winding are excited. A characteristic of the anisotropic magnetisable material relative to a field in the main winding is controlled by means of a field in the control winding.

Rotary electric machine stator having individual removable coils

Abstract: The invention relates to a stator for a rotary electric machine. The stator comprising: a stator magnetic circuit having teeth and individual coils each engaged on a tooth, each coil including connection ends formed by respective flat bundles of stripped wires curved to form respective hook shapes, the connection ends being soldered to locally stripped portions of sheathed electric cables.

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.