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Showing papers on "Magnetic circuit published in 2006"


Journal ArticleDOI
TL;DR: In this article, a Hall thruster with a magnetic circuit designed for high-specific impulse (2000-3000 s) was evaluated to determine how current density and magnetic field affect thruster operation.
Abstract: A laboratory-model Hall thruster with a magnetic circuit designed for high-specific impulse (2000‐3000 s) was evaluated to determine how current density and magnetic field affect thruster operation. Results have shown for the first time that a minimum current density and optimum magnetic field shape exist at which efficiency will monotonically increase with specific impulse. At the nominal mass flow rate of 10 mg/s and between discharge voltages of 300 and 1000 V, total specific impulse and total efficiency ranged from 1600 to 3400 s and 51 to 61%, respectively. Comparison with a similar thruster showed how efficiency can be optimized for specific impulse by varying the shape of the magnetic field. Plume divergence decreased from a maximum of 48 deg at 400 V to a minimum of 35 deg at 1000 V, but increased between 300 and 400 V as the likely result of a large increase in discharge current oscillations. The breathing-mode frequency continuously increased with voltage, from 14.5 kHz at 300 V to 22 kHz at 1000 V, in contrast to other Hall thrusters where a sharp decrease of the breathing-mode frequency was found to coincide with increasing electron current and decreasing efficiency. These findings suggest that efficient, high-specific impulse operation was enabled through the regulation of the electron current with the applied magnetic field.

113 citations


Journal ArticleDOI
P. Zhou, D. Lin, Weinong Fu, B. Ionescu, Z.J. Cendes 
TL;DR: In this paper, an indirect procedure to couple transient finite-element simulation with circuit simulation is proposed, based on extracting lumped parameters from the field simulation and Norton equivalents from the circuit simulation.
Abstract: An indirect procedure to couple transient finite-element simulation with circuit simulation is proposed. The procedure is based on extracting lumped parameters from the field simulation and Norton equivalents from the circuit simulation. This approach provides more stability and accuracy because both winding currents and terminal voltages across coupling branches are free to change. It is also more flexible since the finite-element equations and the circuit equations are solved separately and allows complicated system level simulation

85 citations


Journal ArticleDOI
08 May 2006
TL;DR: In this article, a new permanent magnet (PM) brushless hybrid machine is proposed and implemented for wind power generation, where a small dc field winding and an extra air-bridge are incorporated in the machine so that the air-gap flux can be effectively strengthened or weakened to online keep the output voltage constant throughout the whole wind speed range.
Abstract: In this paper, a new permanent magnet (PM) brushless hybrid machine is proposed and implemented for wind power generation. The originality is that a small dc field winding and an extra air-bridge are incorporated in the machine so that the air-gap flux can be effectively strengthened or weakened to online keep the output voltage constant throughout the whole wind speed range. The characteristics of flux linkage and no-load electromotive force (EMF) are analyzed by using the finite element method (FEM), and these results agree well with those from magnetic circuit analysis. Experimental results also verify that the proposed machine can produce a constant output voltage over a wide wind speed range

73 citations


Journal ArticleDOI
TL;DR: A high-fidelity magnetic equivalent circuit (HFMEC) inductor model that reduces the inaccuracies associated with a traditional MEC approach and makes the model ideal for automated inductor design.
Abstract: We present a high-fidelity magnetic equivalent circuit (HFMEC) inductor model that reduces the inaccuracies associated with a traditional MEC approach. The model can accurately predict the flux linkage versus current characteristic in a fraction of the time needed for finite-element analysis. The accuracy, computational efficiency, and simple inputs (consisting of only geometry and material specifications) make the model ideal for automated inductor design.

67 citations


Journal ArticleDOI
TL;DR: In this article, a comparison of MCR and TCR from the point of view of harmonics, is studied and a detailed model of reactor is used to illustrate the ideas presented throughout the paper.

59 citations


Patent
06 Apr 2006
TL;DR: In this paper, an electromagnetic actuator consisting of a mobile assembly, a fixed ferromagnetic stator assembly, at least one electric field coil, and of at least a permanent magnet, having two stable positions of equilibrium without current at its ends of travel is described.
Abstract: The invention relates to an electromagnetic actuator comprised of a mobile assembly, a fixed ferromagnetic stator assembly, at least one electric field coil, and of at least one permanent magnet, having two stable positions of equilibrium without current at its ends of travel. The invention is characterized in that the mobile assembly has two distinct ferromagnetic armatures placed on both sides of the stator assembly and each forms, together with the stator assembly, at least one magnetic circuit, and is characterized in that the permanent magnet magnetically cooperates with one of the other ferromagnetic mobile parts in a stable position of equilibrium without current at the end of travel.

56 citations


Proceedings ArticleDOI
08 May 2006
TL;DR: In this paper, an outer-rotor stator-doubly-fed doubly-salient permanent-magnet (SDF-DSPM) machine was proposed to provide a compact arrangement of hybrid field excitations.
Abstract: This paper presents a new outer-rotor stator-doubly-fed doubly-salient permanent-magnet (SDF-DSPM) machine, which can be used as the integrated starter-generator for modern automobiles and mild hybrid electric vehicles. The key of the proposed machine is to incorporate both dc field windings and PMs in the inner stator, hence, offering a compact arrangement of hybrid field excitations. While armature windings are located in salient poles of the outer stator, the outer rotor is simply composed of salient poles without windings or PMs. In addition, an air bridge is purposely created in shunt with each PM in the inner stator, hence, providing an amplification effect for flux regulation. With this idea, the air-gap flux can be strengthened or weakened with a small dc field current so that the electromagnetic torque and induced electromotive force (EMF) can be effectively regulated. The newly designed SDF-DSPM machine is analyzed by using both the magnetic circuit model and finite element method, and assessed by performance simulation

54 citations


Journal ArticleDOI
TL;DR: In this article, a small-scale prototype of a controllable shunt reactor with a high-temperature superconductor control winding is presented, and a simple model of the magnetic circuit is presented.
Abstract: Reactive power compensation is vital for obtaining efficient operation of long transmission power lines or cables. A controllable shunt reactor that controls the transmission of power by continuous reactive power compensation will reduce the transmission losses and increase the transmission capacity of active power. We show that the saturation phenomena of iron and the high current density of a high-temperature superconductor can be utilized to design controllable reactors with large dynamic range, low losses, and limited harmonic distortion. We have designed and constructed a small-scale prototype of a controllable shunt reactor with a high-temperature superconductor control winding. We present a simple model of the magnetic circuit of the controllable reactor and we compare calculations from the model to experimental measurements on the controllable reactor

53 citations


Journal ArticleDOI
TL;DR: A moving magnetic domain wall produces an electromotive force (emf), which can read the state of a magnetic memory device via the emf it produces when subjected to an interrogation pulse.
Abstract: A moving magnetic domain wall produces an electromotive force (emf). It is therefore possible to read the state of a magnetic memory device via the emf it produces when subjected to an interrogation pulse. It is also possible to amplify currents in pulse circuits, opening up the possibility of all magnetic logic circuits.

52 citations


Journal ArticleDOI
10 Jul 2006
TL;DR: In this paper, the authors presented accurate determination of major parameters of a three-phase three-stack claw-pole permanent-magnet motor with a soft magnetic composite stator core by finite-element analysis of the magnetic field.
Abstract: Effective and accurate prediction of key motor parameters, such as winding flux, back electromotive force, inductance and core losses, is crucial for design of high-performance motors. Particularly, for electrical machines with new materials and nonconventional topology, traditional design approaches based on the equivalent magnetic circuit, empirical formulas and previous experiences cannot provide correct computation. The paper presents accurate determination of major parameters of a three-phase three-stack claw-pole permanent-magnet motor with a soft magnetic composite (SMC) stator core by finite-element analysis of the magnetic field. The effects of magnetic saturation and armature reaction are considered. The theoretical results by numerical analysis are validated by the experiments on the claw-pole SMC-motor prototype.

50 citations


Patent
Michael Andrew Parker1
13 Nov 2006
TL;DR: In this paper, a thin-film flux generator and a thin film magnetic sensor are combined to form an integrated device for electrical signal processing, where each flux generator includes at least one conductive induction line that is connected to one lead of a pair of input leads, and a yoke that surrounds the conductive line.
Abstract: An electrical signal processing device includes at least one thin film flux generator and at least one thin film magnetic sensor. Each flux generator includes at least one conductive induction line that is connected to at least one lead of a pair of input leads, and a yoke that surrounds the conductive induction line. The yoke has at least one pair of pole tips, and a gap is disposed between the end surfaces of each pair of pole tips. A magnetic sensor is disposed in the gap, and a pair of output leads is connected to the sensor. An alternative embodiment may include two or more conductive induction lines that are connected to respective separate pairs of input leads. Alternatively, two or more conductive induction lines may connect to one another to form an induction coil. The flux generator and magnetic sensor are preferably formed on a single substrate to create an integrated device.

Journal ArticleDOI
R.C. Ireland1, C.R. Torres
TL;DR: In this article, the authors examined finite element (FE) simulations in which a section of line pipe is magnetized along its circumference under both static and moving tool conditions and highlighted difficulties associated with maintaining a stable magnetic circuit for a moving ILI tool.
Abstract: Pipeline integrity is vital and should be maintained through regular inspection. A popular inspection technique is magnetic flux leakage (MFL) where an in-line inspection (ILI) tool magnetically saturates the pipeline locally as it traverses the pipe inner bore. Pipe defects cause magnetic flux patterns to change and this change is detected by a set of magnetic sensors mounted on the tool. For the MFL technique to be optimised, magnetic saturation in the pipe material is required. This paper examines finite element (FE) simulations in which a section of line pipe is magnetised along its circumference under both static and moving tool conditions. Early findings are reported that highlight difficulties associated with maintaining a stable magnetic circuit for a moving ILI tool. The results provide insights into the design considerations and challenges of employing circumferential MFL tools and their associated sensors.

Proceedings ArticleDOI
08 May 2006
TL;DR: In this article, the authors presented a fast and accurate d-q axis equivalent circuit model of linear induction motor (LIM) for drive system simulations based on nonlinear transient finite element analysis to obtain the asymmetric dq equivalent constants for static end effect and the distorted air gap distribution by velocity for dynamic end effect.
Abstract: This paper presents a fast and accurate d-q axis equivalent circuit model of linear induction motor (LIM) for drive system simulations. The developed model was built based on nonlinear transient finite element analysis to obtain the asymmetric d-q equivalent constants for static end effect and the distorted air gap distribution by velocity for dynamic end effect. The model was implemented in a vector control environment through the creation of a d-axis magnetizing inductance to account for the reduction of the magnetizing inductance due to eddy current. Since the d-q axis equivalent circuit model of LIM considering both end effects has not been exactly completed, the significance of the work is that it provides an accurate d-q axis equivalent circuit model of LIM for utilization in simulation environments

Journal ArticleDOI
TL;DR: In this paper, a theoretical study of the calculation of magnetic fields in vicinity of overhead electric power lines is presented, where exact and simplified methods of the determination of the magnetic field of a straight overhead conductor based on the Fourier transform technique and on the concept of complex ground return plane are presented.
Abstract: The paper presents in a tutorial manner a theoretical study of the calculation of magnetic fields in vicinity of overhead electric power lines. Exact and simplified methods of the determination of the magnetic field of a straight overhead conductor based on the Fourier transform technique and on the concept of complex ground return plane are presented. The decomposition of the magnetic fields in two components: magnetic field obtained in free space from the Biot-Savart law and the magnetic field produced by earth current is discussed. It is shown that in practical cases the effects from earth currents can be neglected as compared with effects from line currents. A solution for modeling magnetic fields produced by sagging conductor, described by the catenary equation, is also proposed. The effect of the catenary on the magnetic field spatial distribution is investigated. The calculation results of magnetic field produced by sagging conductor and the magnetic field of a conventional model consisting of a horizontal conductor hanging on the effective height lying between the maximum and minimum heights of catenaries is compared and discussed. As an example the magnetic field of a real-power catenary high voltage 2 × 220 kV power line is demonstrated. Copyright © 2006 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this article, the authors deal with Hall and flux-gate magnetic field sensors consisting of integrated combination of CMOS ASICs and planar ferromagnetic components, which have up to 10 times higher magnetic resolution and respond to a magnetic field parallel with the surface of the chip.
Abstract: The paper deals with Hall and flux-gate magnetic field sensors consisting of integrated combination of CMOS ASICs and planar ferromagnetic components. Ferromagnetic parts are made of a soft amorphous alloy, integrated at the CMOS wafer in a post-processing production phase. When the sensors are exposed to an in-plane magnetic field, under the peripheries of ferromagnetic parts appears a strong magnetic induction perpendicular to the wafer surface. This perpendicular field is sensed either by Hall plates or planar coils. In the case of Hall magnetic sensors, such ferromagnetic parts give a magnetic gain of 2–10. Compared to conventional integrated Hall magnetic sensors, the new sensors have up to 10 times higher magnetic resolution and they respond to a magnetic field parallel with the surface of the chip. They are used as current sensors or angular position sensors. In the case of flux-gate sensors, both the saturation-forcing coil and the pick-up coils are realized as planar coils, using metallization layers that exist in the CMOS process. The integrated flux-gate technology is illustrated by a low-power two-axis magnetic field sensor suitable for a portable electronic compass.

Journal ArticleDOI
TL;DR: In this paper, a new generation of CMOS-compatible micro-inductor prototypes with magnetic cores were realized, characterised as well as theoretically modelled in a frequency range up to 4 GHz, a frequency where, e.g., mobile communication and global positioning systems (GPS) are operated.

Proceedings ArticleDOI
23 May 2006
TL;DR: In this article, a symmetrical short circuit (SSC) is applied only during flux weakening as protection measure, while for the lower speed range the conventional converter shut down is proposed.
Abstract: To enable constant-power areas with permanent magnet synchronous motors, flux weakening has to be applied. In that mode, the inverter protection measure, e.g. in case of overcurrent, is a crucial point, since the open-circuit induced terminal voltage may exceed the allowed inverter limit. That is why a symmetrical short circuit (SSC) is currently favoured as alternative protection measure. Though the steady state short circuit current may be acceptable, this contribution shows that the transient current may seriously exceed the allowed limit. The worst case SSC will not occur during flux weakening but in regenerative operation at rated speed. Such high peak currents include the risk of permanent demagnetization of the magnets. As a result, SSC should applied only during flux weakening as protection measure, while for the lower speed range the conventional converter shut down is proposed

Journal ArticleDOI
05 Jun 2006
TL;DR: In this article, the transient performance of a magnetic core fault current limiter (FCL) saturated by high temperature superconducting (HTS) dc bias winding is investigated by using both 3-D field-circuit coupled simulation and magnetic circuit analysis.
Abstract: In this paper, the transient performance of a magnetic core fault current limiter (FCL) saturated by high temperature superconducting (HTS) dc bias winding is investigated by using both 3-D field-circuit coupled simulation and magnetic circuit analysis. A high voltage is induced on the dc HTS winding during the fault current state. The induced voltage is computed and a short circuit coil for the reduction of induced voltage is studied. The numerical computations are verified by the experiment results on an FCL prototype

Journal ArticleDOI
TL;DR: In this article, the optimum operating condition of a magnetic refrigerator at room temperature for direct air-cooling was analyzed for a variety of conditions such as a volumetric flow rate of air, a packing length of magnetic working substance, and a heat exchange cycle.
Abstract: The purpose of this study is to understand the optimum operating condition of magnetic refrigerator at room temperature for direct air-cooling. The basic components of the target system are a magnetic circuit including two permanent magnets, a test section, an air blower, and an associated instrumentation. The test section consists of 10 test cells which enclose gadolinium chips as a magnetic working substance in a prescribed packing rate. In order to change the applied magnetic field from 0 to 0.9 T, the magnetic circuit is installed on an electric slider which generates reciprocating motion. The system performances are widely investigated both experimentally and analytically for the variety of conditions such as a volumetric flow rate of air, a packing length of magnetic working substance, and a heat exchange cycle. The results reveal that the present magnetic refrigerator has a maximum value of the cooling rate in an appropriate operating condition.

Journal ArticleDOI
Miyoshi Takahashi1, Kazuhide Tanaka, M. Okada, H. Kitaguchi, H. Kumakura 
TL;DR: In this paper, a closed loop circuit with a MgB2 solenoid coil, a PCS and some superconducting joints was fabricated for PC mode operation, and the critical current of the coil reached 166 A and the coil was able to generate a maximum magnetic field of about 2.5 T at 4.2 K without an external field.
Abstract: This paper reports on the relaxation of trapped magnetic field in a MgB2 solenoid coil in PC mode operation. For PC mode operation, we fabricated a closed loop circuit with a MgB2 coil, a PCS and some superconducting joints. The MgB2 coil was fabricated employing a 100 m-long PIT processed MgB2 wire using a wind & react method. The critical current Ic of the coil reached 166 A and the coil was able to generate a maximum magnetic field of about 2.5 T at 4.2 K without an external field. The PCS was fabricated employing a long NbTi wire stabilized Cu-Ni alloy. The joints were fabricated between MgB2 and NbTi conductor, between NbTi (PCS) and NbTi conductor. The resistance of all fabricated joints was estimated to be less than 1.0times10-13 Omega. In PC mode operation with the closed loop circuit, a magnetic field of 1.46 T was trapped for about 50000 s (above 12 hr.) without any detectable decay. These results demonstrate the possible use of the MgB 2 superconductor for applications such as MRI superconducting magnet

Patent
02 Nov 2006
TL;DR: In this article, the authors reveal improvement methods for circuits that use a coupled inductor wherein overshoot and ringing associated with leakage inductance of said coupled inductors is entirely eliminated by addition of non-dissipative active clamp networks that clamp each winding during each operating state of a power supply containing said coupling inductor.
Abstract: The subject invention reveals improvement methods for circuits that use a coupled inductor wherein overshoot and ringing associated with leakage inductance of said coupled inductor is entirely eliminated by addition of non-dissipative active clamp networks that clamp each winding during each operating state of a power supply containing said coupled inductor. A further improvement applicable to zero voltage switching circuits that employ an inductor for driving a zero voltage turn on switching transition of a switch enables elimination of said inductor and preserves said zero voltage switching properties by adding leakage inductance to a coupled inductor without any adverse overshoot and ringing effects associated with said leakage inductance. The subject invention also reveals a coupled inductor with enhanced leakage inductance which can be used with said other improvements. Example circuits including zero voltage switching flyback and forward converters which require only one magnetic circuit element are revealed. Zero voltage switching tapped inductor buck and boost converters with a single magnetic circuit element are also revealed.

Patent
02 Nov 2006
TL;DR: In this paper, a self-fastening cage of a magnetic resonance device (MRD) is presented for providing a homogeneous, stable and uniform magnetic field, characterized by an outside shell comprising at least three flexi-jointed superimposed walls.
Abstract: The present invention discloses a novel self-fastening cage of a magnetic resonance device (MRD) (100) for providing a homogeneous, stable and uniform magnetic field therein, characterized by an outside shell comprising at least three flexi-jointed superimposed walls (1) disposed in a predetermined arrangement clockwise or counterclockwise. In a technology of self-fastening cage, the invention teaches an effective multi-streamed MRD comprising a cage including a closed magnetic circuit constructed from strong permanent magnets; and an optional shimming mechanism selected from an array of active shim coils, passive shimming elements or any combination thereof; a contained cavity within which the magnetic field strength is approximately uniform; and a means, such as a plurality of conveyor belts, pipes or any other transportation means by which a plurality of samples are introduced into the region of uniform magnetic field; such that magnetic resonance measurements are made on a plurality of samples within the region of uniform magnetic field. The invention depicts a cost effective method for obtaining a self-fastening cage of a MRD (100) characterized by an outside shell comprising superimposing at least three flexi-jointed walls (1) so that a homogeneous, stable and uniform magnetic field is provided therein.

Proceedings ArticleDOI
08 May 2006
TL;DR: In this paper, a reluctance network analysis (RNA) model of a switched reluctance motor considering iron loss was proposed, which consists of a multiple number of nonlinear reluctances and magnetic inductances that express magnetic hysteresis.
Abstract: This paper presents a reluctance network analysis (RNA) model of a switched reluctance motor considering iron loss. The proposed RNA model consists of a multiple number of nonlinear reluctances and magnetic inductances that express magnetic hysteresis. The validity of the proposed model is proved by comparing calculated values with measured ones. Furthermore, differences between symmetric and asymmetric excitation are investigated

Journal ArticleDOI
TL;DR: In this paper, the authors proposed an effective method to calculate inductance and static thrust of a permanent magnet (PM)-type transverse flux linear motor (TFLM), which can be used not only in characteristic assessment, but also in the design process.
Abstract: This paper proposes an effective method to calculate inductance and static thrust of a permanent magnet (PM)-type transverse flux linear motor (TFLM). The proposed method is a simple and fast way considering three-dimensional (3-D) flux path of the TFLM, and it can be used not only in characteristic assessment, but also in the design process. Two-dimensional (2-D) finite element analysis (FEA) and 3-D equivalent magnetic circuit network (EMCN) analysis are conducted to analyze the magnetic field. The usefulness of the proposed method is verified by comparison with measurement results.

Journal ArticleDOI
Yoshihiro Kawase1, Tadashi Yamaguchi1, K. Iwashita1, T. Kobayashi1, K. Suzuki 
TL;DR: In this article, the operating characteristics of the electromagnet with permanent magnets were analyzed using the three-dimensional finite element method, and the authors showed that the distribution of flux density is very complex when the voltage is applied to the coil of the magnet.
Abstract: There are many kinds of electromagnets for various kinds of fields. The electromagnet with permanent magnets in this paper is one of them in order to improve energy saving. The distribution of flux density is very complex when the voltage is applied to the coil of the electromagnet with permanent magnets. In this paper, the operating characteristics of the electromagnet with permanent magnets are analyzed using the three-dimensional finite element method

Patent
20 Dec 2006
TL;DR: In this paper, a lamellar high resistance layer having resistivity ten times or higher than that of a mother phase containing iron or cobalt is formed and an oxygen content is controlled to 10 to 10000 ppm so that the reliability and residual magnetic flux density are increased.
Abstract: A lamellar high resistance layer having resistivity ten times or higher than that of a mother phase containing iron or cobalt is formed and an oxygen content is controlled to 10 to 10000 ppm so that the reliability and residual magnetic flux density are increased.

Journal ArticleDOI
TL;DR: In this paper, a triple magnetic circuit type thermomagnetic engine with a water-cooling system has been designed and the performance characteristics such as power, resistance loss, and the relation between the temperature of the rotor and the rotation speed have been measured.
Abstract: The engine essentially consists of a rotor made of temperature-sensitive magnetic material and permanent magnets. When an object made of this material has a temperature distribution in the magnetic field, the force is generated in the direction from the low-temperature side to the high-temperature side by magnetic pressure. This paper describes the fundamental performance of the triple magnetic circuit type thermomagnetic engine. A triple magnetic circuit type engine with water-cooling system has ben designed. The performance characteristics such as power, resistance loss, and the relation between the temperature of the rotor and the rotation speed have been measured, and compared with the characteristics of a single magnetic circuit type engine. The net power is a maximum value of 3.7 W at a rotation speed of 0.4 rps. The power of the triple magnetic circuit type engine per unit magnetic circuit is about 4 times larger than that of the single magnetic circuit type engine. The resistance loss is 1.7 W at the maximum power point. The total power is 5.4 W. Electromagnetic braking loss is about 25% of the total power. The rate of electromagnetic braking loss to the total power increases with the rotation speed. The disk type rotor with small electromagnetic braking loss has been analyzed. Electromagnetic braking loss of the disk type engine becomes about 95% smaller than that of the cylinder type engine. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 154(4): 68–74, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20127

25 Oct 2006
TL;DR: In this paper, a push-pull actuator based on magnetic shape memory alloys (MSMA) is proposed, where the magnetic fields are created by coils and concentrated by ferromagnetic circuits.
Abstract: In the field of micromechatronics, microrobotics and specially microfactories, active materials are used in most cases. They permit high resolution and distributed actuation. In this area, Magnetic Shape Memory Alloys (MSMA) are possible candidates. If a lot of studies deal with MSMA, only few applications use them until now. MSMA are attractive active materials because they have large strain (about 10%) as the classical shape memory alloys (SMA), but can provide a 100 times shorter time response. The main disadvantages of MSMA based actuators are the brittleness of the single-crystal material, the difficulty to apply the strong magnetic field required to obtain sufficient strain and the nonlinear behaviour. We propose in this paper a novel MSMA based actuator changing the disadvantage of the hysteretic behaviour into an advantage. This device is a push-pull actuator: two pieces of MSMA material act in an opposite way. The magnetic fields are created by coils and concentrated by ferromagnetic circuits. In order to move the central part of the actuator, a current pulse in the first coil is generated. The hysteretic behaviour of the material permits to keep a stable position when no current is applied. A current pulse in the second coil permits to displace the central part in the opposite direction. The stable position depends on the magnitude and the time duration of the current pulses and an infinity of stable positions can be reached. The use of current pulses permits also a reduction of the coil heating (Joule effect losses) and a reduction of the magnetic circuit size. The performances and characteristics of MSMA are between these of classical SMA and these of piezo-electric materials. A thermo-magneto-mechanical model of our actuator is currently in development in order to design an efficient control law welladapted to the specific MSMA properties.

Journal ArticleDOI
TL;DR: In this paper, a 64-kHz sandwich transducer employing a tube-shaped Terfenol-D/epoxy pseudo 1-3 magnetostrictive composite with 0.61 terfenol D volume fraction was developed to alleviate the intrinsic eddy-current losses in magnetstrictive alloy-based transducers.
Abstract: A 64-kHz sandwich transducer employing a tube-shaped Terfenol-D/epoxy pseudo 1-3 magnetostrictive composite with 0.61 Terfenol-D volume fraction was developed to alleviate the intrinsic eddy-current losses in magnetostrictive alloy-based transducers. The transducer was designed to operate as a half-wave, longitudinal, mass-spring-mass, linear vibrator. It had a length of 15.7 mm and consisted of a magnetic circuit and a prestress mechanism. The magnetic circuit was composed of the composite tube, a pair of ring-shaped NdFeB permanent magnets, a drive solenoid, and a Ni-based magnetic flux guide. The distributions of the dc magnetic flux lines and magnetic field strength of the transducer were determined using an ANSYS finite-element model. The dynamic performance of the transducer was evaluated by measuring its electrical and vibrational characteristics. The results revealed that the transducer resonates at a frequency of 64.3 kHz with a strain coefficient of 39.2 nm/A, a mechanical quality factor of 39.6, and an effective coupling coefficient of 0.21. Eddy-current losses in the transducer were insignificant in the measured frequency range of 40 Hz-100 kHz. The good transducer performance indicated that Terfenol-D/epoxy pseudo 1-3 composites would be a promising magnetostrictive material for ultrasonic applications.

Journal ArticleDOI
01 May 2006
TL;DR: In this article, an improved dynamic model of the switched reluctance machine for use in design has been developed, which is described in two stages: (i) modelling of iron loss and its effect on current waveform in a rudimentary one-phase static SR machine, and (ii) the development of a dynamic model, including instantaneous torque, of a three-phase machine with eddy-current, hysteresis and additional iron losses.
Abstract: An improved dynamic model of the switched reluctance machine for use in design has been developed. The specific requirement was for the incorporation of iron losses, but a secondary benefit has been the inclusion of the magnetic interaction between phases. The work is described in two stages: (i) modelling of iron loss and its effect on current waveform in a rudimentary one-phase static SR machine, and (ii) the development of a dynamic model, including instantaneous torque, of a three-phase machine with eddy-current, hysteresis and additional iron losses. Both stages include experimental verification. Coupling between the phases through shared portions of the magnetic circuits and also through 'leakage flux' is included. Model results are compared with measured values for a three-phase, 12/8-pole motor.