Showing papers on "Magnetic circuit published in 2007"

Magnetic Equivalent Circuit Modeling of Induction Motors

Abstract: Finite element models are invaluable for determining expected machine performance. However, finite element analysis can be computationally intense; particularly if a large numbers of studies or high bandwidth studies are required. One method to avoid this difficulty is to extract machine parameters from the finite element model and use the parameters in lumped parameter models. While often useful, such an approach does not represent space harmonics or asymmetries in the motor. A methodology for constructing a state-variable model, based on a magnetic equivalent circuit of the motor is described herein. In addition, the parameters for this model are based solely on geometrical data. This approach is an excellent compromise between the speed of lumped parameter models and the ability of finite element methods to capture spatial effects. Experimental validation of the model is provided.

Magnetically activated switch assembly

Abstract: A magnetically activated switch assembly is provided. The magnetically activated switch assembly includes a magnet and a magnetic circuit. The magnetic circuit includes a magnetically activated switch, a first set of flux conductors, and a second set of flux conductors. The first set of flux conductors has first flux conductor flanges adapted to conduct flux from ends of the magnet. The second set of flux conductors is slidingly positioned relative to the first set of flux conductors and is adapted to conduct flux from the first set of flux conductors to the magnetically activated switch. The first set of flux conductors are adapted to rotate clockwise or counter-clockwise and to tilt up or down. The first magnetic circuit is adapted to conduct flux to activate the magnetically activated switch only when the first flux conductor flanges are rotationally aligned with ends of the magnet and tilted to an operational position.

Modeling of magnetic vibrational energy harvesters using equivalent circuit representations

Abstract: This paper develops and analyzes an equivalent circuit model of magnetic energy harvesters using reduced-order lumped element modeling (LEM) methods. This model is intended to enhance the design and analysis of a magnetic energy harvesting system by enabling direct physical insight into the system dynamics and simple circuit analysis techniques to extract all relevant performance parameters. Moreover, the model provides the ability to use circuit simulation software (e.g. PSPICE) to model the entire system in conjunction with nonlinear and/or active power electronic circuits. The circuit model is experimentally validated through electrical and mechanical measurements on a prototypical electromagnetic energy harvester.

Magneto‐Dielectric Properties of Mg–Cu–Co Ferrite Ceramics: II. Electrical, Dielectric, and Magnetic Properties

Abstract: DC resistivity, dielectric, and magnetic properties of Mg-ferrite ceramics (Mg1−xCuxFe1.98O4, with x=0.10–0.30, and Mg0.90−xCoxCu0.10Fe1.98O4, with x=0.05–0.20) were investigated. A primary objective is to develop magneto-dielectric materials with almost equal values of permeability and permittivity, as well as low magnetic and dielectric loss tangent, for miniaturization of antennas. The MgFe1.98O4 ceramic sintered at 1125°C possessed values of permeability and permittivity of ∼6.5, and relatively low magnetic and dielectric loss tangents of <10−2, with a sintered density of only ∼70% of the theoretical density. Incorporation of Cu was found to be able to not only improve the densification and grain growth but also alter the electrical and magnetic properties of MgFe1.98O4. Further modification by Co resulted in promising magneto-dielectric materials, with an almost equal permeability and permittivity of ∼9.5 over 3–30 MHz (HF band). Together with their low magnetic and dielectric loss tangents and good sinterability, this class of magneto-dielectric materials could be potential candidates for the design of small antennas in the HF band (3–30 MHz). The DC resistivities and complex relative permittivities of the ferrite ceramics were discussed with respect to their microstructure, grain size, and the formation of Fe2+ ions. The variation of high-frequency magnetic properties of the ferrite materials with sintering temperature can be quantitatively understood by the magnetic circuit model and the Snoek-like law.

Power Law on Trapped Magnetic Field in Bulk YBaCuO

Abstract: Temperature, current density and magnetic field distributions in YBCO bulk superconductor during a pulsed-field magnetization (PFM) process are calculated using the finite differ- ence method. Simulations are based on the heat diffusion equation with account of the heat produced by flux motion, and Maxwell's equations. A power law with temperature and magnetic field dependent parameters is used to characterize the electromagnetic behavior of the superconducting material. We analyze how the stored magnetic energy depends on the temperature and field dependences of the power law.

Circular Hall Transducer for Angular Position Sensing

Abstract: We developed a new integrated magnetic sensor based on the Hall effect, suitable for contactless 360deg absolute angle encoding. The sensing device consists of a narrow n-well ring with a chain of 64 contacts equally distributed along the ring. It is connected to on-chip biasing and signal conditioning circuits that provides the magnitude and the phase of the in-plane component of the magnetic field. In a homogenous magnetic field, the transducer angular resolution is 0.01deg in the 1 kHz frequency bandwidth and the absolute accuracy is about 1deg and 0.1deg without and with output offset calibration, respectively.

Optimal Design of Magnetically Actuated Optical Image Stabilizer Mechanism for Cameras in Mobile Phones via Genetic Algorithm

Abstract: This paper proposes an optimal electromagnetic actuator for the application of optical image stabilization in cameras of mobile phones. The image stabilization composes of vertical and horizontal moving platforms to compensate the shaking from hands. The platforms are actuated by the magnetic force from voice coil motors (VCMs). For the application of mobile devices, geometry size of the mechanism is extremely limited. However, the larger the size of yoke that covers the magnetic field is, the better uniformity it will perform. This study, therefore, is dedicated to conduct an optimal design with the coupled relationship between magnetic field and mechanical geometry. The magnetic field is converted to equivalent circuit in terms of mechanism geometry, and verified by ANSYS. The genetic algorithm (GA) is then applied for deriving optimal values of geometry dimensions of the system within satisfactory uniform magnetic field

A Magnetic Circuit Model for an IPM Synchronous Machine Incorporating Moving Airgap and Cross-Coupled Saturation Effects

Abstract: A new magnetic circuit model is presented for an interior permanent magnet (IPM) synchronous machine, using a machine with three-phase distributed stator windings and three layers of flux barriers in the rotor as an example topology. The model accounts for: i) the effects of cross-coupled magnetic saturation caused by the salient rotor; ii) variation of magnetic saturation levels in the iron rotor bridges that are key elements of the unitary rotor laminations; iii) the effects of stator lamination slots on the airgap mmf distribution; and iv) the local variation of airgap permeance due to the stator slotting and the relative position of the rotor with respect to the stator. As a result of these features, the new model is capable of significantly improving the accuracy of electromagnetic performance predictions for aggressively-designed IPM machines compared to previously-available magnetic circuit models. Comparisons with finite-element analysis and measurement results are provided showing that the new model is much faster while delivering appealing accuracy compared to the FE method.

Positionally sequenced loudspeaker system

Abstract: A variety of loudspeaker arrangements may have any of multiple adjacent magnetic circuits, single magnetic circuits, an improved loudspeaker voice coil assembly, multiple voice coil windings (124-127, 315-317), and commutated current. The radial direction of flux may alternate at adjacent poles and may have a controller that commands the current through each of the windings. The position of the moving components may be measured or inferred by the controller (213). An encoding track (318a) applied to the surface of the assembly may allow the assembly to function as part of a position transducer to permit appropriate action based on position. Calculated or sensed actual position may be used to determine the relative current in each of the windings and the controller may have compensation such as a motion control algorithm, thermal monitoring, and management of the driver. The voice coil assembly (305 c) may have foil conductors applied to a substrate to connect and interconnect a single or multiple voice coil windings with minimal effect on the magnetic gap (303b) width.

Torque Detection Device

Abstract: An inventive torque detection device includes: a magnetic circuit forming member having a tubular magnet provided at a first rotating body, and a magnetic ring that is located circumferentially of the tubular magnet and rotated together with a second rotating body connected to the first rotating body; a magnetic flux collecting ring part for collecting a generated magnetic flux; a detection part for detecting, based on a density of the collected magnetic flux, a torque applied to the first or second rotating body; and a molded body that is molded at an outer circumferential portion of the first rotating body, and is joined to longitudinal both sides of the tubular magnet so as to fix the tubular magnet to the first rotating body. A molding pressure, generated when the tubular magnet is molded, is applied in the longitudinal direction of the tubular magnet.

Space Mapping Optimization of the Magnetic Circuit of Electrical Machines Including Local Material Degradation

Abstract: Production processes like cutting, performed on electrical steel laminations, influence their magnetic properties locally. Since the magnetic design of electrical machines does not take this effect into account accurately, the design may be suboptimal. Therefore, the need exists to develop a numerical procedure which is capable of optimizing electrical devices, taking into account the local material degradation and featuring high accuracy and acceptable calculation time. We developed a space mapping procedure meeting these requirements and we quantified the influence of the material degradation on the design of a switched reluctance motor (SRM). The results of the optimization show that the local material degradation has a significant influence on the dimensions of stator and rotor yoke

Combined Radial-Axial Magnetic Bearing for a 1 kW, 500,000 rpm Permanent Magnet Machine

Abstract: Ultra-high-speed and high-power-density drives are attracting much interest in today's industry. For instance, there are several investigations into mesoscale gas turbine generator systems and turbocompressors for fuel cells. In all ultra-high-speed machinery the bearing is a key technology. Therefore, this paper focuses on the design of a 500,000 rpm active magnetic bearing suitable for use in a 1 kW PM machine to complete an ultra-high-speed electrical drive system. The design procedure selects the suitable magnetic bearing type to keep the system compact and small. The electromagnetic characteristics are determined, the results for the rotor dynamic analysis are presented and the air friction losses caused by the high frequency operation are evaluated. The final design is a combined radial-axial magnetic bearing with a volume of 50 cm3.

Magnetic Coupling Analysis of Four-Quadrant Transducer Used for Hybrid Electric Vehicles

Abstract: A four-quadrant transducer (4QT), which is a hybrid electric vehicle power train concept, is a structural integration of two permanent-magnet synchronous machines. It comprises three parts: stator, outer rotor, and inner rotor. As the outer rotor is a structural and magnetic common part of the two radial-flux machines, the magnetic circuits of the two machines are coupled. A new method is put forward to solve the permanent-magnet operating point when considering the magnetic coupling during machine design, and a 4QT prototype machine of 60 kW is designed. The influences of the magnetic coupling on flux distribution and electromagnetic torque are discussed by analytical method and finite-element method, respectively. It can be concluded that the decoupling is easy to perform. The magnetization-direction choice of the two layers of the permanent magnets on the outer rotor is also discussed, and the consistent magnetization is preferred

Control of flux in magnetic circuits for Barkhausen noise measurements

Abstract: The consistency of magnetic Barkhausen noise (MBN) measurements under applied sinusoidal magnetic field control and sinusoidal magnetic circuit flux control was investigated under variable circuit permeability conditions. A U-core electromagnet was used to provide the alternating magnetic excitation. The magnetic circuit permeability was changed by varying excitation magnet lift-off and by using samples with known magnetic anisotropy. By controlling the circuit magnetic flux, measured as the flux in one of the U-core poles near the sample, MBN measurements were found to be consistent and independent of the excitation magnet lift-off in both a Si–Fe steel sample and an interstitial free (IF) steel sample at peak sample flux densities greater than 1.16 T and 0.29 T respectively. Consistency within a 95% confidence level was demonstrated for lift-off values of 0.6 mm or less, with decreasing sensitivity to lift-off observed at higher fluxes. MBN anisotropy measurements were also performed using both field control and flux control. Under field control conditions a component of the anisotropy signal was found to be dependent on the magnetic circuit permeability. This permeability dependence was absent when using flux control. The results demonstrated that flux control should be used when performing MBN measurements on samples where lift-off may be an issue, as values obtained will have less dependence on the excitation magnet characteristics than when field control is used.

Applied Electromagnetics : Early Transmission Lines Approach

Abstract: CHAPTER 1. Introduction. 1.1 Electromagnetic Fields. Electric Fields. Magnetic Fields. Field Linkage. 1.2 The Electromagnetic Spectrum. 1.3 Wireless Communications. 1.4 Dealing with Units. 1.5 Working with MATLAB. MATLAB Programs. 1.6 Wave Fundamentals. 1.7 Phasors. Summary. Problems. CHAPTER 2. Transmission Lines. 2.1 Distributed-Parameter Model. Coaxial Cable. Telegraphist's Equations. 2.2 Time-Harmonic Waves on Transmission Lines. Characteristic Impedance. Lossless Line. 2.3 Power Transmission. 2.4 Terminated T-Lines. Voltage Standing Wave Ratio. Input Impedance. Complex Loads. Special Terminations. 2.5 The Complete Circuit. 2.6 The Smith Chart. Smith Chart Derivation. Using the Smith Chart. Impedance Measurement. 2.7 Impedance Matching. Quarter-Wave Transformer. Matching with the Smith Chart. Admittance of Shunt Stubs. Shunt Stub Matching. 2.8 Transients. Pulse Response. Practical Application: Schottky-Diode Terminations. Reactive Loads. Time-Domain Reflectometry. 2.9 Dispersion. Summary. Problems. CHAPTER 3. Electrostatics. 3.1 Vectors in the Cartesian Coordinate System. 3.2 Coulomb's Law. Electric Field Intensity. Field Lines. 3.3 The Spherical Coordinate System. 3.4 Line Charges and the Cylindrical Coordinate System. Infinite Length Line of Charge. Ring of Charge. 3.5 Surface and Volume Charge. Volume Charge. Practical Application: Laser Printer. 3.6 Electric Flux Density. 3.7 Gauss's Law and Applications. Coaxial Cable. 3.8 Divergence and the Point Form of Gauss's Law. 3.9 Electric Potential. Gradient. 3.10 Conductors and Ohm's Law. Current and Current Density. Joule's Law. 3.11 Dielectrics. Practical Application: Electret Microphone. 3.12 Boundary Conditions. 3.13 Boundary Value Problems. 3.14 Capacitance. Electrostatic Potential Energy. Practical Application: Electrolytic Capacitors. Summary. Problems. CHAPTER 4. Magnetostatics. 4.1. Magnetic Fields and Cross Product. Oersted's Experiment. 4.2 Biot-Savart's Law. Solenoid. Surface and Volume Current Densities. 4.3 Ampe're's Circuital Law. 4.4 Curl and the Point Form of Ampe're's Circuital Law. Stoke's Theorem. 4.5 Magnetic Flux Density. 4.6 Magnetic Forces. Force on a Current Element. Magnetic Torque and Moment. Practical Application: Loudspeakers. 4.7 Magnetic Materials. 4.8 Boundary Conditions. 4.9 Inductance and Magnetic Energy. Mutual Inductance. Magnetic Energy. 4.10 Magnetic Circuits. Electromagnets. Practical Application: Maglev. Summary. Problems. CHAPTER 5. Dynamic Fields. 5.1 Current Continuity and Relaxation Time. 5.2 Faraday's Law and Transformer EMF. Transformer EMF. Transformers. Point Form of Faraday's Law. 5.3 Faraday's Law and Motional EMF. Generators. 5.4 Displacement Current. 5.5 Maxwell's Equations. 5.6 Lossless TEM Waves. 5.7 Time-Harmonic Fields and Phasors. Summary. Problems. CHAPTER 6. Plane Waves. 6.1 General Wave Equations. Time-Harmonic Wave Equations. Propagating Fields Relation. 6.2 Propagation in Lossless, Charge-Free Media. 6.3 Propagation in Dielectrics. Low-Loss Dielectrics. Loss Tangent. 6.4 Propagation in Conductors. Current in Conductors. 6.5 The Poynting Theorem and Power Transmission. UPW Power Transmission. 6.6 Polarization. Practical Application: Liquid Crystal Displays. 6.7 Reflection and Transmission at Normal Incidence. General Case. Standing Waves. 6.8 Reflection and Transmission at Oblique Incidence. TE Polarization. TM Polarization. Summary. Problems. CHAPTER 7. Waveguides. 7.1 Rectangular Waveguide Fundamentals. Wave Propagation. Waveguide Impedance. Practical Application: Microwave Ovens. 7.2 Waveguide Field Equations. TM Mode. TE Mode. 7.3 Dielectric Waveguide. TE Mode. TM Mode. Field Equations. 7.4 Optical Fiber. Numerical Aperture. Signal Degradation. Attenuation. Graded-Index Fiber. 7.5 Fiber-Optic Communication Systems. Optical Sources. Optical Detectors. Repeaters and Optical Amplifiers. Connections. 7.6 Optical Link Design. Power Budget. Rise-Time Budget. Summary. Suggested References. Problems. CHAPTER 8. Antennas. 8.1 General Properties. Radiated Power. Radiation Patterns. Directivity. Impedance and Efficiency. A Commercial Antenna. 8.2 Electrically Short Antennas. Vector Magnetic Potential. The Hertzian Dipole. The Small Loop Antenna. 8.3 Dipole Antennas. Derivation of Fields. Antenna Properties. Half-Wave Dipole. 8.4 Monopole Antennas. Image Theory. Antenna Properties. Practical Considerations. 8.5 Antenna Arrays. Pair of Hertzian Dipoles. N-Element Linear Array. Parasitic Arrays. 8.6 The Friis Transmission Equation. Polarization Efficiency. Receiver Matching. 8.7 Radar. Doppler Frequency Shift. 8.8 Antennas for Wireless Communications. Parabolic Reflectors. Patch Antennas. Slot Antennas. Folded Dipole Antennas. Summary. Suggested References. Problems. CHAPTER 9. Electromagnetic Interference. 9.1 Interference Sources. Lightning. Electrostatic Discharge. Power Disturbance Sources. Radio Transmitters. 9.2 Passive Circuit Elements. Conductors. Resistors. Inductors. Capacitors. 9.3 Digital Signals. 9.4 Grounds. Bond Wires. Signal Grounds. Loop Area. 9.5 Shields. Shielded Cable. 9.6 Filters. Reflective Filters. Ferrite Chokes. Summary. Suggested References. Problems. CHAPTER 10. Microwave Engineering. 10.1 Microstrip. Attenuation. Other Planar T-Lines. 10.2 Lumped-Element Matching Networks. 10.3 Scattering Parameters. Reciprocal Networks. Lossless Networks. Return Loss and Insertion Loss. Shift in Reference Plane. The Vector Network Analyzer. 10.4 Couplers and Dividers. Circulators. Three-Port Dividers. Couplers. 10.5 Filters. Simple Filters. Multisection Filters. High-Pass Filters. Bandpass Filters. 10.6 Amplifiers. Designing Matching Networks. Balanced Amplifiers. 10.7 Receiver Design. Oscillators. Mixers. Microwave CAD. Practical Application: Radio Frequency Identification. Summary. Suggested References. Problems. APPENDIX A. Vector Relations 614 APPENDIX B. Coordinate System Transformations. APPENDIX C. Complex Numbers. APPENDIX D. Integrals, Conversions, and Constants. APPENDIX E. Material Properties. APPENDIX F. CommonMATLABMath Functions. APPENDIX G. Answers to Selected Problems. INDEX.

Magnetic Equivalent Circuit Simulations of Electrical Machines for Design Purposes

Abstract: New developments in power electronics technology, materials, and changing application requirements are driving advances in electric machines. But limitations of standard motor design, particularly induction machine design, limit performance capabilities in drive applications. Computer-aided design tools are not available to overcome these limitations. This paper presents a magnetic equivalent circuit modeling approach geared towards design. Magnetic equivalent circuits are flexible in terms of size and accuracy, have moderate computational complexity, are easily parameterized, and can be extended readily to three-dimensional analysis. Comparisons with results from finite element models and measurements indicate that magnetic equivalent circuits, corrected for local saturation, are a promising option for a design tool.

Perpendicular magnetic recording head and magnetic disk apparatus

Abstract: According to one embodiment, a perpendicular magnetic recording head includes a main pole which generates a recording magnetic field, a return pole which forms a closed magnetic circuit for the recording magnetic field, and a side shield magnetically spaced from the main pole in a cross-track direction in which a point on a trailing edge of the side shield which is closest to the main pole is positioned on a leading side of a trailing edge of the main pole.

Optimal Number of Stator Poles for Compact Active Radial Magnetic Bearings

Abstract: We present a method for finding the optimal number of stator poles for active radial magnetic bearings that minimizes the stator outside diameter. We use magnetic circuit analysis to determine the number of turns of wire to generate the worst case load capacity within limits of coil currents and flux densities. Using the analysis, we developed six types of magnetic bearing for a given value of journal diameter. We found that 3-pole bearings yield the smallest outside diameter among the six types of bearing for a journal diameter less than 50 mm; however, all the bearings have almost the same outside diameter for a journal diameter larger than 200 mm. For an infinite-length bearing, the stator diameter is a linear function of the product of numbers of poles and coil turns. We applied a linear controller design method to a heteropolar 3-pole magnetic bearing that has nonlinear coupling between the orthogonal components of bearing force. With this controller, we successfully levitated a slender-rotor system and rotated it at 3571 rpm.This paper treats the optimal number of stator poles for active radial magnetic bearings in a sense of minimizing the stator outside diameter. The magnetic circuit analysis is used to determine the number of turns of wire to generate the worst case load capacity within limits of coil currents and flux densities. Owing to the analysis, six types of magnetic bearing are designed for a given value of journal diameter. The designed stator outside diameters show that 3-pole bearings are the smallest among the six types of bearing for a smaller value of journal diameter than 50 mm, and, however, all the bearing have almost the same outside diameter when a journal diameter is larger than 200 mm. For an infinite-length bearing, the stator diameter is a linear function of the product of numbers of poles and coil turns. A linear controller design method is applied to a heteropolar 3-pole magnetic bearing that has nonlinear coupling between the orthogonal components of bearing force. A slender-rotor system is successfully levitated by the designed controller and rotated at the speed of 3571 rpm.

Modeling of end-effect in flux-switching permanent magnet machines

Abstract: A lumped parameter magnetic circuit model is employed to predict the influence of the finite length of a flux- switching permanent magnet machine on the electromagnetic torque. It enables performance predictions from 2-D finite element analysis to be used to analyze the electromagnetic performance with due account of end-effects. A simplified method for determining the ratio of actual torque to the torque which would be developed when end-effects are neglected is proposed. The torque predicted in this way is validated by 3-D finite element analysis.

Enhanced Modeling of Linear Permanent-Magnet Synchronous Motors

Abstract: Modeling of air-gap flux density distribution produced by magnet poles is essential for analysis and design of linear permanent-magnet synchronous motors. This is usually done by time-consuming numerical methods which are difficult to be incorporated in iterative motor design procedures or by approximate models which lack desirable accuracy. This paper presents an alternative method to model the air-gap flux density distribution which is both accurate and simple enough to be integrated into iterative motor design procedures. It consists of the solution of an improved magnetic equivalent circuit and an air-gap flux density distribution function (FDDF). The end teeth effects and magnetic saturation of iron core can be taken into account in the modeling. Different motor characteristics are calculated by means of the proposed FDDF. The accuracy of the proposed method in modeling of the machines is verified by the finite-element method and its superiority over a recent method based on an extensive machine model is demonstrated

Current detection device

Abstract: The present invention provides a low-cost current detection device having a magnetic sensor easily placed on a choke coil, wherein assembly and manufacturing costs are reduced and a product is miniaturized. A current detection device including a choke coil for smoothing an input current or an output current and a magnetic sensor 1 a built into the choke coil to detect the input current or output current, wherein the choke coil is composed of: a pair of cores 5 provided with an outer magnetic leg 5 a constituting a closed magnetic circuit and a center magnetic leg 5 b for providing a gap; and an air core coil 6 mounted on the center magnetic leg 5 b , and space 6 b is provided to a part of winding of the air core coil 6 with the magnetic sensor 1 a placed in the gap between the space 6 b and the center magnetic leg 5 b.

Magnetic Equivalent Circuit Modeling of Induction Machines Design-Oriented Approach with Extension to 3-D

Abstract: Advances in power electronics technology, materials, and changing application requirements are driving advances in electric machines. But induction machines are not often considered for new design possibilities. One reason is that computer-aided design tools for induction machines are not readily available. Analytical and finite element models have significant disadvantages that limit their effectiveness for induction machine design. This paper presents a magnetic equivalent circuit modeling approach that is geared towards design. Magnetic equivalent circuits are flexible in terms of size and accuracy, have moderate computational complexity, and are easily parameterized. They can be extended readily to three-dimensional analysis. Comparisons with results from finite element models and measurements indicate that magnetic equivalent circuits, corrected for local saturation, are a promising option for a design tool.

Three-dimensional measurement probe

Abstract: A three-dimensional measurement probe that is less likely to break, that is of long lifespan, and that is of low cost, capable of measuring the shape and the like of a measuring object such as an aspheric lens with higher precision is realized. A magnetic force for preventing rotation and axial displacement of a small slidably moving shaft part is generated by constructing a magnetic circuit by a magnet attached to a small air bearing part, a yoke, and a magnetic pin attached to the small slidably moving shaft part. The three-dimensional measurement probe is able to perform measurement from below and from the side since the magnetic force is non-contacting.

Devices and methods for redistributing magnetic flux density

Abstract: A method and devices to redistribute magnetic flux density within electro-magnetic or permanent magnet devices to increase utilization of magnetic core material and increase its power density. Magnetic core bias currents (291, 292), synchronized to the device's magnetizing current, through uniform, longitudinally isolated, magnetic core (302, 301) sections are used. Local core bias currents (292) that generate magnetic flux that oppose the incident magnetizing flux in local magnetic core sections with high flux density concentrations such as core corners may be added. Examples of the types of electro-magnetic and permanent magnet devices that benefit from the appropriate application of magnetic flux density redistribution include electrical devices such as transformers, inductors, delay lines, and electromechanical devices such as motors, generators, relays, solenoids, and rail guns.

Permanent-magnet magnetic actuator of reduced volume

Abstract: A magnetic actuator comprises at least one coil surrounded by a magnetic circuit. The magnetic circuit possesses three legs and two facing end plates. The three legs comprise two outer legs on either side of the coil and an intermediate leg passing through the coil. The legs have no direct mechanical contact with one another. The two facing end plates magnetically interconnect the three legs. The magnetic circuit comprises a moving armature comprising at least one of the end plates, and a stationary portion including a yoke having at least the other one of the end plates and at least one permanent magnet. The permanent magnet is placed at one end of the intermediate leg beside the end plate of the yoke. The magnetic actuator can control medium-voltage and high-voltage circuit breaker vacuum chambers.

Simulation of Vibration Power Generator

Abstract: This paper deals with the simulation of a vibration power generator that has been developed in scope of the European Project “WISE”. The vibration power generator generates electrical energy from an ambient mechanical vibration. The generator is a suitable source of electrical energy for wireless sensors which operate in vibration environment. When the generator is excited by mechanical vibration, its construction produces a relative movement of a magnetic circuit against a fixed coil. Thereby the movement induces voltage on the coil due to Faraday’s law. This paper describes the modelling of the vibration power generator in Matlab/Simulink.

Performance Evaluation of Two Different Bypass-type MR Shock Dampers:

Abstract: This article presents the performance evaluation of two different bypass-type magneto-rheological (MR) shock dampers for high impulsive force systems, one of which is a single-ended damper and the other a double-ended one. First of all, MR shock dampers are designed and manufactured on the basis of the Bingham properties of MR fluid and the result of the magnetic field analysis for the magnetic circuit. After experimental investigations on both the magnetic field-dependent damping force and the response characteristics, the quasi-steady state models describing the dynamic behavior of the proposed dampers are formulated. Then, a simple one degree-of-freedom mass-drop system as a test bench for the MR shock dampers is constructed, and the simple and practical control algorithm is proposed in consideration of dynamic characteristics of the shock control system. Finally, in order to investigate their dynamic characteristics and control performances under shock condition, a comparison study is conducted throug...

Method for the operation of a single-phase electronically commutated motor on a direct current source, and motor for performing such a method

Abstract: The invention relates to an electronically commutated motor (20) operated on a direct current source (UB), for example, a direct current intermediate circuit (46). The motor has a permanent magnetic rotor (28) and a stator having a stator winding phase (26) in which an alternating voltage is induced during operation by the permanent magnetic rotor (28). The motor further has an H-bridge circuit (22) comprising power semiconductors (T1 to T4). The circuit (22) has an upper bridge half (38) that is connected during operation to a pole (46) of the direct current source (UB) and a lower bridge half (56) that is connected during operation to the other pole (50) of the direct current source (UB). The stator winding phase (26) is disposed in the diagonal (24) of the H-bridge circuit (22) and, during operation, a current pulse flows through it, first in one direction and then in the other. One commutation process each occurs between two consecutive current pulses (i1, i1'). At the beginning of a commutation process, the currently conducting semiconductor switch of the one bridge half (38) is switched off in order to interrupt the energy supply from the direct current source (UB) such that a circulating current (i*; -i*) flows through the stator winding phase (26) in the other bridge half (56), the semiconductor circuit, which continues to be controlled in a conductive fashion, and a free-wheeling diode (58; 60) associated with the closed semiconductor circuit of this other bridge half. Said circulating current converts the energy stored in the magnetic circuit of the motor (20) at least partially into drive energy for the permanently magnetic rotor (28), thus adjusting to zero. Said current-free state of the stator winding phase (26) is detected in a sensor-free fashion by measuring the voltage (uind) that is induced in the stator winding phase (26) by the rotor (28). The previously conducting semiconductor circuit of the other bridge half (56) is blocked. The commutation process is completed in that a current is supplied to the stator winding phase (26) from the direct current source (UB) in a direction opposite to the direction in which the current was flowing before the commutation process. The invention further relates to a motor for performing such a method.