Showing papers on "Magnetic circuit published in 2005"

Axial Flux Permanent Magnet Brushless Machines

Abstract: Introduction 11 Scope 12 Features 13 Development of AFPM Machines 14 Types of Axial Flwr PM Machines 15 Topologies and Geometries 16 Rotor Dynamics 17 Axial Magnetic Field Excited by PMs 18 PM Eddy-Current Brake as the Simplest AFPM Brushless Machine 19 AFPM Machines versus RFPM Machines 110 Power Limitation of AFPM Machines Numerical Examples 2 Principles of AFPM Machines 21 Magnetic Circuits 211 Single-Sided Machines 212 Double-Sided Machines With Internal PM DiscRotor 213 Double-Sided Machines With Internal Ring-Shaped Core Stator 214 Double-Sided Machines With Internal Slotted Stator 215 Double-Sided Machines With Internal Coreless Stator 216 Multidisc Machines 22 Windings 221 Three-Phase Windings Distributed in Slots 222 Toroidal Winding 223 Coreless Stator Winding 224 Non-Overlap (Salient Pole) Windings 23 Torque Production 24 Magnetic Flux 25 Electromagnetic Torque and EMF 26 Losses and Efficiency 261 Stator Winding Losses 262 Stator Core Losses 263 Core Loss Finite Element Model 264 Losses in Permanent Magnets 265 Rotor Core Losses 266 Eddy Current Losses in Stator Conductors 267 Rotational Losses 268 Losses for Nonsinusoidal Current 269 Efficiency 27 Phasor Diagrams 28 Sizing Equations 29 Armature Reaction 210 AFPM Motor 2101 Sine-Wave Motor 2102 Square-Wave Motor 211 AFPM Synchronous Generator 2111 Performance Characteristics of a Stand Alone Generator 2112 Synchronization With Utility Grid Numerical Examples 3 Materials and Fabrication 31 Stator Cores 311 Nonoriented Electrical Steels 312 Amorphous Ferromagnetic Alloys 313 Soft Magnetic Powder Composites 314 Fabrication of Stator Cores 32 Rotor Magnetic Circuits 321 PM Materials 322 Characteristics of PM Materials 323 Operating Diagram 324 Permeances for Main and Leakage Fluxes 325 Calculation of Magnetic Circuits With PMs 326 Fabrication of Rotor Magnetic Circuits 33 Windings 331 Conductors 332 Fabrication of Slotted Windings 333 Fabrication of Coreless Windings Numerical Examples 4 AFPM Machines With Iron Cores 41 Geometries 42 Commercial AFPM Machines With Stator Ferromagnetic Cores 43 Some Features of Iron-Cored AFPM Machines 44 Magnetic Flux Density Distribution in the Air Gap 45 Calculation of Reactances 451 Synchronous and Armature Reaction Reactances 452 Stator Leakage Reactance 46 Performance Characteristics 47 Performance Calculation 471 Sine-Wave AFPM Machine 472 Synchronous Generator 473 Square-Wave AFPM Machine 48 Finite Element Calculations Numerical Examples 5 AFPM Machines Without Stator Cores 51 Advantages and Disadvantages 52 Commercial Coreless Stator AFPM Machines 53 Coreless Stator AFPM Microgenerators 54 Performance Calculation 541 Steady-State Performance 542 Dynamic Performance 55 Calculation of Coreless Winding Inductances 551 Classical Approach 552 FEM Approach 56 Performance Characteristics 57 Performance of Coreless Non-Overlap Winding AFPM Machines 58 Eddy Current Losses in the Stator Windings 581 Eddy Current Loss Resistance 582 Reduction of Eddy Current Losses 583 Reduction of Circulating Current Losses 584 Measurement of Eddy Current Losses 59 Armature Reaction 510 Mechanical Design Features 5101 Mechanical Strength Analysis 5102 Imbalanced Axial Force on the Stator 511 Thermal Problems Numerical Examples 6 AFPM Machines Without Stator and Rotor Cores 61 Advantages and Disadvantages 62 Topology and Construction 63 Air Gap Magnetic Flux Density 64 Electromagnetic Torque and EMF 65 Commercial Coreless AFPM Motors 66 Case Study: Low-Speed AFPM Coreless Brushless Motor 661 Performance Characteristics 662 Cost Analysis 663 Comparison With Cylindrical Motor With Laminated Stator and Rotor Cores 67 Case Study: Low-Speed Coreless AFPM Brushless Generator 68 Characterist

Analysis of electromagnetic performance of flux-switching permanent-magnet Machines by nonlinear adaptive lumped parameter magnetic circuit model

Abstract: A nonlinear adaptive lumped parameter magnetic circuit model is developed to predict the electromagnetic performance of a flux-switching permanent-magnet machine. It enables the air-gap field distribution, the back-electromotive force (back-EMF) waveform, the winding inductances, and the electromagnetic torque to be calculated. Results from the model are compared with finite-element predictions and validated experimentally. The influence of end effects is also investigated, and optimal design parameters, such as the rotor pole width, the stator tooth width, and the ratio of the inner to outer diameter of the stator, are discussed.

Inductors and Transformers for Power Electronics

Abstract: FUNDAMENTALS OF MAGNETIC THEORY Basic Laws of Magnetic Theory Magnetic Materials Magnetic Circuits References FAST DESIGN APPROACH INCLUDING EDDY CURRENT LOSSES Fast Design Approach Examples Conclusions Appendix 2.A.1: Core Size Scale Law for Ferrites in Non-Saturated Thermal Limited Design Appendix 2.A.2: Eddy Current Losses for Wide Frequency Appendix 2.A.3: MathCAD Example Files References SOFT MAGNETIC MATERIALS Magnetic Core Materials Comparison and Applications of the Core Materials in Power Electronics Losses in Soft Magnetic Materials Ferrite Core Losses with Non-Sinusoidal Voltage Waveforms Wide Frequency Model of Magnetic Sheets Including Hysteresis Effects Appendix 3.A: Power and Impedance of Magnetic Sheets References COIL WINDING AND ELECTRICAL INSULATION Filling Factor Wire Length Physical Aspects of Breakdown Insulation Requirements and Standards Thermal Requirements and Standards Magnetic Component Manufacturing Sheet References EDDY CURRENTS IN CONDUCTORS Introduction Basic Approximations Losses in Rectangular Conductors Quadrature of the Circle Method for Round Conductors Losses of a Current Carrying Round Conductor in 2-D Approach Losses of a Round Conductor in a Uniform Transverse AC Field Low Frequency 2-D Approximation Method for Round Conductors Wide Frequency Method for Calculating Eddy Current Losses in Windings Losses in Foil Windings Losses in Planar Windings Appendix 5.A.1: Eddy Current 1-D Model for Rectangular Conductors Appendix 5.A.2: Low Frequency 2-D Models for Eddy Current Losses in Round Wires Appendix 5.A.3: Field Factor For Inductors References THERMAL ASPECTS Fast Thermal Design Approach (Level 0 Thermal Design) Single Thermal Resistance Design Approach (Level 1 Thermal Design) Classic Heat Transfer Mechanisms Thermal Design Utilizing a Resistance Network Contribution to Heat Transfer Theory of Magnetic Components Transient Heat Transfer Summary Appendix 6.A: Accurate Natural Convection Modeling for Magnetic Components References PARASITIC CAPACITANCES IN MAGNETIC COMPONENTS Capacitance Between Windings: Inter Capacitance Self-Capacitance of a Winding: Intra Capacitance Capacitance Between the Windings and the Magnetic Material Practical Approaches for Decreasing the Effects of Parasitic Capacitances References INDUCTOR DESIGN Air Coils and Related Shapes Inductor Shapes Typical Ferrite Inductor Shapes Fringing in Wire-Wound Inductors with Magnetic Cores Eddy Currents in Inductor Windings Foil Wound Inductors Inductor Types Depending on Application Design Examples of Different Types of Inductors Fringing Coefficients For Gapped-Wire-Wound Inductors Analitical Modeling of Combined Litz Wire-Full Wire Inductors References TRANSFORMER DESIGN Transformer Design in Power Electronics Magnetizing Inductance Leakage Inductance Using Parallel Wires and Litz Wires Interleaved Windings Superimposing Frequency Components Superimposing Modes References OPTIMAL COPPER/CORE LOSS RATIO IN MAGNETIC COMPONENTS Simplified Approach Loss Minimization in the General Case Loss Minimization Without Eddy Current Losses Loss Minimization Including Low-Frequency Eddy Current Losses Summary Examples References MEASUREMENTS Introduction Temperature Measurements Power Losses Measurements Measurement of Inductances Core Loss Measurements Measurement of Parasitic Capacitances Combined Measuring Instruments References APPENDIX A: RMS VALUES OF WAVEFORMS Definitions RMS Values of Some Basic Waveforms RMS Values of Common Waveforms APPENDIX B: MAGNETIC CORE DATA ETD Core Data (Economic Transformer Design Core) EE Core Data Planar EE Core Data ER Core Data UU Core Data Ring Core Data (Toroid Core) P Core Data (Pot Core) PQ Core Data RM Core Data APPENDIX C: COPPER WIRES DATA Round Wire Data American Wire Gauge Data Litz Wire Data APPENDIX D: MATHEMATICAL FUNCTIONS References INDEX

Implementation and experimental investigation of sensorless speed control with initial rotor position estimation for interior permanent magnet synchronous motor drive

Abstract: In this paper, a new approach to sensorless speed control and initial rotor position estimation for interior permanent magnet synchronous motor (IPMSM) drive is presented. In rotating condition, speed and rotor position estimation of IPMSM drive are obtained through an extended Kalman filter (EKF) algorithm simply by measurement of the stator line voltages and currents. The main difficulty in developing an EKF for IPMSM is the complexity of the dynamic model expressed in the stationary coordinate system. This model is more complex than that of the surface PMSM, because of the asymmetry of the magnetic circuit. The starting procedure is a problem under sensorless drives, because no information is available before starting. The initial rotor position is estimated by a suitable sequence of voltage pulses intermittently applied to the stator windings at standstill and the measurement of the peak current values of the current leads to the rotor position. Magnetic saturation effect on the saliency is used to distinguish the north magnetic pole from the south. To illustrate our work, we present experimental results for an IPMSM obtained on a floating point digital signal processor (DSP) TMS320C31/40 MHz based control system.

Lightweight ironless-stator PM generators for direct-drive wind turbines.

Abstract: A permanent-magnet electrical machine that employs lightweight spoked structures for both rotor and stator is described. The stator is ironless so that there is no direct magnetic attraction between rotor and stator. The lightweight structures are sufficient to carry the small forces due to the interaction of the permanent magnet field with the stator winding current. Despite the absence of stator iron and a large airgap, rare-earth magnets are able to create a working flux density of about 0.25 T at the winding. This is sufficient for an effective generator design because the lightweight structures offer the opportunity to build generators of unprecedented diameter. The outcome is a generator that has a mass typically 20-30% of equivalent designs based on iron-cored magnetic circuits, and with efficiency greater than 90%.

An innovative magnetorheological damper for automotive suspension: from design to experimental characterization

Abstract: The development of a powerful new magnetorheological fluid (MRF), together with recent progress in the understanding of the behavior of such fluids, has convinced researchers and engineers that MRF dampers are among the most promising devices for semi-active automotive suspension vibration control, because of their large force capacity and their inherent ability to provide a simple, fast and robust interface between electronic controls and mechanical components. In this paper, theoretical and experimental studies are performed for the design, development and testing of a completely new MRF damper model that can be used for the semi-active control of automotive suspensions. The MR damper technology presented in this paper is based on a completely new approach where, in contrast to in the conventional solutions where the coil axis is usually superposed on the damper axis and where the inner cylindrical housing is part of the magnetic circuit, the coils are wound in a direction perpendicular to the damper axis. The paper investigates approaches to optimizing the dynamic response and provides experimental verification. Both experimental and theoretical results have shown that, if this particular model is filled with an 'MRF 336AG' MR fluid, it can provide large controllable damping forces that require only a small amount of energy. For a magnetizing system with four coils, the damping coefficient could be increased by up to three times for an excitation current of only 2 A. Such current could be reduced to less than 1 A if the magnetizing system used eight small cores. In this case, the magnetic field will be more powerful and more regularly distributed. In the presence of harmonic excitation, such a design will allow the optimum compromise between comfort and stability to be reached over different intervals of the excitation frequencies.

An integrated magnetic isolated two-inductor boost converter: analysis, design and experimentation

Abstract: This paper presents an integrated magnetic isolated two-inductor boost converter. Patent pending: USPTO/Worldwide filing number 60/444821. All magnetic components are integrated into one magnetic assembly. Two inductor windings are intrinsically coupled to allow input current to increase only when both primary switches are closed. The operation principle, start-up, and protection mechanisms are detailed. A prototype converter has been built. Experimental and simulation results verify the analysis.

Analytical calculation of the magnetic field produced by electric power lines

Abstract: The magnetic field produced by electric power lines is usually calculated numerically with the use of a computer However, the analytical calculation of the magnetic field is preferable because it results in a mathematical expression for showing its dependences on the various parameters of the line arrangement A method to derive the analytical formula of the magnetic field vector produced by any power line is developed in this paper The specific formulas for the magnetic field produced by any single circuit line in flat, vertical, or delta arrangement, as well as for hexagonal lines considered as double circuit lines in super bundle or low reactance phase arrangements or as six-phase lines, are given The derived formulas are valid at any point with practical importance, close to or far from the line The development of the method is made possible with the use of new kinds of numbers, named double complex numbers, to represent the magnetic field vector in the vicinity of power lines Double complex numbers remarkably simplify the mathematical expressions for the magnetic field vector Using these numbers, it is observed that the infinite terms of the magnetic field multipole expansion, for flat single circuit lines and for lines exhibiting polygonal symmetry are contracted, resulting in simple formulas for the magnetic field vector, which is used to derive the formulas for the resultant value of the magnetic field The general formula of the magnetic field vector produced by an arbitrary power line is a rational function of the distance from it Through the given expressions for the coefficients of this function numerator and denominator, the formula for the magnetic field vector produced by any power line can be derived

Development of transverse flux linear motor with permanent-magnet excitation for direct drive applications

Abstract: This paper presents the development of a transverse flux linear motor (TFLM) with permanent-magnet excitation for Stocker system, which is used for transferring glasses in the liquid crystal display industry. Magnetic field is analyzed by three-dimensional equivalent magnetic circuit network method and two-dimensional finite-element analysis is used to determine the influence of the end effect of a mover on the performance of TFLM. The experimental results of a prototyped motor are in good agreement with the analysis ones.

Bipolar Switched Reluctance Machines: A Novel Solution for Automotive Applications

Abstract: Current vehicle architectures utilize belt driven components such as the coolant pump, air-conditioner, power steering pump, etc. However, the trend toward more electric vehicles requires electromechanical energy conversion devices to replace these inefficient mechanical components. It is essential that electrical machines used in automotive applications to be compatible with the corresponding mechanical and electrical terminals. Furthermore, replacement of belt driven components with electrical drives should be performed as efficient and cost effective as possible. Bipolar switched reluctance machines (SRM) are both cost effective and very robust to the effects of temperature variation. They also offer a very wide speed range and an excellent mechanical integrity, which optimally suits a range of automotive applications including electric propulsion. This paper presents a detailed investigation of the performance indices for bipolar SRM drives. Using a Maxwell stress method, variations of radial and tangential force components due to saliency of the machine and saturation have been studied. Access to distribution of the force components acting on the rotor and stator enables us to provide a more accurate picture of the torque generation and vibration in this family of electric machines. Furthermore, distribution of magnetic forces under multiphase excitation has been studied in detail. Our findings show that bipolar excitation of SRM phases, resulting in a short flux path magnetic circuit, favors its efficiency and power quality while generating higher torque with less pulsation. This is a significant improvement, particularly for automotive applications where the difference in the required number of power electronics components can be justified. An experimental, 2-kW, 42-V, 8/6 SRM drive which has been designed and manufactured in our energy system laboratory was targeted for this study. In addition to our extensive finite-element (FE) analysis, experimental results have been provided to prove theoretical claims.

Axial-flux PM wind generator with a soft magnetic composite core

Abstract: This paper presents the potential application of soft magnetic composite (SMC) material in low speed, directly driven, axial-flux permanent magnet (PM) wind generators. Comparative design studies are conducted on PM wind generators of different configurations with both lamination cores and SMC core. Finite element analysis is used to enhance the design precision, from which analytical formulas are modified. Through careful design an axial-flux PM wind generator with slotted SMC core is built and tested, demonstrating the advantages of better performance, reduced size and weight, low part count and low cost.

Torque detecting apparatus and electric power steering apparatus

Abstract: A torque detecting apparatus according to the present invention comprises a first shaft (1) and a second shaft (2) connected coaxially to each other through a connecting shaft (3), a permanent magnet (5) fixed to the first shaft, a plurality of soft magnetic members (4a, 4b) having a collar (25) provided therein, fitted by pressing with the second shaft (2) and disposed in a magnetic field of the permanent magnet (5) to form a magnetic circuit, and a detector (6) for detecting magnetic flux generated from the soft magnetic members (4a, 4b), wherein the soft magnetic members are integrally molded with a mold body made of synthetic resin, and when a torque is applied to the first shaft or the second shaft, the torque is detected based on an output of the detector (6). The collar is made of a non-magnetic material.

Reluctance motors with bulk HTS material

Abstract: In recent years we have successfully designed, built and tested several reluctance motors with YBCO bulk material incorporated into the rotor, working at 77 K. Our last motor type SRE150 was tested up to 200 kW. The aim of our investigations is the construction of motors with extremely high power density and dynamics. In comparison to conventional motor types the advantage of HTS reluctance motors with respect to size and dynamics could be demonstrated. Some fields of possible future applications will be described. These motors show a significant improvement in performance using high quality HTS bulk elements in the rotor. Until now the motor parameters have been limited by the current density which could be obtained in the bulk material at 77 K and by the geometric dimensions of the segments available. Therefore we expect further improvements in the case of these materials. Since the total motor including stator and rotor is working at low temperature we have to optimize the windings and the magnetic circuit to these operation conditions. A new design of a 200 kW motor in order to achieve increased power density and the theoretical results of our calculations will be shown.

Detailed study of the magnetic circuit in a longitudinal flux permanent-magnet synchronous linear generator

Abstract: We present the results of a theoretical study of the magnetic circuit of a longitudinal flux permanent-magnet synchronous linear generator. In our study, we used a coupled field and circuit model solved by a time-stepping finite-element technique to analyze the machine. We investigated the effects of different permanent-magnet shapes and sizes, as well as different stator steel geometries. We noted a significant difference in performance for different magnet shapes. Our results also illustrate how small changes, on a millimeter scale, will affect the flux path, and thereby the overall performance of the machine, highlighting the importance of stator steel geometry.

Analytic model for a nonlaminated cylindrical magnetic actuator including eddy currents

Abstract: The eddy currents induced within a nonlaminated cylindrical magnetic actuator by a changing field have a fundamental influence on the actuator's performance. Understanding of these dynamics is essential in designing high-performance actuators and developing control algorithms for them. This paper presents an analytical approach to modeling the relationship between applied magnetomotive force and mechanical force. The approach is based on dividing the actuator into elements according to the flux distribution inside the actuator and finding the frequency-dependent reluctance of the flux paths of each element. An analytic model and its half-order simplification are derived, both of which are explicitly dependent on actuator material and geometric properties. Performance predictions from both analytic models are compared with finite-element analysis, demonstrating the accuracy of the models.

Saturation control of electric machine

Abstract: The invention includes an electric alternator/motor having a rotor, stator and at least one winding in the stator adapted to conduct a current, the machine also having and first and second magnetic circuits, one of which includes a saturable portion in which saturation may be controlled to permit control of the machine.

Design and analysis of a permanent magnet spherical actuator

Abstract: This paper has proposed a design concept of a spherical actuator including a ball-shaped rotor with a full circle of permanent-magnet (PM) poles and a spherical-shell like stator with two layers of circumferential air-core coils. One key feature of this design is parameterization of the PM pole, which benefits the design optimization of the spherical actuator greatly. According to the magnetic field model, the variation of flux density with respect to PM-pole parameters can be revealed. Therefore, these parameters can be appropriately chosen to achieve a high magnetic flux density. Another advantage of this design is the singularity-free, which is verified within the workspace with torque model and condition numbers.

An investigation on influence of magnet arc shaping upon back electromotive force waveforms for design of permanent-magnet brushless motors

Abstract: This paper presents the technique to effectively obtain required back EMF waveforms, e.g., sinusoidal, for permanent-magnet (PM) brushless motors by magnet arc shaping rather than the common stator arc shaping method. Motor back EMF waveforms partly depend on the air-gap flux distribution produced by magnets. Therefore, in this paper, the relationship between the flux distribution of a magnet and its shape is derived using the Laplace's equation so that the magnet shape can be determined in accordance with the back EMF waveform required. Having determined the magnet shape, finite element analysis is employed to verify the effectiveness of the technique developed by comparing the back EMF waveforms of the unmodified arc-shape magnet, the shaped breadloaf and the idea sinusoids. The simulation results show that, by properly shaping the magnets, a back EMF waveform with close approximation to the ideal sinusoid can be obtained, differing from the quasi trapezoidal waveform generated by the original arc shape magnet. Moreover, the results also show that the cogging torque is significantly improved by the magnet shaping. The major advantage of using the developed method is that the required back EMF waveform can be easily obtained at the preliminary design stage so that the entire design efficiency can be improved.

HF Characterization and Non-Linear Modeling of a Gapped Toroidal Magnetic Structure

Abstract: The frequency dependent characteristics of a gapped toroidal structure are extracted empirically over a bandwidth that exceeds 30 MHz. The analysis is complicated due to non-linear flux distributions, magnetic properties of the core material, leakage inductance, stray capacitances and eddy currents in the windings. A permeance model of the core is implemented to model the magnetic circuit. The model includes a linear lumped element equivalent circuit to approximate the non-linear complex permeability of the core, which was measured empirically. Stray capacitance and inductance of the winding are also modeled. A gyrator is used to couple the electric and magnetic models for circuit simulation. The measured and simulated results of open-circuit impedance from the secondary winding and the transimpedance gain (V/A) of the current sensor are compared and discussed

Investigation of electromagnetic force components in SRM under single and multiphase excitation

Abstract: This paper presents the results of an investigation of components of the electromagnetic force in the air gap of an 8/6 switched reluctance machine (SRM). Using a Maxwell stress method, variations of radial and tangential force components due to saliency of the machine and saturation have been studied. Access to distribution of the force components acting on the rotor and stator enables us to provide a more accurate picture of the torque generation and vibration in this family of electric machines. Furthermore, distribution of magnetic forces under multiphase excitation has been studied in detail. Our findings show that bipolar excitation of SRM phases, resulting in a short flux path magnetic circuit, favors its efficiency and power quality while generating higher torque with less pulsation. This is a significant improvement, particularly for automotive applications where the difference in the required number of power electronics components can be justified. An experimental 2-kW 42-V 8/6 SRM drive which has been designed and manufactured in our energy system laboratory was targeted for this study. In addition to our extensive finite-element analysis, experimental results have been provided to prove theoretical claims.

Design of a miniature permanent-magnet generator and energy storage system

Abstract: The paper describes a methodology for optimizing the design and performance of a miniature permanent-magnet generator and its associated energy storage system. It combines an analytical field model, a lumped reluctance equivalent magnetic circuit, and an equivalent electrical circuit. Its utility is demonstrated by means of a case study on a 15-mW, 6000-r/min generator, and the analysis techniques are validated by measurements on a prototype system.

Common-mode choke coil

Abstract: PROBLEM TO BE SOLVED: To provide a common-mode choke coil suitable for miniaturization capable of preventing common-mode noise over a wide band without upsizing it and without attenuating a high frequency normal mode signal. SOLUTION: A pair of windings 2, 3 are formed by simultaneously winding two insulated wires L1, L2 about a closed magnetic circuit core 1 forming a closed magnetic circuit, and the both ends of the two insulated wires L1, L2 forming the pair of windings 2, 3 are connected to input terminals 4i, 5i and output terminals 4o, 5o, respectively. The pair of windings 2, 3 are formed by winding the two insulated wires L1, L2 about both cores 1a, 1b divided by a straight line L intersecting the closed magnetic circuit 1 at two points x, y from one intersection point x toward the other one y respectively by extending them across the straight line L and over the cores 1a, 1b. COPYRIGHT: (C)2007,JPO&INPIT

Inverse type magnetic flow damper

Abstract: A kind of inversion magnetic current alter amortisseur,which has application in the absorption of vibration of the building structure and the locomotive cars It includes the cylinder body,the piston, the piston rod which connected to it, the confinement gasoline device of the both sides of the cylinder body and the cylinder cap, there has magnetic current alternative liquid in the void of the cylinder body, and institutes the magnetizer that generates the magnetic field and the energizing coil and the electromagnet magnetic circuit component which is unitized of the running void, the cylinder body is composed of the master cylinder, or the master cylinder and the set jar, or the master cylinder and bypass jar, its character is:Institutes both the energizing coil and the permanent magnet magnetic circuit, composes the compounded magnetic circuit with the energizing coil and the permanent magnetic field, and also institutes the administer void in the electromagnet circuit, and when the power is cut, the most of the permanent magnetic field that generated by the permanent magnet will pass through the running void, so the amortisseur can work at the great amortization condition The component of the electromagnet circuit may set at the pertinent position in terms of the different cylinder body This kind of amortisseur can joint with the controlled structure, fulfills the semiactivly controlled with the absorption of vibration

Vibratory apparatus of exercise

Abstract: A vibratory exercise apparatus capable of providing sufficient vertical movement force is provided that adopts a structure of a bobbin coil connected with a vibration plate employed in a magnetic gap of a magnetic circuit using a permanent magnet that can generate a strong magnetic force, thereby providing sufficient vertical movement force to the vibration plate for vibratory exercise.

Brushless DC motors with remote Hall sensing and methods of making the same

Abstract: A brushless DC motor apparatus includes a housing and a stator assembly coupled to the housing. The apparatus further includes a magnetic rotor assembly configured to rotate within the housing in response to electric currents through windings of the stator assembly. The apparatus further includes position sensors which are configured to provide position signals identifying angular position of the magnetic rotor assembly relative to the stator assembly. Each position sensor includes (i) a Hall-effect sensor disposed distally from the windings, and (ii) magnetic circuit members having first end portions adjacent the windings and proximate rotor magnets and second end portions adjacent the Hall-effect sensor. Use of such magnetic circuit members enables the Hall-effect sensors to reside a greater distance from the windings vis-a-vis conventional brushless DC motors which position sensors adjacent to stator coils within motor casings.

Field analysis of the magnetic systems for tubular linear reluctance motors

Abstract: We report a study of tubular linear reluctance motors (TLRMs) in various types of magnetic circuits. We carried out magnetic field analyses and calculated integral parameters of the field. We also determined static characteristics and electromagnetic parameters of the motor. We found good agreement between our calculations and tests of the motor with sinusoidal excitation.

Ferromagnetic RF Integrated Inductor with Closed Magnetic Circuit Structure

Abstract: Closed magnetic circuit type ferromagnetic RF integrated inductors have been fabricated based on MEMS-like micro fabrication techniques. The taper etching process greatly helped to endure sufficient magnetic flux flow at the edge of the top and bottom magnetic layers. Air cores and three different sandwich type ferromagnetic inductos are also microfabricated. Measured results exhibited the quality factor Q=12, being highest among the published data of ferromagnetic RF integrated inductor at 1 GHz.

Modeling and analysis of cage induction motors under rotor misalignment and air gap eccentricity

Abstract: Air gap asymmetry exists in all electric machines. This asymmetry creates unbalanced magnetic forces that act both on the rotor and the stator of the machine. Bearing damages and excessive vibration and acoustic noise could be traced to these forces. In this paper, modeling of squirrel cage induction motor under different air gap asymmetries is presented. Transient and steady state unbalanced magnetic forces at the two ends of the rotor are studied. Using the magnetic equivalent circuit method (MEC) for the modeling of induction motor, the most important factors affecting dynamic behavior of induction motors are also considered. Experimental results are provided to validate theoretical findings.

Steering column torque detecting sensor arrangement for motor vehicle, has magnetic circuit with flux rings designed as ferromagnetic rings, such that sensor unit and wheel are arranged between inner flux ring and outer flux ring

Abstract: The arrangement has a magnetic field sensitive sensor unit (104) analyzing magnetic field information of a magnetic circuit having a magnetic pole wheel. The circuit with flux rings (101, 102) is designed as ferromagnetic rings, such that the unit and the wheel are arranged between the inner flux ring lying on a smaller diameter and the outer flux ring lying on a larger diameter, where the flux rings comprise axially running teeth.

Optimal design of a hybrid excitation claw-pole alternator based on a 3-D MEC method

Abstract: Output performance optimization of a hybrid excitation claw-pole alternator is presented using a three-dimensional (3-D) magnetic equivalent circuit (MEC) method taking the nonlinear magnetic properties of iron into account. A 3-D MEC model of the hybrid excitation alternator is presented. On this basis, the dimensions of permanent magnets and the output currents are optimized using genetic algorithm and the optimization results are presented.