Showing papers on "Magnetic circuit published in 2003"

Inductive write head having high magnetic moment poles and low magnetic moment thin layer in the back gap, and methods for making

Abstract: The present invention provides a write element for use in magnetic data recording system such as a computer disk drive. The write head utilizes the advantageous properties of high magnetic moments while overcoming the corrosion problems engendered by such materials. The write element includes a magnetic yoke constructed of first and second magnetic poles joined to one another at a back gap. While the majority of the poles are constructed of a high magnetic moment material a layer of relatively low magnetic moment material is provided on the first pole at the back gap portion of the first pole. The relatively low magnetic moment material prevents corrosion of the first pole during subsequent manufacturing of the write head. An electrically conductive coil passes through the magnetic yoke and is insulated there from. By passing an electrical current through the electrical coil, a magnetic flux is generated in the yoke. This magnetic flux then generates a magnetic fringing field in at a write gap of the yoke. The fringing field imparts magnetic data onto a recording medium passing thereby.

Modeling of a Magnetorheological Actuator Including Magnetic Hysteresis

Abstract: Magnetorheological (MR) actuators provide controlled torque through control of an applied magnetic field. Therefore knowledge of the relationship between the applied current and output torque is required. This paper presents a new nonlinear modeling of MR actuators considering magnetic hysteresis to determine the torque-current nonlinear relationship. Equations for transmitted torque are derived according to mechanical shear configurations of the MR actuator. Hodgdon's hysteresis model is used to capture the characteristics of hysteresis nonlinearity in the MR actuators. An MR actuator test setup has been constructed using a commercial MR brake to evaluate the proposed model. The measured torque shows hysteresis effects as the current increases and decreases. Using Hodgdon's hysteresis model of the magnetic circuit and Bingham model of the MR fluid, a novel nonlinear model of the MR actuator is obtained as a torque estimator for practical torque control purpose. The validity of the theoretical results is ...

Simple nonlinear magnetic analysis for permanent magnet motors

Abstract: This paper presents a simple nonlinear magnetic analysis for a surface-mounted permanent-magnet synchronous motor as an assistant design tool of finite-element analysis (FEA). The equivalent magnetic circuit of the motor used in the proposed analysis is composed of the saturable permeance tips in the stator teeth for considering the local magnetic saturation. As a result, the proposed analysis is capable of calculating the flux distribution and the torque characteristics in the presence of magnetic saturation. The effectiveness of the proposed analysis is verified by comparing with three-dimensional (3-D) FEA in terms of the analytical accuracy. The computation time is greatly reduced as short as 1.5 s while the 3-D FEA requires as much as 32 min for the same evaluation.

Modeling of a linear PM Machine including magnetic saturation and end effects: maximum force-to-current ratio

Abstract: The use of linear permanent-magnet (PM) actuators increases in a wide variety of applications because of their high force density, robustness, and accuracy. These linear PM motors are often heavily loaded during short intervals of high acceleration, so that magnetic saturation occurs. This paper models saturation and end effects in linear PM motors using magnetic circuit models. The saturating parts of the magnetic circuit are modeled as nonlinear reluctances. Magnetomotive forces represent the currents and the magnets. This paper shows that when saturated, a negative d-axis current increases the force developed by the motor. Although the increase is not large, it is nevertheless useful, because a negative d-axis current also results in a decrease in the amplifier rating. Further, the trajectory for the maximum force-to-current ratio is derived. The correlation between the calculated and the measured force justifies the model.

Bulk amorphous metal inductive device

Abstract: A bulk amorphous metal inductive device comprises a magnetic core having plurality of low-loss bulk ferromagnetic amorphous metal magnetic components assembled in juxtaposed relationship to form at least one magnetic circuit and secured in position, e.g. by banding or potting. The device has one or more electrical windings and may be used as a transformer or inductor in an electronic circuit. Each component comprises a plurality of similarly shaped layers of amorphous metal strips bonded together to form a polyhedrally shaped part. The low core losses of the device, e.g. a loss of at most about 12 W/kg when excited at a frequency of 5 kHz to a peak induction level of 0.3 T, make it especially useful for application in power conditioning circuits operating in switched mode at frequencies of 1 kHz or more. Air gaps are optionally interposed between the mating faces of the constituent components of the device to enhance its energy storage capacity for inductor applications. The inductive device is easily customized for specialized magnetic applications, e.g. for use as a transformer or inductor in power conditioning electronic circuitry employing switch-mode circuit topologies and switching frequencies ranging from 1 kHz to 200 kHz or more.

A novel stator doubly fed doubly salient permanent magnet brushless machine

Abstract: A novel stator doubly fed doubly salient permanent magnet (PM) brushless machine is proposed. The novelty of this machine is to purposely add an extra flux path in shunt with each PM pole, hence amplifying the effect of flux weakening for constant power operation. Magnetic circuit analysis is adopted to illustrate the novelty. Machine flux paths and performance curves determined by a finite-element analysis are presented for various excitations. The corresponding results show that the proposed machine is promising for application to electric vehicles.

Enhanced thermal conductivity ferrite stator

Abstract: A permanent magnet electric machine (i.e.: motor/generator) having a magnetic flux circuit including a stator and a permanent magnet rotor mounted for rotation about an axis relative to the stator. The stator has an electric circuit with windings electro-magnetically coupled to the magnetic circuit. The stator is of material having a Curie temperature, wherein magnetic flux circulation through the stator material is impeded when the stator material acquires a temperature above the Curie temperature. The stator includes heat conducting layers and magnetic flux conducting layers, where the thermal conductivity of the heat conducting layers is greater than the thermal conductivity of the magnetic flux conducting layers. By this means the overall thermal conductivity of the stacked stator assembly is improved and means for quickly effecting shutdown of the electric machine are provided with a heat exchanger thermally coupled to the stator, thereby regulating magnetic flux circulation through the stator material. Preferably the magnetic flux conducting layers are manganese zinc ferrite, and the heat conducting layers are: insulated copper sheets; insulated aluminum sheets; thermally conductive polymer sheets; sheet metal; or plated metal layers deposited on associated magnetic flux conducting layers.

Design and analysis of 42-V permanent-magnet generator for automotive applications

Abstract: The new 42-V automotive electric system comes up with new requirements for alternator design. A three-phase permanent-magnet (PM) synchronous generator for automotive applications is designed using analytical algorithms. The electromagnetic (EM) field for a certain design is analyzed based on a proposed equivalent magnetic circuit model. The proposed model is validated by comparing the analysis results using the model and those based on finite-element analysis under no-load and full-load conditions for saturation considerations. The analysis results demonstrate the effectiveness of the proposed machine design methodology.

Low-frequency magnetic fields from electrical appliances and power lines

Abstract: The relationship between magnetic fields and the health of people is increasingly being investigated. International organizations have proposed bylaws that put limits on the value of the generated magnetic field. In this work, we measure the magnetic field created by electrical appliances and high voltage lines and we analyze the degree of compliance with recent applicable European regulation. The simulation of the magnetic field generated by electrical lines through a simple model accurately predicts the measured values. The model is used to simulate the behavior of the lines under given conditions. In both cases, an FFT analysis of the magnetic field waveform was performed to study the frequency and amplitude of the possible induced currents.

Dynamic analysis of interior permanent magnet motor based on a magnetic circuit model

Abstract: This paper presents a new magnetic circuit model of an interior permanent magnet (IPM) motor for use in SPICE, which is the general-purpose circuit-simulation program. The magnetic circuit model consists of reluctances and permanent magnet magnetomotive-force sources. In the SPICE simulation, a magnetic circuit model of the IPM motor and its driving circuit are coupled by a proper circuit. Using the proposed model, we can calculate dynamic characteristics of the IPM motor easily.

Dynamic simulation model of switched reluctance generator

Abstract: This paper deals with a numerical model of the switched reluctance generator (SRG) for use on a general-purpose circuit simulation program "SPICE". In the model, the electric circuit and magnetic circuit are coupled by proper controlled sources. Using the numerical model, we can readily calculate the dynamic behavior of the SRG. The method presented here is useful for circuit analysis and design optimization of the SRG.

Measurement of magnetic properties under 3-D magnetic excitations

Abstract: In a magnetic material, even under an alternating or a two-dimensional rotating magnetic excitation, the magnetic flux is three dimensional (3-D) due to the rotation of magnetic domains. For measurement of 3-D magnetic properties of materials, a novel tester has been developed. The test principle, construction, and calibration of the 3-D magnetic property tester will be presented. Experimental results of B and H loci and core losses with 3-D magnetic fluxes are included and discussed. The system is working and the results are validated.

Time stepping finite element analysis for the dynamic performance of a permanent magnet synchronous motor

Abstract: A field-circuit coupled time-stepping finite-element method for the study of electric machines is presented. In reality, various circuits such as stator windings, rotor cage bars, and the control electronics are directly coupled with the electromagnetic field of the electric machines, hence, the physical quantities relating to these circuits as well as the field should be taken into account simultaneously. The method is used to simulate the electromagnetic performance of a permanent magnet synchronous motor (PMSM). The dynamic performance for PMSM, both computational and experimental results, is presented. A good match between the two sets has been achieved.

Bulk laminated amorphous metal inductive device

Abstract: A bulk amorphous metal inductive device (1) comprises a magnetic core having at least low-loss bulk ferromagnetic amorphous metal magnetic components (2, 3) forming a magnetic circuit having an air gap therein. The device has one or more electrical windings (25, 27) and may be used as a transformer or inductor in an electronic circuit. The component (2, 3) comprises a plurality of similarly shaped layers of amorphous metal strips bonded together (102) to form a polyhedrally shaped part. The low core losses of the device. e.g. a loss of at most about 12 W/kg when excited at a frequency of 5 kHz to a peak induction level of 0.3 T, make it especially useful for application in power conditioning circuits operating in switched mode at frequencies of 1 kHz or more. The component is fabricated by a process comprising cutting, stacking, registering, and bonding the laminations together by an adhesive agent.

Modules creating magnetic anchorage assemblies and relevant assemblies

Abstract: A module (1, 16, 19, 28, 50, 52, 54, 100) for the creation of assemblies comprising at least one active magnetic element of attraction (2, 3, 17, 20, 33, 34, 42, 47, 48) and at least one ferromagnetic element (6, 21, 22, 30, 40, 44) suitable for defining areas (13, 14, 35, 36, 88, 90, 80, 82, 110, 10, 250, 260, 92, 94) for connection to other modules, with which it is possible to create an assembly of modules (1, 16, 19, 28, 50, 52, 54, 100, 37, 15) which provides a magnetic circuit which closes totally or at least partially via the ferromagnetic elements present (6, 21, 22, 30, 40, 44, 55, 104, 37, 15).

Simulation and design of integrated magnetics for power converters

Abstract: We introduce a method to use z parameters to model the interface between an electric circuit and a magnetic component. With this model, the electrical equivalent circuit of any complex integrated magnetic component can be developed easily. We describe the simulation and design of integrated magnetics using a z-parameter two-port network model. We use a single-switch regulator with power-factor-correction and a single integrated magnetic component as an example to demonstrate the practical applications of integrated magnetics in modern power converters. For the same example, we analyze the problem of uneven magnetic flux density in an integrated magnetic component and propose a possible solution to the problem.

Analysis of generator vibration characteristic on rotor winding interturn short circuit fault

Abstract: Rotor winding interturn short circuit fault is one of the common faults in generator, and analyzing fault mechanism and diagnosis method is very necessary. This paper analyzes generator rotor and stator vibration characteristic caused by the fault. Firstly calculates air-gap magnetomotive force distribution, air-gap magnetic field energy and magnetic flux density on the fault. Then analyzes the frequency characteristic of imbalance magnetic pull acting on rotor and that of pulsating magnetic pull acting on stator core. Finally gets the characteristic of rotor vibration with rotor's rotation frequency and that of stator vibration with one and two rotor's rotation frequency caused by the fault. Using practically acquired MJF-30-6 generator vibration data in rotor winding inter-turn short circuit fault, the results of verification show that the analysis is correct.

Finite element calculation of the saturation DQ-axes inductance for a direct drive PM synchronous motor considering cross-magnetization

Abstract: Direct-drive torque-servo permanent magnet synchronous motor often operates in overload conditions Its characteristic is evidently influenced by magnetic circuit saturation The direct-axis and quadrature-axis inductances of surface mounted permanent magnet synchronous motor are usually considered as constant ie L/sub d/=L/sub q/ In fact, both the d-axis and q-axis inductances vary with load condition because of magnetic circuit saturation A novel procedure is developed to calculate the dq-axes inductance with saturation by finite element method considering cross magnetization Through magnetic field computation, the influence of saturation and cross-magnetization on dq-axes inductance is further investigated

Coupled problem computation of 3-D multiply connected magnetic circuits and electrical circuits

Abstract: This paper presents the theory and the validation of a new finite-element formulation to realize the coupling between electrical circuits and multiply connected magnetic circuits, using a magnetic scalar potential as state variable. For this purpose, we used formulations in reduced magnetic scalar potential versus T/sub 0/ taking into account electrical circuits and a total magnetic scalar potential taking into account cuts.

Modelling of a linear PM machine including magnetic saturation and end effects: Maximum force to current ratio

Abstract: The use of linear permanent-magnet (PM) actuators increases in a wide variety of applications because of their high force density, robustness and accuracy. These linear PM motors are often heavily loaded during short intervals of high acceleration, so that magnetic saturation occurs. This paper models saturation and end effects in linear PM motors using magnetic circuit models. The saturating parts of the magnetic circuit are modelled as nonlinear reluctances. Magnetomotive forces represent the currents and the magnets. This paper shows that when saturated, a negative d-axis current increases the force developed by the motor. Although the increase is not large, it is nevertheless useful, because a negative d-axis current also results in a decrease in the amplifier rating. Further, the trajectory for the maximum force to current ratio is derived. The correlation between the calculated and the measured force justifies the model.

Mobile handset and assembly having multi-loudspeaker system

Abstract: The present invention relates to a mobile handset comprising a handset housing comprising a front and a back cover, display means being visible from the front cover side of the handset housing, the display means being adapted to provide visual information to a user of the mobile handset. The mobile handset further comprises a plurality of loudspeakers being adapted to generate audio signals, wherein each of the plurality of loudspeakers comprises a magnetic circuit comprising a magnet, the magnetic circuit having at least one gap defined between two opposed and substantially parallel surfaces of the magnetic circuit. The magnet of the magnetic circuit causes a magnetic field to exist across the at least one gap. The magnetic circuit is so arranged that it defines magnetic return paths completely encircling the gap.

An input current shaper with boost and flyback converter using integrated magnetics

Abstract: In this paper, with a view to reduce the ripple content of the input current, boost inductor of a single stage single switch input current shaping converter is replaced by a coupled inductor, with one winding in the forward path and another in the return path of power flow However, the input current ripple hinders efforts to meet electromagnetic interference (EMI) requirements Minimization of input current harmonics to meet the agency standards implies improvement of power factor as well For the purpose of economizing on magnetic material and reducing the loss in the magnetic material, the magnetic circuits of the coupled boost inductor and the isolating transformer of the flyback converter are combined on a single magnetic core making sure that they function independently This will make the unit more compact

Analytical model of iron losses in power transformers

Abstract: The authors have improved a circuit model of transformers by defining a conductance whose losses will be close to the iron losses under any circumstance. Connecting a constant conductance G/sub cs/ in parallel with the main magnetizing inductance is very popular in the literature; however, it is acceptable only if the flux amplitude and frequency are reasonably constant during the time of operation, and if the value can be properly adjusted. Here, they replace G/sub cs/ with a nonlinear dynamic conductance G/sub cd/, whose losses are a function of flux amplitude. This conductance is based on the concept of dynamical hysteresis. Its definition is such that it is determined by the same test results used for G/sub cs/. Knowing the values of losses given by the manufacturer of the sheets, and the measured values of iron losses of a transformer, one can then analytically express the building factor as a function of the maximum flux density. The authors have applied the method to a three-leg 10-kVA transformer. It allows one to identify the cases when iron losses may be ignored, when they may be represented by a constant conductance, and when they must be represented by a nonlinear conductance.

Magnetic force control with composite of giant magnetostrictive and piezoelectric materials

Abstract: We propose a new magnetic force control device, composed of a giant magnetostrictive material (Terfenol-D) and a piezoelectric material (PZT), for coilless magnetic force control. The device uses the inverse magnetostrictive effect, whereby the variation of magnetization of a Terfenol-D rod controlled by PZT is converted to the variation of magnetic force by a magnetic circuit. Because PZT is electrically capacitive, the method has the advantage of low power consumption and low heat generation in static operation. We have fabricated several devices with different geometrical shapes of the rods and magnetic yokes, and we describe their characteristics such as power consumption, heat generation, and response. We discuss a magnetic circuit design strategy that uses the /spl Delta/E effect in magnetostrictive materials to increase the energy conversion efficiency.

Measurement and control of magnetomotive force in current transformers and other magnetic bodies

Abstract: A magnetic body having nonlinear permeability is influenced by a magnetomotive force, the magnitude of which is to be measured or controlled. An electric energy source is connected to a winding that is magnetically coupled to the magnetic body. The electric energy source generates an oscillating output so as to cause the magnetic flux within the magnetic body to oscillate at a predetermined frequency. The oscillating flux is associated with an exciting current and excitation voltage, both oscillating at the predetermined frequency. The nonlinear permeability of the magnetic body causes the waveform of the exciting current to have different symmetry than the waveform of the excitation voltage. The difference of symmetry is indicative of the polarity and average value of magnetomotive force experienced by the magnetic body. The difference in symmetry is used to measure the average magnetomotive force experienced by the magnetic body. Alternatively the difference in symmetry may be used as an input to a control system that controls the average magnetomotive force experienced by the magnetic body. When applied to current transformers, the invention enables ordinary current transformers to operate with a-c and d-c primary currents while coupling very little noise to the primary circuit.

Design and analysis of a transverse flux machine with soft magnetic composite core

Abstract: This paper presents the design and performance analysis of a three phase, three stack permanent magnet transverse flux motor with soft magnetic composite core. To predict and optimize the major parameters, three-dimensional finite element analysis is performed. The performance is calculated when the motor operates with a brushless DC drive.

Properties comparison of superconducting fault current limiters with closed and open core

Abstract: The high-T/sub c/ superconducting fault current limiter (SFCL) can be classified into resistive, inductive and hybrid types. The inductive type HTSFCL seems to show most prospect due to the simple design (construction) of the secondary superconducting winding in the form of ceramic type BSCCO and for the reduction of current leads. In an inductive type SFCL, ferromagnetic cores for magnetic flux are applied, however open cores are also taken into consideration in order to simplify the construction. The results of experimental and computational investigations of inductive SFCL parameters are presented in this paper.

Magnetic equivalent circuit of PM hysteresis synchronous motor

Abstract: This paper presents the magnetic equivalent circuit of a permanent magnet hysteresis synchronous motor (PMHS). The hybrid synchronous motor consists of 36% cobalt steel hysteresis alloys with neodymium iron boron permanent magnets to improve the overall performances of such a motor. Based on the magnetic equivalent circuit, the control strategy of the PMHS motor is developed. Experimental results confirm the validity of the proposed magnetic equivalent circuit model and show that the hybrid motor exhibits improved speed stability over a wide range.