Showing papers on "Magnetic circuit published in 2010"
TL;DR: In this paper, the authors proposed topologies of hybrid-excited flux-switching permanent magnet machines incorporating iron flux bridges to enhance the effectiveness of the field coil excitation, and a simple lumped parameter magnetic circuit model was developed to predict the effect of adjusting various parameters.
Abstract: Hybrid-excited machines utilize the synergies of permanent magnet (PM) and wound field machines. Flux-switching PM machines have emerged as an attractive machine type due to the fact that the excitation sources are located in the stator allowing a simple robust rotor whilst providing high torque density. This paper proposes topologies of hybrid-excited flux-switching PM machines incorporating iron flux bridges to enhance the effectiveness of the field coil excitation. A simple lumped parameter magnetic circuit model is developed to predict the effect of adjusting various parameters. Two-dimensional finite-element analysis has also been used to predict the machine performance, while a prototype machine has been built and tested to validate the predicted results.
198 citations
TL;DR: In this article, an improved magnetic equivalent circuit for calculation of the teeth and yoke flux densities in linear permanent-magnet synchronous motors (LPMSMs) is presented, where the magnetic saturation of iron core is considered by nonlinear elements and an iterative procedure is used to update these elements.
Abstract: The aim of this work is to establish an accurate yet simple method for predicting flux density distribution and iron losses in linear permanent-magnet synchronous motors (LPMSMs) for iterative design procedures. For this purpose, an improved magnetic equivalent circuit for calculation of the teeth and yoke flux densities in the LPMSMs is presented. The magnetic saturation of iron core is considered by nonlinear elements and an iterative procedure is used to update these elements. The armature reaction is also taken into account in the modeling by flux sources located on the teeth of motors. These sources are time dependent and can model every winding configuration. The relative motion between the motor primary and secondary is considered by wisely designing air gap elements simplifying the permeance network construction and preventing permeance matrix distortion during primary motion. Flux densities in different load conditions are calculated by means of the proposed model. The effects of saturation and armature reaction on the flux density distribution are shown in detail. Using these flux densities, iron losses in the motor are examined and its variations versus motor parameters are then studied. All results obtained by proposed model are verified by finite-element method based on an extensive analysis.
144 citations
TL;DR: In this paper, a T-model equivalent circuit is proposed which is based on the 1-D magnetic equations of the air gap, where half-filled slots are considered by an equivalent pole number.
Abstract: Single-sided linear induction motors (SLIMs) have lately been applied in transportation system traction drives, particularly in the intermediate speed range. This is because they have merits, such as the ability to exert thrust on the secondary without mechanical contact, high acceleration or deceleration, less wheel wear, small turning circle radius, and flexible road line. The theory of operation for these machines can be directly derived from rotary induction motors (RIMs). However, while the cut-open primary magnetic circuit has many inherent characteristics of the RIM equivalent circuits, several issues involving the transversal edge and longitudinal end effects and the half-filled slots at the primary ends need to be investigated. In this paper, a T-model equivalent circuit is proposed which is based on the 1-D magnetic equations of the air gap, where half-filled slots are considered by an equivalent pole number. Among the main five parameters, namely, the primary resistance, primary leakage inductance, mutual inductance, secondary resistance, and secondary inductance, the mutual inductance and the secondary resistance are influenced by the edge and end effects greatly, which can be revised by four relative coefficients, i.e., Kr, Kx, Cr, and Cx. Moreover, two-axis equivalent circuits (dq or αβ) according to the T-model equivalent circuit are obtained using the power conversion rule, which are analogous with those of the RIM in a two-axis coordinate system. The linear induction motor dynamic performance, particularly the mutual inductance and the secondary resistance, can be analyzed by the four coefficients. Experimental verification indicates that both the T-model and the new two-axis circuits are reasonable for describing the steady and dynamic performance of the SLIM. These two models can provide good guidance for the electromagnetic design and control scheme implementation for SLIM applications.
135 citations
TL;DR: The following paper introduces an alternative analytical modeling technique by means of a hybrid model, which combines the advantages of the MEC and the Fourier analysis.
Abstract: With the emergence of energy related issues in the automotive sector, there is a tendency to find new efficient solutions to replace existing electrical machinery. One promising candidate is the flux switching permanent magnet machine (FSPMM). Due to its challenging structure and nonlinear characteristic, in the investigation of the machine, generally finite element method (FEM), and rarely the magnetic equivalent circuit (MEC), are implemented. The following paper introduces an alternative analytical modeling technique by means of a hybrid model, which combines the advantages of the MEC and the Fourier analysis.
129 citations
TL;DR: In this article, a repetitive unipolar nanosecond-pulse generator is constructed using resonant charging and one-stage magnetic compression circuits, where IGBT and magnetic switches are the key units, respectively.
Abstract: Dielectric barrier discharge excitated by pulsed power is a promising approach for producing nonthermal plasma at atmospheric pressure, but pulsed power generators vary widely in performance and should be chosen according to application requirements. In this paper, a repetitive unipolar nanosecond-pulse generator is constructed using resonant charging and one-stage magnetic compression circuits, where IGBT and magnetic switches are the key units, respectively. The generator is capable of providing repetitive pulses with a voltage of up to 30 kV and duration of 70 ns at a 300 resistive load. Output pulse voltage can be adjusted by varying ac input voltage or trigger pulse-width. This compact and convenient generator has been used successfully to produce stable dielectric barrier discharge.
115 citations
TL;DR: In this article, a novel air gap between the permanent magnet and the stator poles is constructed between the subsidiary air gap, which separates the bias flux paths from the control flux paths.
Abstract: In this paper, we propose a novel structure of permanent-magnet-biased axial hybrid magnetic bearing. It has four segments of poles to control three degrees of freedom (3-DOF). Based on the inner and outer air gaps in conventional axial magnetic bearings, a novel air gap, called the subsidiary air gap, is constructed between the permanent magnet and the stator poles. This air gap separates the bias flux paths from the control flux paths. As a result, lower power loss of the axial magnetic bearing can be achieved due to lower magnetic reluctance of the control flux paths. Furthermore, by means of the equivalent magnetic circuit method and the 3-D finite-element method (FEM), we analyze and model the 3-DOF axial hybrid magnetic bearing. Experimental results show that the presented axial magnetic bearing has good control performance and little coupling among X, Y, and Z directions. However, the rotational power loss will be large at high speed because of the alternating flux density in the thrust plate produced by four segments of stator poles. Therefore, we propose a novel stator, named the parallel-slot stator, and novel thrust plate to reduce the rotational power loss effectively, which is assembled by DT4 and nanocrystalline materials. Meanwhile, we have designed and assembled an axial hybrid magnetic bearing prototype with the novel stator and thrust plate, which is applied in the five-degrees-of-freedom reaction flywheel system with angular momentum of 15 Nms at 5000 r/min. It is validated by the experimental results.
101 citations
TL;DR: In this article, a faster and simpler approach for the calculation of iron and magnet losses and torque of an interior permanent-magnet synchronous machine (IPMSM) than finite-element methods (FEM) is presented.
Abstract: We present a faster and simpler approach for the calculation of iron and magnet losses and torque of an interior permanent-magnet synchronous machine (IPMSM) than finite-element methods (FEM). It uses a magnetic equivalent circuit (MEC) based on large elements and takes into account magnetic saturation and magnet eddy currents. The machine is represented by nonlinear and constant reluctance elements and flux sources. Solution of the nonlinear magnetic circuit is obtained by an iterative method. The results allow the calculation of losses and torque of the machine. Due to the approximations used in the formulation of the MEC, this method is less accurate but faster than nonlinear transient magnetic FEM, and is more useful for the comparison of different machine designs during design optimization.
98 citations
TL;DR: In this article, a mesh-based MEC model of a wound-rotor synchronous machine is developed and is shown to provide a significant advantage over its nodal-based model equivalent.
Abstract: Recent research has compared the numerical efficiency of magnetic equivalent circuit (MEC) models based upon Kirchhoff's voltage law (mesh equations) and Kirchhoff's current law (nodal equations). For stationary magnetic components, it was shown that mesh-based methods converge in significantly fewer iterations. Although the numerical advantages would seemingly apply to electric machines, two issues have limited the application of mesh-based MEC models to electric machines. With movement, the number of meshes (unlike the number of nodes) is position dependent. Additionally, the loss of an airgap element creates an infinite reluctance. In this paper, both issues are addressed. Specifically, it is first shown that a relatively straightforward algorithm can be used to dynamically update meshes with rotor position. In addition, it is shown that the mesh model remains stable for very large values of tube reluctance. Tube reluctance values that are large enough to cause numerical issues can be easily avoided by excluding a very narrow range of rotor positions. Based upon these results, a mesh-based MEC model of a wound-rotor synchronous machine is developed and is shown to provide a significant advantage over its nodal-based model equivalent.
88 citations
TL;DR: This paper presents a simple nonlinear magnetic analysis for axial-flux permanent-magnet machines as an assistant design tool of 3D finite-element analysis (3D-FEA), and presents the analysis-based optimum design, which realizes the maximum torque density while maintaining efficiency at the desired value.
Abstract: This paper presents a simple nonlinear magnetic analysis for axial-flux permanent-magnet machines as an assistant design tool of 3-D finite-element analysis (3D-FEA). The proposed analysis consists of an equivalent magnetic circuit and an analytical model of air-gap permeances, including saturable permeances in the core. The proposed analysis is capable of calculating the flux distribution and torque characteristics under heavy operating conditions. We verify the accuracy of the proposed analysis by comparing the results with those of 3D-FEA for various design free parameters. After verifying the accuracy of the analysis, we present our analysis-based optimum design, which realizes the maximum torque density while maintaining efficiency at the desired value. Compared to the traditional 3D-FEA, the design method proposed here has the same accuracy, while the computation time is as short as 1/21.
80 citations
TL;DR: An axial-axial flux compound-structure permanent-magnet synchronous machine (CS-PMSM) system used for hybrid electric vehicles (HEVs) enables the internal combustion engine (ICE) to operate at optimum efficiency region independent of road conditions, thus decreasing the fuel consumption and emissions remarkably.
Abstract: An axial-axial flux compound-structure permanent-magnet synchronous machine (CS-PMSM) system used for hybrid electric vehicles (HEVs) enables the internal combustion engine (ICE) to operate at optimum efficiency region independent of road conditions, thus decreasing the fuel consumption and emissions remarkably. The axial-axial flux CS-PMSM is a high-degree integration of two axial-flux PMSMs. The magnetic coupling problem of the CS-PMSM is investigated based on magnetic circuit and finite-element method (FEM). The influences of the magnet rotor structures on the magnetic coupling are evaluated. Halbach structure is used for the magnet rotor, which makes the design of CS-PMSM more flexible. Further, a prototype machine of the axial-axial flux CS-PMSM was designed and manufactured. The experimental results show that the magnetic coupling problem can be solved perfectly due to special structural design, which verifies the theoretical analysis.
73 citations
TL;DR: In this article, a minitype magnetic flux pump made of high temperature superconductor has been proposed to compensate the magnetic field decay in HTS magnet and make the magnet operate in persistent current mode, this point is significant to the magnetic resonance imaging (MRI) magnets.
TL;DR: In this paper, a new dynamic model of a three-phase three-leg transformer for steady-state and transient operating conditions is proposed, which includes dynamic-hysteresis behavior (major and minor loops) in asymmetric 3-leg core topologies.
Abstract: A new dynamic model of a three-phase three-leg transformer for steady-state and transient operating conditions is proposed in this paper. With very few exceptions, the existing models oversimplify the magnetic interactions in multileg core topologies and employ single-value nonlinear functions for modeling core nonlinearities. Unfortunately, this does not provide sufficient accuracy for a wide range of dynamic disturbances such as dc bias, ferroresonance, and inrush. For this purpose, a new time-domain model based on magnetic-circuit theory is developed to include dynamic-hysteresis behavior (major and minor loops) in asymmetric three-leg core topologies. Furthermore, a new analysis is performed to study the impacts of hysteresis on no-load and transient inrush current behavior in three-phase transformers. Simulation results have been successfully compared with measurements to verify the accuracy of the proposed model.
CERN1
TL;DR: In this paper, a linear variable differential transformer (LVDT) position sensor with high rejection to external constant or slowly varying magnetic fields is addressed by exploiting the finite element method simulator FLUX.
Abstract: The sensitivity of linear variable differential transformer (LVDT) position sensors to external slowly varying magnetic fields represents a critical issue when these sensors are installed close to high-current cables or electrical motors with significant fringe fields. The resulting position error can reach several hundreds of micrometers against a specified uncertainty normally below a few micrometers. In this paper, the design of a LVDT position sensor with high rejection to external constant or slowly varying magnetic fields is addressed by exploiting the finite element method (FEM) simulator FLUX. A shield, isolated from the sensor's magnetic circuit, has been considered to reduce the effect of magnetic fields on the secondary voltages of the LVDT. In addition, a dc current is used in order to polarize the magnetic circuit to reduce the sensitivity of the sensor to external interferences.
TL;DR: In this article, the authors investigated the use of moving coil linear machines (MCLM) in the internal combustion linear generator (ICLG), which is a novel solution for series hybrid electric vehicles, distributed generation, and emergency power supply.
Abstract: This paper investigates the use of moving coil linear machines (MCLM) in the internal combustion linear generator (ICLG), which is a novel solution for series hybrid electric vehicles, distributed generation, and emergency power supply. According to the analysis of the basic structure of MCLM, an improved tubular MCLM equipped with quasi-Halbach magnetized magnets is suggested and analyzed with a proposed equivalent magnetic circuit (EMC) model. Measurements on a 4-kN prototype show good agreement with the results from the EMC model. Compared with the reported moving magnet linear machines (MMLM) for the same application, the proposed machine has the merit of less moving mass, faster response, and better controllability.
TL;DR: In this article, the design of a normal stress electromagnetic linear actuator for fast tool servos during nonrotationally symmetric diamond turning is described. And a design methodology is presented, which is based on analytical and finite element method magnetic circuit analysis.
Abstract: This paper describes the design of a normal stress electromagnetic linear actuator for fast tool servos during nonrotationally symmetric diamond turning. By using the permanent magnet as the biasing flux generator and the total armature pole surface for force generation, the actuator is designed to achieve both linear operation characteristics and high acceleration. A design methodology is presented, which is based on analytical and finite element method magnetic circuit analysis. For design optimization, a new criterion, high actuating force density, is introduced. Based on the optimized structural parameters and the strategy of design for manufacturing, a novel axisymmetric fast linear actuator is developed that has a stroke of 100 ?m and 500 G acceleration. The linearity of the actuating force versus both the excitation current and the armature displacement is experimentally demonstrated. It is shown that the experimental and calculated results agree well with each other.
07 Oct 2010
TL;DR: In this paper, a flexible wall and ceiling climbing robot with six permanent magnetic wheels is proposed to climb along the vertical wall and overhead ceiling of steel cargo containers as part of an illegal contraband inspection system.
Abstract: Magnetic wall and ceiling climbing robots have been proposed in many industrial applications where robots must move over ferromagnetic material surfaces. The magnetic circuit design with magnetic attractive force calculation of permanent magnetic wheel plays an important role which significantly affects the system reliability, payload ability and power consumption of the robot. In this paper, a flexible wall and ceiling climbing robot with six permanent magnetic wheels is proposed to climb along the vertical wall and overhead ceiling of steel cargo containers as part of an illegal contraband inspection system. The permanent magnetic wheels are designed to apply to the wall and ceiling climbing robot, whilst finite element method is employed to estimate the permanent magnetic wheels with various wheel rims. The distributions of magnetic flux lines and magnetic attractive forces are compared on both plane and corner scenarios so that the robot can adaptively travel through the convex and concave surfaces of the cargo container. Optimisation of wheel rims is presented to achieve the equivalent magnetic adhesive forces along with the estimation of magnetic ring dimensions in the axial and radial directions. Finally, the practical issues correlated with the applications of the techniques are discussed and the conclusions are drawn with further improvement and prototyping.
TL;DR: In this paper, a magnetic gear integrated brushless permanent magnet machine is studied, where the torque produced by the stator windings can be transmitted between the low speed rotor and the high speed rotor through the modulation of ferromagnetic pole pieces; hence it can output a large torque at a low speed.
Abstract: In this paper, a novel magnetic gear integrated brushless permanent magnet machine is studied. The main merit of the machine is that the torque produced by the stator windings can be transmitted between the low-speed rotor and the high-speed rotor through the modulation of ferromagnetic pole pieces; hence it can output a large torque at a low speed. The operating principle of the machine is discussed and its steady-state and transient performances are analyzed using circuit-field-motion coupled time-stepping finite element method. Detailed analysis about its gear ratio, cogging torque, core losses, and power factor are reported. Theoretical analysis agrees well with the FEM computation results.
TL;DR: This work examined how to apply the ON/OFF sensitivity method to the IPM (Interior Permanent Magnet) motor in order to determine the optimal topology of the rotor.
Abstract: The topology optimization by distributing the magnetic material in the design domain, which is called as the ON/OFF method, is attractive for designers of magnetic devices, because an initial conceptual design, that we could not imagined beforehand, may be obtained. We examined how to apply the ON/OFF sensitivity method to the IPM (Interior Permanent Magnet) motor in order to determine the optimal topology of the rotor. A technique to apply the ON/OFF method to the design of motor considering the nonlinearity of B-H curve and rotation of rotor is shown. The effects of the choice of the design region and the phase angle of stator current on the obtained topology of motor core are discussed.
Patent•
HGST1
TL;DR: A magnetic head as mentioned in this paper is defined as a main magnetic pole having a protruding portion such that a distance from a first side of a trailing edge of the main magnet to a leading edge of a main magnet is different from a distance between a second side of the trailing edge to the leading edge, and an auxiliary magnetic pole, and a coil wound around a magnetic circuit.
Abstract: A magnetic head, according to one embodiment, includes a main magnetic pole having a protruding portion such that a distance from a first side of a trailing edge of the main magnetic pole to a leading edge of the main magnetic pole is different from a distance from a second side of the trailing edge of the main magnetic pole to the leading edge of the main magnetic pole, an auxiliary magnetic pole, and a coil wound around a magnetic circuit, the magnetic circuit including the main magnetic pole and the auxiliary magnetic pole. In another embodiment, a disk drive system includes a magnetic storage medium, at least one magnetic head as described previously for writing to the magnetic medium, a slider for supporting the magnetic head, and a control unit coupled to the magnetic head for controlling operation of the magnetic head. Additional systems and heads are also presented.
TL;DR: In this article, a lumped-parameter model based on magnetic monopole approximation is employed to describe the magnetic field generated by the quadrupole magnetic tweezers in the workspace.
Abstract: This paper presents the design, implementation, and force modeling of quadrupole magnetic tweezers, which are capable of exerting magnetic forces in arbitrary 2-D directions on magnetic particles in the workspace. A lumped-parameter model based on magnetic monopole approximation is employed to describe the magnetic field generated by the quadrupole magnetic tweezers in the workspace. In this model, the magnetic field generated by each magnetic pole is approximated by the field of a point magnetic charge associated with the magnetic pole, and the total magnetic field produced by the system is obtained by applying the principle of superposition. An analytical force model considering the interaction between a magnetic particle and the magnetic field is then developed. The derived force model accurately characterizes the nonlinearity of the magnetic force exerting on the magnetic particle with respect to the applied currents to the coils and the position dependency of the magnetic force in the workspace. The directionality as well as the force generation anisotropy of the designed system is then explored using the force model. The model also facilitates the implementation of a feedback control law to stabilize and control the motion of a magnetic particle. Experimental results in terms of the magnetic force in relation to stable motion control of a magnetic particle are used to validate the force model.
TL;DR: It is shown that surface currents due to burrs at the external surface of the machine have an important contribution compared to the increase of eddy currents in the short-circuit volume.
Abstract: This paper presents the results of a research work devoted to the detection of short circuits between stator laminations of an electrical machine using external magnetic field. The theoretical developments lead one to display the influence of various phenomena on this magnetic field in a wide frequency range. It is shown that surface currents due to burrs at the external surface of the machine have an important contribution compared to the increase of eddy currents in the short-circuit volume. Finally, experimental measurements confirm this theory, and an online method of detection for large generators is proposed.
TL;DR: Analyzing snapshots of trajectories of hundred magnetite particles of each size in the water as well as in the air, it is found that optimally designed magnetic circuits of permanent magnets in quadrupolar Halbach array have substantially shorter capture time than simple blocks of permanent magnet commonly used in experiments.
Abstract: Magnetic nanoparticles for therapy and diagnosis are at the leading edge of the rapidly developing field of bionanotechnology In this study, we have theoretically studied motion of magnetic nano- as well as micro-particles in the field of cylindrical Halbach array of permanent magnets Magnetic flux density was modeled as magnetostatic problem by finite element method and particle motion was described using system of ordinary differential equations—Newton law Computations were done for nanoparticles Nanomag®-D with radius 65 nm, which are often used in magnetic drug targeting, as well as microparticles DynaBeads-M280 with radius 14 µm, which can be used for magnetic separation Analyzing snapshots of trajectories of hundred magnetite particles of each size in the water as well as in the air, we have found that optimally designed magnetic circuits of permanent magnets in quadrupolar Halbach array have substantially shorter capture time than simple blocks of permanent magnets commonly used in experiments, therefore, such a Halbach array may be useful as a potential source of magnetic field for magnetic separation and targeting of magnetic nanoparticles as well as microparticles for delivery of drugs, genes, and cells in various biomedical applications
TL;DR: In this paper, a magnetic equivalent circuit (MEC) of a new claw pole alternator where the DC-excitation winding is located in the stator (CPAES), rather than in the rotor in conventional claw-pole alternator is presented.
Abstract: We describe the development and the experimental validation of a magnetic equivalent circuit (MEC) of a new claw pole alternator where the DC-excitation winding is located in the stator (CPAES), rather than in the rotor in conventional claw pole alternator. Thus, we discarded the brush-ring system and achieved crucial cost, compactness, and reliability benefits. The proposed MEC treats both no-load and loaded armature operations. It also accounts for the saturation of the magnetic circuit. We numerically solve the established MEC using the Newton-Raphson algorithm. We validated the established MEC by considering experimental tests carried out on a prototype of the CPAES. We found that the results yielded by the proposed MEC and those given by the experimental tests are in good agreement.
TL;DR: In this article, the shape and size of the giant magneto-resistive (GMR) elements were investigated for 360° angle sensors, and Monte Carlo simulations showed that optimum layout reduces typical angle errors significantly and worst case angle errors moderately.
Abstract: 360° angle sensors use small permanent magnets attached to the shaft. The magnet is polarized perpendicularly to the axis of rotation, and a magnetic field sensor is placed underneath on the axis. The sensor circuit consists of two orthogonal bridges having four giant magneto-resistive (GMR) elements. In a prior work it was shown that even though the magnetic field sensor may be calibrated perfectly, still significant angle errors may result from assembly tolerances of magnet and sensor. This work investigates how shape and size of the GMRs affect this error. Optimum layouts for GMRs fulfill three constraints: (i) the centers of gravity of all GMRs of both bridges lie on the axis of rotation; (ii) the sum over the deviation moments of all GMRs of each bridge circuit vanishes; and (iii) the sums over the moments of inertia around two perpendicular axes in the die surface are equal. Examples of optimized layouts are given. Layout and assembly tolerances interact to give an overall angle error, which is expanded into a second-order Taylor series. Monte Carlo simulations show that optimum layout reduces typical angle errors significantly and worst case angle errors moderately. For Gaussian distributed assembly tolerances with standard deviations of 0.1 mm and 1° and cylindrical magnets with 5 mm diameter 99.7% of all systems have errors less than +/-0.41°. Magnets with 10 mm diameter have only +/-0.16° error. It is shown that magnetic angle sensors are more robust against eccentricities of the shaft than many optical encoder systems.
TL;DR: In this article, a displacement profile control strategy based on pulsewidth modulation (PWM) for improving the dynamic characteristics and reducing the contact bounce of permanent magnet (PM) contactor during the making process is reported.
Abstract: A new displacement profile control strategy based on pulse-width-modulation (PWM) for improving the dynamic characteristics and reducing the contact bounce of permanent magnet (PM) contactor during the making process is reported. Sensorless method of real time displacement signal detection is realized using magnetic circuit model (MCM) and electric circuit model (ECM). Finite element method (FEM) is used to obtain the nonlinear relationships among the flux linkage, displacement and current off-line. The information is then used for subsequent fast simulation of the dynamic characteristics of the contactor. A set of periodically inter-transferred dynamic characteristic equations are built and the complete making dynamic process of the PM contactor is simulated using 4th-order Runge-Kutta method. Experiments are carried out to validate the proposed control method on a prototype.
TL;DR: In this paper, a spatial circular harmonic expansion of the magnetic scalar potential is used to reduce the effects of external magnetic fields on the accuracy of magnetic sensor measurements used for the reconstruction of ac electric currents flowing in massive parallel conductors.
Abstract: In order to reduce the effects of external magnetic fields on the accuracy of magnetic sensor measurements used for the reconstruction of ac electric currents flowing in massive parallel conductors, we use a spatial circular harmonic expansion of the magnetic scalar potential. Thanks to the linearity of the magnetic field problem with respect to the sources, we can then apply the least squares inversion and obtain the set of currents from the knowledge of the magnetic field data collected by the sensor array in the vicinity of the current carrying conductors. Furthermore, we can optimize the positions and the orientations of the magnetic sensors using D-optimality theory and particle swarm optimization.
TL;DR: In this paper, a 4-port lumped circuit is introduced to model a partially coupled pair of microstrip lines known to emulate propagation in an anisotropic medium and a 6-port circuit is also presented to model three partially coupled transmission lines.
Abstract: Multiport circuit models are presented to emulate a new class of periodic anisotropic crystals exhibiting dispersion diagrams with degenerate band edges or stationary inflection points (SIPs). Specifically, a 4-port lumped circuit is introduced to model a partially coupled pair of microstrip lines known to emulate propagation in an anisotropic medium. A 6-port circuit is also presented to model three partially coupled transmission lines. Under specific coupling conditions, the latter circuit can support the SIP associated with the K-? curves of magnetic photonic crystals.
TL;DR: In this paper, a method to eliminate the nonphysical or nonrealistic solutions at the start of the time-stepping finite-element analysis (FEA), when simulating the transient process of electric devices, is presented.
Abstract: The time-stepping finite-element method (FEM) has become a powerful tool in solving transient electromagnetic fields. The formulation can include complex issues such as time harmonics and space harmonics, nonlinear magnetic property of iron materials, external circuit, and mechanical motion in the system equations. However, as the derivatives of physical quantities are usually unknown at the initial step of the time-stepping method, erroneous solutions might appear at the beginning of the transient process. To reduce the number of time steps, an adaptive step size algorithm can be used. In this paper, a method to eliminate the nonphysical or nonrealistic solutions at the start of the time-stepping finite-element analysis (FEA), when simulating the transient process of electric devices, is presented. A practical implementation of adaptive time step size algorithm for coupled problems is proposed. A matrix operation method, which can be understood clearly and implemented easily, that deals with matching boundary conditions in the study of mechanical motion, is also described.
21 Jun 2010
TL;DR: The results of analysis and experiments prove that the novel motor can change the flux of permanent magnet on load and has realization for a variable speed drive with high performance.
Abstract: Reduction of electrical consumption of a electric vehicle (EV) and electrical appliance is one of solutions for reduction of CO2 gas. Then, we have developed a novel permanent magnet motor for energy saving. In this paper, we propose a novel motor that can change magnetic flux by a new method magnetizing a permanent magnet and clarify the principle and unique characteristics. Furthermore, the results of analysis and experiments prove that the novel motor can change the flux of permanent magnet on load and has realization for a variable speed drive with high performance.
TL;DR: In this article, the authors compared the transient and steady-state performances of a 12/8 dual-channel switched reluctance machine (DCSRM) under different modes and excitation conditions.
Abstract: This study deals with the comparison of the dynamic modelling, the transient and steady-state performances analysis and experimental verification for a 12/8 dual-channel switched reluctance machine (DCSRM) under single- and dual-channel operation modes. The DCSRM has inherent short flux paths capability, and the magnetic circuits for both the channels share most of the magnetic real estate in the machine under dual-channel excitation mode. According to the different flux patterns, the dynamic models for the DCSRM operating under different modes are presented. In this proposed dual-channel operation model, the mutual coupling between different phases in each channel of the DCSRM is considered. By using the dynamic models, various transient and steady-state performances such as starting up speed under closed-loop control, phase currents, phase flux linkages, total torque characteristics and sudden change in torque operation are predicted and compared for the DCSRM under different modes and excitation conditions. It is shown that when the DCSRM operation is under dual-channel mode, it has faster acceleration performance and the torque is more than two times of that under single-channel mode. Finally, an experimental laboratory set-up based on digital signal processor and complex programmable logic device (CPLD) is built, which verify the proposed modelling and analysis. The experimental results of transient and steady-state performances are compared with the simulation results in the DCSRM systems under single- and dual-channel operation modes.