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Use of low static magnetic fields for nuclear magnetic resonance (NMR) signal detection remains a challenge due to low signal-to-noise ratio, low energy difference between energy levels, and less spin transitions due to limited availability of spins. Despite these challenges, different measurement techniques based on low static magnetic fields, stray magnetic fields, and non-uniform fields have been implemented. In this paper, an approach toward using low static fields generated by permanent magnets for portable magnetic resonance applications is described. Finite element simulation models of different magnet geometries are used to develop an estimate of the magnetic field distribution exterior to the magnet. A concentric ring magnet geometry is selected to obtain flexible control of localized regions of uniform magnetic field. An estimate of the NMR voltage for different magnet sizes and orientations is presented. It is expected that the findings of this paper would be valuable for design of future portable magnetic resonance systems. [ABSTRACT FROM AUTHOR]

This paper deals with equivalent 2-D finite-element (FE) models of permanent magnet lead screw (PMLS), to accurately predict the thrust force. Due to the helical-shape permanent magnets (PMs), the magnetic fields of PMLS are typically 3-D and non-symmetric. However, the PMLS is approximately symmetric in some cases and an equivalent 2-D axis-symmetric FE model is developed instead of 3-D models. The problem lies in that no evaluation about the accuracy and applicability of the 2-D axis-symmetric FE model was offered in previous literature. In this paper, the 2-D axis-symmetric FE model is derived based on the concept of equivalent current sheets of PMs. The limitations of the existing 2-D axis-symmetric FE model are clarified, and a novel equivalent 2-D torque FE model is then proposed to predict thrust force with the gear ratio when the 2-D axis-symmetric FE model is not appropriate. It is shown that the choice of equivalent 2-D FE model depends on the lead angle of PMLS, 2-D axis-symmetric FE model is applicable in the range of (0°, 15°), and 2-D torque FE model is preferred in the range of (65°, 90°). [ABSTRACT FROM AUTHOR]

Recently, dual-rotor motor (DRM) has emerged as an alternative for an induction motor (IM) or a permanent-magnet (PM) motor for electric vehicle application, due to its better drive performance and better torque density. This paper presents an analytical model for the hybrid IM-PM configuration of DRM. The analytical model can be used to predict induced bar currents, electromagnetic torque generated, and magnetic fields in various regions of the motor. The mentioned calculations are performed under steady-state conditions. The analytical method is developed using the subdomain model approach in 2-D polar coordinates. Appropriate governing equations along with boundary conditions across all the sub-domain regions of the DRM are employed to calculate the magnetic vector potential in all the regions. The developed analytical model has been validated with finite-element analysis for various operating conditions, and high accuracy has been achieved for all the results. [ABSTRACT FROM AUTHOR]

In this paper, two novel double-sided hybrid-excitation flux-reversal linear motors (DSHEFRLM) with the surface (S-) and interior (I-) permanent-magnet(PM) arrangements are proposed and comparatively investigated. The proposed motors feature an asymmetrical double-sided primary configuration which enables the armature and field excitations to be placed separately. Through 2-D finite-element method (FEM), two motor structures with different slot/pole combinations are optimized, and then, the magnetic fields and electromagnetic performances are calculated, including inductances, no-load flux linkage, thrust characteristics, and PM demagnetization capability. By comparison, it is found that S-DSHEFRLMs show larger thrust density while I-DSHEFRLMs exhibit superior flux-adjusting capability. Finally, these predicted results are validated by 3-D FEM. [ABSTRACT FROM AUTHOR]

For testing a conductive pipeline, remote field eddy current testing (RFECT) is used, which is composed of solenoidal exciter coil and receiving sensor coils. In RFECT, there is remote field zone where the eddy current distributions are concentrated on the external surface of the pipe wall. Therefore, it is possible to detect a defect that occurs on the external surface of the pipe wall even if the receiving coils are located inside the pipe. From the measured coil signals, it is necessary to decompose background offset and predict the pattern of defect signal in order to estimate the defect size for the maintenance of underground pipelines eventually. In the process, the amplitude variations of the induced magnetic field at sensor coils are closely related to defect depth. Therefore, it is important to analyze and eliminate distortions of measured RFECT signals. This paper analyzes the effects of the induced magnetic field on the sensing signals with respect to different depth sizes in the RFECT system. The amplitude and the distribution pattern of defect signals are computed by a 3-D finite-element method and the method to eliminate the signal distortions caused by induced magnetic fields are presented. Simulated results in this paper agreed well with measuring ones. [ABSTRACT FROM AUTHOR]

Computer simulations of the magnetizing process have been carried out by applying a numerical model to the theory of magnetization and demagnetization for magnetic materials. The numerical model (written using the Python programming language) is able to calculate the magnetization/demagnetization of the permanent magnet material according to its $B$ – H$ curves. This numerical model is combined with an existing finite-element method (FEM) model in which the result of computations is the approximated potential value in the FEM mesh. The aim of this paper was to develop a tool able to simulate the behavior of an anisotropic sintered permanent magnet during the demagnetization process. The permanent magnet material that has been studied in this paper is sintered Nd–Fe–B and it was modeled taking into account an average misalignment angle related to the magnet easy axis. This model also takes into account different demagnetizing field directions, such as a demagnetizing field perpendicular to the orientation direction, which is often ignored. It is shown that even a demagnetizing field perpendicular to the magnetization direction can produce visible demagnetization effects. A Gaussian distribution of the average misalignment angle in the permanent magnet material is also taken into account as well as its variation. Demag curves have been calculated varying the misalignment angle and the intensity and direction of the external magnetic field. The simulation results are in perfect agreement with the {1}/{\cos \theta} law. The model can be applied in many magnetization and magnetic tuning applications. [ABSTRACT FROM PUBLISHER]

In previous studies on precise computation methods of iron loss, it has been shown that the 1-D dynamic magnetic field analysis with hysteresis in post-processing is effective. However, there is a problem in that the hysteresis makes the convergence of nonlinear iterations unstable. This paper proposes a stabilization method for the 1-D dynamic magnetic field analysis with hysteresis. The proposed method is characterized as an approach for improving the initial value and the step size in the Newton–Raphson method. The results of this paper showed that the convergence characteristic of the nonlinear 1-D magnetic field analysis for variety flux density waveforms of each part in an electric motor is improved using the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach for incorporating noncuboidal and rotated cuboidal sources of magnetic field in 3-D Fourier modeling. Based on the periodicity present in the geometry, a Fourier integral is applied in two directions. By changing the integration boundaries in the $y$ -direction to a linear function of the $x$ -direction, nonideally shaped magnetic field sources (i.e., coils and permanent magnets) are incorporated. From the electromagnetic example geometries analyzed in this paper, the magnetic field as derived with 3-D Fourier is over 99% accurate compared to 3-D finite-element models. [ABSTRACT FROM AUTHOR]

We have previously been proposed a novel adaptive finite-element method (FEM) based on a magnetic field conservation indicator and a non-conforming mesh-refinement technique. However, we have applied to a very simple model consisting of a single permanent magnet for basic verification of the proposed method. In this paper, we have improved an error indicator, and tried to apply a newly proposed adaptive FEM to more complicated models, where ferromagnetic material is included. The newly proposed method is superior in torque error estimation to the Zienkiewicz-Zhu error estimation method in a 3-D permanent magnet motor model. [ABSTRACT FROM AUTHOR]

From a new stator-flux perspective, a comparative study between the series and parallel hybrid excitation machine (PHEM) is conducted and it is revealed that in PHEMs there still exist distinct stator-flux harmonic components during high-speed flux weakening operation, which could be further utilized to improve the torque capability at high-speed range. Inspired by this idea, an auxiliary winding is creatively introduced into PHEMs to recycle and utilize the magnetic field energy generated during the field regulation. A new design case is presented in this paper, in which two sets of armature windings with different pole pair numbers are arranged to realize the function of flux weakening operation and energy recycling, respectively. The feasibility of this new hybrid solution is evaluated by using the finite-element analysis. Furthermore, a prototype is manufactured and relevant experiments are performed. The experimental results agree well with the theoretical analysis and simulation results, which verify that the recycled energy can be effectively used to boost the output torque and power of PHEMs in the high-speed region. [ABSTRACT FROM AUTHOR]

This paper deals with the optimal design of a new synchronous motor particularly suitable for electric vehicles. The unique advantage of this motor is its possibility to realize field weakening at high speeds, which is the most important demand for such drives. The main design goal is to identify the dimensions of certain crucial regions of the machine in order to avoid saturation of the iron and to minimize the mass to volume ratio, while simultaneously maximizing the torque. The originality of the contribution is manifold: formulating the design problem in multiobjective terms, solving it by means of evolutionary computing, solving the associated direct problem based on a three-dimensional finite element analysis (3-D-FEA) field model, considering a reduced set of design variables by means of response surface method, referring to a real-life problem. [ABSTRACT FROM AUTHOR]

This paper presents a new and rigorous analytical calculation of electromagnetic field and eddy current losses in the zones of transformer tanks where bushings are mounted. This is done by solving Maxwell’s equations in the regions surrounding bushings, with the corresponding boundary conditions and considering linear permeability. Then, by solving the modified Bessel’s equation, the analytical formulas to calculate the magnetic field and eddy current losses in these regions are obtained and several cases are studied. The results are compared with 3-D finite element simulations and show very close correspondence. The obtained formulas allow straightforward calculations that can help designers to select proper parameters to optimize the design of transformers. This paper can be taken as the basis for the analysis of the nonlinear permeability case. [ABSTRACT FROM AUTHOR]

This paper investigates the iron loss calculation of permanent magnet (PM) machines undertaking unconventional operations, where the high-frequency alternating armature field is only a fraction of the constant PM field. It is found that the iron loss of PM machines undertaking such unconventional operations cannot be calculated reliably as the conventional summation of all the iron loss harmonics predicted by finite-element (FE) methods due to fake iron loss harmonics. Further investigation is conducted on the influence of current frequency and magnitude, FE mesh, and convergence tolerance on the FE predicted iron loss under unconventional operations. It is then proposed in this paper that the iron loss of PM machines undertaking unconventional operations can be calculated as the summation of only the iron loss harmonics, which are insensitive to the convergence tolerance. The analyses are validated by the experimental results. [ABSTRACT FROM AUTHOR]

This paper presents the characteristic analysis and experiment of surface-mounted type variable-flux permanent-magnet machines considering magnetization and demagnetization based on electromagnetic transfer relations. For this purpose, we derive the analytical solutions for the magnetic fields generated by the magnetization level of AlNiCo magnets and currents on the basis of the transfer relations in terms of a 2-D polar coordinate system. The magnetization levels of the AlNiCo magnets are determined by the magnetic fields generated by the armature reaction field. A 2-D permeance function is also introduced to consider slotting effects. The analytical results of the magnetic field are validated extensively with finite-element (FE) analyses. On the basis of these solutions, the induced voltage is also determined analytically. Finally, the predictions are compared with FE analyses and measured data to confirm the validity of the analysis methods presented in this paper. [ABSTRACT FROM AUTHOR]

Since the steel pipe of a road sign pillar is built for years on the ground, the underground part of its steel pipe may be corroded. In recent years, the accident from which the road sign pillar falls down has increased owing to the corrosion in the underground part of its steel pipe. In this paper, the nondestructive inspection method for detecting the defect in the underground part of its steel pipe using the alternating magnetic field by low exciting frequency is proposed. In this method, both the distance from the electromagnetic sensor to the defect and the depth of the defect are presumed. The usefulness of this proposal inspection method is shown from both the 3-D nonlinear electromagnetic finite-element method analysis and the experimental verification. [ABSTRACT FROM AUTHOR]

This paper presents an exact analytical subdomain model of slotted permanent-magnet (PM) machines, taking into account the diffusion effect. The model gives the magnetic fields, both the eddy currents and the power losses in the PM, the instantaneous and average torque. In the model, eddy currents are not assumed to be resistance limited, contrary to what is done in the conventional exact subdomain models of the slotted machines. The model is hence general and valid both at low and high frequencies. It shows that it is possible to calculate the power losses in the PMs, only knowing the fields in the air gap. The model takes into account the presence of tooth-tips. The comparison with conventional exact subdomain models shows that the model presented in this paper is more accurate. The model is validated using the finite-element methods. [ABSTRACT FROM AUTHOR]

This paper deals with an accelerated implementation of the assembly of the matrices accounting for the magnetic-electric interactions arising from an integral formulation of the eddy current problem. The use of integral formulations leads to fully populated matrices whose assembly requires a computational effort of O(N^2) , $N$ being the number of degrees of freedoms related to the finite-element discretization. Although the inversion procedure is O(N^{3}) for a direct method, the assembly for medium size problems can be very time consuming. In this paper, we prove that a significant speedup can be achieved by means of an optimized ad hoc use of graphical processing units. The price to be paid is a challenging implementation if compared with the traditional parallel systems (CPUs based). Two kinds of applications are considered: one in the framework of non-destructive testing and the other in the field of plasma fusion devices modeling. [ABSTRACT FROM AUTHOR]

The damping and screening system (DSS) is a key structure of the hybrid high-temperature superconducting generator. In this paper, an analytical method was introduced to analyze the performance of the DSS with different time constants on both the $d$ -axis and the $q$ -axis of the generator. First, the distribution of the eddy currents in the DSS was analyzed, and the calculation of the equivalent resistance, inductance, and time constant of the DSS was considered. Then, to analyze the performance of the nonuniform DSS (NDSS), a splitting method was introduced. Using the new method, parameters of the damping part, screening part, and supplementing part of the NDSS were calculated, respectively. At last, the screening and damping performances of the NDSS were evaluated. The finite-element method was also employed to verify the analytical results. An experimental platform was built up to test the screening ratio and verify the simulating results. [ABSTRACT FROM AUTHOR]

This paper presents a synthesis of analytical calculations of magnetic parameters (field, force, torque, stiffness) in cylindrical magnets and coils. By using the equivalence between the amperian current model and the coulombian model of a magnet, we show that a thin coil or a cylindrical magnet axially magnetized have the same mathematical model. Consequently, we present first the analytical expressions of the magnetic field produced by either a thin coil or a ring permanent magnet whose polarization is axial, thus completing similar calculations already published in the scientific literature. Then, this paper deals with the analytical calculation of the force and the stiffness between thin coils or ring permanent magnets axially magnetized. Such configurations can also be modeled with the same mathematical approach. Finally, this paper presents an analytical model of the mutual inductance between two thin coils in air. Throughout this paper, we emphasize why the equivalence between the coulombian and the amperian current models is useful for studying thin coils or ring permanent magnets. All our analytical expressions are based on elliptic integrals but do not require further numerical treatments. These expressions can be implemented in Mathematica or Matlab and are available online. All our models have been compared to previous analytical and semianalytical models. In addition, these models have been compared to the finite-element method. The computational cost of our analytical model is very low, and we find a very good agreement between our analytical model and the other approaches presented in this paper. [ABSTRACT FROM AUTHOR]

This paper deals with analysis and experiment of an axial flux permanent magnet (AFPM) brushless direct current (BLDC) motor with minimized cogging torque. Recently, many optimal designs for the AFPM motor have been done by finite-element (FE) analysis, but such analysis generally is time-consuming. In this study, the equation of magnetic flux lines existing between PMs and cores is assumed mathematically and the minimum cogging torque is calculated theoretically and geometrically without FE analysis. The form of equation is assumed to be a second-order polynomial in this paper. The skew angle that makes the cogging torque minimized is calculated theoretically, and the value of minimum cogging torque is confirmed by FE analyses and experiments. In the theoretical analysis, the maximum cogging torque of a proposed AFPM motor has the smallest value approximately at a skew angle of 4° and that value is about the same as those of FE analyses and experiments. Compared with the nonskewed motor, the cogging torque of the skewed motor can be decreased to over 90%, which has a value of 5% of the rated torque. Two types of stator cores, with the skew angle of 0° (nonskewed) and 4° (skewed optimally), are analyzed, manufactured, and tested experimentally in this paper. [ABSTRACT FROM AUTHOR]

This paper presents three-dimensional expressions for the optimization of permanent-magnet couplings. First, we give a fully analytical expression of the azimuthal field created by one arc-shaped permanent magnet radially polarized which takes into account its magnetic pole volume density. Such an expression has a very low computational cost and is exact for all points in space. Then, we propose two semianalytical expressions of the azimuthal force and the torque exerted between two arc-shaped permanent magnets. These expressions are valid for thick or thin arc-shaped permanent magnets. Furthermore, this approach allows us to realize easily parametric studies and optimizations. The analytical approach taken in this paper, based on the Coulombian model, is a good alternative compared to the finite element method generally used to study such configurations. [ABSTRACT FROM PUBLISHER]

Considering the basic role of the stator magnetic field (MF), this paper presents a synthesis strategy for stator MF of a permanent magnet spherical motor (PMSM). Given the structure of the PMSM, the MF of a stator coil group with unit current is obtained, and the spherical harmonic components are decomposed, so the relationship between the whole stator MF and coils currents can be deduced by the rotary transformation and superposition. Referring to the rotor MF, the expected stator MF is determined; then, the stator coil currents are calculated by solving a constrained optimization. Finally, the current excitation strategy of stator coils is verified by finite-element analysis and experiments. [ABSTRACT FROM AUTHOR]

This paper deals with the magnetic field continuity conditions in finite-element analysis. Our study is based on numerical and analytical models. Different known finite-element codes, based on 2-D nodal finite element or 3-D edge element, are used to analyze the magnetic field in a linear motor-like device. The use of an analytical model gives interesting insight on interface errors problems in finite-element analysis. [ABSTRACT FROM AUTHOR]

In this paper, a new shaded-pole main exciter (ME) with additional short-circuited coils for aircraft three-stage starter–generator (SG) is proposed and investigated. The basic structure, winding configurations, operating principle, and start system structure of the presented shaded-pole ME are illustrated in detail. The comparative study between the original ME and the shaded-pole ME with respect to the starting mode performances is conducted by 2-D finite-element method (FEM). A prototype SG with original ME has been developed, and the experimental results are essentially consistent with the simulation results by the FEM utilized in the predictions in this paper. Simulation data and waveforms verify that the proposed shaded-pole ME is a good candidate for aircraft machines to satisfy the dual function of starter and generator. [ABSTRACT FROM AUTHOR]

As for the steel tube for liquefied natural gas in a petrochemical plant, the steel tube with a large diameter is covered with the thermal insulation material and the sheet metal. Generally, the thickness of its thermal insulation material is about 80 mm. On the inspection of the thickness or the corrosion in this steel tube, the sheet metal and the thermal insulation material are removed from the steel tube. However, much cost and time are needed for this inspection. In this paper, the pulse electromagnetic inspection method for detecting the defect in the steel tube from the upper side of the insulation material and the sheet metal is proposed. The defect is inspected by measuring the slope of the output voltage from the maximum output voltage value obtained immediately after cutting off the pulse wave magnetic field. In addition, the proposed inspection method is investigated by the 3-D nonlinear finite-element method taking into account hysteresis magnetizing properties and eddy current in the steel tube. [ABSTRACT FROM AUTHOR]

Yokeless electric current transducers have compact size, but they are sensitive to external magnetic fields, including those caused by electric currents in their vicinity. It is often believed that this unwanted sensitivity can be effectively suppressed by using a differential sensor. In this paper, we investigate the effect of external current with arbitrary position on busbar differential current sensor. We show the main disadvantage of the differential current sensor: increased sensitivity to currents in the transversal direction, which are not sensed by a single sensor. We analyze by finite element method simulation also the influence of real conductor size and uneven density of ac currents. The results were verified on 1000 A current transducer using a pair of microfluxgate sensors. The realistic suppression of close currents depends on the conductor angular position and in 10 cm distance it can be as low as 50, but it can be corrected if the geometry is known. [ABSTRACT FROM AUTHOR]

In this paper, a permanent magnet (PM) slotless tubular linear generator based on magnet field analysis model is presented for wave energy conversion. To improve air flux density and efficiency of the generator, two improved Halbach PM Arrays (T-PM structure and claw-PM structure) applied in the slotless linear generator is proposed and compared with Halbach PM Arrays. Combined with axisymmetric dimensional finite-element method (FEM), no-load electromagnetic performance is analyzed. Finally, due to test and analysis model results of prototype concordant with the FEM results, the generator model and the analysis method are correct. [ABSTRACT FROM AUTHOR]

Linear magnetic-field modulated (LMFM) motor exhibits high thrust force by effectively employing the magnetic-field modulation effect. In this paper, a new mover separated LMFM (MS-LMFM) motor is proposed, which successfully alleviates the space confliction between permanent magnets (PMs) and windings in the existing LMFM motor. The structure and the operation principle of the existing and proposed motor are described, and the major design parameters are optimized for maximum thrust force. Moreover, electromagnetic performances of both motors are compared by finite-element method. Theoretical and simulation analysis shows that the proposed motor can exhibit enhanced force performance than the existing one under fixed copper loss. Simultaneously, reduced iron and PM losses can also be obtained by proposed motor. Finally, a 3-D modeling MS-LMFM motor is built for a global observation of motor structure and further verification of the 2-D analysis. [ABSTRACT FROM AUTHOR]

Magnetic levitation positioning systems (MLPSs) are of great interest in high-precision applications in vacuum. In this paper, a linear magnetic bearing with rhombus magnet array (RMA-LMB) for MLPS is proposed. With the RMA, the proposed RMA-LMB possesses advantages of excellent force uniformity, high force density, and good manufacturability. First, the basic structure and operating principle of the proposed RMA-LMB are presented. Second, the expressions of magnetic field, static force and torque, and dynamic force and torque are obtained by an equivalent current model. Third, the 3-D finite-element analysis (3-D FEA) is employed to investigate the RMA-LMB, and the magnetic field distribution, the static force and torque, as well as the dynamic force and torque are analyzed. Finally, a prototype is constructed, and experiments show a good agreement with the FEA results. [ABSTRACT FROM AUTHOR]

This paper proposes and implements the concept of time-division multiplexing (TDM) wireless power transfer (WPT) for separately excited dc motor drives. Essentially, the proposed WPT system has only one transmitter that can transfer power to multiple receivers simultaneously while the power transfer to individual receivers can be independently controlled. Thus, the armature and field currents of the separately excited dc motor can be independently controlled, hence achieving the desired constant torque operation and constant power operation. The key is to make use of the TDM scheme to simultaneously transfer powers to both the armature and field windings. Meanwhile, the burst firing control method is incorporated to independently regulate the power flows to the armature and field windings at the resonant frequency, hence retaining the maximum power transfer efficiency. Both finite element analysis and experimentation are given to verify the validity of the proposed system. [ABSTRACT FROM AUTHOR]

Successful analytical formulas have been previously proposed to calculate the losses in tank regions of transformers assuming linear permeabilities in the analyzed boundary-valued problem. This has resulted in easy-to-implement and low-cost computational design procedures from a transformer factory economical point of view. However, designers and analysts of transformers are constantly seeking new ways of reducing transformer losses in actual power networks with thousands of transformers. As a result, this paper has focused on proposing new analytical formulas to determine the electromagnetic field in bushing regions of transformers, taking account of the true nature of the nonlinear permeability behavior of the tank wall. This way, the nonlinear Maxwell’s equations in the regions surrounding the bushings are solved using an integral equation formulation that properly includes boundary conditions. A practical iterative procedure is thus proposed to solve the resulting nonlinear equation. The iterative scheme shows excellent numerical convergence properties with a very low computational demand as compared with finite-element (FE) nonlinear models. A comparison between our analytical results and those of 3-D FE simulations reveals a close match for a wide range of conductor currents. Hence, our new formulas can be used to improve the design of transformers, increasing their efficiency. [ABSTRACT FROM AUTHOR]

This paper proposes a coupled 3-D finite element method (FEM) and particle method for the analysis of cold crucible induction melting. In this method, the magnetic field is calculated by FEM and the fluid motion equation and the heat equation of a molten metal are calculated by the particle method. The effectiveness of this method is verified through the analysis of the molten metal behavior in the crucible. [ABSTRACT FROM PUBLISHER]

This paper presents a line-integral formulation for the computation of the magnetic field in the vicinity of a network of magnetic and conductive wires. The formulation is valid in the time-harmonic case and considers eddy currents. A comparison with the results obtained with the finite-element method confirms the accuracy of the proposed formulation. [ABSTRACT FROM AUTHOR]

This paper proposes a novel estimation method for iron loss considering hysteretic property. In the proposed method, iron loss considering hysteretic property is estimated with play model as a postprocessing of usual finite element magnetic field analysis based on ordinary magnetization curve. Numerical results are compared with measured results to demonstrate the effectiveness of the proposed estimation method for iron losses. [ABSTRACT FROM AUTHOR]

A linear voice coil motor (VCM) with forward winding for linear vibro-impact systems is proposed in this paper. Generally, only increasing the air-gap flux density of VCM, which ignores its bad thrust characteristic condition, is limited to obtain a higher thrust density, due to its intermittent duty and reciprocating linear motion. Thus, the analysis on the thrust characteristic is of momentous significance for VCM design. Considering this fact, we try to adjust the thrust characteristic to obtain the maximum thrust density. Magnetic-circuit analysis method is utilized to analyze the thrust characteristic along with a given total working stroke. Besides, finite-element analysis is also used in the selection of parameters. A series of prototype VCMs for experiments is made. The results from both theoretical simulations and practical experiments show increase of thrust density and decrease of thrust ripple compared with the original design, and prove the superiority of the proposed structure. [ABSTRACT FROM PUBLISHER]

This paper presents a novel method of inductance calculation for the incomplete loop problem. This method is based on the relationship between inductance and induced voltage from the circuit theory. The method embarks from Faraday’s Law, and calculates induced voltage of every flux element. Total induced voltage is given by summation of elements and then the inductance value is obtained. Numerical calculations are made for showing that this method is available and more accurate than partial inductance theory. The method may also be applied toward complete loop problems, and gives identical formulas as existing methods. [ABSTRACT FROM AUTHOR]

This paper presents a new technique for the transient analysis of power transformers under standard impulse excitations. Based on a 2-D finite element method magnetic and electric field simulation coupled to an electric circuit, the technique allows for an analysis of a wide range of winding and insulation designs of a transformer. Also, a 2-D approximation and a direct electric and magnetic field computation (without an equivalent circuit modeling) make this technique effective for engineering applications. Results of calculations of a three-phase power transformer 125MVA-220/10 kV are presented to validate the accuracy of the approach. [ABSTRACT FROM AUTHOR]

The Gauss–Seidel preconditioned conjugate gradient method applying to element-by-element finite-element method (EBE-FEM) is derived and the calculation process is presented in this paper. The EBE-FEM is a parallel numerical algorithm, in which a conjugate gradient (CG) type iterative solution scheme can be entirely decomposed into computations on the element level without assembling the global system matrix. The validity and accuracy of the proposed method have been verified through the applications to magnetic field analysis of a long straight current-carrying wire and a three-phase electric motor. Compared with the Jacobi preconditioned CG method applying to EBE-FEM, less computational time and cost are needed for the proposed method with the same accuracy. The proposed method can be applied to electromagnetic field analysis of power transformer and electric motor, which may be related to large-scale numerical computation. [ABSTRACT FROM AUTHOR]

This paper proposes a homogenization method for a laminated iron core taking into account hysteretic property. The proposed method is applicable to a static or low-frequency problem neglecting eddy currents induced by the magnetic flux parallel to the lamination. Furthermore, we apply the proposed homogenization method to finite-element magnetic field analyses to demonstrate its effectiveness. As a consequence, it is verified that the proposed homogenization method can accurately estimate a hysteresis loss of a laminated iron core and decrease computational costs. [ABSTRACT FROM AUTHOR]

In this paper, four numerical formulas are introduced to calculate possible unbalanced magnetic forces (UMFs) during the assembly process in order to save calculation time and efforts. If the proposed formulas are used to calculate the UMFs according to the degree of rotor eccentricity every time the rotor position is changed relative to the stator position in the axial direction, a fully configured or partial 2-dimensional (2-D) model and 3-D periodic analysis model are used for magnetic field calculation instead of a fully configured 3-D analysis model. The reliance of the formulas is verified by comparing the results calculated by the formulas with each other. Then, the size and the number of guide bars as assembly jigs are selected considering the calculated UMFs. [ABSTRACT FROM PUBLISHER]

This paper presents an extended Field Reconstruction Method (FRM) to model a Switched Reluctance Machine (SRM), which is set apart from other electric machines by its double-saliency and magnetic saturation. Traditional magnetic models of SRM developed using Finite Element Analysis (FEA) are computationally inefficient. This, in turn, limits their application in simulation of SRM drive system especially under iterative optimization procedures. FRM can significantly reduce the computational time by utilizing a small number of static magnetic field snapshots to establish the basis functions which are then used to reconstruct the magnetic field with high accuracy. In this paper an extended version of FRM is introduced within which effects of magnetic saturation and double saliency are taken into account. Results from FRM, FEA and experiments are compared and good accuracy is observed. [ABSTRACT FROM PUBLISHER]

This paper analyzes the torque characteristics of a magnetic rack-and-pinion gear using an analytical method based on the spatial harmonic method. We obtain the magnetic field distribution due to the permanent magnets and derive the magnetic torque from the magnetic field using the Maxwell stress tensor. The analytical results are extensively validated by comparing with finite element analysis results. Finally, we obtain an accurate analytical solution to reduce the analysis time and experimentally verify this solution by applying it to a newly manufactured rack–pinion gear model. [ABSTRACT FROM AUTHOR]

The magnetic susceptibility of pyrolytic graphite (PyG) is temperature dependent. Under an external magnetic field, a levitated PyG sample with a localized temperature change experiences unequal diamagnetic forces. In this paper, we present a study of the macroscale optomechanical displacement of a levitated PyG sample by using a laser source to locally increase the temperature. Dynamic finite-element method simulations show that a localized increase in the sample temperature, simulating a laser source, decreases the diamagnetic force in that local area, leading to the displacement of the PyG sample in the plane of the permanent magnet array. Experimental setups built using different laser sources and samples confirm the range of applicability of the actuation phenomenon to different conditions. An additional setup without moving parts reduced the likelihood by which airflow could have caused the displacement, as we suspect happened in the previous studies. [ABSTRACT FROM AUTHOR]

This paper develops a parallel finite-element method based on a space–time domain decomposition method. The proposed method combines a standard space domain decomposition approach with the parallel time-periodic explicit error correction method as a parallel-in-time integration method. To clarify its parallel performance, numerical results of magnetic field analyses of an interior permanent magnet motor fed by pulse width modulation inverters are demonstrated. [ABSTRACT FROM AUTHOR]

This paper mainly investigates the 3-D resonant cavity problem with anisotropic and lossy media. When the media are electric lossy and not magnetic lossy, we solve the 3-D cavity model with magnetic field as a working variable by mixed finite-element method (MFEM). A Lagrange multiplier is used to enforce divergence-free condition in a weak sense. In the MFEM, we employ edge basis function of the lowest order to expand the electric field or the magnetic field, and linear element basis function to expand the Lagrange multiplier. Numerical experiments show that the MFEM can eliminate all the spurious modes to solve this type of 3-D closed cavity problem. [ABSTRACT FROM AUTHOR]

In this paper, a Halbach array-based nuclear magnetic resonance device for multiphase flow measurement is suggested. The design approach used simultaneously a 3-D finite-element method (FEM)-based software combined with particle swarm optimization algorithm. The goal of the design is to generate a relatively intense and highly homogenous magnetic field inside the target sensing area using a compact and lightweight magnet array. Simulation results on a device consisting of 12 Halbach arrays, each consisting of 12 cuboid permanent magnet elements of size 20 mm $\times20$ mm $\times46.5$ mm size, indicate that a highly homogenous magnetic field distribution of 0.890 T maximal intensity and 606 ppm homogeneity could be achieved within a probe cross section of 40 mm diameter when the Halbach arrays are distant from each other by a distance of 4 mm. This is adequate for the desired application while it leads to a light and compact overall Halbach array of 21.6 kg weight and 600 mm length. Experimental validation which was done using newly constructed two Halbach arrays of cuboid and trapezoid magnet elements, respectively, indicates a good match with FEM simulations. Furthermore, sensitivity analyses were performed to identify significant design variables for further optimization. [ABSTRACT FROM AUTHOR]

This paper proposes a coupled method of 3D-FEM (finite element method) and MPS (moving particle semi-implicit) method for analyzing the electromagnetic levitation of a molten metal. In this method, the magnetic field equation is calculated by FEM and fluid motion equation of a molten metal is calculated by MPS method. To verify the effectiveness of this method, it is applied to analysis of the behavior of molten metal in electromagnetic levitation. [ABSTRACT FROM PUBLISHER]

This paper proposes a coupled method of finite-element method (FEM) and moving particle semi-implicit (MPS) method in order to analyze the spike shape of ferrofluid. In this method, magnetic field equation is calculated by FEM and fluid equation is calculated by MPS method. [ABSTRACT FROM PUBLISHER]

This paper proposes a dynamic analysis method of repulsion forces acting on current-carrying contact. In this method, the dynamic repulsion forces are computed using 3-D FEM coupling with magnetic field analysis, current distribution analysis, and motion analysis of contacts. The effectiveness of this method is clarified through the dynamic analysis of repulsion forces on contacts. [ABSTRACT FROM PUBLISHER]

The inspection of the surface-hardened depth of the mechanical part in a large-sized heavy industrial machine is important in the intensity or the guarantee of quality of these parts. When the size of its hardened steel parts is large, the destructive testing using the Vickers hardness tester is made difficult. Therefore, the non-destructive inspection method is needed for the evaluation of the hardened depth. The electromagnetic characteristic inside the hardened domain is lower than the non-hardening domain. Then, the non-destructive inspection of the hardened depth is possible by detecting the difference of these electromagnetic characteristics. In this paper, the high-sensitivity inspection method for detecting the surface-hardened depth is investigated by a 3-D nonlinear electromagnetic finite-element method using the evolution strategy method. [ABSTRACT FROM AUTHOR]