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Fe-based amorphous magnetic materials are recently attracting strong interests for constructing high-power density and high-efficiency rotating electrical machines due to their attractive properties, such as low core loss and high magnetic saturation. Accurate measurement and modeling of the rotational core losses of the core magnetic materials, and the corresponding patterns of rotating magnetic flux density ( $B$ ) and magnetic field strength ( $H$ ) are important for the analysis and design of electrical machines. This article presents the measurement of rotational core loss of a Fe-based amorphous magnetic material (amorphous 1k101), and its corresponding modelings under two-dimensional (2-D) circularly and elliptically rotating magnetic fields. In addition, an improved and simplified analogical model of rotational hysteresis loss is proposed for such magnetic materials. The circular and elliptical $B$ loci and the corresponding $H$ loci have been investigated to acquire the perception of anisotropy and permeability of the amorphous materials. The proposed theory and models are experimentally verified.

In order to analyze accurately the airgap magnetic field of the slotted permanent magnet synchronous machine (PMSM) taking into account the influence of slotting effects, this article proposes an analytical method for calculating the complex relative permeance function. Based on one tooth pitch of the machine as the solution model, the governing Laplace field equation of the airgap region is solved analytically in the polar coordinate system. According to the boundary conditions between the slot and airgap region, the analytical expressions of the radial and tangential components of the complex relative permeance function are derived. With this complex permeance, the no-load radial and tangential airgap magnetic fields of the internal and external slotted PMSM with different slot/pole combinations are obtained. The accuracy of the analytical model is validated by the results of finite element analysis. With good simplicity and generality, this model can be an effective means for further study of motor performance.

Multi-degree-of-freedom (MDOF) magnetic bearings have been widely investigated and designed for various applications. However, a new design magnetic bearing cannot be directly used without optimization due to the not relatively excellent performance. Besides, there may be a lack of consideration of the interaction of parameters in the design process. Hence, in this article, a three-degree-of-freedom hybrid magnetic bearing (THMB) is optimized as an example. First, a comprehensive sensitivity analysis is carried out to show the relationship between the parameters and optimization objectives in detail. Second, a cross-factor variance analysis is considered due to the possibility of parameter interaction. And then, a hierarchical multi-objective optimization structure is used with the Kriging model and the non-dominated Sorting Genetic Algorithm II (NSGA II). The simulation results verify the validity of the proposed method, and the prototype is under manufacture for further evaluation.

Grain-oriented (GO) sheet steels are widely used as the core material in large power transformers. The strong magnetostriction in GO sheet steels, however, causes undesirable vibrations and acoustic noises, and is difficult to estimate in the design optimization of power transformers. This article proposes a new magnetostriction model of GO sheet steels by combining the Becker-Doring crystal model and the dynamic Jiles-Atherton hysteresis model. Incorporated in the finite-element analysis (FEA), the new model can correctly simulate the butterfly loops of magnetostriction in GO sheet steels. The effectiveness and accuracy of the proposed model are verified by the experimental measurement results on a single sheet sample in a free state with no external stress.

© 2020 IEEE. Extensive research has shown that silicon steel sheets in electrical machines and power transformers are usually working under compressive or tensile stress, which affects both magnetic properties of silicon steel sheets and performance of electromagnetic devices. In this article, a magnetic property measurement system considering the stress effect has been developed and constructed based on the large cross-shaped single-sheet tester (LCSST). The uniformity of the stress distribution for LCSST is verified by the finite-element method. The B-H magnetic property of a specimen of non-oriented silicon steel 50JN470 in the direction of applied stress is measured by the proposed LCSST, and the results are in good agreement with those measured by the rectangle single-sheet tester (RSST) made by the Brockhaus Company. The RSST, however, cannot measure the effects of uniaxial stress on the magnetic properties. This article presents and analyzes the extensive experimental results of magnetic properties with uniaxial stress applied along both transverse and rolling directions ranging from 7 MPa compressive stress to 7 MPa tensile stress.

© 1965-2012 IEEE. Permanent-magnet synchronous hub motors (PMSHMs) have been investigated for electric vehicles. However, there are some challenges such as effective cooling and radial force. As PMSHMs are installed on the wheels, the radial force will directly affect the ride comfort of the vehicle. This article presents the analysis and optimization of the radial force for PMSHMs. The radial force densities of the symmetry and asymmetry PMSHMs are analyzed first. It is found that the symmetry PMSHMs have balanced force, while the asymmetry PMSHMs normally have big unbalanced radial force and vibration. To reduce the radial force of the asymmetry PMSHMs, an improved sequential Taguchi optimization method (ISTOM) with mixed orthogonal array is presented for an asymmetry PMSHM in this article. It can be found that the proposed method is efficient and can significantly reduce the radial force of the hub motor.

© 1965-2012 IEEE. Compared with traditional induction machine and direct current machine, permanent magnet synchronous machine (PMSM) holds many merits like higher torque ability and efficiency when high magnetic co-energy sintered NdFeB magnet is used. However, for the operation with high frequency, the resulted eddy current loss by the permanent magnet (PM) is very high and this kind of loss can bring the PM with high-temperature rise, making the PM face the risk of irreversible demagnetization. To reduce the PM eddy current loss, complete magnet segmentation is an effective method. However, taking this kind of method will increase manufacturing cost and reduce the mechanical robustness of the PMSM. Thus, a partial magnet segmentation method was proposed in the past. In this paper, a new annular partial segmentation (APS) method is proposed for the reduction of the PM eddy current loss, including single-side APS and double-side APS configurations. Considering that the additional process on the PM will reduce the mechanical robustness of the PM and the electromagnetic performance of machine, both the electromagnetic performance and the mechanical strength of the PM have been analyzed, based on 3-D finite-element method. It can be found that if the proposed new annular partial segmentation (APS) method is adopted, the eddy current loss in the PM can be reduced greatly, while the mechanical robustness of the PM can be guaranteed comparing with the traditional partial magnet segmentation method.

© 1965-2012 IEEE. This paper presents a quasi-3-D cylindrical coordinate high-Temperature superconducting (HTS) cable model based on the shell element theory. The quasi-3-D meshing elements are used instead of the traditional 3-D meshing elements to overcome the difficulties in meshing. The improved extended finite-element method (XFEM) is proposed to solve the field problem in close-jointed thin layers. The numerical simulation results are reported compared with the experimental test results for the case of an HTS cable with three layers.

© 1965-2012 IEEE. This paper presents a 3-D magnetic equivalent circuit (MEC) network that integrates the hysteresis model for the analysis of the axial field flux-switching (AFFS) memory (AFFSM) machine. Similar to finite element method, meshing is used to subdivide the model into smaller domains called elements, over which a set of element equations and a reluctance network equation are built. Newton-Raphson method is adopted to handle the nonlinear problems. The fixed-point technique is introduced to cope with the problem involving hysteresis. The proposed method is capable of predicting the operation of the low coercive force permanent magnet during flux regulation and the electromagnetic field distribution of the machine. Finally, the proposed 3-D MEC method is implemented for analysis of the AFFSM machine. MEC results are compared with 3-D finite element analysis and experimental results. The results show that the proposed method offers reasonable accuracy with moderate computational effort.

© 1965-2012 IEEE. High reliability is usually demanded for the design of electromagnetic devices. Interval uncertainties widely exist in the robust optimization problems, and the bounds of the design parameters can be only obtained instead of their specific distributions. To solve this kind of problem efficiently, this paper presents a robust optimization approach based on the Chebyshev interval method to estimate the extreme values of the constraints and objectives. To demonstrate the effectiveness of the method, the Testing Electromagnetic Analysis Methods workshop problem 22 and a brushless dc wheel motor optimization benchmark problem are investigated with interval uncertainties of the relevant parameters. Deterministic and robust optimizations considering the worst case with uniform sampling are also conducted for comparison. The optimization results illustrate the effectiveness of the proposed method.

© 1965-2012 IEEE. In recent years, microgrid technologies have gained considerable interest, where a common dc-bus is generally used to interconnect multiple power sources. The existing technology of common dc bus-based direct integration of multiple sources has some critical problems, such as isolation and the requirement of additional control circuit for voltage imbalance and common mode. A common high-frequency magnetic bus (instead of the common dc bus) is proposed in this paper to overcome the limitations and complications of the existing technology of dc bus-based direct integration of multiple sources. In this paper, an extensive investigation on electromagnetic performance of advanced magnetic materials (amorphous and nanocrystalline alloys) is presented. The design process of an efficient and compact high-frequency common magnetic bus for integration of multiple power sources is also discussed. The new technology will be a fundamental component for the future grids to interconnect various sources magnetically, providing an inherent solution to voltage imbalance and isolation problems.

This paper introduces an elemental operator with biaxial anisotropy to simulate the scalar hysteresis phenomenon of the ferromagnetic materials. The equilibrium position of the magnetization for the elemental operator can be determined by energy minimization. To directly describe the magnetic properties of each operator, an improved analytical expression is deduced by the partial approximate substitutions. Moreover, this approach utilizes the concept of distribution function density in order to consider the interaction field and the coercive force of the elemental operators. To verify the presented model, the magnetic hysteresis of two different magnetic materials under alternating excitations is measured by the magnetic property measurement system and calculated by this elemental operator method, respectively. The comparisons suggest that this elemental operator is effective and can be a useful tool to simulate the scalar magnetic properties of ferromagnetic materials.

© 1965-2012 IEEE. Soft magnetic composite (SMC) materials and SMC electromagnetic devices have attracted strong research interest in the past decades. However, SMC devices have large core loss that needs to be put into consideration even at the design stage. Effective and accurate prediction of the core loss becomes crucial for the design and optimization of high-performance motors with these materials. Equivalent circuit model is a widely used method for machine analysis, due to the advantages in the fast calculation with a clear physical mechanism. This paper presents an equivalent circuit model to predict the core loss of a claw-pole permanent magnet motor with SMC stator core. All the parameters including the equivalent core-loss resistance in the equivalent circuit model are identified based on the finite-element method to achieve high accuracy, and the effectiveness of the parameters identification methods is experimentally verified. The proposed equivalent circuit model can predict the core loss and motor's performance efficiently both under no-load and loading conditions.

© 2017 IEEE. This paper presents a coupled field-circuit analysis method for the high-temperature superconducting (HTS) cable considering magnetic hysteresis by using the improved extended finite-element method (XFEM). The quasi-3-D cylindrical coordinate HTS cable model is first proposed based on the shell element theory. The quasi-3-D meshing elements are used instead of the traditional 3-D meshing elements to overcome the difficulties in meshing. A new Preisach type hysteresis model of HTS tapes is first combined with the improved XFEM to determine the magnetic hysteresis inductance. A magnetic field-circuit coupled program for current analysis of superconducting layers is coded. The numerical simulation results of this field-circuit coupled method are reported compared with the experimental test results for the case of an HTS cable with two layers.

© 2017 IEEE. In this paper, one novel heteropolar radial hybrid magnetic bearing (HRHMB) with low-power loss is proposed for flywheel energy storage system. First, its structure and equivalent magnetic circuit (EMC) are introduced in detail. Then, some main design parameters are analyzed based on EMC, including air-gap bias flux density, magnetic pole area, permanent magnet (PM) dimensions, and control current. Furthermore, to improve the performances of the novel HRHMB, the optimizations are implemented both on its structure and some key size parameters, such as the second air-gap length, PM height, and width. Finally, the optimal scheme is verified by the 3-D finite-element analysis, which indicates the maximum control current can be reduced to only 40% that of initial design by the optimizations.

For accurate computation of core losses, the Jiles–Atherton ( $J$ – $A$ ) dynamic hysteresis model accounting for hysteresis, eddy current and excess losses is incorporated into the finite-element method (FEM). The $J$ – $A$ dynamic hysteresis model is constructed by combining the traditional $J$ – $A$ hysteresis model with the models of instantaneous eddy current and excess losses. The $J$ – $A$ model parameters and dynamic loss coefficients are determined by fitting the models to the measurement data of a single sheet tester (SST 500) and Epstein frame tester. To find the robust best fit, the particle swarm optimization algorithm is employed. By using the proposed $J$ – $A$ dynamic hysteresis model and FEM, the magnetic characteristics of a magnetic core is simulated and the core loss distribution within the core obtained. The calculated and measured results are compared to show the accuracy and effectiveness of the proposed model.

Electromagnetic levitation (EML) melting process is performed by adopting the finite-element method. It is a complicated field-coupled problem, which involves two-way interactions of electromagnetic, thermal, fluid flow fields as well as deformation. Oscillations of a solid titanium metal sample are studied to obtain the time for their balance positions under different electrical factors, such as frequency, current, and the number of coils turn. Droplet size of liquid titanium, which might be affected by different electrical factors, is also studied. It is shown that mathematical model adopted in this paper could be used to dynamically predict the melting process, balance time, and droplets size under the influences different electrical parameters.

© 1965-2012 IEEE. The precise 3-D magnetic property measurement of the silicon steel is important to improve the efficiency and performance in electrical equipment, such as electrical machines and power transformers. An improved 3-D magnetic property measurement method of the silicon steel laminations is proposed by using a novel sensing structure with interconnecting multiple sensing coils covered on the surface of the cubic specimen. Based on the new coil structure with high precise coefficients from comprehensive calibration, the accurate relationship between B and H vectors is obtained and analyzed under alternating and 3-D rotating excitations with the feedback control method, especially when the laminated direction is considered. Consequently, the experimental data of magnetic properties with high precision can be obtained, which can provide important reference in designing and optimizing electrical equipment.

© 1965-2012 IEEE. In this paper, a new 3-D flux transverse flux flux switching permanent magnet machine (3-DFTFFSPMM) is proposed. The cost of this machine is very low since both the soft magnetic composite (SMC) cores and ferrite magnets are very cheap, and the performance of this machine is good due to the special designed topology. For the qualitative analysis and initial design, the simplified power equation is developed to find the optimal design, and the 3-D finite-element method is applied for the quantitative analysis. Considering it is very difficult to obtain a special ferrite magnet in the current market, the 3-DFTFFSPMM for prototyping in the workshop is improved with a new design. For the prototyping, the SMC cores are made by using the manual die compacting technology. Last, the efficiency map of these two machines is obtained to judge the operational performance.

© 2017 IEEE. While having various desired merits of high structural robustness and thus reliability, high thrust density, low fabrication cost, and so on, the stator-magnet moving-iron transverse-flux linear oscillatory machine suffers from high consumption of rare-earth magnetic material (high material cost) and heavy flux leakage at the stator outer region (underutilization of permanent magnets). To mitigate the demerits, a novel stator-magnet moving-iron transversal-flux hybrid-flux-path linear oscillatory machine (SMTHLOM), with additional back iron and auxiliary radially magnetized ferrite magnets, is proposed in this paper. The topology and operational principle of the proposed SMTHLOM are explained in detail. The 3-D finite-element analysis is introduced to investigate the sensitivities of main structural parameters, which enables the selection of optimal dimensions. Based on a set of comparison rules, a comprehensive comparison was conducted between these two topologies on various key indicators, such as the back electromotive force, thrust, and thermal distribution. The simulation results show that the SMTHLOM is low cost and small stator outer flux leakage, and thus is more suitable for some applications, e.g., fridge compressors, requiring low cost and high thrust density.

At present, most of the linear generators contain a heavy translator for converting wave power from the ocean into electrical power. As the translator is connected to the buoy, the buoy dynamic performance is reduced by the large mass and, as a result, low velocity of the translator would degrade the electricity generation of the linear generator. This problem has been minimized by the new design in this paper, where the translator is clipped off at first and split into two separate portions to minimize its weight. The secondary stator is magnetically coupled with a special m-shaped main stator which is used to flow the necessary magnetic flux. The weight of the proposed translator is 21.82% lower than that of conventional one and 49.1% by using a recently available permanent magnet with higher specifications. The finite-element method is applied in ANSYS simulation environment for the analysis and comparison between the proposed and conventional designs. Different parameters of the conventional and the proposed linear generator have been discussed in this paper. The simulation results show that the proposed design can generate the same amount of electricity as the existing one with almost half of the translator size. According to the mathematical model, it is understood that the dynamics of the translator would be higher for its lower mass and vice versa. Therefore, minimizing the translator size would result in decrease of mass, which increases the dynamics of the buoy connected to the translator.

© 1965-2012 IEEE. In this paper, one novel heteropolar radial hybrid magnetic bearing (HRHMB) is proposed for flywheel energy storage system. First, its structure and working principle are introduced in detail. Then, its fundamental equations are derived based on magnetic circuit model, such as displacement stiffness, current stiffness, and load capacity. Furthermore, its suspension performance and magnetic coupling are analyzed based on the 2-D finite-element analysis. Finally, the comparison of main performance indexes between the proposed HRHMB and conventional one under the same constraints is made. It indicates that the displacement stiffness can be reduced by the novel structure. In addition, the rotor core loss of the novel HRHMB is just 22.53 W, which is only 41.6% of the conventional eight-pole HRHMB with the same load capacity.

© 1965-2012 IEEE. This paper introduces a temperature-dependent hysteresis model based on a vectorial elemental operator with temperature-sensitive spontaneous magnetization and biaxial anisotropy for the soft ferrites. Detailed analysis of the temperature-dependent magnetic properties of one elemental operator has been presented thereafter. With the help of the proposed vector elemental operator and the 2-D Gaussian distribution function, the temperature-dependent magnetic hysteresis of soft ferrites can be simulated. This model is validated by the substantial agreement between the simulated and measured major hysteresis loops of a soft ferrite sample Siemens 4C65 at different temperatures with slight acceptable error.

The high-frequency transformer is an important device in the modern electrical system, and the performance requirement for this device has recently become more and more important. Thus, it is necessary to model high-frequency transformer accurately and the key is to calculate the capacitance. In this paper, the capacitance of the foil winding in the high-frequency transformer is calculated by using the static capacitance model and the finite-element method (FEM), respectively. The relative error is about 0.4% by comparing the FEM. To calculate the capacitance of solid wire accurately, a new static capacitance model is proposed considering that the actual electric field lines gradually changed in the windings. Compared with the finite-element model, the proposed model is more accurate than the traditional models. The capacitances of two wires calculated by the proposed model and the finite-element model are 115.56 and 114.76 pF, respectively. The dynamic capacitance of transformer windings is analyzed by considering the uneven charge distribution. A dynamic capacitance analytical model is present by considering the eddy current effect. The result of the dynamic capacitance is 49.81 pF. It is found that the dynamic capacitance is lower than the static capacitance according to the static capacitance and the dynamic capacitance analytical model.

A numerical simulation, considering the two-way interactions of the electromagnetic, thermal, and fluid fields with deformation associated during a levitation melting process, is performed using the finite-element method. Material properties dependent on temperature are applied for the simulation. In addition, surface-to-ambient radiation and phase change are considered, and the arbitrary Lagrangian-Eulerian formulation is employed to model the deformation of a metal sample during the melting process. The oscillations of the metal sample at different times are also simulated. The oscillations, melting time, deformation, and distributions of the electromagnetic-thermal–fluid fields are obtained at different moments. A general way to dynamically predict the melting process of induction heating and its performance evaluations are provided in this paper.

This paper presents a multidisciplinary analysis and a design optimization approach for a permanent magnet (PM) transverse flux machine (TFM) with a soft magnetic composite (SMC) core. First of all, electromagnetic, thermal, and modal analyses, and the manufacturing method of the SMC cores, are investigated for this machine. Meanwhile, a lumped 3-D thermal network model is developed for the thermal analysis. Then, a multidisciplinary optimization design model is proposed to minimize the material cost and to maximize the output power based on the proposed multidisciplinary analysis models. The numerical solutions obtained from electromagnetic and thermal analyses are validated by comparing them with the previous experimental results. As shown, the performance of this PM-SMC TFM can be improved greatly using the proposed approach. Finally, a finite-element model is employed to verify the performances obtained from optimal results in terms of thermal and modal analyses.

Multiple rectifier technology is an effective method to reduce the harmonic current injected from converter to the grid [1], and phase-shifting reactor (PSR) is a kind of magnetic equipment which can be used to realize the function of phase-shifting[2]-[4]. In the multiphase rectifying system, the phase-shifting property of PSR plays an important role in harmonic suppression, meanwhile, as an inductive device, its filtering property cannot be neglected. Therefore, with the purpose of evaluating the phase-shifting and filtering properties of PSR in the harmonic current suppression, three kinds of reactors with approximate harmonic suppression effect in the 6-phase rectifying system are designed, one is without phase-shifting, and the other two are with phase-shifting in different phase-shifting angle. And then, based on the Fast Fourier Transform (FFT) algorithm and the frequency sweep method, the phase-shifting and filtering properties are respectively revealed by the harmonic current spectrum diagram and the amplitude-frequency characteristic curve. Lastly, the idea to introduce the low-pass filter's design method to the design of PSR to strengthen the harmonic suppression effect is proposed.

Previous studies showed that the electromagnetic stimulation could effectively activate damaged neurons. However, electrical stimulation effects would be greatly decayed after penetrating into biological tissues. In this paper, based on the magnetic stimulation system, the principle of magnetic stimulation devices for sciatic nerves recovery is analyzed. The simulation based on Schwarz model and biological experiments are conducted. The selected 20 Sprague Dawley rats were divided into experimental group (Group A) and control group (Group B). Group A was given 30 min magnetic stimulation every day while none was given for Group B. The sciatic functional index and the maximum evoked potential of gastrocnemius muscle were obtained. The recovery rate of gastrocnemius muscle wet weight was obtained. The experimental results showed that Group A was superior to Group B, and the results were statistically significant. It is shown that the magnetic stimulation with appropriate frequency and amplitude is in favor of the recovery of injured sciatic nerve.

Due to the global winding and 3-D flux, the claw-pole machine (CPM) can exhibit higher torque ability than other types of electrical machines. Using the powder metallurgical technology, the manufacture cost of CPMs made of soft-magnetic composite (SMC) material can be much lower than that of the conventional machines, especially with the low density cores. The performance of SMC motor was improved as the material has undergone through substantial improvement in the last decades. To seek better performance, CPMs with different permanent magnet (PM) rotor structures and SMC cores, including the surface mounted PM motor, surface inset PM rotor, V-type PM rotor, and flux concentrating PM rotor, are designed and the performances compared. The magnetic parameters of these machines are obtained by the 3-D finite-element method, and the analysis method is verified by the experiment of a surface-mounted PM CPM with SMC core.

This paper presents a hysteresis model for the high-temperature superconductor using a simplified Preisach model, in which the Preisach distribution function is determined only based on the ${M}$ – ${H}$ limiting loop. The results of simulation and experiment of accuracy of the simplified Preisach model are reported for the case of silver-sheathed Bi2223 superconducting tape samples with an external magnetic field perpendicular to the tape surface.

This paper proposes an improved extended finite element method for modeling electromagnetic devices with multiple nearby geometrical interfaces. In regions near these interfaces, the magnetic vector potential approximation is enriched by incorporating multiple derivative discontinuous fields based on the partition of unity method such that the interfaces can be represented independent of the mesh. The support of a node or an element can be cut by several interfaces. This method results in the high accuracy in the approximation field and derivative field. Numerical examples applied to the iron core in 1-D eddy current field involving level set-based parts, error analysis, and electromagnetic field computations are provided to demonstrate the utility of the proposed approach.

Recently the high-frequency common magnetic-links instead of common dc-links with advanced magnetic materials, such as nanocrystalline and amorphous materials have been considered as viable candidates for the development of medium-voltage power converters. This offers a new route of step-up-transformer-less compact and lightweight direct grid integration of renewable generation systems. Most importantly, it minimizes the voltage imbalance and common mode issues of the converter systems. However, the electromagnetic design of the high-frequency common magnetic-links is a multi-physics problem and thereby affects the system efficiency and cost. In this paper, an optimization technique is proposed and verified with the prototype magnetic-links. The design and optimization, implementation, test platform, and the experimental test results are analyzed and discussed.

A novel 3-D magnetic properties tester for laminated silicon steel specimen has been designed and constructed. The magnetization structure is the critical part of the tester especially for the magnetic properties of the laminated silicon steel in perpendicular direction of grain oriented. To guarantee the experimental precision and accurately analyze the 3-D magnetic properties of the laminated silicon steel, a symmetrical 3-D magnetic flux path in the magnetization structure fit for given dimension of specimen has been calculated and modeled. Magnetic flux in each direction has been homogenized and concentrated on the top of the core poles through finite element analysis. Therefore, magnetic properties in each direction of the laminated specimen can be really concerned and analyzed in practical engineering.

This paper presents a novel rotor structure optimized by using the level set method (LSM) to improve the static torque characteristics of a two-phase 4/2 high-speed switched reluctance motor. The magnetic equivalent circuit approach is used to analyze the influence factors on the static torque. The inner material boundary contained in the rotor saliency, which will be optimized, is implicitly represented by an embedded level set function. The evolution of the inner material boundaries is driven by the normal velocity derived through sensitivity analysis and adjoint variable computation. Optimal rotor configuration produces the nonuniform distribution of magnetic flux density in the air gap at aligned position, which can make the ratio of maximum and minimum inductances increased. High-permeability material is applied to enhance the mean torque. In order to achieve the optimal static torque, the strategy combining finite-element electromagnetic computation with LSM is conducted to optimize the rotor saliency at different rotor positions. The comparison of the optimized rotor configuration using LSM with that using density-based method suggests that the optimized rotor structure obtained using this presented method is easier to implement.

In this paper, the application of field-circuit coupled finite-element method for predicting the performance of induction motor (IM) under a sinusoidal voltage excitation is described. The numerical analysis is performed by solving the nonlinear time-stepping finite-element equations coupled with the circuit equations and mechanical motion equations. The circuit equations are described by means of improved nodal method. The local analytical solution of Laplace equation is used to improve the precision of electromagnetic torque. The performances of both three- and single-phase IMs are simulated using the developed field-circuit coupled code. The comparison among the results calculated by the code, the commercial FE package, FLUX 2-D, and the experiment results suggests the correctness of the field-circuit coupled method and related developed code.

In our previous work, two kinds of permanent magnet (PM) synchronous motors, transverse flux motor (TFM) and claw pole motor, were designed and fabricated using the soft magnetic composite (SMC) cores. This paper presents multiobjective and robust design optimization for high-quality manufacturing of these PM-SMC motors to improve their industrial applications. Meanwhile, an improved multiobjective sequential optimization method is presented to reduce the computation cost. Thereafter, a PM TFM with SMC core is investigated to illustrate the performance of the proposed method. From the discussion, it can be found that six sigma quality manufacturing was achieved for all Pareto design schemes given by the proposed method. Furthermore, manufacturing cost and computation cost have been reduced a lot. © 2014 IEEE.

In our previous work, soft magnetic composite (SMC) material was employed to design cores for two kinds of permanent magnet (PM) motors, namely transverse flux machine (TFM) and claw pole motor. Compared with motors designed by traditional silicon steel sheets, these motors require 3D flux design with new material and new manufacturing method. Meanwhile, the performances of these motors highly depend on the material and manufacturing parameters besides structure parameters. Therefore, we present a robust design optimization method for high quality manufacturing of these PM-SMC motors to improve their industrial applications. Thereafter, from the design analysis of a PM-SMC TFM, it can be found that the proposed method can significantly improve the manufacturing quality and reliability of the motor, and reduce the manufacturing cost.

This paper studies a pulsed magnetic-field generator which provides a noncontact way for functional nerve stimulation. Each component of the device, such as charging circuit, discharging circuit, and control circuit, is described in detail. The feasibility of the device is verified by simulation and experiments. The magnetic field and the induced electric field are produced by a figure-8 coil under excitation of pulsed discharging current. According to the Schwarz model, the action potentials of nerve fiber are simulated, and the neural dynamic response is predicted.

A multiobjective sequential optimization method (MSOM) is presented to deal with practical design problems of industrial electromagnetic devices. MSOM consists of a sequential optimization strategy of multiobjective optimization model and a modified central composite design (CCD) sampling method. To improve the optimization efficiency, Kriging model is employed to construct the approximate multiobjective optimization models. Then a modified CCD sampling method is presented to update the sample sets with the obtained Pareto optimal points and Kriging models. Thereafter, by investigating a test function and a three-dimensional permanent magnet transverse flux machine, it can be found that the proposed method is efficient, and the computation cost of finite element analysis can be saved remarkably.

Soft magnetic composite (SMC) materials are especially suitable for developing electrical machines with complex structure and three-dimensional (3-D) magnetic flux path. In these SMC machines, the magnetic field is in general 3-D and rotational, so the mechanism and calculation of core loss may be quite different from that in traditional electrical machines with laminated steels in which the magnetic field is restrained. This paper investigates the calculation of core loss in a permanent magnet claw pole motor with SMC stator core. First, core loss models are developed based on the experimental data on SMC samples by using a 3-D magnetic property tester. Then, 3-D magnetic time-stepping field finite element analysis (FEA) is conducted to find the flux density locus in each element when the rotor rotates. The core loss is computed based on the magnetic field FEA results by using the developed core loss models. The calculations agree well with the experimental measurements on the SMC motor prototype. © 1965-2012 IEEE.

A three-dimensional analytical modeling of the magnetic field of the stator-ironless axial flux permanent magnet (AFPM) machine under open-circuit condition is presented in this paper. It involves the analytical solution of the governing field equations in the region between back-irons in the cylindrical coordinate, in which the magnets are assumed to be axially magnetized and have constant relative recoil permeability. The proposed modeling method is applied to a specific AFPM machine, and the analytical results are in good agreement with those of three-dimensional finite element analysis (FEA). © 1965-2012 IEEE.

In this paper, two-dimensional finite element analysis (FEA) is used to compute the electric field in stator slot of a synchronous motor. The electrical insulation between the conductors and the edges of slot is evaluated. The relationship between size of air gap and electric field in this air gap is discussed. Secondly the slot-opening electric field, which is not uniform, is calculated by using three-dimensional finite element method. The discussion of insulation structures of slot-opening for anti-corona is conducted. A distributed equivalent circuit model is constructed for the inter-turn insulation under the impulse over voltage excitation. The inductances of the coils are achieved by using magnetic field FEA considering skin effects. The capacitances of the coils are calculated by using electric field FEA and analytic equation respectively. Finally, the evaluation of stator insulation using finite element method is presented.

From our previous study, permanent magnet (PM) transverse flux machine with soft magnetic composite material core is very promising. However, from the point of view of engineering application, at least two more aspects have to be considered. First, not only the machine but also its control system has to be investigated and optimized simultaneously. Second, robust design requirements must be included in the system level optimization, which is a very important issue in modern quality design. Therefore, to improve the applications of this type of machine, we present a system level six sigma robust optimization method to design a drive system with this motor and field-oriented control scheme. The optimal robust solutions obtained are compared with those from deterministic optimization method and initial design scheme. From the comparison, we can see that the system's reliabilities and robust levels are improved significantly by the proposed method, and the probability of system failure can be reduced a lot.

We present two new sequential optimization strategies, a sequential subspace optimization method (SSOM) and an improved sequential optimization method (SOM) with orthogonal experimental design technique, to deal with optimization design problems of electromagnetic devices in this work. To implement the proposed methods, we first divide the whole design factors into three sets, namely highly-significant, significant, and nonsignificant factors. Then the whole design space can be correspondingly divided into three subspaces with these three sets of factors. Thereafter, SSOM is presented to sequentially optimize those subspaces. In the subspace, we present an improved SOM based on orthogonal experimental design technique to get optimal solutions. Finally, by investigating TEAM benchmark problem 22, we can see that the sampling efficiency can be improved significantly and the computational cost of finite element analysis can be saved remarkably by the proposed methods.

Core-loss prediction is an important issue in design and analysis of permanent-magnet (PM) motors. Because of the diverse structure, flux distribution, and rotational variation of flux, it is difficult to predict the core loss in a machine exactly. In this paper, a core-loss model for the PM motor is introduced in which flux variation loci in different parts of the motor are predicted by carrying out a finite-element transient analysis. Since the flux variation pattern is complicated, an improved equation based on the conventional three-term expression is used for core-loss calculation. The core-loss model is developed totally in ANSYS parametric design language as a parametric model and it can be used easily for different types of PM motors. Calculation and experiments on a high-speed PM motor have shown that the model can produce results that agree with the experimental ones. © 2012 IEEE.

The significance of eddy-current in high-speed permanent magnet machines cannot be underestimated in that it has serious implications on the machine's efficiency or even demagnetizes the PMs because of an overheating problem. It is necessary to accurately estimate the eddy-current losses and find an optimal design to minimize the losses and improve the machine's performance. In this paper, the axial segmentation of the PMs is first employed to cut off the eddy-current axial paths. Then, a conductive shield is introduced to smooth the time varying magnetic field in the conductive sleeve and the PMs in order to reduce the eddy-current losses. A nodal method based network-field coupled multislice time-stepping finite element method (TS-FEM) is proposed to analyze the steady-state and dynamic characteristics of the high-speed PM machine; its merit is that sub-block matrixes of the circuit equations are more convenient to be established compared with that of mesh method. Analysis of eddy-current losses in the rotor is reported. © 2012 IEEE.