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Accurate and simple magnetic material behavior law is necessary to correctly model complete electromagnetic systems. In this paper, a new formulation based on the scalar quasi-static hysteresis Preisach model extended to dynamic behavior using fractional derivation dynamic contribution is proposed. The fractional contribution is solved using convolution which highly reduces the numerical issues. The order of the fractional derivation provides a new degree of freedom and allows to correctly obtain simulation results on a very large frequency bandwidth. By using such formulation, space discretization techniques (finite differences, finite elements) are avoided which are highly space and time consuming while keeping the global simulation results precise. The numerical implementation of the problem and some experimental validations are shown in this paper. [ABSTRACT FROM AUTHOR]

In this paper, the mathematical model of an electricity generator with four static magnets and four dynamic magnets is suggested for the electricity generation. The introduced electricity generator is based on the electricity generator with two static magnets and two dynamic magnets, but it has three main advantages: it has more interactions between the static and dynamic magnets, it generates more electricity, and it generates smoother signals. Electricity generators are compared for the electricity generation. [ABSTRACT FROM AUTHOR]

In this paper, an analytical torque ripple model for interior permanent magnet synchronous machine (IPMSM) is introduced at first, which can be used to estimate the torque ripple. Then, the inductance variation due to magnetic saturation is analyzed through experimental investigations, which demonstrates that magnetic saturation has a great influence on the inductances, and hence the torque ripple minimization performance. Thus, this paper proposes an online parameter identification approach to estimate the inductances and incorporates them into the torque ripple minimization. The proposed parameter identification approach can estimate the dq-axis inductances accurately such that it brings significant torque ripple minimization improvement for IPMSMs. Numerical and experimental investigations have been conducted to validate the proposed approach based on a laboratory IPMSM. [ABSTRACT FROM AUTHOR]

This paper proposes a novel hybrid excitation vernier permanent magnet machine (HE-VPM). The characteristics of the proposed machine are: 1) the PMs are embedded in the stator teeth, which is helpful for the heat dissipation; 2) the rotor is salient structure without PMs and windings, which ensures the reliability of high-speed operation; 3) the nonoverlapping concentrated winding shortens the end-connection, and improves the torque density, 4) only half of the stator teeth possess PMs, and the total amount of PMs are decreased; and 5) the dc current are injected to the armature coils, therefore, the exciting field can be adjusted flexibly. In this paper, the electromagnetic performance, including back electromotive force, torque, etc. are analyzed with finite element analysis. The results show that the proposed machine exhibits flexible field adjustment capability, which may be suitable for applications requiring wide speed range operation. Besides, it is found that, compared with the existing pure sinusoidal phase current, higher torque density can be obtained with dc-biased phase current under constant stator copper loss. [ABSTRACT FROM AUTHOR]

Stick-slip motion is the most well-known phenomenon in nanotribology. Maier et al. previously studied the dependence of slip time on contact geometry. In their paper, they were able to identify the intermediate state during slip motion. However, detailed study of this intermediate state is difficult due to the fast dynamics. The advantage of molecular dynamics (MD) simulation is that it can provide detailed information and direct visualization of the tribological phenomena on a time scale of a few nanoseconds. In this paper, we investigate the detailed mechanism of stick-slip motion in nanoscale. MD simulation precisely mimics friction force microscopy experiments. In MD simulations, a crystalline Si tip slides on a graphene surface, and the tip size is varied. The simulation results provide evidence of the intermediate state during slip motion and reveal the hierarchical structure of the stick-slip motion in nanoscale. Detailed relations among stick-slip motion, contact geometry, and energy state are also analyzed. [ABSTRACT FROM AUTHOR]

This paper introduces a possible mechanism to explain the changes in neurons following extremely low frequency magnetic fields (ELF-MFs). The model in this paper contains two parts: the physical part and the bio-trigger part. The first part is an electric current equation, which is a generalization of the Nernst–Plank equation with the exposure of ELF-MF, and the second bio-part is a phenomenological model, which is a simple two-state channel with two steady state open (O) state and closed state (C). The two parts are complementary. The first part is utilized to explain changes about synaptic plasticity following ELF-MF exposure at embryonic and postnatal age. The second part is used to simulate the process of three different types of neurons reported by previous papers. According to the results, the present model is feasible for the simulation process. The concept of ion mobility or permeability is emphasized in this paper in part I, and channel state transition probabilities are paid much attention to in part II. In this paper, the ion mobility or permeability is supposed to have close relationships with ion channel transition probabilities, which connects the two parts of the model together. [ABSTRACT FROM PUBLISHER]

Current transformers (CTs) of the bus bar type are widely used in ultrahigh voltage power systems for monitoring and protection. This paper presents a mathematical model to predict the measured current error caused by tilting and position eccentricity of the primary conductor of a bus bar in a CT. The model is based on actual B–H curve characteristics and is verified by comparing the model predicted results to corresponding 2-D and 3-D transient finite-element model results. [ABSTRACT FROM AUTHOR]

Following a study on the optimal write head design for perpendicular magnetic recording, this paper aims at optimizing the design of write head for shingled magnetic record by applying the Taguchi method and the response surface methodology. The criteria for the evaluation of the write head design are to maximize the signal-to-noise ratio (SNR) and minimize the bit error rate (BER) in the shingled magnetic recording (SMR). In this paper, the magnetic fields of the write head designs are modeled using finite-element analysis, the SMRs are simulated by applying micromagnetic modeling based on Landau–Lifshitz–Gilbert equation, and the SNR and the BER are characterized using the grain flipping probability model. An optimal design of the write head is obtained to achieve the maximum SNR and the minimum BER. A discussion on the erasure band width is also carried out in this paper. Furthermore, the SNR and the BER at different bits and track densities in SMR are compared and discussed. [ABSTRACT FROM PUBLISHER]

This paper proposes to use the nodal shell element in a finite-element multiphysics formulation to simulate the magnetoelectric (ME) laminate composites constituted of the thin magnetostrictive layers. The multiphysics model considers the nonlinearity of the thin-layer magnetostrictive material as well as the electrical load effects of the ME laminate composites. A trilayer ME Metglas/PZT/Metglas problem is solved in order to prove the efficiency of the proposed method. This paper provides the basis to study the ME devices composed of laminated thin layers. [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]

In this paper, the equivalent cable bundle method (ECBM) is used with some modifications to predict crosstalk within a bundle of twisted-wire pairs (TWPs) terminating with differential loads at their far end and colocalized as quads in the frequency domain. When using this method, one can easily calculate crosstalk in many pairs with good reduction of complexity and computation time. In this paper, power loss of crosstalk is calculated for both complete and reduced models using the multiconductor transmission lines method. It is shown that the results are in agreement by applying this modified ECBM, and the number of wires as well as the computation time is successfully reduced. The in-quad is the four conductors located in the same quad and the outside-quad is all other conductors in the bundle. The in-quad and outside-quad architecture results are also discussed, and it is observed that the in-quad crosstalk has an enormous amount of crosstalk compared with the outside-quad crosstalk. A new three-step ECBM for predicting the crosstalk within a TWP network is proposed, the pairs are colocalized as quads, and the use of this method allows an easy modeling of crosstalk within a TWP cable bundle. [ABSTRACT FROM AUTHOR]

This paper presents a hybrid method based on the transmission line modeling method (TLM) aiming to represent the soil ionization effect for grounding systems simulation. This natural phenomenon can be better represented by taking into account the variation of the conductive components present in the TLM circuit and considering the residual resistivity remaining in the soil. The proposed analytical formulation is developed with a focus on the computational implementation of the method. The model is validated by comparing synthetized test results with measured data and other numerical models (residual resistivity, TLM, and analytical model). High precision together with an easy to implement formulation indicates that the methodology presents potential for real-life applications. [ABSTRACT FROM AUTHOR]

This paper presents a simple dynamic vector-play model to calculate the iron loss and describe the vector hysteresis behavior of a non-oriented (NO) electrical steel sheet (ESS) under 50 Hz rotating magnetic fields. Based on the iron loss separation theory, the proposed model is separated to the static hysteresis component and eddy current component. The static hysteresis component is constructed by vector play model, which is identified by using 1 Hz minor B – H loops. And two coefficients \omega x and \omega y are introduced to consider the anisotropic property of NO ESS and the excess loss of eddy-current component under 50 Hz magnetic field. The validity of the proposed dynamic vector hysteresis model is verified by comparing it with the experimental results under various 50 Hz magnetic field conditions. [ABSTRACT FROM AUTHOR]

This paper develops a novel magnetomotive forces (mmfs) distribution model along the transverse direction for the 3-D analysis of linear induction motor, and it investigates the influence of a laterally asymmetric cap-secondary on the thrust, vertical force, lateral force, and efficiency in a prototype single-sided linear induction motor for linear metro. First, the mmf distribution model and its working conditions are defined, and the model is transferred into a mathematical model. Second, the air-gap flux and secondary eddy current in a prototype linear motor with a cap-secondary are obtained by a 3-D space harmonic analytical method. Third, the thrust, vertical force, lateral force, and efficiency of the test motor are analyzed with various lateral deflection, and the power factor in secondary is also presented. Finally, these results are experimentally verified by measurements on the test rig of the linear motor, and the comprehensive effect on the operating performance can be accurately calculated by the mmf model. [ABSTRACT FROM PUBLISHER]

In this paper, we present a micromagnetic modeling study on the switching property of segmented grains assisted by circularly polarized magnetic field at microwave frequencies and the actual recording process. This paper provides insightful understanding of the switching dependence on the Gilbert damping constant and the optimization for suppressing the impact of possible damping constant distribution. The recording processes with ac field generated by a spin torque oscillator on the media consisting of segmented grains are also investigated. In this microwave assisted magnetic recording (MAMR) process, the segmentation of the grains with exchange breaking layers enables the best utilization of the ac field. The MAMR simulations show significant signal-to-noise ratio (SNR) gain over today's perpendicular recording for medium for media with grain pitches <8~nm. Grain-pitch limited SNR performance can be achieved for medium grain pitches as small as 5 nm while achieving sufficient thermal stability simultaneously. At 4.5 nm grain pitch, MAMR shows significantly higher SNR than that predicted by corresponding HAMR simulations. It is concluded that MAMR should enable areal density capability of 4 Tb/in^2 and beyond and its SNR performance is superior to HAMR at all densities. [ABSTRACT FROM PUBLISHER]

This paper presents a method for determination of heat transfer coefficients for finite-element method housing model of medium-voltage switchgear cell. Suggested method is based on the particle swarm optimization algorithm. For that purpose, a real test model of partition wall has been created as well as an equivalent numerical FE model. Since the preciseness of thermal model is dependent on the preciseness of thermal coefficients, the goal of the optimization procedure is to assure even better match between the measured and the FE model calculated temperature values. Because of the fact that the temperature field is a consequence of eddy currents that appear in metal parts of switchgear devices, this paper deals with a coupled problem. Nonlinear calculation of magnetic field is also considered. [ABSTRACT FROM AUTHOR]

The Jiles-Atherthon model is suitable for modeling ferrite-core based inductors and transformers. In this paper it is used to quantify the influence of radially varying magnetizing field on induced voltage in a ferrite inductor, and to compare two conventional average models with a multi-segment model. To accurately model the core when its radial thickness is comparable with its average radius in which average models fail to work, multi-segmentation needs be adopted. In this paper quantification of required segments is presented for different ratios of outer to inner radii of a toroidal core. Such work is meaningful since the ferrite cores used in pulse transformers could be in the scale of meters and dimensional effect on induced voltage cannot be ignored. [ABSTRACT FROM PUBLISHER]

Compared with dc magnetic bearings, an ac magnetic bearing has obvious advantages in cost savings and reducing power consumption. For more precise control of the ac magnetic bearing, it is particularly important to build a correct mathematical model of radial suspension forces. Due to the working principle of the ac magnetic bearing, it has similarities to the suspension subsystem of a bearingless motor, thus the modeling method for radial suspension forces of the bearingless motor could be referenced for modeling the radial suspension forces of the ac magnetic bearing. This paper presents a new modeling method based on the Maxwell tensor method for radial suspension forces of the ac magnetic bearing. Compared with existing methods, the invention method designed specially for the ac magnetic bearing overcomes inaccuracy and possesses advantages of directness and universality. Taking the ac hybrid magnetic bearing (ac HMB), for example, this paper presents the mathematical modeling process of radial suspension forces with the proposed method. The comparison result between the models established by the equivalent magnetic circuit method (the most classical modeling method for magnetic bearings currently) and by the proposed method shows the high uniformity in their forms of expression (the only difference is the coefficient between them). Being different from the traditional modeling method, we do not need the detailed derivation and complex theoretical computation based on the particular magnetic circuit analysis for this particular case but simply modify several key expressions representing magnetic circuit features in the modeling process with this method. Therefore, the proposed method invented especially for the ac magnetic bearing has the greater advantage of directness and universality than previous modeling method. To illustrate the precision of the proposed modeling approach, the verification experiment is designed and the encouraging experimental results show that the model based on the Maxwell tensor method is more close to the test results comparing with equivalent magnetic circuit method. Thus, the proposed modeling method makes the modeling results on radial suspension forces of the ac magnetic bearing more accurate, universal, and direct. [ABSTRACT FROM PUBLISHER]

This paper describes a two-dimensional (2-D) analytical model to predict the magnetic field distribution in axial-field magnetic gears by using the sub-domain method. The sub-domain method consists in solving the partial differential equations linked to the Maxwell's equations in each rectangular region (magnets, air gaps, and slots) by the separation of variables method. The proposed model is based on a two-dimensional approximation for the magnetic field distribution (mean radius model) i.e. the problem is solved in 2-D Cartesian coordinates. One of the main contributions of the paper concerns the analytic solution of the magnetic field in a slot open on the two sides (space between the ferromagnetic pole-pieces). Moreover, it is shown that the analytical model and the 3-D finite elements simulations follow the same trends in the determination of the optimum values for the geometrical parameters. As the analytical model takes less computational time than 3-D numerical model, it can be used as an effective tool for the first step of design optimization. [ABSTRACT FROM PUBLISHER]

Optimal design problems of electromagnetic devices are generally multimodal, nondifferentiable, and constrained. This makes metaheuristic algorithm a good choice for solving such problems. In this paper, a newly developed metaheuristic algorithm is presented to address the aforementioned issues. The proposed algorithm is based on the paradigm of artificial bee colony (ABC). A drawback of the original ABC algorithm is because its solution variation is only 1-D, as this decreases its convergence speed. In this paper, a one-position inheritance scheme is proposed to alleviate this drawback. An opposite directional (OD) search is also proposed to accelerate the convergence of the ABC algorithm. The novel algorithm is applied to both TEAM Workshop problem 22 and a loudspeaker design problem. Both discrete and continuous cases of problem 22 are tested. The effectiveness and efficiency of the proposed algorithm are demonstrated by comparing its performance with those of the original ABC, an improved ABC known as Gaussian ABC, and differential evolution algorithms. [ABSTRACT FROM PUBLISHER]

Signal processing in TDMR encounters several challenges such as read channel modeling and detection in the presence of severe two-dimensional intersymbol interference (2-D ISI). The contribution of this paper is twofold. 1) In this paper, we introduce a novel 2-D read channel model which we call the 2-D Microcell model. In this model, we use generalized 2-D microtracks called microcells to captures the properties of irregular grain boundaries of the medium in a relatively simple yet accurate manner. The data dependent noise (DDN) distributions are analytically derived for this model. The derivation of the DDN distributions makes the 2-D Microcell suitable for detector design purposes. 2) We propose a new framework for designing truly two-dimensional detectors for the Microcell model based on near-optimal generalized belief propagation (GBP). The GBP algorithm is purposefully applied for detection in this model in order to handle the data dependent media noise which is caused by irregular bit transitions in both dimensions. Results are provided to show that the incorporation of the DDN distributions into the GBP detection helps improving the detection performance. [ABSTRACT FROM AUTHOR]

This paper presents an analytical method for evaluating the magnetic flux density produced by spherical permanent magnet arrays used in spherical actuators. To investigate the performances of magnetic arrays, analytical models are used due to their lower computational time compared to 3-D finite element analysis. This paper presents an analytical model for the calculation of the magnetic field produced by a spherical permanent magnet array using magnetic charge modeling. To obtain the total magnetic field solution, first the magnetic field produced by a single spherical tile is considered. By means of superposition, the magnetic field produced by the array is obtained. Two magnet array topologies are modeled and the analytical results are validated using finite element analysis. [ABSTRACT FROM AUTHOR]

In this paper, a study on the demagnetization of ferromagnetic materials is conducted based on both experiments with magnetic treatment facility (MTF), which is a miniaturized experimental model, and numerical analysis methods in which the static magnetic finite-element method and Preisach model are combined. The magnetic hysteresis phenomenon inside ferromagnetic materials is effectively mimicked by means of Preisach model. However, owing to the use of M\-H variables, Preisach model generally bears numerical instability during repetitive computations. A Preisach model with M\-B variables is proposed in this paper to resolve the numerical instability. From the proposed Preisach model with M\-B variables, analysis results that were tantamount to those from the general Preisach model with M\-H variables were obtained. Numerical instability was also resolved by the proposed model. Furthermore, the discrepancy was practically negligible between the experimental result from a practical demagnetization process and the numerical analysis result from the proposed Preisach model with M\-B variables, under the same conditions. [ABSTRACT FROM PUBLISHER]

This paper is the first part of a work which aims at proposing a global approach for the numerical modeling of parasitic capacitances in high-frequency multiwinding transformers. In this first part, various capacitive circuits of n-winding magnetic components are presented. Careful attention is paid to the definition of a rigorous mathematical formalism based on the electrostatic equations, valid for any number of windings. The numerical identification of the proposed circuits is discussed in a companion paper. [ABSTRACT FROM PUBLISHER]

Simulations are successfully utilized to reproduce the behavior of complex systems in many knowledge fields. The computational effort is a key factor when high-cost simulations are required in optimization, principally, if the system to be optimized operates under uncertain conditions. In this context, surrogate modeling is useful to alleviate the CPU time. Hence, this paper presents a methodology to assess three surrogate techniques based on genetic programming (GP), a radial basis function neural network (RBF-NNs), and universal Kriging. These techniques are used in this paper to obtain analytical optimization functions that are accurate, fast to evaluate and suitable for interval robust optimization. The experiments were performed in a robust version of the TEAM 22 problem. The results show that the surrogate models obtained are reliable and appropriate for interval robust methods. The methodology presented is flexible and extensible to other problems in diverse fields of interest. [ABSTRACT FROM PUBLISHER]

In this paper, a semi-analytical model is derived to calculate the magnetic flux density around a magnetic shield with finite dimensions. The proposed modeling is based on Fourier modeling, which is extended with mode-matching. The described model has less than 0.2(%) error with respect to finite element modeling for the given configuration. Furthermore, the paper shows that assuming a magnetic shield with infinite dimensions introduces a significant error with respect to a magnetic shield with finite dimensions. [ABSTRACT FROM AUTHOR]

Permeance variation in the air gap of the permanent-magnet synchronous machine induces eddy-current losses in its permanent magnets even in the absence of stator currents. This paper proposes a new analytical approach to analyze these losses using the permeance-variation vector function introduced for the air-gap magnetic-flux density distribution to take into account the stator teeth. The Laplace equation is employed to derive the radial dependency of the stator slotting effect on the magnetic-flux density distribution. The induced eddy currents are further calculated by using Faraday's law. The analytical results are compared with the numerical ones based on the finite-element analysis. The paper offers a faster alternative to the numerically intensive calculations of eddy-current losses, and the method is especially useful in initial design optimization of the electric machine. [ABSTRACT FROM AUTHOR]

This paper compares the performance of three different topologies of spoke-type permanent-magnet vernier machines (PMVM): 1) dual airgap dual stator winding (DSW); 2) dual airgap single stator winding (SSW); and 3) single airgap (SA). These topologies were compared in terms of torque/machine volume, cogging torque, and torque ripples. The 2-D finite element method was utilized to compare the performance of the three models. The dual airgap PMVM with a SSW showed similar performance with the same machine outer diameter and similar power in terms of torque/machine volume and torque ripples compared with the DSW model. The performance of the SSW model was better than that of the SA model for the same outer diameter and rotor. Furthermore, stator slot optimization was performed to improve torque/machine volume and reduce torque ripples in the SSW model. [ABSTRACT FROM AUTHOR]

In this paper, a novel algorithm “firework optimization” (FO) is introduced, as well as its hybridization with generating set search (GSS). FO is an exploration algorithm, which intends to explore a vast region within the search space in order to determine regions that may contain a regional optimum. As the regions with potential are defined, GSS, the exploitation algorithm is applied to determine whether regions determined by FO contain a local or a global optimum. The validity of FO and GSS hybridization algorithm is verified using Branin and Six-Hump Camel test functions, and the hybridization algorithm is applied to an interior permanent magnet synchronous motor, in order to minimize torque ripple. [ABSTRACT FROM AUTHOR]

In this paper, an exact analytical solution based on Fourier analysis is proposed to compute the cogging torque in a surface-mounted permanent magnet synchronous machine. The analytical solutions are derived by solving the field-governing equations in each simple and regular subdomain, i.e., permanent magnet (PM), air, slot opening, and slot, and then by applying the boundary conditions to the interfaces between these subdomains. Based on these solutions, the cogging torque is also determined analytically. In order to verify the analytical results of the proposed method, an experimental system was implemented on a servomotor and a torque sensor. All analytical results were extensively validated using nonlinear 2-D finite-element analysis and experimental results. Using the proposed method, we investigated the influence on the cogging torque, according to the machine parameters. Therefore, the proposed method should be very useful in the initial design and cogging torque optimization of PM machines. [ABSTRACT FROM AUTHOR]

This paper investigates the vibration and noise characteristics of the coaxial magnetic gear (CMG) by the electromagnetic forces. In the CMG, the vibration and noise can be generated by the exciting forces acting on three parts, namely, low-speed rotor, high-speed rotor, and modulating pieces, respectively. The electromagnetic forces acting on three parts of the CMG and their force frequencies are calculated by using the Maxwell stress tensor method. Also, the mode shapes of the CMG full model and their resonance frequencies are obtained by the modal analysis. Through the electromagnetic forces and the result of the modal analysis, the vibration calculation is performed by using the 3-D-finite element method. Then, the effect of displacement on noise is confirmed by comparing the vibration calculation data and experiment data. The result shows the most affected part among the three parts of the CMG due to the noise is the low-speed rotor. [ABSTRACT FROM AUTHOR]

Using the finite-element model (FEM) to achieve the optimal design of electromagnetic devices is a complex and time-consuming process. Space-mapping techniques reduce computation cost by aligning two models with different granularities, namely, a coarse model and a fine model. In this paper, Kriging output space mapping (OSM), an original space-mapping technique based on adaptive nonlinear corrective projection, is proposed and compared with a conventional OSM technique. The device for optimal sizing is a five-phase linear induction motor, which is represented through two modeling levels: 1) coarse (Kriging model) and 2) fine (2-D FEM). An advantage of this new technique is its ability to provide a sufficiently accurate model for each objective and constraint function and make the coarse model converge effectively toward the fine model. [ABSTRACT FROM AUTHOR]

This paper presents a homogenized analysis of soft magnetic composite (SMC), which is composed of small iron particles embedded in insulating medium. The SMC core is modeled by uniform material with the macroscopic complex permeability which is analytically represented in frequency domain. The Cauer-equivalent circuit is synthesized from the macroscopic permeability for time-domain analysis of SMC. The proposed method is shown valid even when SMC is magnetically saturated. [ABSTRACT FROM AUTHOR]

This paper proposes the optimization of the shape and size of a ferrite magnet and the arrangements necessary to reduce torque ripple and maximize back electromotive force (B-EMF) in a permanent-magnet-assisted synchronous reluctance motor. First, four different models of general magnet arrangements were selected, and analysis using the finite-element method was performed under open circuit and load operations for each of the four models. Next, the relationship between the cogging torque and the torque ripple was analyzed, considering the segment saturation phenomenon. Then, based on the initial model, the design was optimized for maximum B-EMF and minimum torque ripple, and the total harmonic distortion was measured. Finally, the validity and superiority of the optimized design were confirmed by manufacturing a prototype motor and performing the experiment. [ABSTRACT FROM AUTHOR]

The spoke-type permanent magnet synchronous motor (PMSM) is a motor built using nonrare earth elements, which feature low flux density. It has a flux concentrated structure of permanent magnet arrangement to improve power density. Further, the torque in the spoke-type PMSM is composed of a magnetic torque component from the permanent magnets and a reluctance torque arising from the inductance difference between the $d$ - and $q$ -axis. This paper analyzed the $d$ - and $q$ -axes inductances that affect the reluctance torque depending on the magnitude of the applied current and the current phase angle of the spoke-type PMSM at base speed. We also derived the variation of the $d$ - and $q$ - axis inductances, which is shown at the operation speed region. Accordingly, the variation of the current phase angle for generating the maximum output power is analyzed. Based on the above results, we predicted the variation in the driving mode of the spoke-type PMSM, and subsequently verified the prediction experimentally. [ABSTRACT FROM AUTHOR]

Recently, interior permanent magnet synchronous motor (IPMSM) is paying attention because of its high power density and efficiency by adopting permanent magnet. The IPMSM has two control methods: maximum torque per ampere (MTPA) control and flux weakening control. Generally, an MTPA control is applied to a continuous operating point, and in case of a startup point, input current is applied which satisfies required output torque. To control the IPMSM, the various types of inverters with current and voltage limitations are used. The motor cannot be operated if these limitations are not satisfied. This paper proposes a method to satisfy the current and voltage limitations of the inverter with two different operating points. By changing the control method of the rated operating point by a stack compensation method, the current and voltage limitations of the inverter can be satisfied at a startup operating point, where the input current in MTPA control at the continuous operating point cannot be satisfied. The proposed method is verified by a 2-D finite element analysis. [ABSTRACT FROM AUTHOR]

This paper proposes an equivalent magnetic hysteresis (B–H) curve for magnetic multiscale problems of complex materials composed of electrical conductors separated by insulating material. The conventional method, which assigns equivalent material constants to each material, cannot properly express the local eddy current loss and the extra magnetic field derived from the local eddy current. To solve this problem, we derive the magnetic hysteresis curve from the volume-averaged magnetic flux density and the surface magnetic field in the micro-model, and apply this curve to the macro-model. The mesh number of the novel macro-model is reduced to around one-tenth that of the micro-model. Magnetic hysteresis is treated by a free energy magnetic hysteresis model, and the macro-model ignores electrical conductivity. The magnetic hysteresis curve and the numerically calculated losses are consistent in the micro- and macro-models. The proposed method well expresses the local eddy current phenomena. [ABSTRACT FROM AUTHOR]

This paper proposes an enriched performance measure approach to significantly improve computational efficiency of reliability-based design optimization when applied to electromagnetic products. To achieve the goal, three improvements are made over the original performance measure approach: 1) as a way to launch reliability-based design optimization at a deterministic optimum; 2) as a probabilistic feasibility check; and 3) as a fast reliability analysis under the condition of design closeness. Each of the improvements makes a unique contribution to improving numerical efficiency while maintaining stability in the design optimization process. Finally, the proposed method is tested with a mathematical model and the TEAM Workshop Problem 22, and three improvement effects on the reliability-based optimization process are investigated from a numerical efficiency and accuracy point of view. [ABSTRACT FROM AUTHOR]

A new model of the radio frequency identification antenna using the solenoid coil, surrounded by a coaxial ferrite toroid, is proposed in this paper. The truncated region eigenfunction expansion method is adopted to derive the expressions of the magnetic vector potential. Besides, due to the low conductivity and high permeability of the ferrite, a convenient solution region division is introduced to avoid solving the transcendent eigenvalue equation caused by the end effect as usual. Numerical calculations are performed, and the results are in excellent agreement with those obtained from the finite-element method simulations. [ABSTRACT FROM AUTHOR]

Probes used in eddy current testing contain ferrite cores of various shapes. In this paper, an axially symmetric mathematical model of an I-cored coil with an air gap was shown. The coil was placed above a two-layered conductive half-space and the solution domain was truncated radially. Using the truncated region eigenfunction expansion method, expressions describing the magnetic vector potential and the impedance of such a coil were derived. The calculations were carried out in MATLAB, both for an air-cored coil and the I-cored one containing an air gap. The results were verified using the COMSOL Multiphysics package in which the finite-element method is applied and the values show a very good agreement. Moreover, impedance components for the I-cored coil with and without an air gap were compared. The difference between the two types was significant, particularly for low-frequency values. [ABSTRACT FROM AUTHOR]

Metamaterials with tunable negative permeability are proposed and investigated theoretically in this paper. First, the model of the dielectric bilayer sphere embedded in the dielectric substrate is put forward. Second, expressions of the electromagnetic fields in the model are derived based on the Mie scattering theory, and the general formula for the effective permeability of the model is deduced via the Maxwell-Garnett theory, which is further verified through the simulation results. Finally, the tunable bandwidth of the negative permeability of the metamaterials changing with the geometrical parameters is investigated based on the full-wave simulations, and the relative mechanisms are also discussed. It is believed that the results would be helpful for the practical applications of the metamaterials, and the metamaterials with tunable negative permeability proposed in the paper would facilitate the constructions of the left-handed materials in some degree. [ABSTRACT FROM PUBLISHER]

In this paper, a new motor integrated permanent magnet gear (MIPMG) is discussed. The focus is on eddy current loss analysis associated to permanent magnets (PMs). A convenient model of MIPMG is provided based on 2-D field-motion coupled time-stepping finite element method for transient eddy current analysis. The model takes the eddy current effect of PMs into account in determination of the magnetic field in the air-gap and in the magnet regions. The eddy current losses generated in the magnets are properly interpreted. Design improvements for reducing the eddy current losses are suggested. The proposed model and the results presented in this paper will give useful guidelines for a reliable design and design optimization of the MIPMG. [ABSTRACT FROM PUBLISHER]

This paper proposes a magnetic circuit model (MCM) for the design of a brushless doubly-fed machine (BDFM). The BDFM possesses advantages in terms of high reliability and reduced gearbox stages, and it requires a fractionally-rated power converter. This makes it suitable for utilization in offshore wind turbines. It is difficult for conventional design methods to calculate the flux in the stator because the two sets of stator windings, which have different pole number, form a complex flux pattern which is not easily determined using common analytical approaches. However, it is advantageous to predict the flux density in the teeth and air-gap at the initial design stage for sizing purposes without recourse finite element analysis. Therefore a magnetic circuit model is developed in this paper to calculate the flux density. A BDFM is used as a case study with FEA validation. [ABSTRACT FROM PUBLISHER]

A numerical method is presented to study the air-flow pattern and particle trajectory in the head–disk interface (HDI) in this paper. It first solves the generalized steady-state Reynolds equation with slip boundary conditions to get the slider attitude. Then, it solves the reduced Navier–Stokes equation to get the air flow velocity distribution in the HDI. The motion equations of particles are solved to obtain the particle trajectory in the HDI by using the fourth-order Runge–Kutta method. Air flow characteristics and particle behaviors are investigated to illustrate the relationship between the air flow and particle trajectory. The effect of the particle release height is also studied. The simulation results show that particle trajectories basically overlap air flow streamlines in the horizontal plane. The particle moves a longer horizontal distance at a lower particle release height. The difference between the horizontal velocity of the particle and the air flow indicates that the Saffman force points to the disk in the transition region close to the leading edges of leading pads. Moreover, the peak values of the air flow vertical velocity in the previously mention location increase with the reduction of the particle release height. And the air flow vertical velocity along the particle trajectory is almost two times larger than that of the particle at the leading edges of leading pads. The results also show that the drag force of the air flow mainly drives particles up toward the air bearing surface at the leading edges of leading pads, but not the Saffman force. [ABSTRACT FROM PUBLISHER]

Electrodynamic bearings can guide rotating objects without contact and active control means. Consequently, their performance relies on passive phenomena that require specific models to be predicted. In the case of electrodynamic thrust bearings, early models involved assumptions on the rotor axial kinematics. This precludes their use for predicting the bearing behavior in dynamic conditions, which is critical when studying stability aspects. Other models require numerically solving of Faraday’s current law and the rotor equation of motion to obtain the dynamics of the bearing, thereby excluding a fast identification of its stability properties. Recently, a parametric model without these kinematic assumptions was derived. It consists in a linear state-space representation that allows studying the dynamic performance of electrodynamic thrust bearings using conventional system analysis tools. However, this model links up the rotor displacement to the currents in a winding with only two phases. This paper introduces a model free of this limitation, allowing to consider bearings with a higher number of phases, an improved copper usage, and potentially increased performance. Furthermore, the proposed model directly links up the rotor displacement to the force and torque exerted by the thrust bearing without requiring to solve for the currents. This also minimizes the number of state-space equations and model parameters. Finally, in addition to the modeling aspects, a set of bearing topologies that have not been explored yet and can be studied using the proposed model is introduced. [ABSTRACT FROM PUBLISHER]

Spin-transfer-torque random access memory (STT-RAM) is a promising candidate for the next generation of random access memory due to improved scalability, read–write speeds, and endurance. However, the write pulse duration must be long enough to ensure a low write error rate (WER), the probability that a bit will remain unswitched after the write pulse is turned OFF, in the presence of stochastic thermal effects. WERs on the scale of 10^-9 or lower are desired. Within a macrospin approximation, WERs can be calculated analytically using the Fokker–Planck method to this point and beyond. However, dynamic micromagnetic effects within the bit can affect and lead to faster switching. Such micromagnetic effects can be addressed via numerical solution of the stochastic Landau–Lifshitz–Gilbert–Slonczewski (LLGS) equation. However, determining WERs approaching 10^-9 would require well over 10^9 such independent simulations, which is infeasible. In this paper, we explore the calculation of WER using rare event enhancement (REE), an approach that has been used for Monte Carlo simulation of other systems where rare events nevertheless remain important. Using a prototype REE approach tailored to the STT-RAM switching physics, we demonstrate reliable calculation of a WER to 10^-9 with sets of only approximately 10^3 ongoing stochastic LLGS simulations, and the apparent ability to go further. [ABSTRACT FROM PUBLISHER]

This paper describes a new method aiming at the multi-objective optimization of a transverse flux machine with a claw-pole and flux-concentrating structure (CPTFM). Considering the 3-D main magnetic flux in the CPTFM, the time-consuming 3-D finite-element method (FEM) should be used to accurately analyze the performance of the machine. In order to reduce the calculation time for the optimization of the complex CPTFM, the Taguchi method is first applied to evaluate the importance of all the design parameters in the consideration of the predefined five objectives. Subsequently, a mathematical model is developed to replace the 3-D FEM, so that the objectives depending on the selected four critical parameters can be analytically calculated. With its help, the four parameters are further optimized with the multi-objective particle swarm optimization method and nondominated sorting genetic algorithm 2. Finally, the optimal design of the CPTFM is selected from all the searched Pareto solutions with the help of fuzzy logic. It can be concluded that the developed method is effective and efficient, which can make an appropriate compromise between the calculation time and the improvement of the machine performance. [ABSTRACT FROM PUBLISHER]

In this paper, we consider the use of dimensional analysis for modeling electromagnetic levitation and braking problems, which are described by the Lorentz force law. Based on Maxwell’s equations, to illustrate the underlying field problem, we formulate a complete mathematical model of a simple academic example, where a permanent magnet is moving over an infinite plate at constant velocity. The step-by-step procedure employed for dimensional analysis is described in detail for the given problem. A dimensionless model with a reduced number of parameters is obtained, which highlights the dominant dependences, and it is invariant to the dimensional system employed. Using the dimensionless model, a concise parametric study is conducted to illustrate the advantages of the dimensionless representation for displaying complex data in an efficient manner. We provide an exhaustive study of the dependences of the Lorentz force on the dimensionless parameters to complete the analysis, and we give results for a generalized representation of the problem. Finally, scaling laws are derived and illustrated based on practical examples. [ABSTRACT FROM PUBLISHER]

A new designed core tester and its feeding and control devices are presented in this paper. With this workbench, mounted single phase induction motor stators can be magnetically fed with controlled induction waveforms in order to evaluate their quality in the industrial environment. As the measured data involves the machine stator as well as the core of the testing apparatus, Finite Element and iron losses modeling are employed in this paper in order to distinguish the losses of the stator under test and the losses of measurement device itself. Therefore, the main goals of this paper are to propose a new tester design as well as a numerical way allowing the separation of the losses in the stator under test and the losses inherent to the tester itself. [ABSTRACT FROM PUBLISHER]

In patterned media recordings such as discrete track and bit-patterned media (BPM) recordings, the presence of pattern structures on the media surface causes the slider air bearing problems more complicated to be analyzed and studied. Using the 3-D direct simulation Monte Carlo (DSMC) method, the plain slider surface and bit/discrete track-patterned disk surface are designed for case studies in this paper. This paper reports the local bearing pressure variations acted on the slider surface due to the air bearing effects of pattern structures on the disk surface using the DSMC method. From the results obtained under the steady-state condition, it is observed that the bearing pressure profiles will be smoother and the bearing forces will approach to a stable value when the pattern pitch values are smaller than 0.4 \mum. This critical pitch value is close to 0.3 \mum that we reported previously based on modified Reynolds equations. We also investigate the effects of the pattern depth and total recess area ratio on the air bearing characteristics in BPM recording. Furthermore, in order to understand the effect of bit-pattern movements, we simulate the motion of bit-pattern structures by using four typical moving bit-pattern layouts. As of the outcomes, we can conclude that this effect could be negligible if the bit size is in several tens of nanometer scale. [ABSTRACT FROM AUTHOR]