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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]

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]

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]

An exact analytical model of a surface-mounted bearingless permanent-magnet synchronous motor (BPMSM) with rotor eccentricity by a perturbation method is proposed in this paper and its computational accuracy is verified by the finite-element method. Considering the rotor eccentricity, a compensation control system is implemented based on the mathematical model of levitation force by applying a coefficient of the rotor eccentricity calculated by the exact analytical method (EAM). The experimental results suggest the improvements of the dynamic and the static performances of the stable suspension state for the surface-mounted BPMSM and the feasibility and effectiveness of the EAM. [ABSTRACT FROM AUTHOR]

The design of control strategies for permanent magnet synchronous machines (PSM) is almost exclusively based on classical dq0-models. These models are, however, not able to systematically describe saturation or nonhomogenous air gap geometries typically occurring in PSM. This paper deals with a framework for the mathematical modeling of PSM based on magnetic equivalent circuits. Different to existing works, the model equations are derived by means of graph theory allowing for a systematic choice of a minimal set of state variables of the model and a systematic consideration of the electrical connection of the coils of the motor. The resulting model is calibrated and verified by means of measurement results. Finally, a magnetically linear and a dq0-model are derived and their performance is compared with the nonlinear model and measurement results. [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]

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]

Applying the Jiles-Atherton (JA) model to simulate the dynamics of power electronics circuit is a challenge but very attractive since it is possible to carry out continuous simulation with only several input parameters. Although other methods such as the Preisach-model can result in approximate waveforms for such applications, it is still a far distance to reach exact ones to suit chaos and other high accuracy-requiring researches. In this paper, the JA model has been successfully applied to model the dynamics of resonant inverter for driving a nonlinear load: a fluorescent lamp. The circuit is driven by a high frequency square wave voltage source. A semi-theoretical fluorescent lamp model developed from HID lamp model is adopted in the modeling. The simulation waveforms of voltage across the lamp and current through it are close to those measured ones reported in the literature papers. [ABSTRACT FROM AUTHOR]

This paper compares two different identification methods of a static rate-independent energy-based hysteresis model with regard to the dynamic hysteresis loop shape prediction when coupled to the parametric magnetodynamic lamination model. The values of hysteresis model parameters are determined solely based on the quasi-static major loop. A semiphysical approach identifying the reversible and irreversible field components independently and a purely mathematical scheme using a differential evolution optimization algorithm determining all parameters simultaneously are compared. Both variants of parameter identification are analyzed in terms of hysteresis loop shape prediction for quasi-static as well as dynamic loops. [ABSTRACT FROM AUTHOR]

This paper discusses the implementation of the inverse Jiles–Atherton vector hysteresis model with the 2-D Finite Element Method (FEM) for the analysis of an induction machine operating as self-excited generator. A differential reluctivity tensor couples the hysteresis model with the magnetic vector potential-based finite-element model. Experimental and simulated results (transient and steady state) are presented. [ABSTRACT FROM AUTHOR]

Some soft magnetic materials are strongly dependent on the temperature, because of their low Curie temperature. In order to predict their behavior in electrical devices, engineers need hysteresis models able to consider the temperature. This paper is an attempt to consider the temperature in an existing model of static hysteresis through its parameters. Variations of some parameters with temperature are issued or build thanks to the literature. At the end, all needed parameters have an analytical law versus temperature. The simulation results are compared with measurements and discussed. [ABSTRACT FROM AUTHOR]

Recent advances have been made into modeling the soft-magnetic materials using the surface charge model. Until now, the model has only been used to model the field outside the soft-magnetic material. To include the saturation in the future, the magnetic field inside the material should be known. In this paper, the model is used to calculate the field inside the material when three different shapes of boundaries are considered. Comparing the results with Finite Element Method shows that the differences in the air region are <1 mT and those in the soft-magnetic region are <4 mT. Larger discrepancies can, however, occur near the corner of the material. [ABSTRACT FROM AUTHOR]

This paper presents the modeling of a tunable inductor using a low-temperature co-fired ceramic (LTCC)-ferrite tape and subsequent development of a loaded transmission line phase shifter using these inductors. The inductors are initially realized in the form of circular disks fabricated from commercially available ferrite tape (ESL 40011) wound with a copper wire. A complete model of this inductor is obtained between 0.3 and 4 GHz and validated by measurements. The phase shifter comprises these inductors in shunt, thus minimizing the effect of low-field magnetic losses in $L$ -band. The magnetic material is operated below the resonance region in a partially magnetized state with the help of a bias current that configures the phase shifter electronically. The phase shifter exhibits an insertion loss of 2 ± 0.5 dB and a differential phase shift varying between 35° and 10° in the above band. Finally, to demonstrate the feasibility of integration with other RF components, a working prototype of the same phase shifter that is fully integrated in LTCC is also presented with measurements. [ABSTRACT FROM AUTHOR]

This paper describes a mathematical model for the dynamic magnetic power losses in the laminated steel stator of high-frequency permanent magnet machines, such as brushless dc (BLDC) motors. The model presented is based on a utilization of the dynamic Jiles–Atherton model. Accurate dynamic $B$ – $H$ curve fitting and magnetic power loss derivations have been achieved, where the calculated magnetic losses have shown $\sim 95$ % accuracy from 5 to 2000 Hz over a flux density range of 1.0–1.6 T. This approach has been applied to estimate the magnetic power loss of a small scale high-frequency (>10 000 r/min) BLDC motor, with calculated and measured losses being in close agreement. [ABSTRACT FROM AUTHOR]

This paper presents a vector hysteresis model based on micromagnetic theory. In this model, a magnetization state of a magnetic material is described by a collection of single-domain particles, and magnetic reversal processes due to domain-wall motions are treated approximately as a magnetization flip. The present model is applied to calculation of hysteresis properties of grain-oriented silicon steel. The simulation results show that the anisotropic hysteresis properties and iron loss can be reproduced accurately by the present model. [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 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]

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]

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]

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]

This paper deals with the magnet pole shape design of permanent magnet machines for the minimization of torque ripple based on electromagnetic field theory. On the basis of a magnetic vector potential and a two-dimensional (2-D) polar system, analytical solutions for flux density due to permanent magnet (PM) and current are obtained. In particular, the analytical solutions for mathematical expressions of magnets with different circumferential thicknesses can be solved by introducing improved magnetization modeling techniques, resulting in accurate calculations of electromagnetic torque. The analytical results are validated extensively by nonlinear finite element method (FEM). Test results such as back-emf measurements are also given to confirm the analyses. Finally, on the basis of derived analytical solutions, a reduction of torque ripple can be achieved. [ABSTRACT FROM AUTHOR]

This paper presents novel equations that enable the direct analytical calculation of the interaction torque between perpendicularly magnetized cuboidal permanent magnets in free space. These expressions complement the expressions for the interaction force and stiffness that are already available in literature and are computationally inexpensive due to their analytical nature. They are suitable in the design and analysis of ironless structures such as certain types of magnetic bearings or for obtaining the peeling torque on the magnets in devices such as voice coil actuators or electron beam focusing devices. [ABSTRACT FROM AUTHOR]

This paper presents a general analytical model for predicting the magnetic field of slotless permanent-magnet machines. The model takes into account the effect of eddy currents in conductive regions and notably in conductive permanent magnets without neglecting their remanent field. The modeling of this effect is important for the design of very high speed slotless permanent-magnet machines, as the power losses are linked with the frequency of the field. The model takes into account any number of layers. It implies that, for one, the fields can easily be calculated in a design including a permanent magnet and a conductive retaining sleeve. The model is applicable both to internal rotor and external rotor permanent-magnet machines. The effect of the relative permeability and of the conductivity of the permanent magnet or of the yoke on the magnetic fields is also taken into account. Any magnetization can be taken into account, in particular a Halbach type permanent magnet, or a radially magnetized permanent magnet can be considered. [ABSTRACT FROM AUTHOR]

The understanding of the electrowetting phenomenon is essential way for the control of tiny droplets on dielectric material surfaces. From the conventional viewpoint, the shape of a droplet is determined by the contact angle which is influenced by the applied electric field. In this paper, we present a new approach to model and analyze the electrowetting phenomenon. It is based on the electromagnetic body force and surface tension as well as the initial contact angle. The pressures on the droplet surface are calculated using Kelvin's formula, the hydrostatic equation, surface tension due to surface curvature and the volume constraint condition. The electrowetting phenomenon was successfully modeled and analyzed using the proposed approach. Numerical analysis results were in good accord with the experimental results. [ABSTRACT FROM PUBLISHER]

Automatic differentiation (AD) is introduced as a powerful technique to compute derivatives of functions given in the form of computer programs in high-level programming languages such as FORTRAN, C, or C++. This paper applies AD to compute error-free gradients of electromagnetic device sizing models. Then, the obtained gradients are exploited in optimization to size electromagnetic devices by means of minimizing a cost function with constrained parameters and performances. Often, the electromagnetic devices models have to be described not only by analytical formulas, but also by algorithms. This paper proposes an electromagnetic model of a linear actuator dealing with implicit equations solved by numerical algorithms. The ADOL-C package is considered for automatic differentiation. [ABSTRACT FROM PUBLISHER]

This paper deals with the mathematical definition of a general vector hysteresis operator in 3-D, as an extension of previous papers where the theory has been limited to the 2-D case. Although the paper is mainly focused on magnetic hysteresis, the definitions and the results reported can be applied to any general physical phenomenon that exhibits hysteresis. We show here the main general properties of the general hysteresis operator in 3-D. [ABSTRACT FROM AUTHOR]

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]

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]

Linear induction motors (LIMs) are being gradually applied in the urban rail transit due to their simplified mechanical structure and feasibility for both low-speed and high-speed operations. Direct-torque control (DTC) is a classical control scheme that can be readily extended to LIMs. However, due to the high thrust ripple and poor dynamic performance for the low-speed operation, control performance of DTC is not satisfactory. This paper is to propose an explicit model predictive control to be combined with the DTC scheme. First, the LIM model is presented and discretized. Then, the LIM drive and its operating principle are discussed. Thirdly, the controller design, including control variables, and the objective function are depicted. Finally, both the simulation and the experiment are engaged for verifying the proposed control algorithm. [ABSTRACT FROM PUBLISHER]

The knee point in the B – H curve of a permanent magnet (PM) is considered crucial in electric motor applications. In the case of severe fault conditions, such as overheating or a short circuit in electric motors, the working point might fall below the knee point causing irreversible demagnetization of the PM. Hence, the remanence flux decreases and the motor operation would be reduced or stalled. In this paper, two demagnetization models of PMs are investigated, i.e., a linear model and an exponential model. Demagnetization curves for NdFeB were measured at temperatures varying from room temperature to 180 °C. It was found that all the parameters in the exponential model, including Br , H\mathrm {jc} , \mu r , and the fitting parameter K1 , are temperature dependent. Therefore, an exponential model can be developed as a function of temperature which allows a more efficient implementation within electric motor applications using PMs. However, comparison of the exponential and linear models indicates that the latter has a better accuracy near the knee point for the demagnetization curves of NdFeB magnets. [ABSTRACT FROM AUTHOR]

In this paper, a novel approach to numerically design a microwave (MW) shield is proposed. The strategy is based upon the interplay between a reduced model, formed by three periodical element teeth in a waveguide, and a full model composed of an entire shield, a metallic cavity, and the open space. A correlation criterion is implemented to avoid the divergence between the physical responses of the models. In order to save computational time, the evaluation of less influent design variables is included, and preoptimization is performed. The compact range method has been experimentally applied to test the optimized MW shield. A comparison between computed and measured electromagnetic leakages is presented and discussed. Measured scattering parameter S21 is lower than −30 dB over the industrial, scientific, and medical frequency band, confirming the adequacy of the strategy. [ABSTRACT FROM AUTHOR]

Magnetic actuators are successfully used in the control of rotating machinery using feedback to eliminate the undesired vibration. Control algorithms can be implemented through the magnetic forces applied using the magnetic actuator, which are controlled through the current induced in the coils. Throughout this paper, we suggest the elimination of the excessive oil whip vibration excited due to the rotation of flexible rotor supported on fluid film bearings using the magnetic forces. The fluid film bearings and magnetic actuators are integrated into one unit. An \textH\infty controller is designed considering the robustness issues to suit a flexible rotor. The controller performance is successfully tested. [ABSTRACT FROM AUTHOR]

The aim of this paper is to highlight the capabilities of a new hybrid analytical modeling (HAM) approach for the analysis and design of various electromagnetic structures. After an introduction, where the aim of the development of this modeling approach is presented, the modeling approach is described. The new HAM is based on a strong coupling of the magnetic equivalent circuits method and analytical models (AMs). The AM, based on the formal solution of Maxwell’s equations, is established thanks to the separation of variables method. The HAM is applied to different permanent magnet electric machine structures, and the results are validated extensively by comparison with the finite-element analyses. [ABSTRACT FROM AUTHOR]

In this paper, a new stator-permanent magnet (PM) bearingless machine (SPMBM) is proposed. Its suspending windings, armature windings, and PMs are in the stator, while no PMs or windings are in the rotor. However, it is the focus in establishing an accurate mathematical model of radial suspension force to levitate the rotor stably by directly and effectively controlling the rotor eccentric displacement. First, operating principle and air-gap flux density distributions of the SPMBM are analyzed in detail. Then, an accurate mathematical model of radial suspension force is deduced by the Maxwell stress tensor method, and it is verified by the 2-D finite-element method (FEM). Results are consistent both by the radial suspension force mathematical models of the SPMBM and FEM. [ABSTRACT FROM AUTHOR]

A typical eddy-current testing (ECT) process involves scanning of conducting test sample using an EC probe, which can be an air-core coil or ferrite-core coil. Its accurate and efficient modeling is critical to probe and testing parameter optimization. The finite-element method (FEM) has been widely used in ECT simulation. Unfortunately, the conventional FEM is cumbersome and inefficient when the movement of a ferrite-core coil is to be considered, because the change of the coil position results in repetition of meshing as well as generating and preconditioning matrix equation. In this paper, we resolve the problem by dividing the solution domain into subdomains. The test sample and the ferrite core are assigned to different subdomains, and each subdomain is meshed independently. The excitation coil is not included in a subdomain, and its contributions to the magnetic fields in both subdomains are calculated analytically. Solutions of the subdomains are coupled by calculating the contribution of the induced current or magnetization current in a subdomain to the magnetic field in the other subdomain. The proposed method has the merits of easy mesh generation and efficient and accurate solution. [ABSTRACT FROM AUTHOR]

In the domain of numerical computation, proper generalized decomposition (PGD), which consist in approximating the solution by a truncated sum of separable functions, is applied more and more in mechanics, and has shown its efficiency in terms of computation time and memory requirements. We propose to evaluate the PGD method to solve three-dimensional (3-D) quasi-static field problems coupling with an external electric circuit. The numerical model, obtained from the PGD formulation, is used to study the 3-D examples. The results are compared with those obtained when solving the full original problem. It is shown in this paper that the computation time rate versus the number of time steps is very small compared with the one in a classical time-stepping method, and can be very efficient to solve problems when small time steps are required. [ABSTRACT FROM AUTHOR]

To develop efficient silicon steel plates and electric machines using silicon steel laminations, the evaluation of excess loss in silicon steel plates is important. In this paper, investigation on excess loss calculation using the finite element method is carried out. The excess loss, which is mainly due to two factors, lack of flux penetration and domain wall pinning, is considered by the proposed approach using the domain wall bowing degree (DWBD), which depends on the above two factors. The DWBD is obtained using nonlinear eddy-current analysis. The correlation between the excess loss and the DWBD can be expressed as an exponential equation. Using the equation, the excess loss can be predicted under harmonic frequency in the range of 50–2000 Hz. These results can be applied to iron loss estimation, especially, when there are harmonics in the power supply. [ABSTRACT FROM PUBLISHER]

Hysteresis models can incorporate the effects of operating conditions (frequency, stress, and temperature) on iron losses incurred in ferromagnetic materials. Among such models, the Jiles–Atherton (JA) and Preisach models are the most popular and various modifications of these have been proposed in the literature to model the effect of frequency, stress, and temperature on iron losses. Both of these representations produce accurate results compared with the curve fitting models and can be directly implemented in finite element simulations. Unfortunately, it is very difficult to incorporate all these effects into a single iron loss model that is computationally efficient and can predict iron losses with reasonable accuracy for a given range of these parameters. In this paper, an effort has been made to establish a relationship between JA and Preisach models and an interpolation-based approach is presented to predict iron losses that utilizes the Preisach model on top of the JA model and incorporates all of the above factors. It is shown that iron loss can be predicted accurately for any value of frequency, stress, and temperature. [ABSTRACT FROM PUBLISHER]

Projection-based model-order reduction is a powerful methodology for solving parameter-dependent linear systems of equations. The efficient computation of the residual norm is of paramount importance in adaptive model reduction schemes because it is heavily used in error indicators and a posteriori error bounds. These guide the adaptive selection of expansion points in multi-point methods and serve as stopping criteria for subspace enrichment. This paper demonstrates that the standard algorithm for fast residual norm computation leads to premature stagnation, and it presents a new approach of improved accuracy. [ABSTRACT FROM PUBLISHER]

Many reasons may cause malfunction of a proton exchange membrane fuel cell (FC) stack. Moreover, a single defect cell can affect the whole stack functioning; therefore, the localization of this cell is crucial as well as identifying the root causes for such malfunctioning. The diagnosis tool has to be nonintrusive and easy to replicate to a new FC system. This paper explores paths to achieve such monitoring based on the use of the magnetic field induced by the FC stack internal currents. Designing and using a 3-D simulation tool allows to establish a cause and effect relationship between FC defects and specific magnetic signatures. This preliminary work enables to determine the required magnetic sensor accuracy, the sensor orientation and location as well as the experimental precautions for relevant measurements. [ABSTRACT FROM PUBLISHER]

Dual rotor motors (DRMs) for the electric vehicle application are a competitive alternative to the multi-motor drivetrain configuration to meet the high-power density and better vehicle drive performance. In this paper, a steady-state model of a hybrid DRM is developed using electromechanical energy conversion principles. The developed model comprises electrical equivalent circuit and torque equation. The model helps in understanding the motor operation and can be used for quick performance evaluation. The finite element method has been used to validate the developed model and a good agreement has been achieved for the results obtained. [ABSTRACT FROM AUTHOR]

Hard disk drive (HDD) systems today have embedded servo wedges spanning the revolution of the disk that periodically provide the head with crosstrack position information as it flies over the servo wedges. The head is subjected to forces such as from turbulence, disk-waviness, shock, and vibration that cause its position to deviate from its desired on-track position. It is the job of the servo controller to use the information in the position error signal (PES), calculated from the readback signal as the head flies over the servo wedges, to reposition the head back on-track. There are a couple of disadvantages of the embedded servo system in today’s HDDs. The first is that the overhead of the servo wedges consumes some of the areal density reducing the amount of storage capacity for the user’s data. Today, that overhead is in the range of 3%–5% of the total disk surface. The second disadvantage is that between servo wedges, the servo control loop has no position information and the head is flying blind. In this paper, we propose an alternative method for the servo controller to obtain the PES it needs to position the head on-track without the need for servo wedges. Our method assumes the usage of a multiple-reader head that, as of today, seems to be a likely upgrade to HDD systems in view of the benefits promised by shingled magnetic recording and 2-D magnetic recording. [ABSTRACT FROM AUTHOR]

One of the still open issues within low-frequency magnetics is the inclusion of \mu r in the calculations using the magnetic charge method. In this paper, a new iterative method to consider the relative permeability is investigated. This new method assumes a position-dependent surface charge distribution. Comparisons between model and finite element method results show that the model accurately accounts for the permeability of a magnet and a soft-magnet block within four iterations. [ABSTRACT FROM AUTHOR]

This paper investigates the interaction of an initially uniform magnetic field with an electrically conducting slab that moves perpendicularly to the magnetic field with arbitrary time-dependent velocity. It is demonstrated that the problem of determining the time-dependent Lorentz force and the time-dependent Joule heat in the slab is mathematically equivalent to solving a 1-D heat diffusion problem with time-dependent boundary conditions and to submitting the solution to a nonstandard postprocessing procedure. For the particular case of an impulsively driven slab we exploit the mathematical analogy between magnetic diffusion and heat diffusion by translating a textbook solution of the corresponding heat-transfer problem into exact and previously unknown relations for Lorentz force and Joule heat. Moreover, we use a 1-D finite-difference code to investigate more general time dependencies of the velocity including smooth accelerations and random velocity changes. Our numerical determination of reaction times ( \(\boldsymbol {T_{98}}\) ) of the Lorentz force in the case of smooth accelerations provides a useful design tool for the development of Lorentz force flowmeters with short reaction times. [ABSTRACT FROM AUTHOR]

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]

In this paper, a novel method is proposed to detect demagnetization fault in surface mounted permanent magnet synchronous motors (SMPMSMs). Hence, a theoretical analysis is presented for feature extraction and pattern recognition via torque analysis. In this analysis, impacts of the saturation profile, stator slots and the fault severity are taken into account. So, using torque spectra, an efficient index is introduced for demagnetization fault diagnosis in SMPMSMs. Based on the extracted features and the recognized pattern, time delay embedding (TDE) approach as a competent data mining technique is utilized to process the developed torque. Then, a criterion function is proposed to detect demagnetization fault. Furthermore, this criterion is used to estimate fault severity and determine demagnetization percentage. The two-dimensional (2-D) time stepping finite element method (TSFEM) is employed to model the SMPMSM under different demagnetization levels. The 3-D TSFEM is used to prove the theoretical and 2-D TSFEM results. [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 deals with novel formulas for calculating the mutual inductance and the magnetic force between two coaxial coils in air comprising a circular coil of the rectangular cross section and a thin disk coil (pancake). The mutual inductance and the magnetic force are expressed over the complete elliptical integrals of the first and second kinds, Heuman's lambda function, and three terms that must be solved numerically. All singular cases have been resolved analytically. We also give another approach as comparative method that is based on the filament method where all conductors are approximated by the set of Maxwell's coils. The expressions are obtained over the complete elliptical integrals of the first and second kinds. These new consistent expressions are accurate and simple for useful applications. All results obtained by different approaches are in excellent agreement. [ABSTRACT FROM AUTHOR]