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In this paper, the response surface method (RSM) is exploited in the cooling system design optimization of oil-immersed transformers. To generate the training data for RSM, a 3-D computational fluid dynamic model for the transformer under study is constructed and solved, followed by verification on the solutions. Based on the simulation data, two types of RSMs, i.e., the second-order polynomial method and the Kriging method, are employed to evaluate their performance for this specific problem. The response surface with the best performance is used in the optimization process. The solution is compared with that found by the direct optimization method to showcase the effectiveness of applying RSM to oil-immersed transformer cooling system design. Details of implementation of the studied transformer are also presented. [ABSTRACT FROM AUTHOR]

By introducing the SiC/GaN power devices, the high-frequency switching dc–dc converters are expected to have higher efficiency and lightweight. This paper focuses on the Fe-based amorphous alloy powder (Fe–Si–B–Cr–C based) used in the metal composite bulk magnetic core for high-frequency power inductor and transformer. In terms of eddy-current loss at MHz band or beyond, iron-based metal composites are required to have fine magnetic particles with surface insulation layer. In this paper, the finest amorphous powder with a median diameter of 2.57 $\mu \text{m}$ made by water atomization process was used. In order to fabricate the amorphous powder with surface insulation layer, a surface-modification scheme through the two-step acid solution processing using phosphoric acid and hydrochloric acid was introduced. As a result, the surface-modification scheme enabled to make a single-phase silica thin layer on the surface of the amorphous powder, and the silica thin layer was considered to be derivable from the silicon element in the amorphous (Fe–Si–B–Cr–C based) powder. [ABSTRACT FROM AUTHOR]

This paper is performed to apply superconducting magnetic bearings (SMBs) to a high-speed turbine rotor. First, we analyze the system by using the finite-element method and design the structure whose vibrations are suppressed well. Then, we have made an experimental setup using the theoretical result. The experimental setup consists of two SMBs, a permanent magnet motor and a rotor with many turbine blades. We perform some experiments using this experimental setup in a vacuum chamber. In this paper, we discuss the dynamic characteristics of the spinning rotor with many turbine blades. [ABSTRACT FROM AUTHOR]

In this paper, interlaced magnetic recording (IMR) is generalized with a flexible inter-track interference cancellation (F-ITIC) scheme to enhance the overall areal density capability (ADC) by balancing and mitigating the mutual ITI between neighboring tracks. The IMR showed ADC gain by interlaced recording of aggressive bit density (BD) top and relaxed BD bottom tracks, where asynchronous ITI mitigation was applied to the bottom ones. On the other hand, IMR configuration can be generalized by the selective write width control, such that narrower relaxed BD top tracks are recorded over wider aggressive BD bottom tracks. In this generalized IMR (G-IMR), balanced ITI between interlaced tracks can provide ADC gain over legacy IMR (L-IMR) and customized F-ITIC for both tracks can further increase the gain. Note that the ITI processing scheme for G-IMR should be flexible in order to manage the ITI signals from high BD affecting low BD tracks, or vice versa. To evaluate the performance of G-IMR with the F-ITIC, numerical evaluations are conducted with the micro-pixelated magnetic channel model. The results show that G-IMR provides a favorable tradeoff between both tracks’ BDs and track density associated mutual ITIs, which offers a tangible ADC gain with the ITI cancellation over the L-IMR. [ABSTRACT FROM AUTHOR]

Ultrahigh-speed magnetization switching mechanism is strongly pursued, as it can improve the write performance of the magnetic random access memory (MRAM) and further extend the application area of spintronics. Currently, a well-studied switching mechanism is the spin transfer torque (STT), whose speed, however, is limited by an intrinsic incubation delay. Recently, spin–orbit torque (SOT) was proposed to solve the speed bottleneck of the STT. In this paper, we evaluate the potential of two types of SOT-MRAMs, whose data can be ultrafast written based on the recently discovered field-free SOT mechanisms, respectively. A cross-layer analysis is presented involving device modeling, circuit-level optimization, and architecture-level evaluation. First, the principle of the magnetization switching is analyzed with the macrospin simulation. Then, the optimization strategies at the circuit level are generalized through the SPICE-type simulation. Finally, we build up the memory architecture with the SOT-MRAMs, STT-MRAM, and static RAM. Their read/write performances are evaluated with NVSim software. It is demonstrated that one of the studied SOT-MRAMs shows the promising prospect in the non-volatile memory, especially suitable for high-capacity cache. [ABSTRACT FROM AUTHOR]

The Curie temperature distribution induced from grain size variation in heat-assisted magnetic recording (HAMR) can be alleviated by including the thermally insulating magnetic grain boundaries. In this paper, we present a systematic micromagnetic study on this new type of HAMR media, focusing on the impact to the recording behaviors from the exchange coupled magnetic boundary (shell). It is found that the soft magnetic shell of higher Curie temperature is capable of assisting the switching of FePt grain in both magnetization and transition process. The important implication of the proposed media for practical HAMR recording is that optimal performance now can be accomplished with relaxed recording conditions in both head field intensity and the heating source, eventually enhancing area density capability and the overall HAMR system stability. [ABSTRACT FROM AUTHOR]

High-speed electric machines with permanent magnets are sometimes equipped with a shielding cylinder; a conductive sleeve that is wrapped around the magnets in order to reduce the rotor losses and/or retain the magnets. Despite the every increasing popularity of such high-speed permanent-magnet synchronous machines (PMSMs), there are still a lot of question regarding the effect of the shielding cylinder. Earlier work in literature evaluates how the shielding cylinder’s design affects the machine’s performance. However, that work assumes a sinusoidal current, hence neglects the stator current’s higher time-harmonic orders. Therefore, this paper aims at evaluating how different stator sources affect the way in which the shielding cylinder influences the torque production in high-speed PMSMs. The study is performed using a 2-D analytical subdomain model that accounts for slotting and the eddy current reaction field. Both current and voltage sources are considered. The torque is divided in two components, the classical torque due to interaction between the magnets and the stator currents and the torque due to interaction with the eddy currents in the shielding cylinder. This approach results in a better insight in the machine’s physics. [ABSTRACT FROM AUTHOR]

Current density distribution in electric arcs inside low-voltage circuit breakers (LVCBs) is a crucial parameter for us to understand the complex physical behavior during the arcing process. In this paper, we investigate the inverse problem of reconstructing the current density distribution in arcs by inverting the magnetic field. This paper is focused on the modeling and computational phase for the magnetic inverse problem when linear ferromagnetic regions are considered in the model. To address the ill-posedness of the inverse problem, the standard method of least-squares approximation by Tikhonov regularization is studied, complemented with the generalized cross-validation criterion for regularization parameter selection. Considering the inclusion of a ferromagnetic region, two regularization approaches have been analyzed for the formulation of the currents in splitters and their corresponding magnetic field contribution. Effects of several features on the performance of the regularized solution have been investigated, including the signal-to-noise ratio, the value of permeability of the splitters, and the measurement distance. The numerical tests show the direct accessibility for the 3-D current density distribution with the proposed scheme, providing the accuracy and robustness for the applicability to study the arc behavior in LVCBs. [ABSTRACT FROM AUTHOR]

This paper presents a methodology that allows taking advantage of the geometrical periodicity of electrical machines together with the modeling of rotor motion. It enables by means of the discrete Fourier transform (DFT) to reduce the large-scale system obtained from the finite-element model to several smaller independent subsystems, allowing a shortening of the computational time. Due to DFT properties, the computational time can be more reduced especially when we consider the inter-dependence of the spectral components under either balanced or unbalanced supply condition. In addition, a further reduction is possible in the case of balanced regimes where the distribution of the eventual numerical solution is governed by a limited number of prevailing harmonics. [ABSTRACT FROM AUTHOR]

Cogging torque is due to the interaction between a magnet’s magnetomotive force and a slotted stator or rotor structure. In this paper, a compact equation for cogging torque is presented for surface-mounted permanent magnet motors. This equation has four terms of field interactions involving tangential and radial components of airgap flux density. These four terms are considered as sources of cogging. Variations of these sources with pole embrace are examined. In earlier publications, closed-form expressions for pole embrace corresponding to the minimum cogging were presented considering only radial fields. In this paper, an attempt is made to recognize the influence of tangential fields in cogging. The compact form given here distinctly reflects the significance of both radial and tangential field components. Furthermore, to study the trends of cogging sources with pole number and airgap radius, simplified expressions for harmonic content of field components are derived using the first-order binomial approximation. The analysis on cogging presented in this paper helps in determining search domains in which optimum embrace for minimum cogging can be found when both the radial and tangential field components are considered. [ABSTRACT FROM AUTHOR]

As an efficient non-destructive testing method, magnetic flux leakage (MFL) has been widely used for damage detection in ferromagnetic materials. The magnetic dipole theory is a traditional method to calculate the magnetic leakage field. In this paper, the magnetic leakage field functions of a slot in a 2-D infinity plate are obtained using the magnetic dipole theory. Equations of the magnetic leakage field are converted into the convolution of two other functions. Spatial spectral equations of the MFL are developed according to the convolution theorem using the Fourier transform (FT) method. The results are analytical functions different from other numerical methods, such as the discrete FT and fast FT methods, and the calculation speed is fast. The results show that the $y$ -component of the magnetic leakage field has 90° phase shift with the $x$ -component. This result has clear physical significance compared with the traditional MFL equations using the magnetic dipole theory. Different spatial spectral curves for different defects are presented in this paper. Since there is a sinc function for the width value in the equation, the width value can be deduced from the first zero-crossing point in the spatial spectrum curves. A new method is proposed to determine the width value using the relationship $w =1/f_{s}$ , where $f_{s}$ is the first zero cross point. Two specimens with different cracks are investigated, and the experimental results show this method can be used as an inverse MFL data interpretation technique. [ABSTRACT FROM AUTHOR]

Arrays of nanosized hollow spheres of Ni were studied using micromagnetic simulation by the Object Oriented Micromagnetic Framework. Before all the results, we will present an analysis of the properties for an individual hollow sphere in order to separate the real effects due to the array. The results in this paper are divided into three parts in order to analyze the magnetic behaviors in the static and dynamic regimes. The first part presents calculations for the magnetic field applied parallel to the plane of the array; specifically, we present the magnetization for equilibrium configurations. The obtained magnetization curves show that decreasing the thickness of the shell decreases the coercive field and it is difficult to obtain magnetic saturation. The values of the coercive field obtained in our work are of the same order as reported in experimental studies in the literature. The magnetic response in our study is dominated by the shape effects and we obtained high values for the reduced remanence, Mr/MS = 0.8 . In the second part of this paper, we have changed the orientation of the magnetic field and calculated hysteresis curves to study the angular dependence of the coercive field and remanence. In thin shells, we have observed how the moments are oriented tangentially to the spherical surface. For the inversion of the magnetic moments we have observed the formation of vortex and onion modes. In the third part of this paper, we present an analysis for the process of magnetization reversal in the dynamic regime. The analysis showed that inversion occurs in the nonhomogeneous configuration. We could see that self-demagnetizing effects are predominant in the magnetic properties of the array. We could also observe that there are two contributions: one due to the shell as an independent object and the other due to the effects of the array. [ABSTRACT FROM PUBLISHER]

The 3-D modeling technique presented in this paper, predicts, with high accuracy, electromagnetic fields and corresponding dynamic effects in conducting regions for rotating machines with slotless windings, e.g., self-supporting windings. The presented modeling approach can be applied to a wide variety of slotless winding configurations, including skewing and/or different winding shapes. It is capable to account for induced eddy currents in the conductive rotor parts, e.g., permanent-magnet (PM) eddy-current losses, albeit not iron, and winding ac losses. The specific focus of this paper is to provide the reader with the complete implementation and assumptions details of such a 3-D semianalytical approach, which allows model validations with relatively short calculation times. This model can be used to improve future design optimizations for machines with 3-D slotless windings. It has been applied, in this paper, to calculate fixed parameter Faulhaber, rhombic, and diamond slotless PM machines to illustrate accuracy and applicability. [ABSTRACT FROM PUBLISHER]

This paper describes the numerical and experimental validation of a novel non-contact dc electromagnetic propulsion concept. In the proposed approach, a propulsion coil carrying a dc current is surrounded by a dc transversal multipole field created inside of a launch tube. The interaction between the transversal dc magnetic field and a dc propulsion coil results in the generation of axial (thrust) force with no need of sliding contacts. This paper describes a numerical assessment of the field-current-force interactions based on both analytical calculations and finite elements, and the corresponding validation experiments. The experiments demonstrate the generation of contactless axial (thrust) force in a dc launch coil using a dc transversal multipole field, and provide a benchmark for the model-based prediction of the field-current-force interactions. Partial magnetic shielding of the propulsion coil is used to selectively attenuate the magnetic field experienced by the thrust coil in a way that a net thrust force is achieved. Experimental measurements confirmed that it is indeed possible to generate contact-free thrust force on a dc propulsion coil using a dc multipole magnetic field, and the measured values of thrust force are in good agreement with the corresponding predictions. [ABSTRACT FROM PUBLISHER]

The purpose of this paper is to investigate a novel flux-switching permanent magnet (FSPM) machine that is amenable for high-speed operation. The low-pole topology of high-speed machine is favorable to minimize fundamental frequency requirement. The lowest possible three-phase topology of the FSPM machine, with six stator slots and four rotor poles (6/4), has unacceptably large second-order harmonic distortion in the flux linkage and severe cogging torque in its conventional single-stator–single-rotor form. To resolve these challenges, a novel dual-stator structure is proposed that eliminates the even-order harmonics in the flux linkage. Harmonic distortion and cogging torque are notably reduced in the proposed machine. The principles of operation and design methods are described in this paper. The properties of the proposed dual-stator 6/4 FSPM machine are compared with a conventional 6/4 FSPM machine and a conventional 12/10 FSPM machine for a 5 kW, 15 000 r/min design. Comparison results gathered from 3-D finite-element analysis demonstrate that the proposed dual-stator 6/4 FSPM machine achieves significantly better flux linkage, back EMF, and cogging torque than the conventional 6/4 design and better efficiency than the conventional 12/10 FSPM machine. [ABSTRACT FROM PUBLISHER]

Zeroth mode of vibration is investigated in low-speed high-torque surface-mounted permanent magnet (PM) machines with non-overlapping concentrated windings. Magnetic field distribution in the air gap is computed using time-stepping finite-element analysis, and Maxwell stress tensor is then employed to calculate the radial force density. Based on the time variation of the mean value of the radial force density spatial distribution, the zeroth-order radial forces are studied. Simple structural equations are used to compare the stator deformations for the machines under investigation. Contribution of the zeroth mode to produce vibration is analyzed and compared with the lowest non-zero mode. The influence of pole and slot combinations and the effect of rectifier load are discussed. This paper is carried out to investigate whether or not the zeroth-order radial forces can be of importance in the presented surface-mounted PM machines that are not connected to pulsewidth modulation (PWM) converters. [ABSTRACT FROM PUBLISHER]

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

The rare-earth permanent magnet (PM) is commonly used to improve the performance of high-speed electrical machines to compensate for their high production costs, while it is very likely that the demand for high-speed machines will increase in the near future as markets for new technologies continue to grow. However, a high-speed machine is required to have high performance and low manufacturing cost, because mass production is needed for these applications. Therefore, in this paper, a high-speed machine using a ferrite PM was designed to significantly decrease the manufacturing costs. To examine the performance of the high-speed machine suggested in this paper, the performance of a high-speed model using a ferrite PM is compared with that of a SmCo PM model. A high-speed machine with a specification of 3 kW and 30 000 r/min is designed and manufactured. The designed model is analyzed using the finite-element method. Finally, the no-load back electromotive force in each model is examined through a back-to-back experiment. [ABSTRACT FROM PUBLISHER]

The ongoing miniaturization trend of electric machines increases the demand for higher rotational speeds to provide a required power level at decreased size. In this paper, new concepts for bearingless machines with ultra-high rotational speeds exceeding 25 million rotations per minute are researched. While the mechanical properties of the employed sub-millimeter-sized spherical steel rotors are documented, insufficient information is available on the electromagnetic characteristics that are crucial for magnetic levitation and acceleration. This paper outlines the relations between the relative permeability and conductivity of the rotor material and the achievable active magnetic bearing force and angular acceleration. Measured results for complete hysteresis curves of different rotor steels are presented. [ABSTRACT FROM PUBLISHER]

This paper investigates a double stator linear rotary permanent magnet motor (DSLRPMM) with orthogonally arrayed PMs. The DSLRPMM, which involves linear and/or rotary movements, is constituted of two stators and a hollow mover. The aim of this paper is to study the electromagnetic features and optimize the design parameters of the motor using a 3-D finite-element method (FEM). The topology and the operating principle are described, and the original design is given. The influences of the main designed parameters on the electromagnetic torque, force, and total losses are also analyzed. The optimal parameters are given and a prototype is built and tested. The experimental results are in agreement with that of the 3-D FEM analysis. [ABSTRACT FROM PUBLISHER]

This paper presents the magnetic and electrical equivalent circuits of a hysteresis interior permanent magnet (IPM) motor. A hysteresis IPM motor is a solid rotor hybrid synchronous motor combining hysteresis phenomena and permanent excitation in the rotor. When installed in thousands of feet under the sea to drive an electric submersible pump (ESP), it can self-start the ESP without the need of any position sensors, and can improve the efficiency, the performance, and the reliability of the ESP. In this paper, equivalent circuit models are used to predict the transient run-up responses of a 2.5 kW prototype hysteresis IPM motor. Analysis results are compared with 2-D finite-element analysis (FEA) results as well as experimental results. There exists a reasonably close agreement between analytical, FEA, and experimental results, which validates the accuracy of the equivalent circuit models of a hysteresis IPM motor. [ABSTRACT FROM PUBLISHER]

In this paper, a new method for achieving absolute position information is proposed. As opposed to the common approach of matching magnetoresistive (MR) sensors to specific pole pitch patterns on medium, this paper validates the possibility of mismatching between the two with the same element spacing in MR sensors over pole pitch variation from 1.1 to 1.3 mm in two-row magnetic patterns. The first row is the incremental row, which has the same 1 mm pole pitch as the sensor. The second row serves as the absolute row with the tweaked pole pitch pattern. With different pole pitches in the two rows, an offset between each pole exists before the two different pole pitches reach their common multiple. Through analyzing Lissajous profiles resulted from both rows, it is found that the relation between two rows on each position is unique, and hence can be used as a mean to determine absolute position. [ABSTRACT FROM PUBLISHER]

In recent studies, we introduced the concept of functionalized magnetic force as a method to prevent nanoparticles from sticking to vessel walls caused by extensive simulation and in vitro experiments involving a Y-shaped channel. In this paper, we further investigated the effectiveness of the functionalized magnetic force with a realistic 3-D vessel through simulations. For the simulations, we considered a more realistic continuous injection of particles with different magnetic forces and frequencies. Based on the results from our simulation studies, we performed in vivo mice experiments to evaluate the effectiveness of using a functionalized magnetic force to aid magnetic nanoparticles (MNPs) in crossing the blood–brain barrier (BBB). To implement the functionalized magnetic force, we developed an electromagnetic actuator regulated by a programmable direct current power supply. Our results indicate that a functionalized magnetic field (FMF) can effectively prevent MNPs from sticking, and also guide them across the BBB. We used 770 nm fluorescent carboxyl MNPs in this paper. Following intravenous administration of MNPs into mice, we applied an external magnetic field to mediate transport of the MNPs across the BBB and into the brain. Furthermore, we evaluated the differential effects of FMFs (0.25, 0.5, and 1 Hz) and constant magnetic fields (CMFs) on the transport of MNPs across the BBB. Our results showed that an FMF is more effective than a CMF in the transport and uptake of MNPs across the BBB in mice. In particular, applying an FMF with a 3 A current and 0.5 Hz frequency mediated the greatest transport and uptake of MNPs across the BBB in mice. [ABSTRACT FROM PUBLISHER]

This paper investigates the influence of mutual fluxes (inductances) on the resultant torque in three-phase conventional switched-reluctance machine (CSRM) and mutually coupled SRM (MCSRM) using the frozen permeability (FP) method. Under saturation conditions, the FP method allows accurately separating the torques due to self-flux and mutual flux, hence quantifying their contributions to torque generation. Then, appropriate current waveforms (unipolar or bipolar, square wave or sinewave) can be established to maximize the output torques. It is well known that the mutual torque of CSRM can be negligible. However, this paper has shown that when sinewave current is employed and under full or overload conditions, the torque will be significantly reduced due to non-negligible negative mutual torques. Different from CSRM, the self-torque and the mutual torque of MCSRM can be added if current waveform is properly chosen, e.g., sinewave currents. This can significantly boost the resultant torque. The predictions have been validated by experiments. [ABSTRACT FROM AUTHOR]

On behalf of the Publications Committee, I am pleased to present a selection of papers from the 11th edition of the European Magnetic Sensors and Actuators Conference (EMSA 2016), which was held in Torino, Italy, on July 12–15, 2016. [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]

This paper proposes a new design of SPOKE-type PM brushless direct current (BLDC) motor without using neodymium PM (Nd-PM). The proposed model has an improved output characteristic as it uses the properties of the magnetic flux effect of the SPOKE-type motor with an additional pushing assistant magnet and subassistant magnet in the shape of spoke. In this paper, ferrite PM (Fe-PM) is used instead of Nd-PM. First, the air-gap flux density and backelectromotive force (BEMF) are obtained based on the field model. Second, the analytical expressions of magnet field strength and magnet flux density are obtained in the air gap produced by Fe-PM. The developed analytical model is obtained by solving the magnetic scalar potential. Finally, the air-gap field distribution and BEMF of SPOKE-type motor are analyzed. The analysis works for internal rotor motor topologies. This paper validates results of the analytical model by finite-element analysis for wing-shaped SPOKE-type BLDC motors. [ABSTRACT FROM AUTHOR]

Cogging torque is a source of vibration and noise in PM machines. Its reduction is always sought by electrical machine designers. While its study, in radial-flux PM machines, can often be done using 2-D finite element analysis (FEA), 3-D FEA is always required when it comes to its study in axial-flux PM machines (AFPM). AFPM machines have an inherent 3-D electromagnetic structure. There is a rich literature concerning the study of cogging torque in AFPM machines. Indeed, most of the authors use 3-D FEA for its study. However, 3-D FEA is time consuming and always requires expertise to be done correctly. The goal of this paper is to show that alternative techniques, to study cogging torque in AFPM machines, do exist. It is shown that the analytical approach, used in this paper, can be as efficient as the 3-D FEA while saving a huge amount of time and necessitating less initial expertise. [ABSTRACT FROM AUTHOR]

In the design of high-temperature superconductor (HTS)-based electromagnetic devices, some of the major challenges include ac loss reduction, minimization of heat leakage, and reduction of the amount of HTS material used to decrease costs. This paper considers a computer model of HTS-based leads involving a multiphysics scenario that considers the electromagnetic and thermal behavior of the system. This paper attempts to address the requirements mentioned and provides an optimum solution by applying an approach based on multiobjective optimization. The differential evolution technique, a stochastic method, widely known for the ease of use and its ability to handle adequately non-differentiable, non-linear, and multimodal cost functions was used. The proposed framework provides a technique to optimize effectively HTS leads, which not only deals with the non-linear aspect of HTS materials, but also includes a multiphysics environment. [ABSTRACT FROM AUTHOR]

This paper investigates the stray magnetic and electric fields of a multifunctional power converter operation while connected to a system involving an induction motor. The impacts of the switching techniques on the radiated fields of the converter were studied for the purpose of electromagnetic interference (EMI) evaluation and fault detection. This was achieved through the inspection of the magnetic and electric fields. Two of the most commonly used switching techniques were implemented through a hardware-in-the-loop system studied in terms of the stray. Various fault and failure conditions were applied to the converter to monitor the converter condition through the stray field observations. A coil and a rod antenna were connected to an EMI receiver to capture the fields. The fields were employed in further analyses. The harmonics and interharmonics of the stray fields were studied in detail for system monitoring purposes. The importance of this paper is to enable the evaluation of the optimum switching pattern for lower EMI field levels from the converter and for condition monitoring and fault diagnosis purposes. [ABSTRACT FROM AUTHOR]

This paper analyzes the incline unbalanced magnetic pull (IUMP) generated in the permanent magnetic synchronous motor (PMSM) with the rotor misalignment. The motor magnetic field in such a motor is asymmetric, and both the magnitude and the action point of UMP vary in motor operation. This paper presents an analytical model for analyzing the 3-D effects of the UMP induced by the misalignment rotor. The numerical simulation results prove the effectiveness of the proposed analytic model. [ABSTRACT FROM PUBLISHER]

Viterbi detectors are widely used in all communication systems dealing with transmission and storage. In this paper, we develop the theory and design architecture for a 2-D separable iterative soft-output Viterbi detector (SISOVD) for applications in 2-D storage channels extending the original work from Wu et al. (IEEE Trans. Magn., vol. 39, no. 4, pp. 2115–2120, Jul. 2003). The contribution of this paper is twofold. First, we design a non-binary soft Viterbi detector that will be used as the core engine for the SISOVD and show its equivalence to the max-log-MAP algorithm implementation. We also study the performance of the algorithm through simulations under various design parameter constraints toward a systems architecture. Second, we propose a novel digital circuit that incorporates non-uniform quantization within a sliding block design framework. The proposed detector system architecture is tested within an field programmable gate array platform and proved to be efficient in terms of resource utilization, timing, and power compared with a conventional uniform quantizer with no signal-to-noise ratio performance degradation. It shows a 13.28% reduction in the total number of slice registers, 30.26% reduction in the slice lookup tables, 21.23% reduction in the critical path delay, and 14.84% reduction in the power consumption compared with the uniform quantizer. [ABSTRACT FROM AUTHOR]

In this paper, optimization of the control of an electrical machine allowing a minimization of its total losses is described. It is based on the use of an iron loss model [loss surface (LS) model] coupled to the electromagnetic finite-element simulations of the machine. The LS model is a scalar and dynamic hysteresis model developed many years ago at G2Elab and tested for iron loss prediction in several cases of electric machines. It is first characterized and improved in this paper for M330-35A SiFe sheets. Then, it is associated with a finite-element analysis to compute, in a post-processor mode, the local and global magnetic losses in the machine. For electric vehicle application, the whole torque–speed variation should be investigated. To do that, a quick response surface is constructed from a small number of simulations and the iron loss is determined. Then, a suitable optimization algorithm is developed. This approach is then illustrated by a case study and compared with classical optimization in which only the copper losses in conductors are considered. Gains of up to 50% reduction in the total losses of the machine in certain operating areas are observed. [ABSTRACT FROM AUTHOR]

This paper describes the application of polyharmonic sinc signals in devices for metal object detection. A basic problem of conventional eddy current metal detectors (induction devices in general) lies in their limited possibilities of discrimination or identification of detected objects. To better characterize the detected object, the excitation signal and the following signal processing in the detector should be done. The application of polyharmonic excitation signal and its processing could bring an opportunity to improve the determination ability. This paper is focused on the polyharmonic sinc signal. Spheres of different diameters and from different ferrous and non-ferrous materials were used as specimens. Experimental measurements were processed in frequency-domain amplitude, and phase spectra were calculated and presented. As part of the work, classifications of ferrous and non-ferrous materials were done based on measured data as well as the classification of individual ferrous, including non-ferrous materials and estimation of the size of the classified object. Support vector classifier was primarily used for data classification. [ABSTRACT FROM AUTHOR]

The vibration of permanent magnet synchronous motor (PMSM) cores is related to the rotation speed. This paper presents a generalized magnetoelastic 3-D finite-element model, which can be used to calculate the magnetic field and structural vibration of laminated cores, including magnetostrictive effect. Magnetostriction (MS) is a property of electrical steel and causes the vibration of motor cores, the primary cause being electromagnetic forces. To implement the model, the vibration of a PMSM core was numerically analyzed under excitation with different frequencies. The speed and vibration were measured simultaneously by pulse and accelerometer sensors, and the variation of speed and vibration features was analyzed by Fast Fourier Transformation (FFT) versus Revolutions per minute (RPM). The numerically analyzed results showed that the vibration due to MS is important, and the magnitude of vibration is related to the operating speed. Vibration and speeds of the motor were tested and analyzed. The results showed that there is a vibration peak in the range of 600–2000 r/min (30–100 Hz), which is acceptable in calculation. [ABSTRACT FROM AUTHOR]

Bidirectional inductive power transfer (BIPT) systems enable power transfer between stationary electricity sources and movable consumers in each direction through electromagnetic coupling. Due to its complexity, a mathematical model is required to design and to control these systems. This paper presents the mathematical analysis and the frequency-domain analysis for two different compensated (series–series and parallel–parallel) BIPT systems. This paper contains the modeling procedure of the BIPT system’s coils in the frequency domain. The prediction of its equivalent circuit values, magnetic stray field values, and coil positioning tolerance are determined as well using the JMAG field simulation software. Furthermore, the transmission characteristics and the efficiency of the two compensation topologies are discussed. [ABSTRACT FROM AUTHOR]

In this paper, field projection methods are used to couple finite-element analysis carried out on different meshes and different temporal discretization bases. The prior-art mesh-to-mesh spatial field projection is extended to the time domain in this paper. We first define a space-time error norm between a given field distribution and the target field to be determined, and then minimize it using the Galerkin method. Biorthogonal test functions are also introduced into the projection process to replace inner product matrices with diagonal matrices and reduce the computation cost in terms of memory as well as the calculation time required. [ABSTRACT FROM AUTHOR]

This paper deals with the modeling and simulation of the effect of rotor eccentricity in permanent magnet synchronous machines. Static eccentricity is analyzed in a 2-D setting. The 3-D effect of an inclined rotor shaft is accounted by considering 2-D slices and interpolating on a grid constructed from finite-element simulations [response surface model (RSM)]. Common tools of uncertainty quantification, i.e., generalized polynomial chaos and Monte Carlo, are used to study the effect on the electromotive force. The novelty of this paper is the twofold use of the RSM: 1) to speed up the calculations in the 2-D setting and 2) to mimic a multislice model for inclined eccentricity. [ABSTRACT FROM AUTHOR]

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 describes the coupled electromagnetic–thermal analysis of gradient coils for magnetic resonance imaging. This application deserves special attention because the eddy-current analysis of gradient coils is usually performed using filamentary and shell elements, while thermal analysis requires volume elements. This paper aims to present a seamless method to couple the mixed-element discretizations (1D, 2D, and 3D) and to project the outputs of eddy currents simulation into the corresponding thermal sources. Special attention is devoted to the management of closed domains within the integral shell element formulation. [ABSTRACT FROM AUTHOR]

Social-spider optimization (SSO) is a new nature-inspired algorithm of the swarm intelligence field to global optimization applications, which is based on the simulation of cooperative behavior of social spiders. To enhance the performance of the standard SSO, a modified SSO (MSSO) approach based on beta distribution and natural gradient local search was proposed in this paper. In order to verify the performance of the MSSO, tests using Loney’s solenoid benchmark and a brushless direct current motor benchmark are realized comparing the effectiveness of the SSO and the proposed MSSO. The results of this paper demonstrated that the MSSO performance is promising in electromagnetics optimization. [ABSTRACT FROM AUTHOR]

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

In this paper, we propose a microwave imaging technique that involves an adaptive back-projection (BP) algorithm based on a climb method. In general, the range migration algorithm (RMA) provides high computational efficiency and high accuracy for synthetic aperture radar (SAR) imaging. However, RMA involves wavenumber domain interpolation, which may adversely affect the accuracy of the target imaging. The BP algorithm, which has its origins in medical imaging techniques, has been studied to overcome this problem in SAR imaging, because it avoids interpolation associated with domain conversion, but it also has a huge computational cost. Therefore, this paper proposes adaptive processing based on a climb method to find the target indicator as real target responses. The real target responses are predetermined and the raw data are reproduced to reduce the computational cost and to improve the image quality. Finally, the superiority of proposed algorithm is demonstrated using both the simulated and experimental data. [ABSTRACT FROM AUTHOR]

This paper presents an analytical calculation method for the computation of the magnetic vector potential of an axisymmetric solenoid in the presence of an iron shield and a ferromagnetic core. The proposed method can be used as a fast analytical computation technique for accelerating the design optimization process of the solenoid systems. In this paper, the analysis of the current carrying coil in the presence of the ferromagnetic materials is treated as a boundary value problem. The solution approach is based on partitioning the solution domain into distinct regions. The general form of the solution to Maxwell’s equation in each region along with the corresponding boundary conditions is obtained using the Fourier analysis and the separation of variables. The final solution to the boundary value problem is constituted by considering the continuity of the magnetic vector potential, as well as the magnetic field, on the interfaces between the regions. Finally, the proposed analytical computation method is applied on an electromagnetic actuator. The magnetic vector potential is computed over the entire solution domain, and the result is compared with that of the finite-element method. [ABSTRACT FROM AUTHOR]

The multiple multipole program (MMP) is a boundary method for computing electromagnetic fields, which is well established in high-frequency electromagnetics and computational optics due to its flexibility in terms of accuracy control, field excitation, and fast convergence. As any other boundary method, MMP cannot efficiently solve nonlinear problems. The purpose of this paper is to show a novel numerical method for treating local nonlinear regions within a large linear MMP model. The main idea of this approach is to apply the well-known discretization scheme of the domain finite-element method (FEM) within the nonlinear region and to couple it over a special numerical interface with the linear MMP model surrounding it. The theoretical details of this FEM-MMP coupling and practical examples are presented in this paper. [ABSTRACT FROM AUTHOR]

In this paper, a 3-D multiphysics finite-element study of microelectromechanical systems (MEMS) reed magnetic sensors is presented. This paper employs several governing equations to simulate the MEMS reed sensors, calculate their magnetostatic body force, and track the resultant mechanical displacements. The MEMS beams used are trilayer gold/Ni/gold, and the sensing ranges of the sensors are in milli-Tesla. The results in this paper point to an optimal sensor design, which is then fabricated and verified by the experimental tests. This paper presents a general performance map of the MEMS reed sensors, illustrating their performance under various field conditions. Several sensor devices are fabricated and tested, with the measured data showing good agreement with the simulation results. [ABSTRACT FROM AUTHOR]

Dynamic grain state estimation (DGSE) algorithms for 2-D magnetic recording (TDMR) employ probabilistic message-passing algorithms that jointly estimate magnetic grain configurations and coded data bits, in order to iteratively assist channel decoding. At high densities (e.g., between 1 and 3 magnetic grains per coded bit), occasionally, a bit will not be written on any grain, and hence will effectively be overwritten (or erased) by bits on surrounding grains. DGSE enables the detection of overwritten bits so that their log-likelihood ratios are assigned small magnitudes, effectively making them erasures, which are easily filled in by linear channel codes. Past papers employing Bahl-Cocke-Jelinek-Raviv-based detectors on a simple four-rectangular-grain model have shown that the DGSE is surprisingly resilient to mismatch between the detector’s assumed grain model and the actual model generating the data. This paper presents a novel DGSE–TDMR detector based on the generalized belief propagation (GBP) algorithm. The new detector employs a random discretized-nuclei Voronoi grain model. Simulation results show that the GBP-based TDMR turbo-detector accurately detects the overwritten bits and that it achieves low decoded bit error rates at densities as high as 0.4966 user bits per grain. [ABSTRACT FROM AUTHOR]

Today, adaptive equalization is generally used to capture the run-time read channel dynamics in the presence of a random read-head offset. An adaptive equalizer updates its coefficients using a certain adaptive signal-processing algorithm, e.g., least-mean-square algorithm. This paper proposes a self-directed equalization strategy for the emerging very high-density magnetic recording drives with a multi-sensor read head. The key idea is to exploit the spatial diversity of readback signals from different read sensors to accurately estimate run-time read-head offsets, based upon which the equalizer coefficients are accordingly self-configured in order to improve the equalization performance. This paper presents specific methods to practically implement this design strategy, and its effectiveness has been well demonstrated through the simulations with a Voronoi-based channel model. [ABSTRACT FROM PUBLISHER]

This paper proposes an extended set of variables for numerical optimizations of tooth-coil permanent magnet synchronous machines (TC-PMSMs). The design variables for the extended set are chosen based on the magnetic asymmetries introduced by the saturated core under the loading conditions. The extended set allows to reach considerably higher values of torque density and significant reduction of torque ripple in comparison with a conventional set of optimization variables. The conventional and extended sets are compared on an example of an finite element method simulation of a double-layer winding surface permanent magnet-rotor TC-PMSM. A considerably better optimal machine is obtained when the extended set of variables is utilized. The paper showcases the design and the optimization of electrical machines using only free and open-source software. [ABSTRACT FROM PUBLISHER]

Among various types of motors, permanent magnet (PM) motors, due to their high energy density, are mainly used for electric-based propulsion systems. In this paper, an improved analytical model for PM motor has been presented. The model considers important factors, such as armature reaction, slotting effect, and influence of non-linear material property on motor’s behavior. Moreover, the main contributions of this paper are the representation of stator windings with exact winding width using Fourier series and the consideration of effects of non-linear ferromagnetic material property. Using this model, it is possible to determine air-gap magnetic field, flux linkage, back electromotive force, cogging torque, and electromagnetic torque with high accuracy. Results from the proposed model are compared with other analytical model and also with those from a finite-element analysis (FEA). The results obtained from the proposed method match closely with the FEA. [ABSTRACT FROM PUBLISHER]