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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]

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]

Recently, the demagnetization has been actively researched to reduce the magnetic field of a warship according to the development of the magnetic detection technology of the magnetic mines. In these studies, it was assumed that the warship was composed of one magnetic material in order to establish an effective deperming protocol. However, since the actual warship was composed of various materials, the magnetic interaction between the materials inevitably occurs during the demagnetization process. Due to the interaction, demagnetization may not be performed well. Therefore, in this paper, the effects of interactions in demagnetization of multiple materials were studied by using the Preisach model, and the optimal protocol was proposed. [ABSTRACT FROM AUTHOR]

In this paper, the dc biasing magnetomotive force (mmf) in presaturated core fault current limiter (PCFCL) is replaced with permanent magnet (PM) to overcome the well-known drawbacks of the dc biased PCFCLs. These drawbacks are excessively induced voltage across the terminals of the dc coil during fault condition and high total power losses during the steady-state condition. The novel contributions of this paper are the introduction of the selection criteria of PM material and its representation by actual nonlinear $B$ – $H$ hysteresis loop of Jiles-Atherton method, and the use of PM alone as an equivalent to the dc biasing coils for three-phase fault current limiter (FCL), contrary to work reported in earlier papers. Single- and three-phase PCFCLs are modified by replacement of dc saturation coil by the equivalent PM through time-domain finite element (FE) simulation of COMSOL Multiphysics package. Experimental verification shows that the implementation of accurate nonlinear representation of PM demagnetization curve with FE simulation gives a realistic performance of the PM biased PCFCL, especially in the fault condition. The performance of PCFCL can be evaluated through the voltage drop and total power losses during the steady-state condition and the fault current clipping ratio during fault condition of the grid. Furthermore, a comparative investigation of dynamic behavior is considered between dc and PM biased PCFCLs. It is found that the PM biased PCFCL has enriched capability of limiting any type of fault current with leading advantages of reduced voltage drop and power losses significantly together with risk elimination of the high induced voltage across dc coil terminals. Moreover, the governing parameters of PM biased PCFCLs are subjected to performance analysis to study their inherent effects. [ABSTRACT FROM AUTHOR]

Gyrotrons are high-frequency, high-power microwave sources with potential applications in plasma generation, energy generation, spectroscopy, and security. The Department of Science and Technology initiated the development of a 42 GHz, 200 kW, continuous wave (CW) gyrotron for the Indian Tokamak system through a multi-institutional project. The activity is targeted toward indigenous development of India’s first high-power gyrotron. In gyro-devices, frequency of operation is determined by the cyclotron frequency, and thereby the magnetic field. The development of a high-field intensity normal conducting cavity magnet was an imperative step during the testing and integration of the gyrotron tube assembly to achieve the desired beam transmission with a moderate operating cost. A high and spatially homogeneous magnetic field (1.61 T) is required to be established in the beam–wave interaction region by the cavity magnet. The desired magnetic field, as a function of axial distance from the gun to the collector, is governed by the requirements of gun optics, focusing field in the interaction region, and the adiabatic expansion of the beam into the collector. A water cooled electromagnet has been designed to produce the requisite magnetic field in the cavity region over an axial length of 40 mm with field homogeneity better than ±0.35%. Magnet design was optimized to meet the field requirements in the cavity and cathode gun. Magnetic field simulations were carried out in conjunction with the electrostatic field and space charge analysis. This paper presents finite element computations, design optimization, development and testing of a continuous duty iron core electromagnet for a first harmonic interaction mode (TE03) gyrotron cavity. Magnetic, electrical, thermal, and hydraulic design of the electromagnet is discussed in this paper. [ABSTRACT FROM AUTHOR]

Brushless doubly fed generator (BDFG), a class of adjustable-speed machine with a special structure, shows great prospect in wind power generation. Since different rotor structures lead to great differences in the BDFG performance, the research of BDFG rotor structure has been a hotspot. However, only a few of the research studies have paid attention to the rotor and stator slot combination of the BDFG, especially for the BDFG with a novel hybrid rotor. Improper slot combination will lead to efficiency decrease, additional loss increase, and undesirable torque in an electrical machine. In order to study the principle of slot combination of the BDFG with the hybrid rotor, the combination approach of theoretical analysis and experiments is presented in this paper. Furthermore, a coupling factor which reflects the coupling ability of the BDFG with different slot combinations is proposed. Moreover, the best slot combination of the proposed BDFG is determined, and several parameters such as useful harmonic contents, total harmonic voltage distortion (THDu), core loss, and copper loss are considered as major criteria for judgment. [ABSTRACT FROM AUTHOR]

Smart living is a trending and connected lifestyle that envisions efficient and sustainable energy utilization, stable and reliable power supply, intelligent and coordinated transportation and mobility, and personalized and cost-effective healthcare. Its realization needs the Internet of Things (IoT). IoT is a compelling platform connecting trillions of sensors and collecting data for connectivity and analytics. It is more advanced than traditional monitoring systems where limited sensors and wired communication can merely collect fragmented data in the application domains. Spintronic sensors with the superb measuring ability and multiple unique advantages can be one of the critical sensing devices supporting the IoT and enabling smart living. In this paper, we review successful applications of individual spintronic sensors in electrical current sensing, transmission and distribution lines monitoring, vehicle detection, and biodetection that can help to fulfill the promises of smart living in energy management, power delivery, transport, and healthcare. The wireless spintronic sensor networks (WSSNs) working at the massive interconnected network level are proposed and illustrated to provide pervasive monitoring systems, which facilitate the intelligent surveillance and management over building, power grid, transport, and healthcare. The database of collected information will be of great use to policy making in public services and city planning. This paper provides insights for realizing smart living through the integration of IoT with spintronic sensor technology. [ABSTRACT FROM AUTHOR]

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]

In this paper, we propose an approach to the design of a magnetostrictive electric power generator for energy harvesting from traffic, and we validate it experimentally. We use the dynamic Preisach hysteresis model (DPM) for magnetostrictive materials, operating in hysteretic and time-varying nonlinear regimes to design and simulate a magnetostrictive electrical power generator. The DPM is a development of the classical Preisach model, which is able to include the dynamical features in the mathematical model of hysteresis. We measure the output power capability of the generator, and we show how it is comparable to other energy-harvesting technologies. [ABSTRACT FROM AUTHOR]

This paper presents the reduction of noise and vibration concerning the magnetostriction effects for a single-phase power transformer with a large capacity of 200 MVA. Two magnetic core shapes are investigated: 1) D-yoked core and 2) square-yoked core. The D-yoked core is used for the construction of the transformer prototype in this paper. The magnetostriction and the hysteresis loop of the core material are measured for the simulation and analysis of noise and vibration. The transformer prototype is assembled with an external clamping force applied on the core, and the core vibration and sound-level are observed. The transformer operates with a periodic excitation that may induce resonance in the core. To avoid this, a finite-element analysis is used for modal analysis to identify the natural frequencies of the core. A tank is also designed with a sufficiently rigid structure to avoid resonances. The sound-level of the fully assembled transformer prototype is measured, and it is found to have a low-noise level below 65 dB. [ABSTRACT FROM AUTHOR]

This paper develops an approach that is capable of accurately predicting the performance of synchronous reluctance motors (SynRMs). The SynRMs receive increasing attention and have been used in many industrial applications. The 2-D finite element analysis (FEA) is usually considered to be competent for design and analysis of SynRMs. However, the power factor of SynRMs is likely to be considerably overestimated. This would then lead to an underestimation of current required and cause problems for the design of electronic drivers. Compensation should be made to improve the accuracy of the analysis for SynRMs although there does not seem to be a solution put forward so far. The research in this paper shows that the exclusion of end turn leakage inductances in 2-D analysis is a key factor to cause such a significant difference. To resolve this problem, this paper analytically calculates the end turn leakage inductance, which is then incorporated into the 2-D FEA. The developed method is found to agree well with the experimental results, and it significantly improves the design accuracy and efficiency using only the 2-D FEA. [ABSTRACT FROM AUTHOR]

This paper presents a study of the effects that the shoe shape of the teeth of electrical machines has on the performance and losses. This is done by considering a concentrated wound, high-speed permanent magnet generator. The paper investigates the influence of the tooth shoe shape on the machine magnetic circuit and the losses distribution based on analytical and finite-element analysis (FEA). A shape coefficient K {t} is proposed to provide an optimized design reference. A comprehensive analytical tool able to study the variations of the machine performance parameters is proposed. The deduced optimization function is normalized using the non-equilibrium relative weighting method, and then, it is processed via a genetic algorithm to achieve the optimized design. FEA is used to validate the proposed analytical tool and the optimum design. [ABSTRACT FROM AUTHOR]

This paper presents a novel analysis and a design method of surface-mounted permanent magnet (SPM) machines with fractional slot concentrated windings (FSCWs) for a given constant power region ratio. The characteristics of working points in the constant power region are analyzed, and a method of quantifying important parameters, magnet flux, and synchronous inductance is proposed. According to the analysis, the design method of SPM machines with the FSCWs and notes is provided. Based on the proposed method, a double-layer 20-pole/24-slot SPM machine is taken as an example and designed. The designed machine is analyzed by the finite element method (FEM), and the constant power experiment is carried out on the prototype manufactured as design. The results validate the analysis and the design method in this paper. [ABSTRACT FROM AUTHOR]

Spin waves are a promising prospect for the development of microwave information processing devices. A major obstacle in the study of spin waves is the large intrinsic spin-wave damping in most known magnetic materials. Viable spin-wave amplification techniques are thus required to make further progress in the development of spin-wave-based logic devices. In this paper, we investigate a novel technique of parametric modulation of spin waves using bulk acoustic waves. Although it is not a conclusive proof of parametric amplification, we show that bulk acoustic waves at twice the frequency of the propagating spin waves on coupling into an yttrium iron garnet film can modulate the amplitude of the spin wave. This paper provides insight into magnon-phonon interactions, and suggests a new mechanism to compensate for inherent losses in spin-wave propagation in spin-wave-based logic devices. [ABSTRACT FROM AUTHOR]

Advanced sensing techniques are key technologies required for the smart grid. Magnetic tunnel junction (MTJ) sensors hold great promises in the distributed linear current sensing, with small size, low price, and excellent performances. In this paper, MTJ Wheatstone bridge sensors were fabricated, attaining a typical sensitivity of 4.94 mV/V/Oe with an offset of −2.84 mV/V. A contactless current sensor based on the MTJ sensor was designed and realized, achieving a sensitivity of 7.75 mV/A and an offset of −8.68 mV. We can adjust the sensitivity and the linear range of the sensor by changing the gap of the magnetic core, and make the sensor much less susceptible to electrical wire’s location and orientation. This paper provides a practical current sensing technique for smart grid applications. [ABSTRACT FROM AUTHOR]

In this paper, we proposed and verified the feasibility of a unique wireless power transfer structure called a rail transformer to drive multiple low-power devices such as electronic shelf label (ESL) devices. The rail transformer is composed of a rectangular, circular-shaped transmitting yoke and two transmitting coils to provide wireless power. Multiple receiving yokes coupled with receiving coils are installed across the elongated edge of the transmitting yoke. It can be driven by low-frequency ac power at 50/60 Hz. In our prototype, the transmitting yoke is 900 mm long and 15 mm wide. We obtained the minimal induced wireless power, and the voltage was $\sim 61$ mW and 3.5 V, which is sufficient to drive a typical ESL device. By designing a nonuniform gap thickness between the transmitting and the receiving yokes at the specific locations, we improved the uniformity of the induced power for multiple ESL devices. [ABSTRACT FROM AUTHOR]

In this paper, the design and development of a double-sided air-cored tubular generator (DSTG) is presented. The characteristics of air-cored slot-less structures are investigated in terms of power density and efficiency. This is highly desirable for small- and medium-sized renewable energy conversion systems. In this paper, an analytical tool based on the magnetic vector potential method is built in order to achieve a fast but accurate method by which the machine is analyzed. The analytical model is validated by finite-element (FE) analysis. Further design improvements based on the analytical and FE models are then suggested in order to enhance the performance of the DSTG. The final design of the DSTG is validated by the test results from a developed prototype of the DSTG. [ABSTRACT FROM AUTHOR]

This paper proposes a novel machine termed the axial-flux brushless doubly fed reluctance machine (AF-BDFRM) suitable for high-torque, low-speed direct drive applications. The main potential advantages of AF-BDFRM are its higher torque and power density compared with the radial-flux BDFRM. In addition, the proposed machine utilizes a bidirectional power converter of much lower rating as compared with the machine rating depending on the range of speed variation. The proposed machine axial-flux topology is composed of two stators and a reluctance iron rotor. The upper stator winding which is connected directly to the power grid, transfers active power to the grid and lower stator winding creates excitation for the machine and connects to the grid through a partially rated converter. The design principles of the proposed AF-BDFRM are studied in this paper. Furthermore, the transient 3-D finite-element analysis result of the improved design is presented. [ABSTRACT FROM AUTHOR]

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

In the fabrication of linear magnetic tunnel junction (MTJ) sensors, the utilization of magnetic bias field along the easy-axis direction makes the response of MTJ nonlinear, and the Néel and magnetostatic coupling usually induces a strong interlayer coupling field along the hard-axis direction. In this paper, we investigated the influence of hard-axis and easy-axis bias fields on the linearity of MTJ magnetic sensor. The prediction and optimization of linearity were done by applying an appropriate hard-axis bias field in the specific easy-axis bias field and the practical tunnel magneto-resistance (TMR) ratio, and the model was verified by experiments. This paper can give guidance to improve the linearity and to maximize the practical TMR ratio of the MTJ sensors under a given linearity requirement. [ABSTRACT FROM AUTHOR]

In order to design a permanent magnet synchronous motor (PMSM), the inductance must be computed. In this paper, the flux concentrating PMSM (FCPMSM) is introduced. Calculating the inductance is difficult because of the complex structure of the rotor. Because the rib and the bridge consist of an iron core, they have nonlinear characteristics. In order to obtain the effective value of the inductance, nonlinear characteristics must be considered in a magnetic equivalent circuit (MEC). In this paper, to calculate the inductance of an FCPMSM, the relative permeance of the rotor was analyzed. Then, the dq-axis MEC, including the nonlinear magnetic reluctance, was created using the flux line. Finally, we verified the validity of the proposed inductance calculation method by comparing the results between the finite-element method and the proposed method. [ABSTRACT FROM AUTHOR]

The saturated-core superconducting fault current limiter (SCSFCL) is an important facility for limiting the short-circuit fault current of the power grid. However, the cognition or the judgment on the current-limiting effect, which is the key indicator of the SCSFCL, is not unique. This is because the nonlinear property of the steel cores in the limiting state makes the voltage on the SCSFCL and the current passing through the SCSFCL not sinusoidal any more. In this paper, it is presented that the equivalent limiting reactance, which is commonly used currently, cannot reflect the current-limiting effect, nor is the induced voltage. It is pointed out that for a certain SCSFCL, the current-limiting effect is not fixed, and it depends on the parameters of the power grid as well as the position, where the SCSFCL is installed. It is clarified that only the current reduction rate by comparing the short-circuit fault current before and after the installation of the SCSFCL in a certain power grid can correctly reflect the current-limiting effect. Certainly, the calculation for the current-limiting effect must be conducted by the field-circuit coupled method, where the field concerns the property inside the SCSFCL and the circuit concerns the property of the power grid. This paper does not mainly focus on the simulation method, but provides the means of judging or evaluating current-limiting effect of the SCSFCL. [ABSTRACT FROM AUTHOR]

This paper investigates the rotor losses of coaxial magnetic gears (CMGs) with surface-mounted permanent magnets. The iron losses and PM eddy current losses that occurred in the two rotors of an existing gear are calculated and analyzed by the finite-element method. Using magnetic flux barriers in the outer rotor, a novel rotor structure for CMGs is proposed to reduce the rotor losses, in which subharmonics are considered. A 1-D magnetic permeability model is also introduced to understand the principle of reducing the main subharmonics. Then the outer rotor losses of the existing gear and proposed gear are compared. The proposed model and the results presented in this paper will give useful guidelines for a reliable design and design optimization of the CMGs. [ABSTRACT FROM AUTHOR]

This paper proposed a temperature-dependent iron loss model and corresponding dynamic hysteresis model, where temperature coefficient k is introduced to consider the thermal effect on eddy-current loss. The iron loss model is validated by massive experimental measurement of test samples, 1174 combinations of various temperatures, magnetic inductions, and frequencies for nonoriented silicon steel specimen. The relative error of the model is $\sim 11$ % in a wide range of 50–400 Hz, 26 °C–200 °C, and 0–2 T. The proposed method can be applicable to other types of magnetic materials as long as whose resistivity rate exhibits approximately linear thermal dependence within a temperature range of 26 °C–200 °C. [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]

Traditionally, flux distributions in transformer cores are modeled as a 2-D problem. However, experimental studies indicate that 3-D models are needed. The main reason is that limbs of circular cross section are combined with roughly semi-circular yokes. At the joints, this yields shifts of overlap regions as a reason of significant (off-plane) normal direction (ND) induction B\mathrm {ND} . This paper reports a first corresponding 3-D modeling of a two-package one-phase core with the consideration of non-linear characteristics of material. For corners, the so-called critical induction B\mathrm {CRIT} of joints—as arising close to 1.4 T—is considered. Two instants of the cycle of global magnetization are addressed, i.e., B\mathrm {GL} = 1.7 T for normal operation and 1.9 T as a value that may arise for dc bias. For 1.7 T, the results indicate strong inhomogeneity, in particular in the wide main package of the core. On the other hand, 1.9 T is characterized by distinct homogenization. As 3-D effects, the cycle of magnetization involves distinct changes of flux in ND, with values up to more than 0.2 T. Half-cycle saturation is indicated especially for inner (window-sided) corner regions. The corresponding consequences on local magnetostriction (MS) values are over-proportional due to the complex dependence of strain $\lambda$ and induction. The so-called butterfly curve is dynamically passed beyond the turn point and even into its positive range. In particular, this yields distinct distortion of $\lambda$ , which can be assumed as a source of over-proportional rises of A-weighted noise. Apart from MS, further enhancement is to be expected from inter-laminar forces. [ABSTRACT FROM AUTHOR]