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This paper proposed a simulation method for the charge transport in single-layer oil-paper insulation. The method of transient upstream finite-element method (FEM) is derived in order to calculate the time variation of charge densities in medium. The numerical simulation of charge transport in the single-layer oil-paper insulation is realized by applying the transient upstream FEM to the transport equations of bipolar charges. With reasonable microparameter, the charge transport in an experimental object is simulated. The simulation results are consistent with the experimental data. A bent model of oil-paper insulation is analyzed to study the charge distribution under the actual condition. This paper provides an exploratory research to the simulation of charge phenomenon in oil-paper, and has guiding significance to the design of oil-paper insulation. [ABSTRACT FROM AUTHOR]

This paper employs an overhang structure for axial flux permanent magnet motor to enhance the torque density. However, the overhang structure requires a computationally expensive 3-D finite-element method (FEM) for analysis, because a quasi-3-D FEM cannot be applied to such a geometry. Thus, in order to reduce the computational cost of above-mentioned topology, this paper adopts a field reconstruction method (FRM). The conventional FRM is applicable only in the case, where the slot pitch to teeth length ratio is the same along radial direction. To address this problem, we introduce a virtual air gap concept so that it can take into account parallel slot effect as well as overhang effect. In this paper, the effectiveness of the proposed method is verified by the 3-D FEM and experimental results. [ABSTRACT FROM AUTHOR]

The wirelessly transferred power as well as charging efficiency will significantly drop due to the large misalignment between the transmitting coil and receiving coil for roadway electric vehicles (EVs). A low-cost and reliable misalignment-tolerant wireless charging technique is indispensable for the rapid commercialization of wireless EV charging. This paper presents a technique to achieve the misalignment-tolerant wireless charging for the dynamic wireless charging (DWC) system by means of a tunneling magnetoresistive (TMR) sensor array as well as the easy-to-fabricate receiving coils. The TMR sensor array provides the coil-misalignment position by measuring the magnetic field component generated from the transmitting coil. The corresponding receiving coils are selected to be in resonance according to the measured coil-misalignment positions. In this paper, a sensor array composed of 29 uniaxial TMR sensors was utilized to measure the magnetic field component. This effectiveness of the proposed technique has been validated by both the finite-element method (FEM) simulations and laboratory experiments. The experimental results demonstrated that the proposed misalignment-tolerant wireless charging system can operate in a relatively wide misalignment range of ±120 mm with charging efficiency higher than 76.2%. [ABSTRACT FROM AUTHOR]

Magnetic flux leakage (MFL) response predicting is important for defect estimation. This paper first proposes a concept of basic signal by discovering the combination property of the MFL response. The basic signal can be used to predict the MFL response conveniently by a basic signal combination method (BSCM), which is also innovatively put forward in this paper. In this method, the basic signal is calculated in advance, and the MFL response can be calculated by several transformation and combination operations. Both the simulation and experimental results demonstrate the feasibility of BSCM. Compared with other traditional methods (magnetic dipole method and finite-element method), BSCM shows a good performance on both the computational speed and accuracy. [ABSTRACT FROM AUTHOR]

This paper presents models developed through analytical or numerical computation and finite-element analysis to improve the resolution of a new kind of vibrating magnetometers. This peculiar magnetometer uses the piezoelectric transduction to actuate a quartz resonator at its resonance frequency taking advantage of the high $Q$ factor of a quartz resonator to achieve high resolution. The magnetic sensitive element is a thin ferromagnetic film of nickel–cobalt, which is sputtered on the moving beams of the resonator. This magnetic thin film applies a periodic torque on the resonator, shifting its resonance frequency. This torque depends on the magnetic field applied; therefore, the value of the magnetic field can be deduced from the frequency shift measurement. The aim of this paper is to develop and improve sensitivity models, which will be useful tools in the future work to establish the optimal geometry for a resonator and the best position of the magnetic thin film on it in order to improve the sensitivity and resolution of the global sensor. [ABSTRACT FROM PUBLISHER]

Space charge distribution is a valuable indicator of ion flow field and is widely utilized to assess electromagnetic environment for transmission line. The finite-element method (FEM) is widely used to solve this problem. However, Kaptzov assumption in FEM assumes that onset voltage is unchangeable after corona occurs, which does not tally with the actual situation. This paper adopted the finite-element iteration method (FEIM), which uses empirical formula instead of assumptions to calculate the charge density. The surface field intensity is not constant in the empirical formula because the empirical formula takes the effects of space charge on surface field into consideration. So this is more consistent with actual situation. In order to verify the accuracy of the algorithm, sound pulse method is applied to measure the charge density around the conductor in the laboratory. Simulation results show that the charge density obtained in this paper agrees with the data in the experiment, which verifies the validity of the empirical formula for calculation of space charge density. Compared with a method considering Kaptzov assumption, FEIM is closer to the experiment in area around conductor line and near the ground. This indicates that empirical formula in FEIM is more effective than Kaptzov assumption in these two domains. [ABSTRACT FROM AUTHOR]

For the purpose of saving energy resources, it is extremely expected to develop highly efficient electric motors. Different types of permanent magnet (PM) arrangement can significantly affect the performance of the motors. Conventionally, the arrangement of the PMs is determined by designer’s experience. This paper focuses on the optimal design of PM arrangement in PM synchronous motors (PMSMs). We present a general pattern of the PM arrangement in PMSM. By varying the parameters of the general pattern, it can produce different types of PM arrangement in the rotor. The employed approach combines the global optimization method with the finite-element method for solving the optimization of the PM structures. Based on the proposed general pattern and optimization methods, the best PM arrangement in the motor can be automatically determined. In order to reduce computing loading, this paper employs the response surface models for reducing the computing time of objective functions. In the end, numerical tests are designed to showcase the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper introduces an analytical approach for an effective evaluation of the variation of the magnetic field generated by complex coils due to deformations with respect to the nominal configuration. The coils are described with a set of synthetic design parameters, and the deformations can be described as variations of such parameters. This paper proposes a method to evaluate the derivatives of the magnetic field with respect to the design parameters by splitting them into a magnetic factor and a geometrical factor. A comparison with the classical finite-differences approach is carried out. This paper focuses on the context of sensitivity analysis, but the methodology is quite general and can easily be extended in other fields. [ABSTRACT FROM AUTHOR]

This paper presents an analytical model of magnetic field of a permanent magnet synchronous motor (PMSM) with a trapezoidal Halbach permanent magnet array (THPMA). Compared with conventional Halbach array, the shape of each magnet in THPMA is transformed from rectangle to trapezium in polar coordinates. The THPMA is delaminated indefinitely radially and each layer is approximately considered to be a conventional Halbach array. The air-gap magnetic field of each layer is analyzed with the scalar magnetic potential. Then, the air-gap magnetic field of the THPMA is obtained by superposing magnetic fields of all layers. The validity of the analytical model is verified by a finite-element model (FEM). The air-gap flux density is optimized by adjusting the center angle coefficients of the THPMA, and a no-load phase back electromotive force (EMF) with the harmonic distortion rate (THD) of 0.75% is obtained by FEM. The back EMF is basically consistent with the measured result of a prototype motor. [ABSTRACT FROM AUTHOR]

This paper applied the finite-element method (FEM) with topological data structures to the optimization of electrical devices. A generic modifiable graph data structure is built according to the graph-theoretic foundation for these data structures. The employed topological FEM avoids rebuilding of the mesh in traditional FEM method while geometrical variations happen. It is an effective algorithm which can save computer storage and working time when applied to successive optimization. The effectiveness is verified by numerical example and comparison of the topological FEM with traditional FEM on storage load and working time is shown in this paper. [ABSTRACT FROM AUTHOR]

A novel interior permanent magnet linear vernier machine (IPM-LVM) is proposed and analyzed in this paper. Compared to the existing surface-mounted permanent magnet linear vernier machine (SPM-LVM) and the SPM-LVM with Halbach arrays, the proposed machine can offer higher flux density in both the air-gap and armature iron core, which lead to a higher back electric motive force (back EMF) and higher thrust density under the same mover volume and heat capacity. Besides, it is proven that the proposed IPM-LVM also has a lower demagnetization risk compared to the SPM-LVM. Furthermore, in order to reduce the thrust ripple of the proposed machine, the three-sectional structure is adopted in this paper, which makes the proposed IPM-LVM exhibit high thrust density and low thrust ripple at the same time. [ABSTRACT FROM AUTHOR]

This paper presents a disk-spacer damper (DSD), a new damper structure, for reducing disk flutter. Three types of DSD structures, which consist of an aluminum disk spacer having grooves embedded with viscoelastic (VE) films, have been developed in this paper. First, we investigated the material properties of the VE film, such as shear modulus and discrete relaxation spectra, and then carried out numerical analysis of the damping effect using the material properties. Further, we measured the damping effect of each DSD structure and confirmed that the proposed DSD reduces the disk flutter amplitude between the (0,1) mode and the (0,4) mode by 20%–30%. [ABSTRACT FROM AUTHOR]

Linear antenna arrays consisting of dipole antennas find wide applications in wireless communication systems. Typically, arrangements with uniform spacing between the array elements are applied to gain highly directive radiation patterns while controlling the radiation intensity in the side lobes. To describe such arrangements, the so-called pattern multiplication (PM) technique is frequently applied, which inherently neglects the inter-element coupling. In this paper, an antenna array arrangement with non-uniformly spacing between the array elements is synthesized in the multi-objective sense. Therefore, the PM technique is deficient. Hence, numerical techniques have to be applied to compute the electromagnetic field during the optimization process. Due to its simplicity and the consequently reduced computational costs, the partial element equivalent circuit method is applied within the field computation process. The optimization relies on a stochastic particle swarm optimization strategy, namely the firefly algorithm. In this paper, an extended version of the general algorithm with additional hierarchical clustering is applied. Special attention is drawn to the development of a suitable objective function. [ABSTRACT FROM AUTHOR]

After designing and optimizing an electric machine, efficiency maps are needed to predict a vehicle’s performance in a dynamic simulation. Calculating efficiencies at various torque and speed points, however, requires prior knowledge of the input excitation conditions, such as the current magnitude and advance angle, in an electromagnetic finite-element analysis simulation. Hence, this paper derives and uses nonlinear motor control equations (MTPA, FW, MTPV) in the study of efficiency map calculation while accounting for both saturation and cross-coupling effects. Two synchronous ac motors are considered in this paper, including the 2010 Prius IPM and a PM-assisted synchronous reluctance machine, with all procedure steps outlined in detail. [ABSTRACT FROM AUTHOR]

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]

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]

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 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]

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]

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]

In this paper, open boundary techniques are employed to represent the Cauer ladder network (CLN) for unbounded eddy-current problems. Recently, a novel and effective model order reduction method, called the CLN method, has been proposed in which linear eddy-current fields are represented by a CLN. The CLN method was initially formulated for closed domain eddy-current problems. This paper demonstrates that the CLN method can be extended to unbounded-domain problems when combined with conventional open boundary techniques. The CLN network parameter extractions of two parallel busbars are demonstrated as a numerical example. [ABSTRACT FROM AUTHOR]

This paper presents a composite solid rotor designed to improve starting performance of the line-start permanent-magnet synchronous motor (LSPMSM). The rotor is mainly constituted by the solid steel which can inherently generate high starting torque. Moreover, the axial slots milled on the rotor surface deepen the flux penetration into core and a brass made cage attached to the rotor enlarges the eddy current density. With above promotions, the induction torque increases, and hence drives the motor to startup and synchronize under heavy load conditions. The enhanced starting capability by applying the proposed rotor for an LSPMSM is validated by the 2-D time-stepping finite-element method (FEM). To guarantee a well match with the 3-D construction where end effects occur, an equivalent circuit is built in the 2-D method to represent the uneven ring fractions. Simultaneously, considering the non-axial currents in core ends, conductivity of the solid-rotor segments in 2-D field is corrected by a multistep optimum-seeking technique. Calculation precision of the 2-D FEM covering end effects is certificated by the corresponding 3-D FEM with good results agreement. [ABSTRACT FROM AUTHOR]

Electromagnetic devices containing permanent magnet (PM) are common and typical electromagnetic devices that have advantages of low-power consumption, small size, high sensitivity, and its optimization problem has aroused widespread concern. Calculation accuracy of electromagnetic properties and efficiency of optimization processes are two important factors that affect the optimization effect of electromagnetic devices. A fast calculation method was proposed in this paper that aimed at electromagnetic devices with PM characteristics of strong non-linearity and low solving precision. The response surface method was used to derive the basis function, and the error between actual measured values and calculated values was modified by the Kriging method. On the basis of the calculation model, the distributed collaborative strategy was adopted to fulfill the parallel execution of the fast computation. Simultaneously, the updating strategy of particles was improved, and the robustness of the multi-objective particle swarm optimization algorithm in solving the optimization problem of electromagnetic devices with PM was enhanced. Effectiveness of the method proposed in this paper was verified by the case study of a specific type of electromagnetic relay with PM. [ABSTRACT FROM AUTHOR]

This paper provides an alternative approach to the finite elements method of solving magneto-static field for an efficient pre-design of electrical rotating machines. First, the 2-D volume integral formulation will be presented. Second, this formulation will be extended to periodic systems. Comparisons to the finite elements, methods will be carried out to conclude on the performances of the new method presented. [ABSTRACT FROM AUTHOR]

We have previously been proposed a novel adaptive finite-element method (FEM) based on a magnetic field conservation indicator and a non-conforming mesh-refinement technique. However, we have applied to a very simple model consisting of a single permanent magnet for basic verification of the proposed method. In this paper, we have improved an error indicator, and tried to apply a newly proposed adaptive FEM to more complicated models, where ferromagnetic material is included. The newly proposed method is superior in torque error estimation to the Zienkiewicz-Zhu error estimation method in a 3-D permanent magnet motor model. [ABSTRACT FROM AUTHOR]

In this paper, the robust control method is proposed for air-gap positioning of magnetic levitation systems considering levitation disturbance forces caused by propulsion systems. Even though the disturbance effect occurs inevitably by propulsion systems, it is very difficult or impossible to be measured by sensors in real time. In order to maintain the constant air-gap position according to the reference command in the propulsion state of the vehicle, robust control for electromagnetic suspension against levitation disturbance force is highly required. The disturbance force caused by propulsion systems is predicted by the finite-element method analysis of the magnetic flux distribution. Based on the analyzed result, the robust and optimal levitation controller is designed by the convex optimization method for the proposed proportional integral derivative controller with the inner feedback compensator stabilizing the nonlinear plant. The proposed controller has the formulation of the conventional full-state feedback optimal controller based on state-output matching for the unmeasured state. The effectiveness of the proposed controller is verified by simulation and finite-element method analysis. [ABSTRACT FROM AUTHOR]

This paper describes a method to reduce cogging torque in permanent magnet (PM) machines by shifting elementary-cogging unit (ECU). The ECU division principle and the feature of cogging torque produced by ECU are also discussed. The proper shift angles for each ECU are deduced according to both fractional and integral slot number per pole, by which any order harmonic cogging torque could be eliminated without the introduction of any new harmonic torque. This paper investigates the validity of the effectiveness of ECU shifting techniques using PM machines with different match of slot number per pole in 2-D finite-element models. [ABSTRACT FROM AUTHOR]

This paper presents an improved magnetic circuit (MC) model considering the leakage, cross coupling, and saturation effects for the performance analysis of an integrated 3 degrees of freedom magnetic bearing (3-DOF MB). Compared with the conventional MC model, this paper analyzes the permanent-magnet bias field, radial and axial control current fields together. By using this improved MC model, it reveals the cross-coupling effect between radial and axial directions in such an integrated 3-DOF MB. The stiffnesses of radial force are significantly influenced by the axial control current, while the stiffnesses of the axial force are independent of the radial control current. Its accuracy is verified by the 3-D finite-element method. [ABSTRACT FROM AUTHOR]

This paper aims to analyze the characteristics of a surface permanent-magnet Vernier motor (SPMVM) according to the pole ratio among the rotor magnet pole pairs, stator teeth, and winding pole number. The SPMVM has the same operational principle as a magnetic gear, and it is operated using the space harmonics of the air-gap flux density due to the magnetomotive force and air-gap permeance. In this paper, first, the design parameters of the SPMVM are specified based on an analytical calculation of the air-gap magnetic flux density. Moreover, various combinations of the rotor magnet pole pairs and stator teeth number are made and compared according to the operational principle of a Vernier motor using a 2-D finite-element method. [ABSTRACT FROM AUTHOR]

This paper manufactures a prototype of DC motor made of soft magnetic composite (SMC) core, and compares the motor efficiency with that of a motor made of the laminated core. Next, this paper develops a method for DC motor simulation, where the 2-D FEM is directly coupled with brush and commutator circuit. Finally, in order to improve the motor efficiency, eight geometry design parameters are optimized by using the experimental design method. The highest efficiency of the optimized motor is improved from 53.7% to 68.9%, that is, the improvement of 15.2%. [ABSTRACT FROM PUBLISHER]

Designing a high-frequency power transformer is a complicated task due to its multiple interrelation design procedures, large number of variables, and other relevant factors. Traditional transformer design relies on manual paper work and personal experience, which requires engineering design man-hours and long delivery cycles. In this paper, a developed transformer computer design environment is addressed. It helps engineers to automatically model, simulate, and optimize transformer design using an artificial neural network algorithm and the finite-element method, and delivers a reliable design result. Utilizing the proposed platform, an 8 kW coaxial transformer is successfully designed, tested, and manufactured. [ABSTRACT FROM PUBLISHER]

This paper proposes an optimal rotor design method of an interior permanent magnet synchronous motor (IPMSM) by using a permanent magnet (PM) shape. An IPMSM is a structure in which PMs are buried in an inner rotor. The torque, torque ripple, and safety factor of IPMSM can vary depending on the position of the inserted PMs. To determine the optimal design variables according to the placement of the inserted PMs, parameter analysis was performed. Therefore, a response surface methodology, which is one of the statistical analysis design methods, was used. Among many other response surface methodologies, Box–Behnken design is the most commonly used. For the purpose of this research, Box–Behnken design was used to find the design parameter that can achieve minimum experimental variables of objective function. This paper determines the insert position of the PM to obtain high-torque, low-torque ripple by using a finite-element-method, and this paper obtains an optimal design by using a mechanical stiffness method in which a safety factor is considered. [ABSTRACT FROM PUBLISHER]

This paper deals with an effective reduction method of torque ripple by adopting novel asymmetric pole structure of wound-field synchronous motor. In general, skewed pole structure of a rotor is used to reduce torque ripple despite decreasing an average torque. This paper introduces the design parameter of shift angle of an asymmetric pole-plate for effective elimination of torque ripple. In addition, the design can maintain the length of field winding compared with skewed pole structure, which means low copper loss in field winding and low material cost. In addition, average torque can be increased at the same input voltage over the driving region as well. The 2-D finite element method is used for the analysis of proposed model and skewed model. For the comparison of characteristics between the skewed model and proposed model, skewed pole with three steps is introduced with low torque ripple. [ABSTRACT FROM PUBLISHER]

In the numerical analysis of electrical machines, accurate computation of the electromagnetic torque is desired. Maxwell stress tensor method and Coulomb’s method are the most commonly used methods for computing torque numerically. However, several other methods have also been developed and are being used. These methods are observed to have several accuracy issues related to the finite element discretization used in the air gap of the machine. In this paper, the effect of various finite element meshes in the air gap of the machine and the effect of the shape of the elements used to compute the torque are studied and discussed. This paper carefully compares the torques obtained from a direct method and a method based on the power balance of the machine. [ABSTRACT FROM AUTHOR]

This paper focuses on the performance analysis of linear flux-switching permanent magnet (LFSPM) motor. The analysis of electrical machines is mostly done by finite element method (FEM) and analytical method. However, it is time-consuming to determine the effects of the design parameters on the motor performance with FEM. It is also difficult to utilize the analytical technique for the intricate structure of LFSPM motor. In this paper, the response surface methodology in conjunction with FEM is proposed to analyze the LFSPM motor efficiently. As a demonstration, the influence of design parameters on the motor net thrust force is analyzed with the proposed method. Analysis of variance and comparison between the fitted response and results obtained from FEM all confirm the validity of the proposed method. [ABSTRACT FROM AUTHOR]

Electro-quasi-static (EQS) field problems involving nonlinear materials are commonly discretized in space using finite elements. In this paper, it is proposed to solve the resulting system of ordinary differential equations (ODEs) by an explicit Runge–Kutta–Chebyshev time-integration scheme. This mitigates the need for Newton–Raphson iterations, as they are necessary within fully implicit time integration schemes. However, the EQS system of ODE has a Laplace-type mass matrix such that parts of the explicit time-integration scheme remain implicit. An iterative solver with constant preconditioner is shown to efficiently solve the resulting multiple right-hand side problem. This approach allows an efficient parallel implementation on a system featuring multiple graphic processing units. [ABSTRACT FROM AUTHOR]

This paper proposes a coupled analysis method to deal with ion generation and ion drift in the air. Electric discharge is utilized in various products, and it is very important to clarify not only how much ion is generated but also where ion drifts in the air. The proposed method, which modeled interactions between electric field and ion behavior, including ion generation, ion drift, and charging of a dielectric body, has succeeded in calculating charge removal of a metallic target, which was tens of millimeters away from a pin electrode as a source of generated ion. The calculated results show that the amount of generated ion is drastically changed because electric field is affected by electric charge of ion in the air and charging of a dielectric body. This paper also reports a comparison of measured and calculated results of charge removal time of a metallic target, which were found to be in good agreement. [ABSTRACT FROM AUTHOR]

This paper presents an efficient method to calculate the magnetic forces on bodies in contact. The forces are computed through the local application of the virtual work principle on degenerated air-gap elements. The results from this method are compared with those from other software and validated with measurements on a permanent magnet setup. Not only is this technique very accurate, but it also reduces the computational burden related to the problematic meshing of thin layers. The implementation of this method in an open source finite element software having facilities for higher order elements and parallel computation unlocks a cost effective and effectual platform for an electromechanical computation of electromechanical devices and magnetic materials. [ABSTRACT FROM AUTHOR]

In this paper, a lithium ion cobalt polymer battery cell is modeled using 3-D finite elements (3DFE) for the study of its performance under a wide range of operating scenarios. The electrochemistry is modeled and coupled to an electromagnetic model to forecast the cell voltage overpotential as a result of charging and discharging under six current densities. To study this phenomenon, light ( $C$ /10), medium ( $C$ /2), and high ( $1C$ ) charging and discharging currents are imposed at the battery terminals and compared with experimental results. The electric field inside the electrodes and electrolyte is analyzed at each case highlighting regions where loss occurs. A magnetic field analysis depicts the total electrochemical generation of current densities inside the cell while identifying how the development of gradient currents occur, a mechanism which can shorten the life span of the battery. This paper distinguishes where 3DFE analysis battery models can be useful in studying how lithium ion batteries will behave given a particular loading or a charging profile before placing them in service. [ABSTRACT FROM AUTHOR]

Proper generalized decomposition (PGD) is a recently developed model-order reduction method based on the use of variable-separated representations. In this paper, space variable-separated PGD is applied on the 3-D capacitance extraction of interconnects in integrated circuits to reduce its computational complexity. To make the PGD solver feasible, the complex boundary conditions are simplified by a characteristic function technique. 3-D singular-value decomposition of the coefficient functions is avoided by using a reformulated PGD algorithm, and therefore, the proposed method can effectively deal with problems with inhomogeneous dielectric layers and dummy fills. Numerical examples are given to verify the method. [ABSTRACT FROM AUTHOR]

This paper presents an electrodynamic/magnetorheological fluid (MRF)-based clutch activated using permanent magnets (PMs) attached to one shaft. During the electro-mechanical transient phase, when the two clutch shafts rotate at different speed, the PMs induce eddy currents on some conductive materials strategically placed in the system. The interaction between these currents and the magnetic induction produces an electromagnetic torque, which is added to that of the MRF, helping the clutch engagement in the start-up phase when an extra torque is necessary to overcome possible static frictions. Once the two shafts have reached the same speed, the eddy currents (and, consequently, the electromagnetic torque) vanish and the torque transmission is assured by the MRF only. The conductive material is arranged as a copper sheet and the performance of the device is investigated. The proposed clutch is analyzed using a 3-D finite-element code, which considers the $B$ – $H$ curve of the nonlinear materials (e.g., MRF, PMs, and ferromagnetic materials) and the movement of the different parts. Finally, in order to verify the finite element method model, some experimental measurements are performed on a prototype. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of low space order of the air-gap radial Maxwell pressures in surface permanent magnet synchronous machines with fractional slot concentrated windings. The air-gap Maxwell pressures result from the multiplication of the flux density harmonics due to magnetomotive forces and permeance linked to the magnet, the armature, and the stator slots and their interactions. One low space order is selected, and different approaches are compared to determine the origin of this pressure. First, an analytical prediction tool analytical calculation of harmonic force orders (ACHFO) is used to calculate the space and time orders of these magnetic pressure harmonics while identifying their origin in terms of interactions between magnet, armature, and teeth effects. In addition, the analytical prediction of ACHFO is compared with the flux density convolution and finite-element approaches. The main advantage of our tool is the speed of computation. Finally, an experimental operational deflection shape measurement is performed to show the deflection shape of the low space order selected. [ABSTRACT FROM PUBLISHER]

This paper presents the methodology and validation of high-frequency (HF) transformer simulations, which take into account the frequency dependence of the winding resistances and inductances. The parameters’ frequency dependence is approximated by curve fitting of the values computed by the finite element method (FEM) simulations in the frequency domain. After inverse Fourier transformation into the time domain, the convolution integrals are solved efficiently by the trapezoidal integration rule. The simulation results are validated using measurement data. [ABSTRACT FROM AUTHOR]

In order to calculate eddy current testing (ECT) signals due to a complex natural crack by using a regular mesh, the multi-media element (MME) was proposed by authors. In this paper, a new high-precision method for calculating the MME coefficient matrices is proposed and implemented in the finite-element method (FEM)–BEM hybrid code for ECT of narrow cracks. Through the comparison of the new MME solutions with those of the conventional FEM–BEM method, validity and efficiency of the new method and the corresponding numerical code are demonstrated. Eddy current perturbations and distributions of the magnetic flux density affected by a narrow crack of different directions are also numerically analyzed by using the new MME. In addition, the measurement results from the experiments give further support to the validity of the new MME method. [ABSTRACT FROM AUTHOR]

The soft magnetic composite (SMC), which consists of insulated iron particles, has been used for electric machines and devices. The magnetic permeability of SMC is underestimated when it is assumed that SMC is composed of homogeneous particles without magnetic contact. In this paper, SMC is modeled by the discrete element method, considering the inhomogeneity in particle size and contact among particles. It is shown that the measured permeability of SMC can be reproduced by considering these effects. Moreover, the frequency characteristics of SMC are evaluated by the proposed method, and the Ollendorff formula modified with an anomaly factor is introduced. [ABSTRACT FROM AUTHOR]

This paper presents the fast topology optimization methods for rotating machines based on deep learning. The cross-sectional image of electric motors and their performances obtained during a multi-objective topology optimization based on the finite-element method and genetic algorithm (GA) is used for training of the convolutional neural network (CNN). Two different approaches are proposed: 1) CNN trained by preliminary optimization with a small population for GA is used for the main optimization with a large population and 2) CNN is used for screening of torque performances in the optimization with respect to the motor efficiency. [ABSTRACT FROM AUTHOR]

The Cauer ladder network (CLN) method provides an efficient representation of eddy-current fields. This paper proposes a reformulation of the CLN method that considers expansion points using the magnetic/current vector potential. To cover a wide range of frequencies, the expansion point may be changed at a later stage of the network. Only a few stages of the ladder network are required for the eddy-current field to be reconstructed accurately around the target frequency using the expansion points. [ABSTRACT FROM AUTHOR]