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In this paper, a novel dual-rotor axial-gap flux-switching permanent-magnet machine with dc excitation winding is proposed. First, the topology and operation principles of the proposed topology are clarified. Basic design equations and parameters are provided, and the electromagnetic analyses of the proposed flux-switching machine with 3-D FEA are performed. Parametric optimizations using 3-D FEA are completed for different dc excitations. A prototype machine is manufactured, tested, and validated. It is shown that the air-gap flux of the proposed axial-gap machine can be controlled in a wide range compared to conventional surface magnet machines. [ABSTRACT FROM AUTHOR]

A semi-high-speed magnetic levitation (maglev) train with a maximum speed of 200 km/h is being developed in Korea. It utilizes linear induction motors for propulsion and adopts electromagnetic suspension for levitation. For high-speed operation, guidance systems should be adopted to stabilize the train especially on curved tracks. For compatibility of the rail with previously developed urban maglev trains, the installation of the guidance electromagnet has to be restricted to be placed near the levitation electromagnet. Owing to the spatial closeness, mutual magnetic flux by the levitation and guidance electromagnets is produced at an overlapping portion of the rail. For stable control of the two systems, the coupling effects must be analyzed, because the levitation and guidance electromagnets are not operated independently. This paper aims to analyze the coupling effects by considering the magnetic field and a magnetic equivalent circuit. This paper suggests levitation and guidance systems for the semi-high-speed maglev train by considering each electromagnetic characteristic depending on the current direction. [ABSTRACT FROM AUTHOR]

Advanced power systems for electromagnetic propulsion depend on capacitor banks as the first stage of pulsed power. Significant electrical energy is required to support a number of anticipated launch applications. In support of successful integration of these technologies, TPL has developed an improved dielectric material for high energy density capacitors. Recent developments have led to a novel dielectric film that can be fabricated and incorporated into innovative, high-voltage designs using conventional manufacturing processes. Full-scale (100 kJ) capacitors incorporating TPL's established film technology is projected to provide an energy density between 3.5 and 4.0 J/cm3. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the direct- and quadrature-axis inductances for linear tubular actuators with permanent magnet arrays, highlighting and featuring how they are affected by the end effects. A semi-analytical and an experimental analysis are performed to prove the influence of end effects on self- and mutual inductances. The synchronous parameters, i.e., d - and q -axis inductances of the actuator, are determined using a semi-analytical method and an experimental method. Once the synchronous parameters are all identified, high performance control methods (such as direct force control and vector control) may be implemented. [ABSTRACT FROM AUTHOR]

This paper presents the newly proposed heating method named “secondary current heating method” to reduce the iron loss on laminated electrical steel sheet cores for high-efficiency electrical motors. It is well known that the magnetic properties of electrical steel sheets, which are used for electrical motor cores, are deteriorated by the residual stress during manufacturing of the electrical motors, and then the iron loss of the laminated electrical steel sheet cores of the electrical motors increases inevitably. The newly proposed secondary current heating method can improve the magnetic properties on laminated electrical steel sheet cores and reduce the iron loss of them in the very short time in comparison with conventional methods. In this paper, the electromagnetic and heating characteristics of the specimens by the proposed method were confirmed, and then it was applied into the laminated cores to reduce iron loss. [ABSTRACT FROM AUTHOR]

Recently, dual-rotor motor (DRM) has emerged as an alternative for an induction motor (IM) or a permanent-magnet (PM) motor for electric vehicle application, due to its better drive performance and better torque density. This paper presents an analytical model for the hybrid IM-PM configuration of DRM. The analytical model can be used to predict induced bar currents, electromagnetic torque generated, and magnetic fields in various regions of the motor. The mentioned calculations are performed under steady-state conditions. The analytical method is developed using the subdomain model approach in 2-D polar coordinates. Appropriate governing equations along with boundary conditions across all the sub-domain regions of the DRM are employed to calculate the magnetic vector potential in all the regions. The developed analytical model has been validated with finite-element analysis for various operating conditions, and high accuracy has been achieved for all the results. [ABSTRACT FROM AUTHOR]

The article presents the authors' views on issues discussed at the 2005 Conference on the Computation of Electromagnetic Fields, which was held on June 26-30, 2005. The conference was important for the scientific community working in computational electromagnetics. It mainly dealt with numerical computation of electric fields. A total of 680 two-page papers were submitted for the conference. The authors tried to maintain a fair and uniform evaluation scale among reviewers, whose nationality differed from that of the authors.

In the case of designing high-speed surface-mounted permanent magnet synchronous motor (SPMSM), the rotor retaining sleeve is inserted into the rotor to prevent the permanent magnet’s damage. It is quite an efficient way to consider manufacturability, but the sleeve becomes the major source of ohm loss in high-speed operation. In this paper, the high-speed motor for a turbo blower at the rating of 100 kW, 20000 r/min was introduced. To improve its efficiency, the retaining sleeve’s optimal design was needed. For this, parametric analysis on the shape of the retaining sleeve was carried out in a different type of motor. Within a range that meets the mechanical safety, sleeve designs have been changed. The effect of changing design variables of the sleeve was studied. This paper presents the optimized sleeve’s advantages in electrical efficiency from the results of the electromagnetic finite element analysis software. Finally, it suggests the optimal sleeve design to reduce eddy-current loss, which is related to motor shape. [ABSTRACT FROM PUBLISHER]

In this paper, different ways to compute electromagnetic source fields for non-meshed coils will be described for magnetic vector potential \mathbf A and electric scalar potential V formulation ( \mathbf {A}- V formulation). The originality of this paper is demonstrated by the source computations for \mathbf {A}- V formulation with non-meshed coils. Usually, coils for \mathbf A- V formulation are meshed, and non-meshed coils are studied with reduced magnetic vector potential \mathbf Ar and electric scalar potential V formulation ( \mathbf {A}_{r}-V formulation). Different source computations for \mathbf {A}- V$ formulation will be applied on an induction machine with non-meshed coils. [ABSTRACT FROM PUBLISHER]

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

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

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

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

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

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 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]

The results of the 3-D finite-element method electromagnetic analysis of the constant speed variable output permanent magnet synchronous motor including the rotor retaining plate structure confirmed that the eddy current flow was induced in the rotor part. Eddy current flows from the permanent magnet to the rotor retaining plate, and it was found that there is induced voltage that generates eddy currents in the retaining plate from the aspect of eddy-current distribution. The eddy current flow from the permanent magnet to the retaining plate is related to the change in magnetic resistance during rotation and is also related to the effect of slot harmonics on the air-gap magnetic flux density. In this paper, the characteristics of the eddy current flow in the rotor assembly were investigated when the retaining plate is included for various slot combinations. The eddy-current generation according to the slot combination is analyzed and the cause of such tendency was investigated. Furthermore, from the pattern of eddy-current formation, it was noted that the aperiodic pole–slot combination models may have a larger eddy-current loss increase when combined with the retaining plate. [ABSTRACT FROM AUTHOR]

This paper deals with the determination of parameters in the motor module of advanced vehicle simulator (ADVISOR) which is an advanced vehicle simulation software. In the ADVISOR, the traction motor of vehicle is defined by efficiency map, maximum torque/speed curve and so forth. Due to the prevalence of interior permanent magnet synchronous motor (IPMSM), this paper mainly focuses on the calculation of efficiency map of IPMSM considering magnetic nonlinearity. Firstly, by means of numerical methods, the inductance and iron loss resistance are calculated. Next according to equivalent circuits, the motor characteristics including speed, torque and efficiency are investigated. Finally, the calculated efficiency result is verified by the experiment data, and all parameters are loaded and implemented in ADVISOR for testing. [ABSTRACT FROM AUTHOR]

This paper systematically presents the development of novel stator electrically field excited synchronous machines having salient pole rotors without any coils or magnets. This kind of new machine does not use slip-rings/brushes required in the conventional rotor wound field machines and combines the synergies of wound field machines, permanent magnet (PM) machines, switched reluctance, and synchronous reluctance machines. This paper describes the machine topologies, winding configurations, electromagnetic performance, and torque/power density, as well as acoustic noise and vibration, together with a comparison with the Toyota Prius interior PM machine in terms of torque/power speed characteristics. [ABSTRACT FROM AUTHOR]

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 presents the characteristic analysis and experiment of surface-mounted type variable-flux permanent-magnet machines considering magnetization and demagnetization based on electromagnetic transfer relations. For this purpose, we derive the analytical solutions for the magnetic fields generated by the magnetization level of AlNiCo magnets and currents on the basis of the transfer relations in terms of a 2-D polar coordinate system. The magnetization levels of the AlNiCo magnets are determined by the magnetic fields generated by the armature reaction field. A 2-D permeance function is also introduced to consider slotting effects. The analytical results of the magnetic field are validated extensively with finite-element (FE) analyses. On the basis of these solutions, the induced voltage is also determined analytically. Finally, the predictions are compared with FE analyses and measured data to confirm the validity of the analysis methods presented in this paper. [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]

Magnetic shape memory (MSM) alloys are relatively new smart alloys, which have enormous potential to be used in actuators, sensors, and other electrical devices. Their large strain and considerable stress output can be controlled by magnetic fields or mechanical stresses. Maximum magnetic field-induced strain varies from 6% to 12% of the MSM element’s length depending on its microstructure. However, very low operational temperature limit is one of the main drawbacks of conventional MSM alloys. This makes their application in high-performance actuators challenging due to considerable power losses. This paper discusses different MSM actuator designs, optimized particularly for large force output for pneumatic electromagnetic valve applications. The thermal problem is addressed through analyzing the heat transfer conditions of each particular design and the effects of different cooling systems. An energy-efficient operating cycle for varying actuator loads that takes advantage of the shape memory effect is also proposed. This allows the minimization of energy losses, resulting in an acceptable increase in the temperature ensuring stable continuous actuation. [ABSTRACT FROM AUTHOR]

The paper presents a new method to solve the electromagnetic field in 2-D cylindrical geometries. The method is based on the analytical solution of the magnetic potential. The method can be used to compute inductor or transformer winding resistance or leakage inductance with high accuracy up to several megahertz. The proposed method assumes no simplification of the problem, and then achieves higher accuracy than the classical method such as homogenization techniques. The method requires no meshing unlike finite-element analysis (FEA) resulting in shorter computation time. The method is compared with FEA on the bifilar line. The method overperform existing methods in terms of accuracy and computation time. [ABSTRACT FROM AUTHOR]

This paper presents a new numerical and experimental method of the electromagnetic vibration analysis of amorphous alloy (AA) permanent magnet synchronous machines (PMSMs) whose stator cores are made from AA materials. A numerical model which is used to calculate the electromagnetic vibration of AA PMSMs is developed on an experimental basis. Concerning the magnetic performance of AA cores greatly affected by stresses and the elasticity modulus parameters affected by the loose structure of AA cores, data for magnetostriction (MS) curve of AA materials and magnetization curve of AA-stacked core are obtained experimentally, and the elasticity modulus parameters are updated based on the modal testing of the AA-stacked core. The electromagnetic vibration of a 2.1 kW radial flux AA PMSM is analyzed using the proposed calculation method. The electromagnetic vibration of the AAPMSM under two different conditions, which are 1) only radial forces (RFs) and 2) both RFs and MS, is calculated, respectively; then, the effect of MS on the electromagnetic vibration of the AA PMSM is obtained. The accuracy of the calculation method is verified by comparing the calculated results with the experimental results. [ABSTRACT FROM AUTHOR]

This paper introduces a novel hybrid-excited stator slot opening permanent magnet (PM) machine (HSSPMM). The operation principle of the machine is described and the effects of rotor eccentricity and magnetic saturation due to PMs on electromagnetic performance, with particular emphasis on back electromotive force (EMF), are analyzed by finite element method (FEM). It shows that different from the conventional PM machines, the open-circuit back EMF in this novel HSSPMM should be zero but may become non-zero if significant magnetic saturation exists, and furthermore, the rotor eccentricity has a detrimental effect on the waveforms, amplitudes, and symmetries of three-phase back EMFs, as confirmed by FEM and tests. [ABSTRACT FROM AUTHOR]

A revolution in power transmission and distribution, driven by environmental and economic considerations, is occurring all over the world. This revolution is spearheaded by the development of the smart grid. The smart grid is bringing profound change to both the power systems and many related industries. This paper reviews the development of the smart grid and its correlation with magnetics, including electromagnetic compatibility issue, magnetic-field-based measurement/monitoring, and magnetic energy storage/conversion. The challenge to the field of magnetics and the usage of the cutting edge magnetics technology in the development of the smart grid are discussed. This paper enables researchers in the magnetics community to be acquainted with the progress in the smart grid and inspires innovative applications of state-of-the-art magnetics technologies in the smart grid. [ABSTRACT FROM PUBLISHER]

The simulation of coupled electromagnetic/thermal problems with high resolution requires efficient numerical schemes. High-performance computing languages like CUDA help in unlocking the massively parallel capabilities of graphic processor units (GPUs) to accelerate those calculations. This reduces the time needed to solve real-world problems. In this paper, the speedup is discussed, which is obtained using NVIDIA's recently presented Kepler architecture as well as by GPU-accelerated algebraic multigrid preconditioners. In particular, extended memory allows for the solving of larger problems with more degrees of freedom without swapping. We discuss a new host-based multigrid setup for GPU-accelerated iterative solvers. [ABSTRACT FROM AUTHOR]

Computing the first cohomology group generators received great attention in computational electromagnetics as a theoretically sound and safe method to produce cuts required when eddy-current problems are solved with the magnetic scalar potential formulations. This paper exploits the novel concept of lazy cohomology generators and a fast and general algorithm to compute them. This graph-theoretic algorithm is much faster than all competing ones being the typical computational time in the order of seconds even with meshes formed by millions of elements. Moreover, this paper introduces the use of minimal boundary generators to ease human-based basis selection and to obtain representatives of generators with compact support. We are persuaded that this is the definitive solution to this long-standing problem. [ABSTRACT FROM AUTHOR]

The selective passively compensated pulsed alternator has wide applications in military and civil areas such as power source for electromagnetic launch, electrothermal chemical gun and plasma sprayed coating. It can produce wide range of current waveforms realized by shorted compensating windings. In this paper, two cases of winding arrangements and their corresponding circuit models are presented to further discuss on the power waveform regulations. The effects of the phase angles between different windings and the switching time on the pulsed power are presented in this paper as well. The results indicate that the output power waveform is possible to be regulated flexibly especially through the new winding arrangements proposed in this paper. This work may extend the applications of selective passively compensated pulsed alternator where different output waveforms are required. [ABSTRACT FROM PUBLISHER]

The strong correlation between the level of eddy current losses and the winding geometry shows the necessity to pay attention to the manner of disposition of coils in machine slots. The conductor type, whether it is solid or stranded, also has a crucial influence. This paper suggests an electromagnetic analysis of complex stranded conductors, such as litz wire (LW) and twisted wire. Each conductor is composed of individual strands that are woven or twisted in the slot throughout the machine length. Combined with several electric circuit relationships that interpret the strands transposition, a 2-D finite-element (FE) model is developed in this paper so that the copper losses in each strand can be calculated individually. A model reduction is also proposed in the case of LWs. This allows the benefit of only one complete FE solution to find fast solutions in the slots’ domains when any variation of geometrical data occurrs. It allows adapting non-conforming subdomains’ meshes and seeing that it prevents the Newton–Raphson iterations and the moving band technique, the model reduction presents clear interests in repetitive analysis, such as winding optimization processes. [ABSTRACT FROM AUTHOR]

Electromagnetic levitation is a kind of magnetohydrodynamic phenomena, which is used for measuring the thermophysical properties of pure metals under high temperature. However, this phenomenon is complicated, and detailed mechanisms have not been clarified yet. This paper proposes the meshless method based on weighted least square method for the analysis of electromagnetic levitation. In this method, the fluid motion equation and the magnetic field equation are weakly coupled. The effectiveness of this method is verified through the analysis of the molten metal behavior. [ABSTRACT FROM AUTHOR]

This paper focuses on the 3-D effects associated with rotor step-skews performed in permanent magnet-assisted synchronous reluctance machines (PMA SynRMs). It analyzes and quantifies these effects via comparisons between 2-D and 3-D finite-element analyses (FEA) of skewed and unskewed machines. The 3-D phenomena manifested in the skewed PMA SynRM are identified into end-effects and axial interactions between skewed steps, and their influence on its electromagnetic performance is examined under load and no-load conditions. This paper exemplifies the significance of the skew-associated 3-D effects, which can result in considerable decrease of the back electromotive force and a substantially increased electromagnetic torque ripple. It, thereby, highlights the inability of the typically employed multislice 2-D FEA or other existing 2-D-based modeling techniques in taking their influence into account. The validity of the findings is experimentally verified with measurements acquired from a prototype PMA SynRM using skewed and unskewed shafts in the rotor. [ABSTRACT FROM AUTHOR]

This paper presents a methodology based on multiobjective evolutionary optimization and a phase control scheme to design a microwave heating applicator for water sterilization. The optimization problem is formulated in terms of two objective functions: one to maximize the amount of water and the other to minimize the energy spent. The device is modeled as a lossy dielectric multilayer irradiated by two microwave sources. The phase control is done by allowing one of the sources to move. By applying the developed methodology, an efficient applicator is obtained. [ABSTRACT FROM PUBLISHER]

When applied to the topology optimization of electromagnetic devices, gradient-based algorithms suffer from a lack of convexity. They usually converge to local minimizers and the obtained designs depend on the initial material distributions. This paper focuses on avoiding these local minimizers for the optimization of ferromagnetic moving parts in electromagnetic actuators. The proposed method intends to maximize the average reluctant force computed from the difference of magnetic energy between two positions of the ferromagnetic part. It relies on a problem relaxation: distinct design variables are defined to describe the ferromagnetic part in each position. Thanks to convexity-oriented constraints, the differences between the two obtained topologies are progressively reduced in order to converge towards the optimal design. The paper besides highlights sensitivity issues related to the high permeability of iron and recommends using a geometric mapping to guarantee a fast convergence. The efficiency of the method is underlined for the design of the rotor of a switched reluctant actuator. The method succeeds in avoiding local minimizers and producing efficient topologies. The method is then combined with another method dedicated to the design of parts composed of iron and coils in order to realize the global optimization of the actuator. [ABSTRACT FROM AUTHOR]

There are many kinds of electromagnets for various kinds of fields. The electromagnet with permanent magnets in this paper is one of them in order to improve energy saving. The distribution of flux density is very complex when the voltage is applied to the coil of the electromagnet with permanent magnets. In this paper, the operating characteristics of the electromagnet with permanent magnets are analyzed using the three-dimensional finite element method. [ABSTRACT FROM AUTHOR]

This paper is focused on the on-load back-electromotive force (EMF) assessment in a permanent magnet synchronous machine (PMSM) using Maxwell stress tensor along with the frozen permeability method (FPM). Although the back EMF is only measured at open-circuit condition, it is known that the on-load back EMF is heavily affected by electric loading and magnetic saturation. Since the main torque component of the PMSM is the mutual torque and it is based on the interaction between the back EMF and stator current, any distortion in the on-load back EMF will affect the electromagnetic torque and increase the torque ripple. A misleading on-load back-EMF waveform with some spikes around the commutation points is found if the on-load back EMF is assessed by means of differentiating the on-load PM flux linkage. This way, this paper proposes a new numerical method to assess the on-load back EMF in order to avoid all the shortcomings of the existing method. First of all, a quick review on the results achieved by other researchers is shown. Next, a review on the FPM is done in order to clarify the points where this method will be changed to overcome the drawbacks highlighted previously. Furthermore, a new method is introduced and explained in small details. Finally, the results for different rotor configurations and different electrical loads are presented in order to validate the proposed method’s accuracy against experiments and other numerical techniques. [ABSTRACT FROM AUTHOR]

A mixed finite-element method based on constant transversal and linear normal element and standard linear element, linear transversal and quadratic normal element, and standard quadratic element is used to solve the closed waveguide problem filled with anisotropic media. This numerical method is free of nonphysical modes for solving the closed waveguide problem, which is governed by both electric field and magnetic field. Numerical experiments show that the numerical propagation constants for TEM modes are of high accuracy, and the numerical method given in this paper can support an effective interval for the exact propagation constants of hybrid modes in the waveguide; hence, it is easy to know the numerical accuracy of the approximate propagation constants for the hybrid modes. [ABSTRACT FROM AUTHOR]

Transcranial magnetic stimulation (TMS) is a painless, non-invasive brain nerve stimulation technique, which has been a common diagnosis and treatment method for psychiatry and neurology in recent years. Compared with traditional single-channel magnetic stimulation coil, multi-channel coil array can achieve multi-point synchronous stimulation, scanning stimulation, and flexible switching of various stimulation patterns. Therefore, it has a great development prospect. However, the multi-channel TMS device is still in experimental stage due to the complexity of the drive circuit and the electromagnetic coupling between the coils. Aiming at these two difficulties, this paper developed a novel multi-channel TMS device. By using two closely linked coils with opposite rounded direction to replace one coil, the complexity of the drive circuit can be greatly reduced. Then, the experiment was taken to study the effect of electromagnetic coupling on pulse current in different stimulation patterns. The results show that the coupling coefficient between the adjacent coils limits the minimum amplitude ratio of the auxiliary current to main current. Therefore, the measure of reducing the coupling coefficient was studied in detail. Adding a 6.5 cm-high and 1 mm-thick copper plate in the middle of the adjacent coils was proven to be effective by simulation and experiment. [ABSTRACT FROM AUTHOR]

Four modular permanent magnet linear machines (PMLMs) with E-core and C-core primary segments and 12-slot/13-pole (12s/13p) and 12-slot/14-pole (12s/14p) slot/pole combinations are compared in this paper. The influences of flux gap width on the electromagnetic performances and power losses have been investigated based on 2-D finite-element modeling. It has been found that, by choosing proper flux gap width, not only the average thrust force can be improved but also the force ripple and iron losses can be reduced for all the machines. Also, the E-core modular PMLM has higher thrust force and lower detent force compared with the C-core modular PMLM with respect to the same slot/pole combination. Moreover, the 12s/13p modular PMLMs can achieve better electromagnetic performances than the 12s/14p ones regardless of E-core or C-core primary structures. Finally, by shaping the end teeth, the detent force and force ripple of the four modular PMLMs are further mitigated. The 12s/13p E-core modular PMLM is proven to be the best type among these four modular machines. [ABSTRACT FROM AUTHOR]

Electromagnetic (EM) brakes are gaining importance in aerospace vehicles for various critical applications. In guided missiles, they are primarily used for locking the actuator when the missile is in carriage either by road or by air such that the position of the actuator is not changed when servo is in the off condition. In this paper, a new EM brake is designed which is more energy efficient and reliable compared to a conventional solenoid operated brake. The nonlinear magnetic analysis is carried out on the brake, and the hardware is realized and tested. The test results are promising and this topology can be adapted for aerospace and other critical applications. [ABSTRACT FROM AUTHOR]

In this paper, a permanent magnet (PM) slotless tubular linear generator based on magnet field analysis model is presented for wave energy conversion. To improve air flux density and efficiency of the generator, two improved Halbach PM Arrays (T-PM structure and claw-PM structure) applied in the slotless linear generator is proposed and compared with Halbach PM Arrays. Combined with axisymmetric dimensional finite-element method (FEM), no-load electromagnetic performance is analyzed. Finally, due to test and analysis model results of prototype concordant with the FEM results, the generator model and the analysis method are correct. [ABSTRACT FROM AUTHOR]

This paper explores some of the key electromagnetic design aspects of a synchronous reluctance motor that is equipped with single-tooth windings (i.e., fractional slot concentrated windings). The analyzed machine, a 6-slot 4-pole motor, utilizes a segmented stator core structure for ease of coil winding, pre-assembly, and facilitation of high slot fill factors (~60%). The impact on the motors torque producing capability and its power factor of these inter-segment air gaps between the stator segments is investigated through 2-D finite element analysis (FEA) studies where it is shown that they have a low impact. From previous studies, torque ripple is a known issue with this particular slot–pole combination of synchronous reluctance motor, and the use of two different commercially available semi-magnetic slot wedges is investigated as a method to improve torque quality. An analytical analysis of continuous rotor skewing is also investigated as an attempt to reduce the torque ripple. Finally, it is shown that through a combination of 2-D and 3-D FEA studies in conjunction with experimentally derived results on a prototype machine that axial fringing effects cannot be ignored when predicting the q-axis reactance in such machines. A comparison of measured orthogonal axis flux linkages/reactances with 3-D FEA studies is presented for the first time. [ABSTRACT FROM AUTHOR]

This paper explores the tradeoff between the electromagnetic and mechanical performances with regard to the design of a synchronous reluctance machine rotor with fine features in the lamination profile—the analyzed machine consists of four rotor poles and its stator is equipped with single tooth coils. The change in the electromagnetic characteristics of the d - and q -axis reactances is explored for variation in radial and tangential rib widths and the impact of increased rib width on the saliency ratio of the machine. It is shown that the increased radial and tangential rib widths impair electromagnetic performance, with the tangential rib having the most pronounced effect on performance in this rotor design. The mechanical performance of the design is also explored in a similar manner, where it is shown that the high stress concentration in the rotor radial and tangential ribs limits the maximum speed of the machine in the field weakening region. The radial rib is found to have the dominant impact on supporting the flux guides. It is shown that the prototyped machine can achieve good electromagnetic performance while maintaining mechanical integrity up to a 25% overspeed of 10 000 r/min with features as small as 0.3 mm. Additionally, the challenges associated with manufacturing, selecting a higher rotor pole number, and the possibility of mechanical failure are also discussed in the context of electromagnetic–mechanical design of such rotors, with important avenues of further research suggested. [ABSTRACT FROM AUTHOR]

This paper proposes a principle to regulate the high-efficiency region of permanent magnet (PM) machines according to a given driving cycle. The key of this method is to establish the relationship between the highest efficiency point and the other around four points (top, bottom, left, and right points). Then, the loss (e.g., copper loss, iron loss, and PM eddy current loss) combination of these points is obtained. By optimizing the loss matching of these points, the high-efficiency region can be adjusted to be suitable area for a given driving cycle. In order to verify the effectiveness of proposed principle, a 12-slot 10-pole surface-mounted PM machine based on finite-element method is built, and several loss regulation methods are demonstrated. The results shows that the high-efficiency region can move from high-torque area to low-torque area according to the demand. [ABSTRACT FROM AUTHOR]

In this paper, one novel heteropolar radial hybrid magnetic bearing (HRHMB) is proposed for flywheel energy storage system. First, its structure and working principle are introduced in detail. Then, its fundamental equations are derived based on magnetic circuit model, such as displacement stiffness, current stiffness, and load capacity. Furthermore, its suspension performance and magnetic coupling are analyzed based on the 2-D finite-element analysis. Finally, the comparison of main performance indexes between the proposed HRHMB and conventional one under the same constraints is made. It indicates that the displacement stiffness can be reduced by the novel structure. In addition, the rotor core loss of the novel HRHMB is just 22.53 W, which is only 41.6% of the conventional eight-pole HRHMB with the same load capacity. [ABSTRACT FROM AUTHOR]

Human motion energy harvester can offer clean and continuous power, and therefore plays an important role in powering mobile devices, which suffer from short standby time because of the limited capability of the battery. In this paper, we investigate an electromagnetic resonance wearable kinetic energy harvester, which is comprised of an oscillator and a carbon fiber tube with two coils wound on its surface. The oscillator is comprised of a columnar PM connected to the two end covers with two elastic strings. The designed resonant frequency is 8–10 Hz, which is higher than the major frequency range of human motion (2–4 Hz), but it can absorb high frequency energy of impulse, such as footfall. Thus, the harvester can wear on legs to absorb the kinetic energy of footfall by resonance. The ferrofluid is adopted to decrease friction, which is one of the main challenges for improving efficiency of this type of energy harvester. The ferrofluid prevents the PM from touching the wall of the tube resulting in significant friction reduction. The FEM simulation results indicate that the ferrofluid can keep the vibrator (a permanent magnet) contactless even subjecting to ten times gravity acceleration. The maximum average output power of 9.5 mW is obtained with a total weight of 80.5 g when running at a speed of 10 km/h. A energy harvest circuit is carried out and an average power of 0.28 s can be stored. [ABSTRACT FROM PUBLISHER]

The complete electromagnetic-mechanical-thermal modeling approach is demonstrated on the Thomson’s levitating ring experiment. This problem, but with a different set of parameters, was also described by Laithwaite and defined by Freeman and Lowther as TEAM17 problem. This paper presents its most complete solution. The factors for determining the vertical displacements and influence of the height of the ring are explained. The whole apparatus is explained in detail so that an accurate computer model can be made. The model introduced is validated against measurements and transient finite-element method (FEM) solvers. All the results prove the applicability of using steady-state FEM analysis with lumped parameter approach for a fast and effective fully coupled modeling. [ABSTRACT FROM AUTHOR]

Researches on the biomedical wireless microrobot are being actively carried out. In particular, compared with conventional catheter intervention, the wireless locomotive microrobot using an electromagnetic navigation system (ENS) can have many advantages in ischemic heart disease therapy. The ENSs generally use a uniform magnetic field and gradient magnetic field for the actuation of microrobots. However, because most ENSs require many coils, they have severe limitations, including a complex structure, large energy consumption, increased power supply, and large system volume. This paper proposes a new ENS for a 3-D locomotive microrobot using only four electromagnetic coils. The proposed ENS has a very simple structure, which consists of two circular coils and two saddle coils. The alignment and propulsion of the microrobot are determined by the generated magnetic field and gradient magnetic field from the four coils. This paper proposes a control algorithm and a gravity compensation for a 3-D locomotive microrobot and validates the performance of the microrobot using the proposed ENS. Finally, through a locomotion test of a blood vessel phantom, it was demonstrated that the microrobot can move to a target position in the phantom and deliver a drug to the target lesion. [ABSTRACT FROM AUTHOR]