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An increasing need for fast and reliable models has led to a continuous development of Fourier-based (FB) analytical modeling. This paper presents an overview of the techniques that are currently available in FB modeling for electric machines. By coupling that overview to the most relevant literature related to the subject, an interesting starting point is provided for anyone who wants to use or improve FB models. The following seven aspects of FB models are discussed in detail: 1) the magnetic potential (scalar or vector potential); 2) the coordinate system and the solution of the partial-differential equations for each magnetic potential and for each coordinate system; 3) the way in which time dependence is accounted for; 4) the implementation of the source terms; 5) the possibilities to account for slotted structures; 6) the modeling of eccentricity; and 7) the post-processing computation of physical quantities, such as flux density, electromotive force, torque, losses, and eddy currents in conductive objects. Furthermore, this paper gives the closed form solution of the Laplace, Poisson, and Helmholtz equations in each coordinate system. In addition, this paper tackles other important features of FB models such as computational time reduction and coupling the machine model to an electric circuit. [ABSTRACT FROM AUTHOR]

This paper proposes an all-in-one system for hyperloop that conducts propulsion, levitation, and guidance. Currently demand on high-speed long-distance transportation is increasing, so that hyperloop is getting attention and studied hard globally. Hyperloop is a new innovative transportation in which a levitated subsonic speed train travels through a vacuum cylindrical tube. Hyperloop needs functions of propulsion, levitation, and guidance for its service, and many devices are necessary for those functions. In the tube, a constrained space, many devices make the entire system complicated, and the size of the vehicle and tube are increased. Therefore, the costs of maintenance, manufacture, and construction are increased and control of each device becomes very difficult. But a non-symmetric double-sided linear induction motor (NSDLIM), the subject of this paper, is an all-in-one system that could conduct all functions. In this paper, the concept of NSDLIM was introduced and its possibility was suggested. Requirements of NSDLIM were investigated considering very high acceleration, velocity, and low air pressure. An NSDLIM model was designed and analyzed by using the finite-element method. Then, NSDLIM parameters that affect performance were investigated and adjusted to improve performance. The derived model performance was shown, and its possibility was considered. [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]

On the wheel-rail supported hybrid railway system, the linear synchronous motor (LSM) for very high-speed transit must be a system that can maintain a large air gap, and the maximum vertical displacement must be taken into consideration in designing the LSM. As such, this paper designs two small-scale LSM models that produce equal output power—one with the normal-conducting magnet and the other with the superconducting magnet. In addition, this paper conducts a comparative analysis of the various characteristics by applying the electromagnetic numerical analysis method. Furthermore, this paper manufactures two small-scale LSM prototypes which have the normal-conducting magnet and the superconducting magnet, while also conducting a no-load and load test. Through such comparisons, this paper attempts to verify the characteristic values of the two models. [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]

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]

For the safety of the wound-rotor synchronous machine (WRSM) in aircraft applications, the overvoltage at the motor terminals, electromagnetic interference (EMI) performance, and bearing currents as well as the loss analysis are the core areas to be addressed. The high-frequency (HF) modeling method of the WRSM, which has a strong relationship with all these core areas, is a very critical theme. In this paper, a measurement-based wide-frequency (WF) modeling method to characterize the impedance of the WRSM is proposed to build a straightforward correlation between fundamental models and HF parasitic circuit elements. In this paper, the voltage-behind-reactance method is applied to demonstrate the rotor-angle-dependent characters in the low-frequency domain, while the vector fitting method is used to parameterize the HF branch for high-accuracy consideration. By doing this, a WF electrical model with multistage RLC units is formed, which comprehensively considers both the saliency character of the machine and frequency range. The WF model is also compatible with the circuit-based simulation. Finally, the EMI prediction orientated simulation and experimental results are implemented on a 10 kVA WRSM prototype to verify the correctness and advantages of the proposed modeling method. [ABSTRACT FROM AUTHOR]

Rotary-linear switched reluctance motors (RLSRMs) have been introduced to realize simultaneous rotary and linear motions in one structure. This paper proposes the modeling of RLSRM in two manners: analytical and finite-element methods. In the first approach, a model is proposed based on position-wise functions which describe the governing equations of the motor. The derived equations are utilized in a block diagram to comprise the model. In the second approach, static FEA is utilized to improve the former model by obtaining the inductance profile of the motor. The models separate the rotary motion from the linear motion in order to calculate the torque and force. The analytical model is faster than the FEA-based model because of the independency to FEA. However, it is less accurate. The FEA-based model needs prior static FEA and considers the fringing and saturation effects more accurately. The FEA-based model is computationally more efficient than the 3-D transient FEA. The motor’s performance parameters obtained via the models versus the 3-D transient FEA as well as the experimental test results indicate the accuracy and efficiency of the proposed models. [ABSTRACT FROM AUTHOR]

This paper is a study on the application position of skew in order to reduce the cogging torque of a magnetic geared synchronous motor (MGM). The cogging torque affects the noise and vibration of the motor, so it should be reduced as much as possible. To solve this problem, a conventional permanent magnet (PM) synchronous motor is skewed to a PM. However, unlike other synchronous motors, the MGM has pole pieces (PPs), and a larger cogging torque is generated due to a larger reluctance difference. There have been few studies on the reduction of cogging torque of MGM, so it is essential to study the skew structure of MGM. Therefore, this paper has derived the optimum skew method by comparing and analyzing three models of MGM skewed to PM, PP, and PM and PP simultaneously. [ABSTRACT FROM AUTHOR]

In recent years, the increasing need in small satellite solutions triggers the miniaturization of attitude control systems. Reaction spheres were proposed as promising replacements of conventional reaction wheels for their $4\pi $ rotations. Since the generated control torques could be about any desired axes, a single reaction sphere is sufficient for three-axis stabilizations of spacecraft. This paper presents an innovative design of reaction spheres. Its driving unit is a combination of permanent magnets (PMs) and electromagnetic induction. This enables the generation of torques about three principle axes simultaneously. Meanwhile, a contactless bearing is integrated into the actuator design. Detailed designs and working principles of the reaction sphere are described. To investigate performance characteristics of the actuator, field modeling is of great importance and provides the basis for dynamics modeling. In this paper, an improved analytical model for dynamic fields excited by slotless distributed windings is presented for the first time. To study the cross coupling between PMs and electromagnetic induction, the static field generated by PMs is also modeled analytically. These developed models are validated through comparisons with numerical simulations. Electromagnetic torques generated by the actuator are calculated through the approaches of the Maxwell stress tensor and the Lorentz force law. Torque calculations based on the analytical field models deviate from those based on the numerical model slightly, with the maximum error within 4%. This means the presented analytical models allow to predict the electromagnetic field distribution and torques precisely. [ABSTRACT FROM AUTHOR]

In this paper, the iron loss models for electrical machines are first reviewed. One of the most accurate iron loss models, when the temperature is constant, is identified. An improved temperature-dependent iron loss model is also introduced. By applying the improved iron loss model to the electrical machine thermal analysis, the thermal and loss analyses can be fully coupled. Based on this, an improved thermal-loss coupling analysis method for electrical machine is developed in this paper. The electrical machine iron loss tests are carried out. The analysis and measurement results are then compared in order to validate the improved thermal-loss coupling analysis method. The comparison results indicate that the temperature prediction accuracy can be significantly improved by using the improved thermal-loss coupling analysis method. [ABSTRACT FROM AUTHOR]

This paper deals with an analytical model of the virtual air gap (VAG) function in order to define design rules when this technique is used inside complex devices. The establishment of those design rules constitutes the main originality of the developments presented in this paper, which are about a single-phase magnetic core. It is based on the definition of a nonlinear reluctance network that takes simultaneously into account the effects of dc and ac magnetic flux components in the disturbed area that contains the VAG. The results are validated using a finite-element analysis and experimentally. [ABSTRACT FROM AUTHOR]

The use of power electronics has led to a growing importance of higher time-harmonic content in electrical machines. To gain insight in phenomena related to these higher harmonics, such as noise and losses, a good understanding of the magnetic field’s harmonic content is mandatory. Moreover, the development of fast and accurate, harmonic-based, analytical models requires a qualitative knowledge of the machine’s time- and spatial-harmonic content. Although the harmonic content of electric machines is an extensively studied topic, previous publications tended to focus on one type of synchronous machines and often did not consider higher time-harmonic orders. This paper complements the existing theory by providing a more general approach, thereby covering machines and operating points that were not covered until now. It considers both three-phase and multi-phase machines with an odd number of phases. The winding distribution can either have an integer or a fractional number of slots per pole and per phase, and higher time-harmonic content is regarded as well. Note that the saturation is neglected. Despite its general validity, this paper succeeds at providing one simple equation to determine the machine’s time-and spatial-harmonic content. Moreover, this paper also extensively discusses the physical causes of the harmonic content. The combination of this general validity, the simple result, and the insight in the physics makes that this paper is a strong tool to both study harmonic-related phenomena in electric machines and to develop harmonic-based analytical models. [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]

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

The isolation bandwidth of zero stiffness permanent magnet bearing (ZSPMB) is limited by the stiffness variation near the zero stiffness point. This paper proposes an accurate and effective modeling technique to analyze and optimize the stiffness of ZSPMB in working range. Since the stiffness of ZSPMB is very sensitive to modeling errors, the variable current model of the permanent magnet is first derived considering magnetic permeability, the influences of which on the magnetic field and force are attributed to the reluctance effect in this paper. Then, the force exerted between permanent magnets (PMs) is equivalently decomposed into Lorentz force and reluctance force. Based on the Biot–Savart law and elliptic integral, the magnetic field of rings with axial, radial magnetizations and the equivalent Lorentz force (ELF) of typical ZSPMB topologies are calculated analytically. The equivalent reluctance force (ERF) is subsequently obtained by combining the finite element method. Compared with the ELF, the ERF is about one order of magnitude smaller and in the opposite direction and it causes the stiffness-displacement curve to drift and deflect. Finally, a Halbach ZSPMB is optimized with the ELF model, and then the ERF is suppressed by fine-tuning the structural size. The finite element analysis results show that the stiffness variation in the working range is effectively reduced, and the validity of the proposed hybrid analytical-finite element model modeling technique is verified. [ABSTRACT FROM AUTHOR]

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

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

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

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 proposes a novel permanent magnet planar motor with moving multilayer orthogonal overlapping windings. This novel motor topology can achieve a five-degrees-of-freedom drive using two sets of $x$ -direction windings and two sets of $y$ -direction windings in a coreless configuration. The orthogonal multilayer construction guarantees a high utilization of the magnetic field and realizes decoupling between the $x$ -direction thrust and the $y$ -direction thrust. The topology and operating principle of the planar motor are introduced in this paper. The analytical modeling of the motor is established based on the equivalent current method, and the expressions of forces are derived. The force characteristics of the two-layer and three-layer winding topologies are compared, and the design guidelines of a planar motor are proposed. The analytical and 3-D finite-element model results are validated with the experimental results of a tested prototype. [ABSTRACT FROM AUTHOR]

This paper discusses the analysis and simulation method and the test method for a two-degree-of-freedom (2-DOF) actuator torque. The previous studies on the analysis of 2-DOF motor’s tilting torque were carried out only by finite element method (FEM), not by analytic method. This paper describes the operating principles of and the processes of inducing a tilting torque and a holding torque both of which exist only in special purpose electric machines. This allowed us to establish a design process. By overcoming the limits of the 3-D FEM, this paper introduced the 2-D model analysis by considering a real coil shape. Finally, this paper manufactured and tested the 2-DOF actuator to verify the introduced analytic analysis method. [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]

This paper presents a new type electromagnetic lead screw (EMLS) intended for wave energy application. Similar to the mechanical lead screw, this electromagnetic version can transfer slow linear motion to high-rotational motion, offering gearing effects. Compared with the existing pure magnetic lead screw (MLS) employing permanent magnets only, the new EMLS proposed uses dc current to provide the required helical-shape magnetic field, offering a much simpler, robust structure compared with the MLS. The working principle and the performances of this EMLS are analyzed in this paper. Comparison with PM-type lead screw is given. In addition to this, the theoretical analysis to support the use of a 2-D finite element model to analyze the 3-D magnetic-type lead screw is given, which has not been well covered in the existing literature. [ABSTRACT FROM AUTHOR]

This paper presents a study on the braking effect of the electromagnetic forces produced by eddy currents induced in nonmagnetic materials. The purpose of this paper analyzes the behavior of a moving device within ducts when a constant magnetic field is applied on its inner surface, causing induction of eddy currents in pipeline walls, and verifies how the interaction effects of these currents with the field that induced them might be significant on the device movement. [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]

A good magnetic design of a wireless electric vehicle (EV) charging system requires accurate characterization of the equivalent circuit parameters. This is while considering the effect of the magnetic core and the conductive shielding layers. In the literature, such an analysis is done using 3-D finite element analysis, which makes the design and optimization process time-consuming and computationally expensive. In this paper, an integrated analytical model for the characterization of a circular wireless power transfer EV pads is utilized. This analytical model provides a valuable tool to optimize the design process. This model is utilized when evaluating the objective function for each individual in the multiobjective Pareto Optimality optimization algorithm. The objective is optimizing the pads with three decision variables and four constraints. [ABSTRACT FROM AUTHOR]

In this paper, a general analytical model is proposed to calculate the back electromotive forces of various manufacturing imperfections in the double-rotor axial flux permanent magnet machine. First, the axial and circumferential flux density in the air gap under healthy condition is developed by Maxwell’s equations and Schwarz–Christoffel mapping. Second, the equations of air gap length and radii are introduced to calculate the flux density with manufacturing imperfections. The back EMFs of each case are calculated. For each case, finite-element (FE) method models are developed to validate the analytical model, and the results show that the analytical model predictions match well with the FE results. Finally, the analytical model is verified by experimental results. [ABSTRACT FROM AUTHOR]

With an increased mobility, hard disk drives (HDDs) now use ramp load/unload technology, and multiple disks are used to increase the data capacity. This can result in contact between the ramp and the disks, which negatively affects the slider dynamics under operational shock conditions. There are several types of ramp–disk contact, such as simultaneous, successive, and single contact, and these depend on the distance between the ramp and each disk in a multi-disk HDD. This paper examines the effect of ramp–disk contact on the slider dynamics using a transient shock analysis. The ramp–disk contact affects the head stack assembly bending mode and slider dynamics. The effect of irregular gaps between the disks and adjacent ramp on the slider dynamics is analyzed with the ramp–disk contact force. The simulation shows that the gap irregularity between the ramp and each disk should be as small as possible to improve the stability of the slider dynamics. [ABSTRACT FROM AUTHOR]

Analytic modeling techniques of a double-sided interior permanent-magnet flat linear brushless motor (IPM-FLBM) with slot-phase shift and alternate teeth windings are proposed in this paper. Since the buried-type IPM-FLBM with the slot-phase shift and alternate teeth windings is fairly new compared with conventional linear motors, little research has been previously done in modeling and analysis. The analytic models presented in this paper provide the effective and reliable methods for this new type of linear motor. For this purpose, a simplified magnetic equivalent circuit and superposed winding function are investigated. A variable winding function is newly developed in order to evaluate the inductances of the salient motor with the alternate teeth windings. All analytic models are verified with 3-D finite-element analyses (FEAs) step by step. The steady-state thrust force is modeled using a classical closed-form solution for linear brushless ac motors. The static end-effect and cogging forces for the ripple force evaluation are investigated using FEA. The validities for performance parameters are demonstrated experimentally. [ABSTRACT FROM PUBLISHER]

The brushless doubly fed induction machine (DFIM) shows great potential as a generator in large-scale wind turbines. The motion of the magnetic field in this machine is not a simple rotation, which makes it not so straight forward to understand its operating principles. This paper develops an analytical magnetic field model for the brushless DFIM that includes the effects of rotor time harmonics and space harmonics due to the winding distribution and slotting. Using a case study machine, the developed analytical model is then validated by comparison with finite-element (FE) calculations. In addition, a 2-D spectral analysis is applied to the FE derived radial air-gap magnetic field as a function of time. This analysis verifies the space–time relations of the rotating magnetic field components in the airgap of the brushless DFIM. Finally, the developed analytical magnetic field model is used to analyze the brushless DFIM operating principles. The interaction of the stator magnetic field with the rotor nested loops is explained, as well as the development of electromagnetic torque. [ABSTRACT FROM PUBLISHER]

A novel electrodynamic suspension device using an asymmetrical double-sided Halbach array is proposed in this paper. A 3-D analytical model describing the eddy current field and the electromagnetic force is established via the second-order vector potential formulation. The validity of the analytical model is verified by both finite-element simulations and an experiment. The configuration of the proposed suspension device is optimized exploiting a dynamic kriging surrogate model assisted by a multi-objective genetic algorithm. The multi-objective optimization is performed utilizing the 3-D analytical model. [ABSTRACT FROM AUTHOR]

This paper investigates the effectiveness of the Cauer circuit modeling for dynamic hysteretic property in iron loss analyses of rotating machines. We apply the method to an interior permanent magnet synchronous motors fed by pulsewidth modulation inverter and compare their performance with a conventional iron loss estimation method based on 1-D finite-element analyses. As a result, almost the same iron loss is obtained by using the Cauer circuit modeling with lower computational cost. [ABSTRACT FROM AUTHOR]

Overhang is a useful structure for increasing the torque and power densities of permanent-magnet (PM) machines without expansion of the machine space. A 3-D finite-element method (FEM) is needed to evaluate the performances of PM machines with an overhang structure because the overhang structure results in non-uniform magnetic flux distributions in the axial direction. However, it is computationally expensive, especially in the early design stage. In this paper, we propose a magnetic equivalent circuit (MEC) model considering the overhang effects of interior PM (IPM) machines. With the proposed MEC, the performances of IPM machines with an overhang structure were precisely calculated and the computational time was significantly reduced. The proposed MEC was verified by the 3-D FEM. [ABSTRACT FROM AUTHOR]

This paper analyzes the effect of the operation frequency of an inductive charging system on the heat generation and its impact on the overall system efficiency. This is done considering the change of the material properties due to both frequency and temperature changes. The analysis is achieved using FEA modeling software ANSYS workbench. For faster subsequent optimization, an order-reduced model is implemented in a system-level simulation. Various tests show the good agreement of the results between the reduced order model and those of dynamically coupled-field solvers. Our implementation allows for precise calculation of the losses of the different system parts. Furthermore, an experiment has been conducted to validate the simulation results. [ABSTRACT FROM AUTHOR]

This paper presents a developed 2-D analytical subdomain model for design and analysis of the double-stator permanent magnet linear synchronous machine (DS-PMLSM) to account for both the primary and secondary end effects. First, considering the time constraint, polar transformed method is adopted to establish the 2-D subdomain analytical model, the DS-PMLSM is deformed into a ring-segment PMLSM, and the analytical model is calculated in polar coordinates instead of Cartesian coordinates. Then, the subdomain method is adopted to analyze the analytical model by solving Laplace’s equation and Poisson’s equation, and 2-D relative permeance function is used to consider the slot effect. The flux density and back electromotive force are calculated based on the developed analytical model. Finally, the analytical results are verified by the finite-element method and experiment. The results show that the proposed analytical model can accurately predict the electromagnetic performance, which is useful for the initial design of the DS-PMLSM. [ABSTRACT FROM AUTHOR]

This paper proposes an optimal design of quadrature-shaped pickup to satisfy various demands on performance at special positions for omnidirectional wireless power transfer (WPT). Omnidirectional WPT technology as a brand new way of energy supply has shown great potentials for charging objectives at all directions. In order to ensure the energy can be transmitted to arbitrary spatial directions, the orthogonal structure of three circular transmitting coils has been widely accepted matched with non-identical current control scheme. However, there are still some special positions where the transmitted power drops to the bottom which is not suitable for applications. Accordingly, this paper proposes an optimal design analysis for the quadrature-shaped pickup to satisfy different demands on either power or efficiency at such positions. The simulated analysis and experimental results are both given to verify the enhancement of the proposed quadrature-shaped pickup, which aims to provide a reference to fabricate an appropriate pickup up for utilizations. [ABSTRACT FROM AUTHOR]

Stator winding inter-turn (SWI) short-circuit fault and broken rotor bar (BRB) fault are two common faulty modes of the squirrel cage induction motors (SCIMs). These faults have various impacts on the motor performance and may be rooted in each other; therefore, they may be presented at the same time in an SCIM. This paper proposes an exact analytical model for the SCIMs, which is able to include the SWI and BRB faults presenting simultaneously or individually with variable severities. Multiple coupled circuit modeling is applied to achieve such analytical model. The magnetic saturation effect is included in the model by applying appropriate air gap function and the rotor bars skew effect is taken into account by using 2-D winding function theory. Simulation results as well as the corresponding experimental results approve the presence of the same harmonics in the stator line currents due to the proposed faults. However, more detailed study gives solution for discrimination of the faults. The attained analytical model can be applied to examine the performance of the related fault diagnosis methods and to design novel fault diagnosis techniques including the model-based ones. [ABSTRACT FROM AUTHOR]

This paper presents a 2-D hybrid analytical modeling method for the analysis of the magnetostatic field distribution with the capability of including nonlinear materials. The model combines Fourier modeling, which is accurate and fast, with meshed magnetic equivalent circuits that have unique permeability in mesh elements and, therefore, can model local saturation. To present the diverse applicability of the proposed method, it is applied to a linear machine with permanent magnet excitation and a rotary machine with current excitation. Magnetic field calculations are compared with finite-element analysis (FEA) with good agreement. [ABSTRACT FROM AUTHOR]

Due to their high efficiency and power density, permanent magnet synchronous machines (PMSMs) operating at high speed have recently gained a lot of attention. The development of high-speed PMSMs requires a good understanding of the physics related to the operation of such machines. Moreover, accurate modeling tools are needed when designing high-speed electrical machines. In this paper, the subdomain modeling technique is used to analytically compute the magnetic field of an electrical machine. The idea behind this technique is to divide the machine in a number of subdomains, in which the problem is simplified. The solutions in the different subdomains are then linked by imposing physical boundary conditions. The described model immediately considers the slotting effect and the eddy-current reaction field of a shielding cylinder (SC). The SC is a conductive sleeve, which is wrapped around the magnets. Its goal is to reduce the rotor losses at high-speed operation. This paper starts by introducing the applied modeling technique and the studied machine. Second, the basics of the model and its development are discussed. Finally, the results are compared with results of a finite-element (FE) model. A very good agreement between the proposed model and the FE model is observed. This implies that the developed model is indeed a powerful modeling tool for high-speed PMSMs. Moreover, it provides great insight in the machine’s physics as well. [ABSTRACT FROM PUBLISHER]

The aim of this paper is, first, to extend the application of the hybrid analytical modeling (HAM) approach for the analysis of tubular linear machines (TLPM), something that has never been reported yet in the scientific literature. The HAM consists of a strong coupling between the reluctance network and the Fourier series solution of magnetic scalar potential. In order to assess the merits and capabilities of the HAM, it is applied to the study of the cogging force in linear machines and compared with finite element analyses (FEA). The cogging force is a global quantity, which is very sensitive to magnetic field computation accuracy and constitutes, therefore, a good measure of the accuracy of the HAM as compared with FEA. The HAM should require less computation time as compared with FEA, and is then more suitable for predesign stage. Three different structures are analyzed: a flat linear machine, a TLPM with internal mobile armature, and, finally, a TLPM with external mobile armature. The analyses are conducted, considering the effect of magnetic saturation. [ABSTRACT FROM PUBLISHER]

With the recent advances, data storage industries are pushing the limits of recording devices by heating the media with a pulsing laser. Although high-temperature operations may be favorable for the magnetic recording process, it increases the instability of the whole system. Lubricant molecules on the media surface can greatly be affected by this change. Previous experiments have reported signs of unknown substances contaminating the head component during the operation of heat-assisted magnetic recording (HAMR) which hinders the read/write capabilities of the device. In this paper, we have analyzed the nanoscale physical phenomena of several lubricant/organic molecules in the head–disk interface under the harsh conditions of HAMR via molecular dynamics simulation using the united atom model, coarse-grained, bead-spring model, and simple reactive sphere model. Our models simulated extreme temperature, high magnetic field strength, and effects of different media for two different perfluoropolyether molecules. Our preliminary simulation results provided few possible sources of the unknown materials and of those possibilities, evaporation seemed to be dominant. [ABSTRACT FROM PUBLISHER]

Following a study on the optimal write head design for perpendicular magnetic recording, this paper aims at optimizing the design of write head for shingled magnetic record by applying the Taguchi method and the response surface methodology. The criteria for the evaluation of the write head design are to maximize the signal-to-noise ratio (SNR) and minimize the bit error rate (BER) in the shingled magnetic recording (SMR). In this paper, the magnetic fields of the write head designs are modeled using finite-element analysis, the SMRs are simulated by applying micromagnetic modeling based on Landau–Lifshitz–Gilbert equation, and the SNR and the BER are characterized using the grain flipping probability model. An optimal design of the write head is obtained to achieve the maximum SNR and the minimum BER. A discussion on the erasure band width is also carried out in this paper. Furthermore, the SNR and the BER at different bits and track densities in SMR are compared and discussed. [ABSTRACT FROM PUBLISHER]

Helical windings (or zigzag windings) are used in a number of applications, however, in electrical machines, mainly employed in low-power, high-speed permanent magnet (PM) brushless dc machines due to the cost effectiveness of the winding type while maintaining reasonable performance. Typically, helical windings are used for low-voltage applications due to their spiral form, which makes them most suitable for a small number of turns. In high-speed electrical machines, such a low number of turns are applicable. It is apparent that high-speed PM machines suffer from rotor eddy-current losses, which in some cases may lead to PM demagnetization due to overheating. The performance of the machine is compromised by these losses; hence, they have to be considered during the design procedure. There are many papers analyzing the magnetic field of these machines employing helical windings; however, none of them present a simple and precise electromagnetic model of a machine with the helical winding. This paper presents an analytical approach to model the resulting 3-D magnetic field of the helical winding, considering eddy currents in the conducting media of the rotor. The model is verified with the 3-D finite-element method by means of comparing magnetic field and rotor eddy-current losses. [ABSTRACT FROM AUTHOR]

This paper presents an exact analytical subdomain model of slotted permanent-magnet (PM) machines, taking into account the diffusion effect. The model gives the magnetic fields, both the eddy currents and the power losses in the PM, the instantaneous and average torque. In the model, eddy currents are not assumed to be resistance limited, contrary to what is done in the conventional exact subdomain models of the slotted machines. The model is hence general and valid both at low and high frequencies. It shows that it is possible to calculate the power losses in the PMs, only knowing the fields in the air gap. The model takes into account the presence of tooth-tips. The comparison with conventional exact subdomain models shows that the model presented in this paper is more accurate. The model is validated using the finite-element methods. [ABSTRACT FROM AUTHOR]

Lightning shielding failure accounts for the highest proportion of lightning accidents for transmission systems above 500 kV. The leader propagation model (LPM) was found to be effective in the analysis of lightning shielding failure of high-voltage transmission lines, especially for the ultrahigh voltage (UHV) transmission systems. However, it was generally inefficient to calculate the shielding failure rate by LPM, since the progress of lightning development must be simulated repeatedly, which is time-consuming, and no adaptive implementation of LPM has been reported. In this paper, adaptive strategies to accelerate the computation of shielding failure analysis by LPM were proposed, which include the adaptive time step control according to the electric field at the conductor surface, non-uniform lightning current sampling based on the lightning current amplitude probability distribution, and the adaptive lightning location sampling based on recursive adaptive Simpson’s method. The analysis results were validated by the field data of the UHV transmission line in Japan, and the efficiency of the adaptive strategies was shown by the shielding failure analysis of a typical 500 kV ac transmission line. [ABSTRACT FROM AUTHOR]

This paper addresses the calculation of Lorentz forces generated by axially or radially magnetized ring magnets due to passing ferromagnetic conductors. The boundary value problem is solved using the Fourier transform while considering the interaction between the magnetic field of the ring magnet and the induced eddy currents. The Lorentz force and the induced eddy current density are evaluated in integral form, including modified Bessel functions of the first and the second kind. The famous creeping magnet problem where a magnet travels inside a conducting pipe is extended to ring magnets. The obtained expressions are evaluated and compared with the finite-element solutions. It is observed that radially magnetized ring magnets generate higher Lorentz forces compared with their axially magnetized counterparts. The described scenario is applicable in the framework of flow rate evaluation, non-destructive testing, or electromagnetic damping. We provide supplementary material in the form of MATLAB functions to efficiently analyze such problems in similar areas of application. The present contribution is of great interest for theoretical, pedagogical, and practical reasons. [ABSTRACT FROM PUBLISHER]

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

This paper presents the development of a simultaneous dual frequency (SDF) induction hardening apparatus for gear hardening. First, a 2-D finite-element (FE) modeling for a thermal-electromagnetic coupled field is introduced for gear hardening and then the analytical results are investigated. By modeling the gear hardening as 2-D FE model, we can calculate for the coupled field more efficiently. In addition, optimum process parameters can also be found through this analysis. A real SDF heat treatment equipment is manufactured using analytical results, like input frequency, and gear hardening experiments are conducted. Through analysis and experiments, we can validate the performance of the developed machine. [ABSTRACT FROM AUTHOR]

Most investigations of all spin logic (ASL) have been based on the monodomain approximation of magnetization switching. The sensitive and stochastic nature of spin transfer torque (STT) switching creates pressing requirements for analyzing ASL from a micromagnetic perspective also. Hence, in this paper, ASL is studied from a micromagnetic perspective by developing a simulation framework that can capture diffusive spin transport. The spin transport model is calibrated from the existing experimental results on nonlocal spin valve measurements. Then, using this framework, STT switching is studied for input–output nanomagnets with in-plane and perpendicular magnetic anisotropy for ASL devices (ASLDs). Precisely defined architecture and design constraints for such input–output nanomagnets are presented. Further, a previously proposed switching mechanism by driving the nanomagnet into a metastable state is also incorporated into micromagnetic framework. Using the aforementioned mechanism, the critical current required for STT switching can be reduced to as low as 20 $\mu $ A. Moreover, the graphene channel ASLD using tunnel contact at the injector is demonstrated for copy and invert logic operations. [ABSTRACT FROM AUTHOR]