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Purpose: To improve the output torque density of the machine and to be better suited for automation applications, this paper aims to propose a double-permanent-magnet enhanced hybrid stepping machine (DPMEHSM) with tangential and radial magnetization. Design/methodology/approach: First, the structure of DPMEHSM is introduced and its operation principle is analyzed by describing the variation in stator poles versus time. Second, based on the similar electrical load and amount of PM, the size equations of the DPMEHSM are designed and the main parameters are presented. Third, the electromagnetic performances including the PM flux linkage distribution, magnetic density distribution, air-gap field, back electromotive force (back-EMF), detent torque, holding torque and output torque of DPMEHSM and stator-PM hybrid stepping machine (SPMHSM) are analyzed based on the finite element method. Findings: The results show that the DPMEHSM has superiority in back-EMF, holding torque and output torque. Originality/value: This paper proposes a DPMEHSM with tangential and radial magnetization to improve the output torque density. [ABSTRACT FROM AUTHOR]

Purpose: To address the issues of the insufficient output torque associated with the application of intensifying-flux permanent magnet (PM) machines in electric vehicles, this paper aims to propose an intensifying-flux hybrid excitation PM machine. It is possible to adjust the air gap magnetic field by adjusting the field current in the excitation winding, thereby increasing the torque output capability and speed range of the machine. Design/methodology/approach: First, a novel intensifying-flux hybrid excited permanent magnet synchronous machine (IF-HEPMSM) is proposed on the basis of intensifying-flux permanent magnet synchronous machine (IF-PMSM) and an equivalent magnetic circuit model is established. Second, the tooth width and yoke thickness of the machine stator are optimized to ensure the overload capacity of the machine while effectively improving the wide flux regulation range. Furthermore, the electromagnetic characteristics of the IF-HEPMSM are investigated and compared with the IF-PMSM and conventional permanent magnet synchronous machine (PMSM) by using finite element simulations. Findings: The id of IF-HEPMSM and IF-PMSM is greater than zero low-speed magnetizing current. And the flux-weakening current of the IF-HEPMSM is 18% and 3% smaller than of the conventional PMSM and IF-PMSM. Practical implications: Aiming at the problems of IF-PMSM applied to electric vehicles, this paper proposes an IF-HEPMSM. The air gap magnetic field is adjusted by controlling the current of the excitation winding to improve the reliability of the machine. Therefore, the IF-HEPMSM combines the advantages of high-power density and high efficiency of the PMSM and the controllable magnetic field of the electro-excitation machine, which is of great engineering value when applied in the field of electric vehicles. Originality/value: The proposed IF-HEPMSM offers better flux regulation capability with electromagnetic characteristics analysis and maps of dq-axis current as compared to IF-PMSM and conventional PMSM. Moreover, the improvement of the torque can make up for the shortcomings of the insufficient torque output capability of the IF-PMSM. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of the study is to design the compensation network of a dynamic wireless power transfer system, considering the movement of the receiving coil along an electrified track with a large number of inductors buried on the road. Design/methodology/approach: A finite element model has been developed to calculate the self-inductances of transmitting and receiving coils as well as the mutual inductances between the receiving coil and the transmitting ones in the nearby and for various relative positions. The calculated lumped parameters, self-inductances and mutual inductances depending on the relative positions between the coils, have been considered to design the compensation network of the active coils, which is composed of three capacitive or inductive reactances connected in the T form. The optimal values of the six reactances, three for the transmitting coils and three for the receiving one, have been calculated by resorting to the Genetic Algorithm NSGA-II. Findings: In this paper, the results obtained by means of the optimizations have broadly discussed. The optimal values of the reactances of the compensation networks show a clear trend in the receiving part of the circuit. On the other hand, the problem seems very sensitive to the values of the reactances in the transmitting circuit. Originality/value: Dynamic wireless power transfer system is one of the newest ways of recharging electric vehicles. Hence, the design of compensation networks for this kind of systems is a new topic, and there is the need to investigate possible solutions to obtain a good performance of the recharging system. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of the paper is to make a high speed motor based on the characteristics of high strength silicon steel. With the higher requirements for torque density and power density of the driving system of electric vehicles (EV), conventional magnetic materials have been difficult to meet the demands in the future. In this paper, a new type of high-strength non-grain-oriented (NGO)material is tested. Design/methodology/approach: Through analyzing the characteristic of high strength silicon steel, it is applied to the rotor part of a high-speed motor. A topological optimization is applied to achieve higher power density and higher efficiency of the motor. Findings: The feasibility of the scheme was analyzed by the finite element method, and a prototype was also fabricated to verify the analysis. Originality/value: In this paper, the characteristics of new soft magnetic materials as a breakthrough to manufacture a new generation of high-performance electrical machine (EM) are discussed. Consequently, the presented work greatly facilitates further explorations and guides the innovative application of soft magnetic materials and the iterative optimization of motor structure. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to introduce a new numerical model that predicts the flashover voltage (FOV) value in the presence of polluted air surrounding a high-voltage insulator. The model focuses on simulating the propagation of arcs and aims to improve the accuracy and reliability of FOV predictions under these specific conditions. Design/methodology/approach: This arc propagation method connecting the high voltage fitting and the grounded insulator cap involves a two-step process. First, the electric field distribution in the vicinity of the insulator is obtained using finite element method analysis software. Subsequently, critical areas with intense electric field strength are identified. Random points within these critical areas are then selected as initial points for simulating the growth of electric arcs. Findings: by increasing the electric voltage applied to the insulator fittings, the arc path is, step by step, generated until a breakdown occurs on the polluted air surrounding the insulator surface, and thus a prediction of the FOV value. Practical implications: The proposed model for the FOV prediction can be a very interesting alternative to dangerous and costly experimental tests requiring an investment in time and materials. Originality/value: Some works were done trying to reproduce discharge propagation but it was always with simplified models such as propagation in one direction from a point to a plane. The difficulty and the originality of the present work is the geometry complexity of the insulator with arc propagation in three distinct directions that will require several proliferation conditions. [ABSTRACT FROM AUTHOR]

Purpose: Topology optimization (TO) methods have shown their unique advantage in the innovative design of electric machines. However, when introducing the TO method to the rotor design of interior permanent magnet (PM) synchronous machines (IPMSMs), the layout parameters of the magnet cannot be synchronously optimized with the topology of the air barrier; the full design potential, thus, cannot be unlocked. The purpose of this paper is to develop a novel method in which the layout parameters PMs and the topology of air barriers can be optimized simultaneously for aiding the innovative design of IPMSMs. Design/methodology/approach: This paper presents a simultaneous TO and parameter optimization (PO) method that is applicable to the innovative design of IPMSMs. In this method, the mesh deformation technique is introduced to make it possible to make a connection between the TO and PO, and the multimodal optimization problem can thereby be solved more efficiently because good topological features are inherited during iterative optimization. Findings: The numerical results of two case studies show that the proposed method can find better Pareto fronts than the traditional TO method within comparable time-consuming. As the optimal design result, novel rotor structures with better torque profiles and higher reluctance torque are respectively found. Originality/value: A method that can simultaneously optimize the topology and parameter variables for the design of IPMSMs is proposed. The numerical results show that the proposed method is useful and practical for the conceptual and innovative design of IPMSMs because it can automatically explore optimal rotor structures from the full design space without relying on the experience and knowledge of the engineer. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to provide an analysis of the performance of a new five-phase doubly fed induction generator (DFIG). Design/methodology/approach: This paper presents the results of a research work related to five-phase DFIG framing, including the development of an analytical model, FEM analysis as well as the results of laboratory tests of the prototype. The proposed behavioral level analytical model is based on the winding function approach. The developed DFIG model was used at the design stage to simulate the generator's no-load and load state. Then, the results of the FEM analysis were shown and compared with the results of laboratory tests of selected DFIG operating states. Findings: The paper provides the results of analytical and FEM simulation and measurement tests of the new five-phase dual-feed induction generator. The use of the MATLAB Simscape modeling language allows for easy and quick implementation of the model. Design assumptions and analytical model-based analysis have been verified using FEM analysis and measurements performed on the prototype. The results of the presented research validate the design process as well as show the five-phase winding design advantage over the three-phase solution regarding the control winding power quality. Research limitations/implications: The main disadvantage of the winding function approach-based model development is the simplification regarding omitting the tangential airgap flux density component. However, this fault only applies to large airgap machines and is insignificant in induction machines. The results of the DFIG analyses were limited to the basic operating states of the generator, i.e. the no-load state, the inductive and resistive load. Practical implications: The novel DFIG with five phase rotor control winding can operate as a regular three-phase machine in an electric power generation system and allows for improved control winding power quality of the proposed electrical energy generation system. This increase in power quality is due to the rotor control windings inverter-based PWM supply voltage, which operates with a wider per-phase supply voltage range than a three-phase system. This phenomenon was quantified using control winding current harmonic analysis. Originality/value: The paper provides the results of analytical and FEM simulation and measurement tests of the new five-phase dual-feed induction generator. [ABSTRACT FROM AUTHOR]

Purpose: The goal of this research is to investigate the convergence behavior of the Newton iteration, when solving the nonlinear problem with consideration of hysteresis effects. Incorporating the vector hysteresis model in the magnetic vector potential formulation has encountered difficulties. One of the reasons is that the Newton method is very sensitive regarding the starting point and states distinct requirements for the nonlinear function in terms of monotony and smoothness. The other reason is that the differential reluctivity tensor of the material model is discontinuous due to the properties of the stop operators. In this work, line search methods to overcome these difficulties are discussed. Design/methodology/approach: To stabilize the Newton iteration, line search methods are studied. The first method computes an error-oriented search direction. The second method is based on the Wolfe-Powell rule using the Armijo condition and curvature condition. Findings: In this paper, the differentiation of the vector stop model, used to evaluate the Jacobian matrix, is studied. Different methods are applied for this nonlinear problem to ensure reliable and stable finite element simulations with consideration of vector hysteresis effects. Originality/value: In this paper, two different line search Newton methods are applied to solve the magnetic field problems with consideration of vector hysteresis effects and ensure a stable convergence successfully. A comparison of these two methods in terms of robustness and efficiency is presented. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to design metaguide- or metasurface-based compact inexpensive beam-steering devices, which play an important role in modern cellular networks, radar imaging and satellite communication. Design/methodology/approach: This paper uses finite element analysis to study, design and optimize arrays of resonating elements as beam steering devices. The first set of such devices involves metamaterial-based apertures fed by a waveguide, tunable via the permittivity of the host material. In the second approach, dynamic beam steering is effected by alternating between two or more waveguide feeds. Findings: Particular examples show how the direction of the main lobe of the radiated beam can be reliably switched by approximately 30° in one of the quadrants by changing a single global control parameter within a very reasonable range. Research limitations/implications: The findings pave the way for the design and fabrication of inexpensive compact beam steering devices. This study anticipates that the proposed designs can be further improved and fine-tuned using "heavy duty" optimization packages. Originality/value: In many published designs of similar beam-steering devices, the radiation pattern of an array of resonating elements is controlled by complex circuitry, so that each radiating element is tuned separately. In contrast with these existing approaches, the designs rely just on a simple global control parameter. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to present the principle of virtual air gap inductance and the design of a voltage regulation device based on this principle. The authors provide a comprehensive analysis of this specific application that consists of locally saturating the magnetic circuit of the voltage regulator to modify its global properties. This saturation is created by a direct current flowing in a small auxiliary coil inserted in the specific area of the magnetic circuit to saturate this zone. Design/methodology/approach: Analytical calculation and finite elements simulations are used to optimize the device for a specific application tied to the supply of electrical ovens in metallurgic usage. Experimental results are presented at the end of the paper. Findings: The experimental results presented in this paper are in concordance with the analytical calculation and with the finite element simulations for different operation points. The difficulty of the study of the virtual air gap comes mainly from the nonlinearity of the phenomena because the principle is based on a local and controllable saturation of the magnetic circuit. Originality/value: The originality of the paper concerns the introduction of virtual air gap principle in a specific industrial application. [ABSTRACT FROM AUTHOR]

Purpose: Various iron loss models can be used for the simulation of electrical machines. In particular, the effect of rotating magnetic flux density at certain geometric locations in a machine is often neglected by conventional iron loss models. The purpose of this paper is to compare the adapted IEM loss model for rotational magnetization that is developed within the context of this work with other existing models in the framework of a finite element simulation of an exemplary induction machine. Design/methodology/approach: In this paper, an adapted IEM loss model for rotational magnetization, developed within the context of the paper, is implemented in a finite element method simulation and used to calculate the iron losses of an exemplary induction machine. The resulting iron losses are compared with the iron losses simulated using three other already existing iron loss models that do not consider the effects of rotational flux densities. The used iron loss models are the modified Bertotti model, the IEM-5 parameter model and a dynamic core loss model. For the analysis, different operating points and different locations within the machine are examined, leading to the analysis of different shapes and amplitudes of the flux density curves. Findings: The modified Bertotti model, the IEM-5 parameter model and the dynamic core loss model underestimate the hysteresis and excess losses in locations of rotational magnetizations and low-flux densities, while they overestimate the losses for rotational magnetization and high-flux densities. The error is reduced by the adapted IEM loss model for rotational magnetization. Furthermore, it is shown that the dynamic core loss model results in significant higher hysteresis losses for magnetizations with a high amount of harmonics. Originality/value: The simulation results show that the adapted IEM loss model for rotational magnetization provides very similar results to existing iron loss models in the case of unidirectional magnetization. Furthermore, it is able to reproduce the effects of rotational flux densities on iron losses within a machine simulation. [ABSTRACT FROM AUTHOR]

Purpose: Detection of low-frequency pressures such as heart rate in the range of 1 Hz is one of the applications of low-frequency resonator. In this paper, the structure of the resonator is in the form of a plate, whose mathematical model has been extracted according to past works and is reported. Design/methodology/approach: This paper presents an electromechanical microresonator that can be used as an ultra-low-frequency pressure sensor. It is very important to choose the right material for the sensors to have the optimal conditions. In this work, by proposing the innovative use of polytetrafluoroethylene material with low stiffness coefficient, the necessary conditions are provided to reduce the vibration frequency of the resonator. Findings: The proposed design is simulated with the help of COMSOL, and its results are compared with the results of the mathematical model, which are very close to each other. Therefore, by inferring the results, the authors can rely on accurate simulations and finalize the similar designs with full confidence before fabrication. Originality/value: There are important advantages regarding the geometry of the proposed design structure that is the possibility of detecting a pressure of 1 Pa only with voltages less than 2 V. On the other hand, the pull-in effect causes very low frequencies to be achieved in detection with the help of the proposed resonator. Also, the linear and nonlinear behavior of the resonator by applying different pressures has been studied and reported to find the appropriate operating range of the resonator and its limitations. [ABSTRACT FROM AUTHOR]

Purpose: This paper proposes a spoke-type fractional-slot concentrated windings (FSCW) permanent magnet (PM) machine for special vehicle driving systems to obtain higher torque and power density, high efficiency and wide field-weakening range. To enhance the efficiencies of multi-objective optimization processes, the respond surface (RS) method and black-hole (BH) algorithm are used. Design/methodology/approach: The spoke-type FSCW PM machine is optimized to meet the requirements of the special vehicle driving system. The combination of the RS and BH algorithm is used to obtain high torque, low torque ripple and high efficiency. Findings: The optimal spoke-type PM machine is obtained, and it has higher torque density, lower torque ripple, cogging torque and wider magnetic field weakening range. Finally, a 15-kW prototype machine is fabricated and tested to verify the results of the optimization method and finite-element analysis. Originality/value: This paper designs a high torque density and efficiency spoke-type FSCW PM machine, which is superior for special vehicle driving systems. Meanwhile, the RS model combined with BH algorithm is applied to the field of electrical machine multi-objective optimal design. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to provide a new method of generating relatively accurate and smooth saturated B-H curves based on reliable measurement data to improve the accuracy and efficiency of electromagnetic simulation. Design/methodology/approach: The characteristics of different B-H curve extrapolation models are summarized, and an improved method is proposed. The fitting procedure in low fields and extrapolation procedure in high fields are presented in detail. The saturated B-H curves generated by various methods are compared and discussed. Finally, a simulation case study proved the advantages of the new method in terms of simulation accuracy and efficiency. Findings: The B-H curve created by the new method avoids extrapolation from a single point and simultaneously smoothens the entire B-H curve, thereby improving the simulation accuracy and efficiency. The low magnetic potential requirements for closed measurements and the small deviation with open measurements indicate that this method is well-suited for implementation. Research limitations/implications: The results are applicable for materials subject to such excitation levels that saturation has to be taken into account. Originality/value: While some extrapolation models of B-H curves have been investigated in reference papers, there is still room for improvement in accuracy and smoothness. The new method processes low fields and high fields magnetization data and then connects them based on third-order boundary equations for the first time. This method can generate saturated B-H curves with good accuracy and smoothness while retaining outstanding operability. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to propose a novel multiple transient modeling scheme for the 12-pulse phase-shifting reactor (PSR) rectifier to enhance the efficiency of full-cycle design evaluation. Design/methodology/approach: The detailed time-domain method is adopted to model the rectifier at the behavioral layer. The diode bridges/transformer model at the architecture layer is established by using the switch function and Park transformation. The frequency domain model at the functional layer is derived with the time-varying Fourier decomposition and frequency-shifting. At the component layer, the magneto-thermal characteristics of the rectifier are analyzed with field-circuit and magnetic-thermal coupling methods. A computer-aided design program integrating multiple modeling is also developed for industrial product design. Findings: The function layer modeling is preferred in the initial design stage, making up for the lack of modeling accuracy at the architectural layer and the lack of modeling rapidity at the behavioral layer. The component modeling is irreplaceable for the detailed evaluation in the latter design stage. The multiple modeling scheme based on the four-layer modeling helps the designers achieve high-quality products with a short development cycle. Originality/value: The singular transient modeling cannot cover the needs of different stages in the full-cycle design evaluation. This paper fills this gap with a novel multiple modeling scheme. Meanwhile, the proposed multiple modeling scheme and developed computer-aided design program provide a great convenience for full cycle design evaluation of the 12-pulse PSR rectifier. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to further improve the efficiency of multi-objective optimization design of synchronous reluctance motors (SynRMs) using the level set (LS) method, which has the advantage of obtaining a practical shape. The solutions obtained by gradient methods tend to be local ones due to the multi-modality of the objective function, especially when multiple objective functions. A huge number of trial calculations are required to obtain a high-quality and broadly distributed Pareto front. Therefore, it is indispensable to effectively get out of the local solutions in the optimization process with the LS method. Design/methodology/approach: The authors propose a novel method appropriately switching multiple objective functions with high independence of sensitivity information. The authors adopt highly independent mathematical expressions for the objective functions of the average torque and torque ripple. In addition, the authors repeatedly perform the optimization while appropriately selecting the sensitivity information of one objective function from multiple ones, which enables the authors to effectively break out of local solutions in the optimization process. Findings: The proposed method was applied to the shape optimization of SynRM flux barriers and successfully searched a more extensive and advanced Pareto front in comparison with the conventional method. Originality/value: The proposed method adopts search spaces with mathematical high independence for average torque and torque ripple. In the optimization process, when the solution search is judged to get stuck by several criteria, the search space is alternately switched to effectively get out of local solutions. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to propose a two-dimensional (2-D) hybrid analytical model (HAM) in polar coordinates, combining a 2-D exact subdomain (SD) technique and magnetic equivalent circuit (MEC), for the magnetic field calculation in electrical machines at no-load and on-load conditions. Design/methodology/approach: In this paper, the proposed technique is applied to dual-rotor permanent magnet (PM) synchronous machines. The magnetic field is computed by coupling an exact analytical model (AM), based on the formal resolution of Maxwell's equations applied in subdomains, in regions at unitary relative permeability with a MEC, using a nodal-mesh formulation (i.e. Kirchhoff's current law), in ferromagnetic regions. The AM and MEC are connected in both directions (i.e. r- and theta-edges) of the (non-)periodicity direction (i.e. in the interface between teeth regions and all its adjacent regions as slots and/or air-gap). To provide accurate solutions, the current density distribution in slot regions is modeled by using Maxwell's equations instead to MEC and characterized by an equivalent magnetomotive force (MMF) located in the slots, teeth and yoke. Findings: It is found that whatever the iron core relative permeability, the developed HAM gives accurate results for both no-load and on-load conditions. Finite element analysis demonstrates the excellent results of the developed technique. Originality/value: The main objective of this paper is to achieve a direct coupling between the AM and MEC in both directions (i.e. r- and theta-edges). The current density distribution is modeled by using Maxwell's equations instead to MEC and characterized by an MMF. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to propose an analytical model with consideration of the permeability of soft-magnetic materials, which can predict the magnetic field distribution more accurately and facilitate the initial design and parameter optimization of the machine. Design/methodology/approach: This paper proposes an analytical model of stator yokeless radial flux dual rotor permanent magnet synchronous machine (SYRFDR-PMSM) with the consideration of magnetic saturation of soft-magnetic material. The analytical model of SYRFDR-PMSM is divided into seven regions along the radial direction according to the different excitation source and magnetic medium, and the iron permeability in each region is considered based on the Maxwell–Fourier method and Cauchy's product theorem. The magnetic vector potential of each region is obtained by the Laplace's or Poisson's equation, and the magnetic field solution is determined using the boundary conditions of adjacent regions. Findings: The inner and outer air-gap flux density, flux linkage, output torque, etc., of SYRFDR-PMSM are predicted by analytical model, resulting in good agreement with that of finite element model. Additionally, the SYRFDR-PMSM prototype is manufactured and the correctness of analytical model is further verified by experiments on no-load back electromotive force and current–torque curve. Reasonable design of the slot opening width and pole arc coefficient can improve the average output torque and reduce output torque ripple. Research limitations/implications: The analytical model proposed in this paper assumes that the permeability of soft-magnetic material is a fixed value. However, the actual iron's permeability varies nonlinearly; thus, the prediction results of the analytical model will have some deviations from the actual machine. Originality/value: The main contribution of this paper is to propose an accurate magnetic field analytical model of SYRFDR-PMSM. It takes into account the permeability of soft-magnetic material and slot opening, which can quickly and accurately predict the electromagnetic performance of SYRFDR-PMSM. It can provide assistance for the initial design and optimization of SYRFDR-PMSM. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to develop a multi-material topology optimization method for permanent magnet-assisted synchronous reluctance motors. Design/methodology/approach: In the proposed method, the optimization procedure consists of two steps. In the first step, the entire rotor area was selected for the design region and the distribution of the core and air materials was optimized. In the second step, the design region was limited to the air region of the former solution and the distribution of magnets and cores or magnets and air was optimized. Findings: Because of the two-step process of the proposed method, the design parameters can be reduced compared to the conventional method. As a result, this study can prevent the solution space from becoming more complex and superior solutions can be founded effectively. Research limitations/implications: Since limited case study is denoted in this paper, much more case studies, for example, three-dimensional optimization problems, are needed to be discussed. Practical implications: The optimal solutions obtained by the proposed method have a smaller magnet volume and higher average torque than that of the conventional method. Originality/value: In the proposed methods, optimization methodology, which consists of two-steps process, is differed from the conventional method. [ABSTRACT FROM AUTHOR]

Purpose: The paper aims to propose a a field-circuit method for investigating the magnetic behavior of a wireless power transfer system (WPTS) for the charge of batteries of electric vehicles. In particular, a 3D model for finite element analysis (FEA) for the field simulation of a WPTS is developed. Specifically, the effects of aluminum shield and steel layer, representing the car frame, on the self and mutual inductances are investigated. An equivalent electric circuit is then built, and the relevant lumped parameters are identified by means of the FEAs. Design/methodology/approach: The finite element model is used to evaluate self and mutual inductances in several transmitting-receiving coil configurations and relative positions. In particular, the FEA simulates the aluminum and steel layers as shell elements in a 3D domain. The self and mutual inductance values in the aligned coil case are also used as input parameters in a circuit model to evaluate the onload current. Findings: The use of shell elements in FEA substantially reduces the number of mesh elements needed to simulate the eddy currents in the steel and aluminum layer, so putting the ground for low-cost field analysis. Moreover, the FEA gives an accurate computation of the self and mutual inductance to be used in a circuit model, which, in turn, provides a fast update of the onload induced current. Originality/value: To save computational time, the use of 2D shell elements to model thin conductive regions introduces a simplified FEA that could be used in the WPTS simulation. Moreover, the dynamic behavior of WPTS, i.e. the operation when the receiving coil is moving with respect to the transmitting one, is considered. Because of the lumped parameters' dependence upon the relative positions of the two coils, the proposed method allows identifying the circuit parameters for several configurations so substantially reducing the computational burden. [ABSTRACT FROM AUTHOR]

Purpose: The horizontal rotational single-sheet tester (RSST) suffers from weaknesses such as the reduced size of test samples, measurement disturbances due to magnetic flux leakage and nonhomogeneity of field in the measurement area. Although the vertical RSST allows to overcome the first two aforementioned drawbacks, the heterogeneity of the field in the test sample remains an issue. In addition, there is still a lack of device standardization to ensure test repeatability, as already is well established with the Epstein frame. This paper aims to investigate the influence of several parameters on the field homogeneity in the test sample. Design/methodology/approach: A fully 3D finite element model of a vertical RSST is developed and used to perform a sensibility study on several geometrical parameters. Findings: The influence of several parameters on the field homogeneity in the test sample, such as the geometrical dimensions of the yokes, the presence or not of holes drilled inside the test sample for B-coil placement as well as the size of the H-coils and B-coils, is addressed. Originality/value: It is expected that this study will contribute to the optimization and standardization vertical RSSTs. [ABSTRACT FROM AUTHOR]

Purpose: This paper presents the design techniques applied to a novel fractional-slot 6/4 pole permanent magnet brushless direct current (PMBLDC) motor, for cogging torque reduction. The notable feature of this motor is the simplicity of the design and low production cost. The purpose of this paper is to reduce the peak cogging torque of the motor. The focus is put on the stator topology tuning, and a new design for the stator poles is proposed. By determining the optimum stator pole arc length and the best pole shoe thickness, the cogging torque is significantly reduced. This new optimised motor design has been analysed in detail. The validation of the results is documented with respective figures and charts. Design/methodology/approach: At the beginning, the design data for the 6/4 pole PMBLDC motor with concentrated three phase windings and asymmetric stator pole arcs is presented. In the study, this motor is taken as a reference model (A0, T0). A full performance finite element analysis of the reference motor has been carried out, and the weak points in the motor design have been identified. By simple design techniques, tuning the stator pole geometry, a two-stage design optimisation for cogging torque minimisation has been performed and the solution array has been derived. The optimised model is selected and proposed (Aopt, Topt). The comparative analysis of the reference and optimised motors show the advantages of the proposed novel design and prove the methodology. Findings: The results of the work demonstrate how simple design techniques can minimise the peak of the cogging torque profile, while maintaining the specified electromagnetic torque value. The sensitivity of the cogging torque profile because of changes of the stator pole design inside the prescribed constraints is apparent. The stator poles of the reference motor have an arc length of 85° and pole shoe thickness of 6 mm. The newly shaped stator poles have an arc length of 78.5° and pole shoe thickness 4.8 mm. The peak-cogging torque has been reduced from 0.158 Nm to a respectable value of 0.066 Nm. However, to reduce electromagnetic torque ripple and pulsations, further investigations are required. Originality/value: The paper presents an approach to cogging torque reduction for a 6/4 PMBLDC motor. A two-step original design procedure is introduced and an optimised stator pole geometry is defined. The minimised cogging torque has been demonstrated with improved usage of the active materials. This work could serve as a good basis for further optimisation of the motor design. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to obtain an accurate methodology for modelling and analysis of the permanent magnet synchronous generator connected to power electronic components. Design/methodology/approach: This paper presents the methodology of the co-simulation of a permanent magnet synchronous generator. It combines Simulink, Maxwell and Simplorer software to demonstrate the electrical machine behaviour connected with the power electronics' circuit. The finite element analysis performed on the designed machine exhibit a more accurate behaviour over simplified Simulink models. Results between both simulation and co-simulation are compared to measurements. Findings: The co-simulation approach offers a more accurate depiction of the machine behaviour and its interaction with the non-linear circuits. Research limitations/implications: This paper focuses on the interior permanent magnet type of PMSG and its interaction with a passive rectifier (nonlinear circuit). Practical implications: The advanced capabilities of the co-simulation method allow to analyse more variations (geometry, materials, etc.), and its interaction with non-linear circuits, than previous simulation techniques. Originality/value: The co-simulation as a tool for analysis and design of systems interconnected with unconventional and conventional electrical machines and prototypes, and the comparison of the obtained results with classical analysis and design methods, against measurements obtained from the prototype. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to clarify the relationship between stator tooth shape and DC voltage fluctuation of a double salient hybrid excitation generator (DSHEG). It analyzes the asymmetrical characteristics of the magnetic circuit and inductance between each phase. The study aims to reduce voltage fluctuation by using a stator shape optimization scheme, which helps reducing inductance difference. Design/methodology/approach: This paper opted for a method combined with theoretical analysis, simulation and experimental verification. The stator tooth optimization scheme is given based on theoretical asymmetrical analysis and Taguchi method. A series of two-dimensional finite element analysis simulation of different conditions are conducted. Two prototypes with different stator tooth shape are made and experiments are carried out. Findings: The paper provides empirical insights into how the stator tooth shape influences the asymmetry of inductance and DC voltage fluctuation. Compensation adjustments to the stator tooth shape can narrow the inductance differences of each phase. It suggests that "LTL" shaped DSHEG has lower voltage ripple than "III" shaped DSHEG without sacrificing output power. Research limitations/implications: Because of the chosen research approach, the gap between magnets and stator and end effect are not considered. Errors exist between simulation and experimental results. Practical implications: The paper includes implications for other "C" shaped tooth optimization. Study on phase asymmetry of the special machine can further improve quality testing and simplify control strategy. Originality/value: This paper analyzes the asymmetry of DSHEG and proposes an optimized stator tooth shape to reduce DC voltage fluctuation. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to present the applicability of data-driven solvers to computationally demanding three-dimensional problems and their practical usability when using real-world measurement data. Design/methodology/approach: Instead of using a hard-coded phenomenological material model within the solver, the data-driven computing approach reformulates the boundary value problem such that the field solution is directly computed on raw measurement data. The data-driven formulation results in a double minimization problem based on Lagrange multipliers, where the sought solution must conform to Maxwell's equations while at the same time being as close as possible to the available measurement data. The data-driven solver is applied to a three-dimensional model of a direct current electromagnet. Findings: Numerical results for data sets of increasing cardinality verify that the data-driven solver recovers the conventional solution. Additionally, the practical usability of the solver is shown by using real-world measurement data. This work concludes that the data-driven magnetostatic finite element solver is applicable to computationally demanding three-dimensional problems, as well as in cases where a prescribed material model is not available. Originality/value: Although the mathematical derivation of the data-driven problem is well presented in the referenced papers, the application to computationally demanding real-world problems, including real measurement data and its rigorous discussion, is missing. The presented work closes this gap and shows the applicability of data-driven solvers to challenging, real-world test cases. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to use a history-dependent vector stop hysteresis model incorporated into a two dimensional finite elements (FE) simulation environment to solve the magnetic field problems in electrical machines. The vector stop hysteresis model is valid for representing the anisotropic magnetization characteristics of electrical steel sheets. Comparisons of the simulated results with measurements show that the model is well appropriate for the simulation of electrical machines with alternating, rotating and harmonic magnetic flux densities. Design/methodology/approach: The anisotropy of the permeability of an electrical steel sheet can be represented by integrating anhysteretic surfaces into the elastic element of a vector hysteresis stop model. The parameters of the vector stop hysteresis model were identified by minimizing the errors between the simulated results and measurements. In this paper, a damped Newton method is applied to solve the nonlinear problem, which ensures a robust convergence of the finite elements simulation with vector stop hysteresis model. Findings: Analyzing the measurements of the electrical steel sheets sample obtained from a rotational single sheet tester shows the importance to consider the anisotropic and saturation behavior of the material. Comparing the calculated and measured data corroborates the hypothesis that the presented energy-based vector stop hysteresis model is able to represent these magnetic properties appropriately. To ensure a unique way of hysteresis loops during finite elements simulation, the memory of the vector stop hysteresis model from last time step is kept unchanged during the Newton iterations. Originality/value: The results of this work demonstrates that the presented vector hysteresis stop model allows simulation of vector hysteresis effects of electrical steel sheets in electrical machines with a limited amount of measurements. The essential properties of the electrical steel sheets, such as phase shifts, the anisotropy of magnetizations and the magnetization characteristics by alternating, rotating, harmonic magnetization types, can be accurately represented. [ABSTRACT FROM AUTHOR]

Purpose: Inverse problems in electromagnetism, namely, the recovery of sources (currents or charges) or system data from measured effects, are usually ill-posed or, in the numerical formulation, ill-conditioned and require suitable regularization to provide meaningful results. To test new regularization methods, there is the need of benchmark problems, which numerical properties and solutions should be well known. Hence, this study aims to define a benchmark problem, suitable to test new regularization approaches and solves with different methods. Design/methodology/approach: To assess reliability and performance of different solving strategies for inverse source problems, a benchmark problem of current synthesis is defined and solved by means of several regularization methods in a comparative way; subsequently, an approach in terms of an artificial neural network (ANN) is considered as a viable alternative to classical regularization schemes. The solution of the underlying forward problem is based on a finite element analysis. Findings: The paper provides a very detailed analysis of the proposed inverse problem in terms of numerical properties of the lead field matrix. The solutions found by different regularization approaches and an ANN method are provided, showing the performance of the applied methods and the numerical issues of the benchmark problem. Originality/value: The value of the paper is to provide the numerical characteristics and issues of the proposed benchmark problem in a comprehensive way, by means of a wide variety of regularization methods and an ANN approach. [ABSTRACT FROM AUTHOR]

Purpose Synchronous Reluctance (SynRel) motors are known to suffer from excessive torque ripples. The classical way to avoid this drawback of the motor is skewing the slots. This paper aims to provide an analytic estimation of the best skew angle to minimize the ripples in such SynRel motors with tooth windings. The approach used in this paper consists of the minimization of the spectral components of the magnetic energy that cause these oscillation torques. The method was validated by means of a multi-slice finite element model (FEM).Design/methodology/approach An analytic model, based on permeance theory, is derived to analyse the electromagnetic phenomena taking place inside of the motor. This model allows the identification of the causes underlying the torque ripple production. Based on this understanding, the most suitable skew angle can be determined. The analytic method, together with the best skew angle, is validated by means of an FEM of a SynRel machine.Findings A method to determine the optimum skew angle for a SynRel machine is presented. It depends on the wave-number of the magnetic waves producing the torque ripple. It is twice the one typically chosen for induction machines.Practical/implications The proposed approach allows improving on the design methodology for the production of smoothly running SynRel machines.Originality/value The methodology utilized in this paper is based on the relationship between the mechanical torque and the magnetic energy stored in the motor (virtual work law). From this, the best skew angle to eliminate the magnetic energy causing torque ripple can be determined. It, therefore, proposes an effective alternative to the common use of inductance models to determine such angles. [ABSTRACT FROM AUTHOR]

Purpose: To improve the power density and generation efficiency of the tubular permanent magnetic linear generators (TPMLGs) under realistic sea-stator condition, a TPMLG with 120° phase belt toroidal windings (120°-TPMLG) for wave energy conversion is proposed in this paper. Design/methodology/approach: First, the structure of the 120°-TPMLG is introduced and its operation principle is analyzed. Second, the design process of the 120°-TPMLG is described. Meanwhile, the finite-element models of the 120°-TPMLG and the TPMLG with traditional fractional pitch windings (T-TPMLG) are established based on the similar overall dimensions. Then, the electromagnetic characteristics of the 120°-TPMLG are analyzed, such as air gap flux density, back electromotive force and load voltage. Finally, a comparative analysis of the magnetic flux density, flux linkage, load and no-load performance of the two generators are conducted. Findings: The result shows that the 120°-TPMLG has higher power density and generation efficiency than the T-TPMLG. Originality/value: This paper proposes a TPMLG with 120° phase belt toroidal windings (120°-TPMLG) to improve the power density and generation efficiency. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to unveil the generation mechanism of the thrust force in a tubular flux-switching permanent magnet (PM) linear (TFSPML) machine; the operation principle of the TFSPML machine is analyzed. Design/methodology/approach: First, the air-gap flux density harmonic characteristics excited by PMs and armature windings are investigated and summarized based on a simple magnetomotive force (MMF)-permeance model. Then, the air-gap field modulation theory is applied in analyzing the air-gap flux density harmonics that contribute to the electromagnetic force. In addition, a simple method for separating the end force of the TFSPML machine is proposed, which is a significant foundation for the comprehensive analysis of this type of machine. As a result, the operation principle of the TFSPML machine is thoroughly revealed. Findings: The analysis shows that the average electromagnetic force is mainly contributed by the air-gap dominant harmonics, and the thrust force ripple is mainly caused by the end force. Originality/value: In this paper, the operation principle of the TFSPML machine is analyzed from the perspective of air-gap field modulation. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to analyze the characteristics of the factors influencing the effect of magnetic levitation, including the impedance angle of the levitated coil, number of turns, material parameter, frequency of excitation and geometric parameters. The final purpose is to provide approaches to increasing the levitation effect. Design/methodology/approach: Some design principles and strategies for levitation systems are suggested, such as selecting the number of turns of the levitated coil, choosing the frequency of excitation considering the saturation phenomenon of levitation force against frequency and deciding the section area of the excitation coil and its ratio of height and thickness. Findings: The magnetic force is not always repulsive in a cycle. Therefore, the key approach to increasing the levitation is to increase the period when the force is repulsive and decrease the time when attractive. The impedance angle of the equivalent circuit of the levitated coil determines the ratio of the two periods, and the larger the angle, the longer the repulsion period. A valuable finding is that a saturation situation exists between the levitation force and frequency; that is, when the frequency increases to a certain value, the increasing degree of force tends to decrease as the frequency increases. Originality/value: Some influential characteristics were found in some factors against the effect of the levitation system, which is beneficial for improving the efficiency of systems. For example, owing to the saturation phenomenon of the frequency, it is useless to continue increasing the frequency and the copper-levitated coil does not bring much greater force effectiveness than the aluminum coil. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of the paper is to present an analysis of an influence of shape and material of rotor bars on the process of self-excitation and performance characteristics of single-phase, self-excited induction generator (SP-SEIG). Design/methodology/approach: The presented analysis is based on the results of transient simulations of SP-SEIG performed with the use of field-circuit model of the machine. Four various shapes of the rotor bars and two different conductor materials were investigated. The results for the base model with rounded trapezoidal rotor slots were validated by measurements. Findings: An improvement of the performance characteristics – the extension of the stable operating range of the generator – was obtained for rectangular copper rotor bars. The improvement is the result of strong skin effect in the squirrel rotor cage. Application of round rotor slots results in shorter time of voltage build-up during the self-excitation of the generator caused by less apparent deep bar effect in round bars. Originality/value: The originality of the paper is the application of the copper rotor cage in the single-phase, self-excited induction generator. Its use is beneficial, as it allows for extension of the range of stable operating range. The results may be used for designing new constructions of the single-phase, self-excited induction generators, as well as the constructions based on general purpose single-phase induction motors. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to propose a spoke-type fractional-slot concentrated windings (FSCW) PM machine for EVs driving system to improve torque density. To further improve electromagnetic performance, the multi-objective optimization design is processed based on response surface (RS) model and simulated annealing cuckoo search (SA-CS) algorithm. Design/methodology/approach: The spoke-type FSCW PM machine is designed and optimized to meet the requirement of EVs driving system. First, a spoke-type FSCW PM machine is designed and some of key parameters are obtained based on equivalent magnetic circuit (EMC) method. Then, the RS model and modified SA-CS algorithm are proposed to obtain higher torque, lower torque ripple and higher efficiency. Findings: After verification by finite element method for no-load and load performance, the optimal machine has higher torque density, lower torque ripple and higher efficiency compared with initial machine. Finally, a 20 kW prototype is manufactured and tested to verify the validity of the proposed optimization design method. Originality/value: This paper designs a high torque density spoke-type FSCW PM machine, which is superior for EVs driving system. Meanwhile, a novel modified SA-CS algorithm is applied to the field of electrical machine multi-objective optimal design. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to propose a new magnetic-geared motor (MGM) which can easily increase the gear ratio up to approximately several hundred. The operational principle is described, and the relationship between the maximum transmission torques of each layer of the differential harmonic magnetic gear is investigated using a mathematical model and finite element method (FEM). Design/methodology/approach: The operational principle and maximum transmission torque are described using a mathematical model. The FEM is used to investigate the operational principle and torque characteristics. Findings: As the proposed model can realize a larger gear ratio than the conventional model, the torque constant can be approximately 100 times as large as that of the conventional model. Research limitations/implications: The proposed and conventional models have the same shape stator, and it is not optimized. Originality/value: The relationship between the maximum transmission torques of each layer is described, and this helps the design of a differential type MGM. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to use a scaling approach to scale the solutions of a beforehand-simulated finite element (FE) solution of an induction machine (IM). The scaling procedure is coupled to an analytic three-node-lumped parameter thermal network (LPTN) model enabling the possibility to adjust the machine losses in the simulation to the actual calculated temperature. Design/methodology/approach: The proposed scaling procedure of IMs allows the possibility to scale the solutions, particularly the losses, of a beforehand-performed FE simulation owing to temperature changes and therefore enables the possibility of a very general multiphysics approach by coupling the FE simulation results of the IM to a thermal model in a very fast and efficient way. The thermal capacities and resistances of the three-node thermal network model are parameterized by analytical formulations and an optimization procedure. For the parameterization of the model, temperature measurements of the IM operated in the 30-min short-time mode are used. Findings: This approach allows an efficient calculation of the machine temperature under consideration of temperature-dependent losses. Using the proposed scaling procedure, the time to simulate the thermal behavior of an IM in a continuous operation mode is less than 5 s. The scaling procedure of IMs enables a rapid calculation of the thermal behavior using FE simulation data. Originality/value: The approach uses a scaling procedure for the FE solutions of IMs, which results in the possibility to weakly couple a finite element method model and a LPTN model in a very efficient way. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to propose a method to estimate the magnetic saturation and end effect of linear switched reluctance machines (LSRMs) with fully pitched winding configuration used in the wave energy conversion. Design/methodology/approach – The magnetic saturation and strong coupling make it very difficult to derive a comprehensive mathematical model for the behavior of the LSRMs. Meanwhile, the various end effects could not be comprehensively considered in the two-dimensional model which is widely studied. Therefore, the magnetic equivalent circuit model including the three-dimensional (3-D) effects is presented in this paper and 3-D finite element analysis (FEA) is used to validate the mathematical model. Findings – The results from 3-D FEA are in good agreement with the numerical simulation, which validates the accuracy of the magnetic equivalent circuit modeling method. Practical implications – This technique helps one to know the influence exerted by the magnet saturation and end effect of LSRMs and provides a powerful computer-aided analysis tool. Meanwhile, this modeling method supplies accurate values for the following study of reliable control algorithm. Originality/value – The paper presents a magnetic equivalent method to estimate the magnetic saturation and end effect of LSRMs with fully pitched winding configuration used in the wave energy conversion. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to present the electromagnetic phenomena in permanent magnet synchronous generator (PMSG) suited for wind turbines with uniquely designed system of two windings. The machine’s windings allow for application of a reliable and low-cost power electronic converter.Design/methodology/approach The 2D field-circuit model has been developed and used in comparative analysis between reference design PMSG with concentrated three-phase winding and two-windings PMSG to facilitate application of a low-cost and reliable AC/DC power electronic converter. The paper focuses on comparison of radial force density, core losses and torque waveforms in the proposed and reference machine with sinusoidal load currents.Findings The usefulness of the proposed approach for analysis of the two-winding PMSG performance by means of the field-circuit model has been proved. The obtained results show practically no drop off of performance of proposed machine in relation to reference PMSG. Moreover, it has been shown that both machines are characterized by the same level of radial force density. Therefore, the lower cost and reliable power electronic converts can be applied in the wind power energy systems (WPES) by slightly more complex design of the stator winding.Originality/value The proposed 2D field-circuit numerical model makes it possible to analyze the performance of the star-delta winding PMSG dedicated to be loaded by the AC to DC converter specially designed to achieve high reliability and efficiency of the system. Presented comparative studies on generator performance show that proposed modulated synchronous flux generator characterize with the same output torque at given supply current and core losses level like conventional PMSG with sinusoidal load. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to propose the complementary design rules, give a quantitative comparison and analyze the force production mechanism of two kinds of primary wound field flux-switching linear (PWFFSL) motors.Design/methodology/approach PWFFSL motors have the merits of no use of rare-earth magnet, low cost and a wide operation range in which the armature windings and the field windings are all located at the short primary mover and the secondary is very robust. Hence, the PWFFSL motor is ideal for rail transportation systems which need a long stator and a wide speed range. To overcome the disadvantages of the existing PWFFSL motors, new complementary design rules will be proposed. Also, to offer a better PWFFSL motor for the rail transportation systems, it is necessary to investigate different structures of PWFFSL motors and give a comprehensive comparison. To predict the force performance of two kinds of PWFFSL motors with different secondary types, their flux density analysis and force production mechanism will be presented and compared.Findings The comparison result shows that the PWFFSL motor with toothed secondary can offer larger thrust force, higher force density and higher efficiency, whereas the PWFFSL motor with segmented secondary has the merits of lower force ripple, less use of stator iron, higher power factor and less critical saturation.Research limitations/implications Many PWFFSL motors with different primary/secondary pole pitches based on the proposed design principle have not been considered in this paper.Originality/value This paper has presented the air-gap flux analysis, proposed the complementary design rules for two kinds of PWFFSL motors with different secondary types and compared the electromagnetic performance of the two motors. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to analyze electromagnetic performance and develop an analytical approach to find the suitable coil combination and no-load flux linkage of the proposed hybrid excited consequent pole flux switching machine (HECPFSM) while minimizing the drive storage and computational time which is the main problem in finite element analysis (FEA) tools. Design/methodology/approach: First, a new HECPFSM based on conventional consequent pole flux switching permanent machine (FSPM) is proposed, and lumped parameter magnetic network model (LPMNM) is developed for the initial analysis like coil combination and no-load flux linkage. In LPMNM, all the parts of one-third machine are modeled which helps in reduction of drive storage, computational complexity and computational time without affecting the accuracy. Second, self and mutual inductance are calculated in the stator, and dq-axis inductance is calculated using park transformation in the rotor of the proposed machine. Furthermore, on-load performance analysis, like average torque, torque density and efficiency, is done by FEA. Findings: The developed LPMNM is validated by FEA via JMAG v. 19.1. The results obtained show good agreement with an accuracy of 96.89%. Practical implications: The proposed HECPFSM is developed for high-speed brushless AC applications like electric vehicle (EV)/hybrid electric vehicle (HEV). Originality/value: The proposed HECPFSM offers better flux regulation capability with enhanced electromagnetic performance as compared to conventional consequent pole FSPM. Moreover, the developed LPMNM reduces drive storage and computational time by modeling one-third of the machine. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to develop an analytical approach to validate the finite element analysis (FEA) results. FEA itself is a powerful tool to evaluate the performance of electrical machines but takes more time and requires more drive storage. To overcome this issue, subdomain modeling (SDM) is used for the proposed machine. Design/methodology/approach: SDM is developed to validate the electromagnetic performance of a new linear hybrid excited flux switching machine (LHEFSM) with ferrite magnets. In SDM, the problem is divided into different physical regions called subdomains. Maxwell's governing equation is solved analytically for each region, where the magnetic flux density (MFD) is generated. From the generated MFD, x and y components are calculated, which are then used to find the useful force along the x-axis. Findings: FEA validates the developed SDM via JMAG v. 20.1. The results obtained show excellent agreement with an accuracy of 95.13%. Practical implications: The proposed LHEFSM is developed for long stroke applications like electric trains. Originality/value: The proposed LHEFSM uses low-cost ferrite magnets with DC excitation, which offers better flux regulation capability with improved electromagnetic performance. Moreover, the developed SDM reduces drive storage and computational time by modeling different parts of the machine. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this paper is to find a fast-acting numerical model of the phase shifter. Design/methodology/approach: The 3D FE model of the investigated unit is presented and compared with the results of the measurements. Due to its size, it is not suitable for transient analyses. The simplified 2D finite elements approach is discussed afterwards, with the identity of the magnetic energy stored in both models as the criterion of similarity between 2D and 3D models. Findings: The introduction of scaling factors for the magnetic permeability values in particular volumes of the two-transformer set of the phase shifter enabled acceptable accuracy in calculations of the basic exploitation parameters of the phase shifter. Research limitations/implications: The developed methodology allows the analysis of the exploitation conditions of two separated transformers connected in a power grid inside the single finite elements model. Originality/value: Although the numerical models of power transformers are extensively discussed in the literature, the usage of the equivalent fast 2D model for the representation of two cooperating transformers at load conditions was not published yet. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to investigate a novel rotor design model to improve the technical performance of a superconducting synchronous generator. Design/methodology/approach: Superconducting synchronous generators with a modular rotating cryostat for a single coil of the superconducting winding instead of an old-style single cryostat in which all rotor components are cold are briefly discussed. Subsequently, a new method of cryostat arrangement in the magnetic system of a rotor is considered. Different options were compared for the cryostat placement. The advantages of the novel rotor design model are noted. Findings: In the novel rotor design model, the leakage coefficient of the excitation winding decreases, and the air gap magnetic flux increases, which will save on a superconductor material. Research limitations/implications: For the purposes of this investigation, a finite element study of flux distribution in the cross section of a superconducting synchronous generator with a 10 MW rating at 10 rpm was conducted, and the magnetic fluxes and air gap flux densities were obtained for different modes. For direct-drive superconducting synchronous generators with distributed winding and different pole numbers, the calculations of magnetic fluxes were carried out by calculating the magnetic conductivities. Originality/value: A new method of the cryostat arrangement in the magnetic system of a rotor has been classified as an invention and was protected by a patent. This paper is directly applicable to the field of superconducting synchronous generators. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to go deeper on the analysis of the shaft voltage of large turbogenerators. The main interest of this study is the investigation process developed. Design/methodology/approach: The analysis of the shaft voltage because of several defects is based on a two-dimensional (2D) finite element modeling. This 2D finite element model is used to determine the shaft voltage because of eccentricities or rotor short-circuit. Findings: Dynamic eccentricities and rotor short circuit do not have an inherent impact on the shaft voltage. Circulating currents in the stator winding because of defects impact the shaft voltage. Originality/value: The original value of this paper is the investigation process developed. This study proposes to quantify the impact of a smooth stator and then to explore the contribution of the real stator winding on the shaft voltage. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to propose a method to create 3-D finite element meshes automatically using the Delaunay tetrahedralization with the weighted node density technique. Using this method, the adaptive finite element analysis (FEA) was carried out for the calculation of the magnetic field of an eddy current verification model to clarify the usefulness of the method. Moreover, the error evaluation function for the adaptive FEA was also discussed. Design/methodology/approach: The method to create the 3-D finite element meshes using the Delaunay tetrahedralization is realized by the weighted node density technique, and Zienkiewicz-Zhu's error estimator is used as the error evaluation function of the adaptive FEA. Findings: The magnetic flux density vectors on the node in the error evaluation function for the adaptive FEA should be calculated with the weighted average by the reciprocal of the volume of elements. Originality/value: This paper describes the method to create 3-D finite element meshes and the comparison among calculation methods of the magnetic flux density vectors on the node for the error estimator. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is the presentation of an electrical equivalent circuit for inductive components as well as the methodology for electrical parameter extraction by using a 3 D finite element analysis (FEA) tool. Design/methodology/approach: A parameter extraction based on energies has been modified for three dimensions. Some simplifications are needed in a real model to make the 3 D finite element method (FEM) analysis operative for design engineers. Material properties for the components are modified at the pre-modeling step and a corrector factor is used at the post-modeling step to achieve the desired accuracy. Findings: The current hardware computational limitations do not allow the 3 D FEA for every magnetic component, and due to the component asymmetries, the 2 D analysis are not precise enough. The application of the new methodology for three dimensions to several actual components has shown its usefulness and accuracy. Details concerning model parameters extration are presented with simulation and measurement results at different operation frequencies from 1 kHz to 1 GHz being the range of switching frequencies used by power electronic converters based on Si, SiC or GaN semiconductors. Practical implications: This new model includes the high-frequency effects (skin effect, proximity effect, interleaving and core gap) and other effects can be only analyzed in 3 D analysis for non-symmetric components. The electrical parameters like resistance and inductance (self and mutual ones) are frequency-dependent; thus, the model represents the frequency behavior of windings in detail. These parameters determine the efficiency for the inductive component and operation capabilities for the power converters (as in the voltage boost factor), which define their success on the market. Originality/value: The user can develop 3 D finite element method (FEM)-based analyses with geometrical simplifications, reducing the CPU time and extracting electrical parameters. The corrector factor presented in this paper allows obtaining the electrical parameters when 3D FE simulation would have developed without any geometry simplications. The contribution permits that the simulations do not need a high computational resource, and the simulation times are reduced drastically. Also, the reduced CPU time needed per simulation gives a potential tool to optimize the non-symmetric components with 3 D FEM analysis. [ABSTRACT FROM AUTHOR]

Purpose: Reliable modeling of induction hardening requires a multi-physical approach, which makes it time-consuming. In designing an induction hardening system, combining such model with an optimization technique allows managing a high number of design variables. However, this could lead to a tremendous overall computational cost. This paper aims to reduce the computational time of an optimal design problem by making use of multi-fidelity modeling and parallel computing. Design/methodology/approach: In the multi-fidelity framework, the "high-fidelity" model couples the electromagnetic, thermal and metallurgical fields. It predicts the phase transformations during both the heating and cooling stages. The "low-fidelity" model is instead limited to the heating step. Its inaccuracy is counterbalanced by its cheapness, which makes it suitable for exploring the design space in optimization. Then, the use of co-Kriging allows merging information from different fidelity models and predicting good design candidates. Field evaluations of both models occur in parallel. Findings: In the design of an induction heating system, the synergy between the "high-fidelity" and "low-fidelity" model, together with use of surrogates and parallel computing could reduce up to one order of magnitude the overall computational cost. Practical implications: On one hand, multi-physical modeling of induction hardening implies a better understanding of the process, resulting in further potential process improvements. On the other hand, the optimization technique could be applied to many other computationally intensive real-life problems. Originality/value: This paper highlights how parallel multi-fidelity optimization could be used in designing an induction hardening system. [ABSTRACT FROM AUTHOR]

Purpose: The aim of the paper is to investigate the impacts of simplifications of a reduced-order simulation model of squirrel cage induction machines (SCIMs) by numerical experiments. Design/methodology/approach: Design of setups to isolate the main influences on the results of the reduced-order model of SCIMs. Results of time-stepping finite element calculations are used as benchmark. Findings: Whereas neglecting eddy current effects and the assumption of a sinusoidal rotor current distribution leads to acceptable deviations in regular inverter operation, the sampling and interpolation of the machine parameters in a two-axis coordinate system considerably deteriorate the model accuracy. Using a polar coordinate system for this purpose is expected to significantly improve the model quality. Originality/value: Preparing the ground for a successful, both fast and accurate simulation model of SCIMs as parts of electrified drivetrains. [ABSTRACT FROM AUTHOR]

Purpose: Acoustic noise is a crucial performance index in the design of electrical machines. Due to the challenges associated with modelling a complete motor, the stator is often used to estimate the sound power in the prototyping stage. While this approach greatly reduces lengthy simulations, the actual sound power of the motor may not be known. But, from the acoustic noise standpoint, not much is known about the correlation between the stator and complete motor. This paper, therefore, aims to use the sound pressure levels of the stator and the full motor to investigate the existence of correlations in the interior permanent magnet synchronous motor. Design/methodology/approach: A multiphysics simulation framework is proposed to evaluate the sound pressure levels of multiple motor geometries in a given design space. Then, a statistical analysis is performed on the calculated sound pressure levels of each geometry over a selected speed range to compare the correlation strength between the stator and the full model. Findings: It was established that the stator and the complete motor model are moderately correlated. As such, a reliance on the stator sound power for design and optimization routines could yield inaccurate results. Originality/value: The main contribution involves the use of statistical tools to study the relationship between sound pressure levels associated with the stator geometry and the complete electric motor by increasing the motor sample size to capture subtle acoustic correlation trends in the design space of the interior permanent magnet synchronous motor. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to compare the hybrid FEM-BEM and FEM-DBCI methods for the solution of open-boundary static and quasi-static electromagnetic field problems. Design/methodology/approach – After a brief review of the two methods (both coupling a differential equation for the interior problem with an integral equation for the exterior one), they are compared in terms of accuracy, memory and computing time requirements by means of a set of simple examples. Findings – The comparison suggests that FEM-BEM is more accurate than FEM-DBCI but requires more computing time. Practical implications – Then FEM-DBCI appears more appropriate for applications which require a shorter computing time, for example in the stochastic optimization of electromagnetic devices. Conversely, FEM-BEM is more appropriate in cases in which a high level of precision is required in a single computation. Originality/value – Note that the FEM-BEM considered in this paper is a non standard one in which the nodes of the normal derivative on the truncation boundary are placed in positions different from those of the potential. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to propose a permanent magnet-assisted synchronous reluctance machine (PMASynRM) using ferrite magnets with the same power density as rare-earth PM synchronous motors used in Toyota Prius 2010.Design/methodology/approach A novel rotor structure with rectangular PMs is discussed with respect to the demagnetization of ferrite magnets and mechanical strength. Some electromagnetic characteristics including torque, output power, loss and efficiency are calculated by 2D finite element analysis.Findings The results of the analysis show that a high power density and high efficiency for PMASynRM can be achieved using ferrite magnets.Originality/value This paper proposes a novel rotor structure of PMASynRM with low-cost ferrite magnets that achieves high power density as permanent machines with rare-earth PMs. [ABSTRACT FROM AUTHOR]