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A novel asymmetric interior permanent magnet (AIPM) machine is proposed in this paper. The machine's rotor consists of asymmetric poles and auxiliary flux barriers. The torque ripple of the machine is weakened by the asymmetric design of the left and right sides of the magnetic poles. The magnetic‐field‐shifting (MFS) effect improves the electromagnetic torque after adding the auxiliary flux barrier to shift the magnetic axis. The influence of critical geometrical parameters on the electromagnetic performance of the machine is investigated under the condition that the stator and permanent magnet volume remain unchanged. The relevant geometrical parameters of the machine are optimized and designed through the improved Taguchi method. The performance of the AIPM machine and the conventional machine under no‐load and load conditions are further compared by simulation analysis with finite elements, verifying the increase in electromagnetic torque and the reduction in torque ripple. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The axial flux permanent magnet (AFPM) machines with the parallel magnetic circuit (PMC) rotor can effectively improve its torque density. The PMC rotor consists of two sub‐rotors, radial Halbach array permanent magnet (PM) and tangential PM. The magnetic fields generated by two sub‐rotors are not in the same 2‐D analytical planes. In this paper, an equivalent analytical model of PMC‐AFPM machines is proposed to solve this problem. The radial Halbach array PM rotor is equated to the axial Halbach array PM rotor based on the equivalent transformation principle. The exact subdomain models of equivalent axial Halbach array PM rotor and tangential PM rotor are built respectively and then superimposed to obtain the magnetic field distribution. The electromagnetic characteristics of the PMC‐AFPM machine under no‐load and load conditions are calculated by the proposed analytical model and compared with calculations of the finite element model (FEM). The results verify the accuracy of the equivalent analytical model. The comparative analysis of the AFPM machines with PMC rotor and tangential PM rotor verifies the advantage of PMC rotor configuration to improve the torque density. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The permanent magnet claw pole machine (PMCPM) with soft magnetic composite (SMC) cores has shown better performance than the traditional transverse flux machine, and its performance can be improved by developing its stator with hybrid silicon sheet and SMC cores, and this kind of PMCPM is named as HPMCPM. Due to its complex 3D magnetic structure, analyzing its performance by using the traditional finite element method (FEM) is time-consuming. To overcome this constraint, this paper proposes a magneto-electric-thermal coupling network (METCN) model with bidirectional data transmission to calculate the electromagnetic performance and temperature distribution and the calculation results are verified by the FEM method and experimental measurement results. Compared with the 3D FEM, the proposed METCN method has the advantage of fast calculation speed and similar accuracy. [ABSTRACT FROM AUTHOR]

In this paper, three typical permanent magnet machines for All-Electric aircraft propulsion are designed, optimized and compared. Firstly, the necessary performances are determined based on the requirements of high power/torque density and an aircraft with a maximum takeoff weight of 1500 kg. The initial structures of interior permanent magnet (IPM) synchronous machine, vernier permanent magnet (VPM) machine and flux-switching permanent magnet (FSPM) machine are designed with identical stator outer radius and rotor shaft length. Then, parametric sensitivity analysis and multi-objective particle swarm are combined as an optimization methodology to optimize these machines. Based on the finite element analysis, the electromagnetic performances such as no-load airgap flux density harmonic spectrum, cogging torque, average output torque, losses, efficiency and power factor, etc., are generally compared and analyzed. Subsequently, the discussions are carried out, where the strength and weakness of these three machines are concluded and the future prospects are suggested. Finally, it is concluded that if effective measures are implemented to reduce the permanent magnet eddy current loss and improve the power factor, the VPM machine would be the most suitable choice among these machines for All-Electric aircraft propulsion. [ABSTRACT FROM AUTHOR]

By designing stator teeth using grain-oriented sheets (GO) and other parts still with non-grain-oriented sheets (NGO), the electromagnetic performance of the interior permanent magnet synchronous machine (GO-IPMSM) can be improved greatly. As the stator core of the designed GO-IPMSM is a hybrid core that is composed of two different silicon sheets, both the electromagnetic and mechanical performances are affected by the stator joint shape between GO and NGO sheets. Meanwhile, with the adoption of GO, the torque ripple of GO-IPMSM is increased though the average torque is increased as well. For reducing the torque ripple, optimizing the rotor barrier shape is an effective way. In this paper, the piecewise linear interpolation method is employed for establishing the stator joint shape between GO and NGO sheets, and the polynomial method is proposed to establish the rotor barrier shape. Through the analysis, it can be seen that the stator joint shape plays a strong role in affecting the mechanical performance of the GO-IPMSM, while the effect on the electromagnetic performance is weak. The genetic algorithm is used to optimize the rotor barrier shape for achieving high average torque and low torque ripple. Lastly, a quick and accurate efficiency map calculation method based on the Kriging model is proposed for GO-IPMSM with less finite element method (FEM) samples are required. [ABSTRACT FROM AUTHOR]

In this paper, a new axial-type magnetic gear with an auxiliary flux-enhancing structure (AFS-AMG) is proposed. Compared to conventional AMGs, it has a higher torque density and higher permanent magnet (PM) utilization factor. Firstly, the design rules and operating principles of the proposed AFS-AMG are elaborated. Then, the mapping relation between the radial-type magnetic gears (RMGs) and AMGs are elucidated. Compared to its counterparts in RMGs, the AFS-AMG achieves a small size. Then, the geometrical parameters of the AFS-AMG are optimized to obtain better electromagnetic performance, where the torque density per volume and per PM volume is adopted as the evaluation standard. Finally, three different AMG topologies are constructed in finite element analysis (FEA) software for comparison. It is proven that the AFS-AMG has the largest torque density per volume and per PM volume. [ABSTRACT FROM AUTHOR]

Permanent magnet synchronous motors (PMSMs) have a scale of applications linking to the industrial machines. As these machines often work in a wide temperature range, the PMSM quality consistency is threatened by the temperature fluctuate. In fact, at the start of the production of the PMSMs, the quality consistency distribution already exist due to the manufacturing dispersion. However, traditional experiment‐based consistency analysis method is inadequate for the PMSM, due to its inevitable destructive measurement for the magnetic properties. To deal with the problem, this paper proposed a model‐based quality consistency analysis method. In this paper, mechanism analysis of the temperature influence on PMSMs is carried out by the finite element analysis and the digital modeling method, so that the impact of dispersion can be depicted by model rather than destructive measurement. The relationship between the temperature and PMSM cogging torque as well as other features is quantitatively revealed. To obtain the NdFeB temperature coefficient, magnetic samples were prepared and measured. Then, the temperature characteristics of the sensitive components of PMSM are established, and the PMSM temperature characteristics can be simulated by integrating temperature coefficients into the PMSM digital model. The qualitative and quantitative temperature characteristics of cogging torque are verified by experiments with a batch of PMSMs. [ABSTRACT FROM AUTHOR]

In this paper is presented a two-dimension analytical model for linear permanent magnet inner armature double-sided synchronous motors (LPMIADSSMs). The flux density in all areas of the proposed machine is calculated based on the sub-domain method. According to this method, the machine areas are divided into eleven sub-regions such as first external, first mover, first PM, first air gap, first winding, stator, second winding, second air gap, second PM, second external and second mover, which sign as FE, FR, FP, FAG, FW, S, SW, SAG, SP, SE and SR. To find the flux density equations, it is mandatory to solve the extracted Maxwell equations and apply the boundary conditions between each two sub-regions, which lead to find the unknown coefficients for flux density in each sub-region. In addition, the influences of magnetization patterns, i.e., parallel, ideal Hal Bach, 2-segment Halbach and bar magnet in the shifting direction of the flux distribution and armature reaction (AR), are investigated. To validate the obtained results, the proposed model results are compared with those obtained from finite element method (FEM) and Maxwell software. [ABSTRACT FROM AUTHOR]

This paper presents a two-dimensional analytical model for brushless double-rotor flux-switching permanent magnet machines (BDRPFSPMM) with yokeless stator recognized as a type of partitioned-structure flux-switching permanent magnet that is an appropriate machine to be employed as the electric motor in industry. The most salient advantages of the proposed machine are low iron loss due to volume of iron in stator and high space of stator slot for winding. The radial and tangential components of the magnetic flux density due to permanent magnets and armature currents in each active domain of the machine, electromagnetic torque, self- and mutual inductance, unbalanced magnetic force (UMF), and local traction are calculated based on the subdomain method. Teethes on both rotor and stator structures are effective on magnetic quantities, so interactions of rotor and stator saliency are considered. The method is general for the magnetic field calculation with any combination of rotor- and stator-pole number. To validate the proposed model, the analytical outputs are compared with those obtained from the finite element method (FEM). [ABSTRACT FROM AUTHOR]

In order to reduce the cogging torque of a symmetrical V-type line-start permanent magnet synchronous (LSPMS) motor, this paper proposes a multi-objective optimization method based on the combination of design parameter stratification and response surface methodology (RSM). The optimal solution to the RSM model is acquired using the max–min ant algorithm. The permanent magnet width, pole opening angle, stator slot width, rotor axial length, and rotor tooth width are selected as optimization variables. The cogging torque and average torque are the optimization objectives. Finite element method (FEM) results show that the cogging torque is reduced by 71.5%, the torque ripple is reduced by 65.6%, and the average torque is improved by 12%. Finally, the effectiveness of the algorithm is verified with simulation results. [ABSTRACT FROM AUTHOR]

This paper presents the results of a comprehensive investigation into the comparative analysis and design optimization of ferrite-based surface permanent magnet vernier machines (SPMVMs). While SPMVMs boast a simple mechanical structure and enhanced torque density attributed to the flux modulation effect, they suffer from a persistent challenge of low power factor. Several factors hinder the adoption of low-cost ferrite magnets in SPMVMs. First, ferrite magnets are prone to irreversible demagnetization, constraining the allowable range of magnet thickness. Second, the reduced residual magnetic flux density of ferrite magnets exacerbates the decrease in power factor and machine efficiency. Thus, achieving optimal performance in ferrite-based SPMVMs necessitates the careful selection of various design parameters. To address these issues, this study employs a surrogate-based metaheuristic optimization algorithm with adaptive sampling to identify the optimal solution. Additionally, the integration of a Halbach array is explored to further enhance the performance of the three-slot/two-pole SPMVM topology. Subsequently, two ferrite-based SPMVM baseline models—one with a conventional SPM structure and another with a Halbach magnet array—are thoroughly designed, optimized, and subjected to detailed performance analysis using the 2D finite element method. [ABSTRACT FROM AUTHOR]

In this paper, an electromagnetic analysis method is proposed to improve force characteristics by using spring permanent magnets (PMs) along the axial and circumferential directions of a linear oscillatory generator (LOG). For accurate electromagnetic analysis, a detailed analysis model of the LOG is developed, and the governing equations of each subdomain are derived based on Maxwell's equations and electromagnetic theory. Analytical solutions of the magnetic vector potential in each subdomain are derived using boundary conditions. The reliability of the proposed method is verified through a comparison with the results of a two-dimensional finite element analysis (FEA). In particular, the force characteristics depending on the spring PM is effectively derived by considering the three-dimensional (3D) circumferential and axial end effects. The proposed analysis method is used to determine the thickness of spring PM that transforms the detent force of the LOG with the spring PM into restoring force. The reliability of the proposed analysis method is verified through comparison with the results of a 3D FEA. [ABSTRACT FROM AUTHOR]

This paper proposes an analytical model of the double-stator spoke-type permanent magnet vernier machine (DSSTVM) using the subdomain method (SDM), which can be used to calculate the magnetic field distribution and corresponding electromagnetic parameters of the DSSTVM. The whole field domain is divided into several subdomains according to the magnetic characteristics of each region, within which Laplace's and Poisson's equations are solved accordingly in terms of magnetic vector potential (MVP). Then, the corresponding magnetic flux density distribution, back electromotive force (EMF), and electromagnetic torque of the DSSTVM can be obtained. Ultimately, finite element analysis (FEA) is adopted to validate the proposed analytical model's effectiveness for quickly predicting the no-load and on-load performances of the DSSTVM. [ABSTRACT FROM AUTHOR]

This paper introduces a technique aimed at improving the performance of an interior permanent magnet synchronous machine (IPMSM) by reducing torque ripple and radial force harmonics. Unlike conventional IPMSMs, the proposed method employs a variable airgap length that is defined by a mathematical function. Two distinct rotor shapes are investigated to determine the most efficient design. Finite Element Analysis is employed to assess both the electromagnetic and mechanical attributes of the proposed motors. It compares the results for three operating points of the shaped motor with those of a conventional one. The investigation delves into the influence of rotor geometry on key output parameters, including Back Electromotive Force (back‐EMF) harmonics, average torque, cogging torque, torque ripple, efficiency, power factor, and radial force harmonics. The findings indicate that optimising rotor shape can significantly enhance IPMSM performance by reducing torque ripples and radial force harmonics, while simultaneously increasing average torque and efficiency at different operating points. [ABSTRACT FROM AUTHOR]

This research paper represents the estimation and reduction of eddy current loss in a Magnetic Fault Current Limiter (MFCL). The nonlinear model of the device is established using electromagnetic coupled circuit supported by Finite Element Model. The current limiting performance of the MFCL is investigated by simulation study as well as laboratory testing. It is further observed that a significant amount of eddy current loss takes place inside the core and permanent magnet of the device. Different methods (shorting ring, lamination of permanent magnet and variation of magnet length) are proposed to reduce the eddy current. The advantages and disadvantages of these methods are discussed. Some design modifications are also proposed to minimize the temperature rise caused by the eddy current. [ABSTRACT FROM AUTHOR]

In this paper, a pole-changing (PC) flux reversal permanent magnet (FRPM) motor is proposed for obtaining a wide speed range. According to the general air-gap field modulation theory, the permanent magnet (PM) magnetic field is modulated into a series of harmonics with different pole numbers by rotor teeth. By introducing an especial PM arrangement, two groups of working harmonics with different pole-pair numbers are generated in the proposed 12-7 PC-FRPM motor due to the modulation of rotor teeth. Based on the calculated slot pitch angles of these harmonics, two winding connections can be obtained for PC operation to achieve two operating modes. The electromagnetic performance of PC-FRPM motor before and after PC are analyzed using finite element analysis and verified by the experimental test results. [ABSTRACT FROM AUTHOR]

The permanent magnet electrodynamic suspension (PMEDS) owns the promising application prospect, due to its simple structure, low cost and reliable load capacity. However, the underdamping of the PMEDS system is still a challenge in engineering applications of transportation. This paper proposes a passive damping method and its implementation structure to improve the underdamping characteristics. This method utilizes the inherent magnetic leakage of on-board magnets technically. The principle of passive damping and its implementation structure is introduced in detail. And the kinetic models of ordinary and improved structure are established based on the topology graph. Besides, the magnetic field and the electromagnetic force involved in the kinetic models are analyzed, and the numerical analysis method of the drag force is verified by the high-speed test rig. Furthermore, the performance of passive damping is verified by finite element method (FEM) and the time-domain response analysis. The results show that the improved damping structure can effectively suppress vibration and improve the dynamic stability of the PMEDS system. It is beneficial to the engineering application of the PMEDS in the future. [ABSTRACT FROM AUTHOR]

This paper presents the efficiency improvement of a pole-changing vernier machine (PCVM) by considering the residual magnetic flux density ( B r ) of low coercivity force (LCF) permanent magnets (PMs). The PCVM operates in two modes: vernier machine (VM) mode and permanent magnet synchronous machine (PMSM) mode, achieved through pole-changing. Pole-changing involves reversing the magnetic flux direction of LCF PM to alter the number of rotor pole pairs. By changing the number of rotor pole pairs, the PCVM operates as a VM mode at low speeds, providing high torque, and as a PMSM mode at high speeds, offering high efficiency. To achieve this, a combination of high coercivity force (HCF) PM and LCF PM is utilized in a single structure. The magnetic flux direction in the LCF PM is determined by B r , and the highest efficiency is achieved when B r reaches its maximum value | B r m |. This paper focuses on improving efficiency by obtaining B r m in VM mode and − B r m in PMSM mode through the design process. Additionally, finite element analysis (FEA) is employed to compare the performance of the improved model, which considers B r , with that of the conventional model, designed without considering B r . The improved model achieves higher B r values in each mode compared to the conventional model, resulting in increased torque density. Consequently, this leads to improved efficiency. [ABSTRACT FROM AUTHOR]

The ironless linear permanent magnet synchronous motor (ILPMSM) is highly compact, easy to control, and exhibits minimal thrust fluctuations, making it an ideal choice for direct loading applications requiring precise positioning accuracy in linear motor test rigs. To address the issue of temperature rise resulting from increased primary winding current and to simultaneously enhance thrust density while minimizing thrust fluctuations, this paper introduces a bilateral-type ILPMSM with a cooling water jacket integrated between the dual-layer windings of the primary movers. The primary winding of the motor adopts a dual-layer coreless structure where the upper and lower windings are closely spaced and cooled by a non-conductive metal cooling water jacket, while the dual-sided secondary employs a Halbach permanent magnet array. The motor's overall braking force is a combination of the electromagnetic braking force generated by the energized windings and the eddy current braking force induced on the cooling water jacket. This paper specifically focuses on the analysis of the eddy current braking force. Initially, the motor's geometry and working principle are presented. Subsequently, the equivalent magnetization intensity method is employed to determine the no-load air gap magnetic density resulting from the Halbach array. An analytical model is then developed to derive expressions for the eddy current density and braking force induced in the water-cooling jacket. The accuracy of the analytical method is validated through finite element analysis. Then, a comparative analysis of the braking forces in two primary cooling structures, namely the inter-cooled type and the two-side cooled type ILPMSM, is conducted. Moreover, the characteristics of the eddy current braking force are thoroughly examined concerning motor size parameters and operating conditions. This paper provides a solid theoretical foundation for the subsequent optimization design of the proposed motor. [ABSTRACT FROM AUTHOR]

Axial flux permanent magnet motors have attracted increasing attention due to their compact topology and high torque density. Many topological variations have arisen over time; however, limited research has directly compared the differences in magnetic performance of these topologies. This paper carries out a comprehensive investigation, employing both analytical and 3D finite element analyses, to compare the magnetic performance of three topologies: yokeless and segmented armature (YASA), axial flux internal rotor (AFIR), and offset AFIR. The findings reveal that each topology offers specific advantages for different applications. The YASA topology excels in minimizing core losses; the AFIR configuration achieves the highest torque density; and the offset AFIR topology shows the highest efficiency. The offset AFIR topology appears to offer advantages for a wide array of applications due to its higher power factor and lower permanent magnet loss, leading to reduced costs for converter design and cooling system design. [ABSTRACT FROM AUTHOR]

Fractional slot concentrated winding (FSCW) permanent magnet (PM) machines are gaining more attention for low‐speed applications because of their great advantages. This paper proposes a new structure for an FSCW double rotor axial flux PM synchronous machine (DRAFPMSM) with counter‐rotating rotors. In addition, an analytical formula for the Back EMF waveform of the proposed structure is presented. The accuracy of the formula is investigated by designing a 40 W sample machine. The rotors of this machine rotate with speeds of 600 and 428 rpm in opposite directions. The Back EMF of the sample machine is calculated using the suggested formula. In addition, the finite element method (FEM) is used to determine the Back EMF waveform. Comparison of the obtained results confirms that the new formula yields the Back EMF precisely such that the results well match to those of FEM. The effect of the relative position of two rotors on the Back EMF waveform is investigated using the proposed formula. In addition, the optimum relative position of two rotors for minimizing the Back EMF THD of the case study machine is determined. [ABSTRACT FROM AUTHOR]

Cogging torque can affect the performance of permanent magnet (PM) homopolar inductor machines (HIMs). In order to find the reduction methods of the PM HIM cogging torque, it is necessary to investigate its production mechanism and analytical model. In this paper, the production mechanism of the PM HIM cogging torque is revealed from the perspective of air‐gap field modulation principle. It is found that the air‐gap permeance of PM HIMs can modulate their air‐gap magneto‐motive force (MMF) and then a large number of modulated air‐gap magnetic fields are generated. These magnetic fields with identical production condition but different rotation speeds or rotation directions can interact with each other, hence the production of the PM HIM cogging torque. By the combination of energy method and air‐gap field modulation principle, the cogging torque analytical model of PM HIMs is derived. Based on the obtained analytical model, the methods for reducing the PM HIM cogging torque are further analyzed. Finally, a 48‐slot/4‐pole (48S4P) PM HIM is designed and exampled. The air‐gap flux density of the 48S4P PM HIM is simulated by three‐dimensional (3‐D) finite element analysis (FEA). Based on the harmonic analysis for the simulated results, the correctness of the proposed cogging torque production mechanism is validated. In addition, a prototype of the 48S4P PM HIM is manufactured. The cogging torque in the prototype is obtained by the analytical model, 3‐D FEA and experiments, respectively. The simulation and measurement results verify the correctness of the cogging torque analytical model. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

A transverse flux linear motor is a special type of linear motor with a high thrust force density, and it has broad application prospects in the field of linear direct-drive systems. In the process of oil production, the vibration of the linear motor poses a significant amount of harm to the system due to its special slender structure. This paper focuses on the electromagnetic vibration of a transverse flux permanent magnet linear submersible motor (TFPMLSM). Firstly, the no-load air gap flux density is calculated based on the field modulation principle. Secondly, the radial electromagnetic force (REF) of the TFPMLSM is calculated, and the finite element method (FEM) is used to analyze the time-space and spectral characteristics of the REF. Then, the influence of secondary eccentricity on the frequency spectrum of the REF is further concluded. Finally, the natural frequencies of each vibration mode are calculated using the modal superposition method and the influence of the REF on the motor vibration is obtained through magnetic-structural coupling analysis. The research results found that the motor does not cause resonance at low speeds, and the fundamental frequency of REF has the greatest impact on electromagnetic vibration. [ABSTRACT FROM AUTHOR]

With the development of eddy current brake (ECB), they are widely used in life and military. Through the ECB, the resistance is converted into thermal energy and dissipated in the air. Thermal energy will make the temperature rise and the heat cannot be dissipated quickly. The electromagnetic characteristics of many parts in the ECB are very sensitive to temperature. Therefore, the study of temperature field is very important for it. This paper takes the linear cylindrical ECB as an example to study the heat generated under the intense impact and high speed condition. The temperature field is calculated through finite element method (FEM) ways. According to the temperature distribution characteristics, the cooling measures of permanent magnet brake are studied to effectively reduce the temperature rise of the brake, ensuring its reliability. [ABSTRACT FROM AUTHOR]

The main objective of the paper is to demonstrate the functionality and reliability of a hydrokinetic turbine system -- a submersible electric generator, suitable for very low watercourses. To achieve this goal, it is necessary to design and build a prototype of a hydrokinetic turbine, coupled with an electric generator with excitation made with permanent magnets. This paper presents an analytical model and a finite element numerical model for estimating the electrical parameters of the generator (voltage, current, power, etc.). The two models were compared, and the results were extrapolated, in the analytical model, for several speed values. [ABSTRACT FROM AUTHOR]

In this paper, an improved Halbach array structure of a direct-drive linear motor for wave energy conversion is proposed, and its magnetic circuit structure is modeled and the induced electromotive force (EMF) generated by vertical wave energy conversion is deduced. Then, using the internal and external parameters of the wave energy conversion direct-drive motor, that is, four internal parameters of the magnetic circuit topology and two external parameters of the mover motion, the influence of these parameters on the induced EMF of the direct-drive motor in the wave energy conversion is analyzed. Since the theoretical analysis results of the model are consistent with the results of the two kinds of permanent magnet materials analyzed by the finite element method (FEM), the model and analysis method of the direct drive motor are correct. The investigation show that the modeling method proposed in this paper can be used to optimize the energy conversion of the direct-drive motor from two aspects: the internal parameters of the magnetic circuit topology of the direct-drive motor and the external parameters of the mover motion. [ABSTRACT FROM AUTHOR]

Direct-torque-control-driven permanent magnet synchronous machines eliminate the need for a position sensor while providing improved torque dynamics. However, the structure, regulation principle and nature of compensation of hysteresis-based controllers used in direct torque control impacts performance under faulty operating conditions. This paper analyzes the reaction of direct torque control to the presence of various faults that occur in permanent magnet synchronous machines. The analysis presented reveals that the direct torque control injects a negative sequence voltage and manipulates the torque angle to meet the control objectives when a fault occurs. The co-simulation of finite element analysis and a multi-physic circuit simulator is used to validate the response of the hysteresis-based controller to the machine health. The results indicate that the hysteresis comparators have the ability to mask the impact of the faults in the direct-torque-control-driven permanent magnet synchronous machines. [ABSTRACT FROM AUTHOR]

Magnetotactic bacteria have great potential for use in biomedical and environmental applications due to the ability to direct their navigation with a magnetic field. Applying and accurately controlling a magnetic field within a microscopic region during bacterial magnetotaxis studies at the single-cell level is challenging due to bulky microscope components and the inherent curvilinear field lines produced by commonly used bar magnets. In this paper, a system that integrates microfluidics and electromagnetic coils is presented for generating a linear magnetic field within a microenvironment compatible with microfluidics, enabling magnetotaxis analysis of groups or single microorganisms on-chip. The platform, designed and optimised via finite element analysis, is integrated into an inverted fluorescent microscope, enabling visualisation of bacteria at the single-cell level in microfluidic devices. The electromagnetic coils produce a linear magnetic field throughout a central volume where the microfluidic device containing the magnetotactic bacteria is located. The magnetic field, at this central position, can be accurately controlled from 1 to 10 mT, which is suitable for directing the navigation of magnetotactic bacteria. Potential heating of the microfluidic device from the operating coils was evaluated up to 2.5 A, corresponding to a magnetic field of 7.8 mT, for 10 min. The maximum measured heating was 8.4 °C, which enables analysis without altering the magnetotaxis behaviour or the average swimming speed of the bacteria. Altogether, this work provides a design, characterisation and experimental test of an integrated platform that enables the study of individual bacteria confined in microfluidics, under linear and predictable magnetic fields that can be easily and accurately applied and controlled. [ABSTRACT FROM AUTHOR]

Based on the magnetic gear effect, the field-modulated permanent-magnet machine (FMPMM) can realize the unequal pole design of the rotor PM field and the stator armature magnetic field. With the advantages of high torque density and high efficiency, the FMPMM has been widely studied in low-speed direct-drive applications. As a kind of machine excited by PMs, the performance of the FMPMM was affected by the demagnetization state. However, the method for establishing the FMPMM demagnetization model based on a finite element analysis (FEA) presented some problems, including tedious repeated modeling work and long calculation time-consuming under fine subdivision. Therefore, in this paper, a six-phase surface-mounted FMPMM was taken as an example, and an equivalent magnetic network (EMN) model was proposed for evaluating the machine performance under demagnetization. In order to realize the rapid establishing EMN models under diverse demagnetization types, the variable coercivity of PM was introduced. Furthermore, for the purpose of improving the calculation accuracy and shortening the calculation time, the least square method was used in fitting and analyzing the discrete results. Then, in order to verify the validity of the proposed EMN model, a prototype was fabricated and a testing platform was built. The air-gap flux density and the no-load back EMF obtained by the FEA, the proposed EMN model, and the experimental testing were compared. The results showed that the proposed EMN model can realize the rapid modeling and accurate analysis of the six-phase surface-mounted FMPMM under diverse demagnetization types. [ABSTRACT FROM AUTHOR]

In this paper, two H-type flux switching permanent magnet linear generators with outer-translator and inner-translator configurations are discussed and compared to a more conventional flux switching topology. The stators consist of H-Type modules housing circumferential coils and are surrounded by two annular permanent magnets. In conventional flux switching machines, the windings are orientated perpendicular to the direction of motion and the conductors twist around the magnets. In H-type topologies, the orientation of the windings is in the same plain as the magnets and parallel to the direction of motion, resulting in an increase in flux linkage. The proposed topologies are designed for a low operating speed and a large magnetic gap, as found in wave energy converters. All topologies are optimized using the Taguchi optimization approach with the goals of reducing force ripple and increasing the average thrust force and efficiency. The 2D finite element method (FEM) is used in the optimization stage to calculate the optimized parameters of the presented generators, after which the optimized structures are simulated using 3D FEM, and the results are extracted. The results of the optimization show that the H-type topologies deliver a 20% higher shear stress whilst offering an easier to assemble structure. [ABSTRACT FROM AUTHOR]

Because the magnetic circuits of homopolar inductor machines (HIMs) are three‐dimensional (3‐D), a 3‐D finite element model (FEM) is usually built to accurately compute the cogging torque in HIMs, but the drawback is very time‐consuming in modeling and computing. Therefore, a two‐dimensional (2‐D) FEM of HIMs is needed to simplify the computation of the 3‐D FEM. However, the existing odd harmonic 2‐D FEM cannot accurately predict the cogging torque in HIMs. To address this problem, this paper proposes a full‐order harmonic 2‐D FEM. First, the analytical expressions of HIM cogging torque are derived by the combination of energy method and air‐gap field modulation principle. Based on the obtained analytical expressions, the equivalent principles between the 3‐D and 2‐D FEMs are analyzed. According to the above equivalent principles and taking a 48‐slot/4‐tooth (48S4T) permanent magnet (PM) HIM as an example, a full‐order harmonic 2‐D FEM of the example machine excited by a field winding is proposed. The structure of the full‐order harmonic 2‐D FEM is described in detail. The turn number of field winding and field current amplitude of the proposed 2‐D FEM are investigated. The differences between the odd harmonic 2‐D and full‐order harmonic 2‐D FEMs are also analyzed. Finally, the cogging torque in the 48S4T PM HIM with distinct rotor tooth‐arc to tooth‐pitch ratios is computed by 3‐D, odd harmonic 2‐D and full‐order harmonic 2‐D FEMs of the machine, respectively. The results illustrate that compared with the odd harmonic 2‐D FEM, the full‐order harmonic 2‐D FEM can shorten the calculation time and has the similar computation accuracy as the 3‐D FEM. Moreover, the experimental validation is performed on a prototype of the 48S4T PM HIM. The error between the maximum cogging torque obtained by the full‐order harmonic 2‐D FEM and experiments is only 2.12%. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

This paper proposes a new design method for sleeve thickness and interference based on a multi-dimensional visualization algorithm that overcomes difficulties in solving. The contact pressure between the rotor core and the permanent magnet, the maximum equivalent Mises stress of the permanent magnet, and the maximum equivalent Mises stress of the sleeve are selected as the optimization objectives. The stress limit strength of the permanent magnet and sleeve are taken as constraints, and the sleeve thickness and interference are selected as decision variables. Then the multi-dimensional visualization algorithm is used to find the optimal region of sleeve thickness and interference. Finally, the design solution is validated by the finite element method. The results show that the design method proposed in this paper can obtain the optimal region of sleeve thickness and interference with the characteristics of a simple solution process and intuitive results. [ABSTRACT FROM AUTHOR]

Factors such as insufficient heat dissipation and excessively high temperature can easily lead to demagnetization of the PMs in permanent-magnet (PM) motors. As a result, the magnetic field distribution of the motor will not be uniform, producing fault harmonics and lowering the operational performance of the motor. An essential stage in the diagnosis of faults and the monitoring of motor condition is the establishment of an accurate model of motors with demagnetization faults. In this paper, demagnetization faults are modeled by changing the Fourier coefficients in the Fourier expansion of the magnetization of PMs. This model can be used to determine the motor performance under various types of demagnetization, including radial air gap flux density, back electromotive force (EMF), and torque. On this basis, the corresponding relationship between the demagnetization degree and the fault signature is established, to provide a theoretical foundation for the subsequent demagnetization fault diagnosis. The finite element analysis (FEA) verifies the effectiveness and superiority of the proposed analytical model. The modeling method proposed in this paper can be applied to PM motors with PMs having different magnetization directions and shapes because it is based on the demagnetization region of PMs. [ABSTRACT FROM AUTHOR]

The reluctance machine is a potential candidate for electrical vehicle propulsion because of its reliable structure, low cost, flexible flux regulation ability, and wide speed range. However, the torque density is unsatisfactory because of the poor excitation ability and low stator core utilization factor. To solve this problem, in this paper, a novel hybrid reluctance machine (HRM) with the skewed permanent magnet (PM) and the zero-sequence current is proposed for electric vehicles. The skewed PM has two magnetomotive force (MMF) components with different functions. The radial MMF component provides extra torque by the flux modulation effect. The tangential MMF component can generate a constant biased field in the stator core to relieve the saturation caused by the zero-sequence current and thus improve the utilization factor of the stator core. Therefore, torque improvement and the relief of stator core saturation can be simultaneously achieved by the skewed PM. In this paper, the machine structure and principle of the proposed machine are introduced. And ultimately, the machine's electromagnetic performances are evaluated under different PM magnetization directions and zero-sequence current angles by using finite element analysis (FEA). [ABSTRACT FROM AUTHOR]

In this paper, a novel variable‐leakage‐flux interior permanent magnet (VLF‐IPM) motor is proposed, which is a kind of mechanical flux‐adjusting PM motor. The VLF‐IPM motor can obtain the advantages of the IPM motor and overcome the difficulty to adjust PM airgap flux by locating a self‐activating device that is introduced in this paper on the rotor. The effect of the flux barriers on the flux leakage circuit is analysed by establishing a rotor parametric model to clarify the influence of flux barriers of the VLF‐IPM motor on flux‐adjusting performance. Then, the electromagnetic performance of VLF‐IPM motors with different volume ratios of cylindrical permanent magnets (CPMs) and rectangular permanent magnets (RPMs) are compared by using the finite element analysis (FEA) method, and the experiment results show that VLF‐IPM motor with characteristics of 0 < κrc < 1 has more advantages comprehensively. Moreover, a multi‐objective optimization process is adopted based on sensitivity analysis which can reflect the influences of geometric parameters on the optimization objectives including average torque, torque ripple and cogging torque. Then, the Non‐dominated Sorting Genetic Algorithm II(NSGA‐II) is utilised to determine the optimal model. Finally, a prototype is manufactured and tested, and the effectiveness of the novel VLF‐IPM motor and the self‐activating device are verified by the simulation and experiments. [ABSTRACT FROM AUTHOR]

An analytical subdomain model is employed in this paper for predicting the magnetic field distributions in a three-phase double-stator permanent magnet synchronous machine (DSPMSM) during open-circuit and onload conditions. Due to the stator cores are located in the outer and inner parts of the motor, the DS-PMSM construction is quite complex. The rotor magnets are positioned between these two stators. The stator inner radius, stator outer radius, slot opening, magnet arc, magnet thickness, inner and outer air-gap thickness and number of windings turns will directly influence the motor performance in DS-PMSM. The analytical subdomain model employed in this paper has a significant advantage as a rapid design tool since it is capable of precisely predicting the performance of DS-PMSM while requiring less computational effort. The analytical model was initially created using the separation of variables technique in four subdomains based on the Poisson’s and Laplace’s equations: inner air-gap, inner magnet, outer magnet and outer air-gap. Applying the appropriate boundary and interface conditions yields the field solutions in each subdomain. Besides, the fractional DSPMSM with different number of slots between outer and inner stators to rotor poles can result in low cogging torque and non-overlapping winding configuration. The analytical results are validated by Finite Element Analysis (FEA). The slotted air-gap flux density, back-emf, and output torque have all been evaluated as electromagnetic performances. The results demonstrate that the suggested analytical model is capable of accurately predicting the DSPMSM performance. [ABSTRACT FROM AUTHOR]

Permanent magnet synchronous machines (PMSMs) have garnered increasing interest because of their advantages such as high efficiency, high power density, wide speed range, and fast dynamics. They have been employed recently in several industrial applications including robotics and electric vehicles (EVs). However, PMSMs have highly nonlinear magnetic characteristics, especially interior PMSMs, due to the existence of reluctance torque. Nonlinearity complicates not only machine modeling but also control algorithms. An accurate machine model is the key aspect for the prediction of machine performance as well as the development of a high-performance control algorithm. Hence, this paper presents an accurate modelling method for PMSMs. The proposed model method is applicable for all PMSMs, even multiphase machines. This paper considers a fractional slot concentrated winding 12/10 interior PMSM (IPMSM) for this study to demonstrate the effect of magnetic saturation and special harmonics. The developed model considers accurately the magnetic saturation, mutual coupling, spatial harmonics, and iron loss effects. It utilizes finite element analysis (FEA) to estimate the precise magnetic characteristics of IPMSM. The finite element model is calibrated precisely using experimental measurements. The iron losses are estimated within the simulation model as d- and q-axes current components. The model accuracy is validated experimentally based on a 12/10 IPMSM prototype. [ABSTRACT FROM AUTHOR]

In this paper, the boundary discretization method is used to improve the traditional subdomain model. The improved model can be used to calculate the magnetic field distribution in the region containing non-orthogonal boundary, avoiding the influence of the simplified stator slot or permanent magnet shape on the results in calculating the motor magnetic field using the traditional subdomain model. In addition, the improved subdomain model can also be used to calculate the air-gap flux density when the rotor is eccentric, instead of segmenting the air-gap to an equivalent state without eccentricity. The calculation object of this paper is a surface-mount permanent magnet motor with a rectangular stator slot. The air-gap flux density under no-load and load conditions is calculated, respectively. Since the improved subdomain model does not need to simplify the stator slot shape, the magnetic potential in the stator slot is also calculated. Finally, the air-gap flux density under rotor eccentricity is calculated, and the influence of the calculating parameters on the results of the improved subdomain model is discussed. All the calculated results are compared with those obtained by the finite element method, which verifies the accuracy of the improved calculation model. [ABSTRACT FROM AUTHOR]

The development of high-temperature superconducting (HTS) electrical machines results in applications of various fields, as they have higher efficiency and power density. Numerical modeling of superconducting electrical machines is usually performed by finite element method based their electrical behavior, and H-Formulation of the Maxwell's equations is one of the models that are used tremendously due to its high flexibility and simplicity. Axial field machine (AFM) is a machine topology with higher efficiency and power density, but with more complexity when modeling. This paper proposed a new 2D model for the superconducting AFM, where the superconducting coil is simulated with a 2D infinitely long model, this model also divides the electrical machine into two parts: the superconducting parts (HTS coils, bulks, etc.) and non-superconducting parts (e.g., conventional conductors, machine structure). This paper compares the results of H-A Formulation and T-A Formulation with this approach, which requires appropriate boundary conditions and continuity between the two regions, along with correct modeling of fixed and moving parts of the electrical machine, where the geometry of this model is based on a linear synchronous machine, which means the rotor is moving linearly instead of rotation. [ABSTRACT FROM AUTHOR]

The dual‐stator permanent magnet (PM) machine has the advantages of high torque density, high efficiency, and compact size, which makes it suitable for low‐speed high‐torque applications. A dual‐stator low‐speed high‐torque permanent magnet drive machine (DLHPMDM) is discussed and studied in this paper, which is applied to the ball mill application. First, in order to meet the requirements of high efficiency and high reliability, a DLHPMDM with the inner and outer windings connected in parallel is obtained through the designs carried out in terms of the magnetic circuit structure, structural size, and the pole‐slot number combination. However, for the DLHPMDM with the inner and outer windings connected in parallel, the power allocation between the inner and outer machines is a critical problem that needs to be accurately analyzed, and the circulating current between the two sets of windings is also a particular issue that merit attention. Therefore, a new modeling method is proposed for the DLHPMDM to solve such cases more accurately. The proposed new method combines the advantages of the rapidity of the finite element analysis (FEA) with current excitations and the accuracy of the FEA with voltage excitations. Finally, a prototype of the DLHPMDM is manufactured and tested. The feasibility of the design theory and the validity of the proposed modeling method is verified by both the tested and simulated results. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

In recent years, the permanent magnet synchronous motor (PMSM) has garnered significant attention due to its high power density and efficiency in applications such as electric vehicles, aviation, and other domains. This paper proposes a stator field control permanent magnet synchronous starter–generator (SFC-PMSSG) system. The starter–generator system comprises the SFC-PMSSG and a field controller (FC). A mathematical model of the SFC-PMSSG is established. Finite element analysis (FEA) is employed to obtain the electromagnetic parameters of the SFC-PMSSG, and the characteristics of the SFC-PMSSG are analyzed. A circuit simulation model of the FC is established to assess the control effect and the loss of the FC. A co-analysis of the system is conducted, and the results demonstrate that the SFC-PMSSG system can maintain output voltage stability as load and speed conditions vary. [ABSTRACT FROM AUTHOR]

This paper proposes a general analytical model for large-power surface-mounted permanent magnet (SPM) wind generators under inter-turn short-circuit (ITSC) faults. In the model, branch currents rather than phase currents are used as state variables to describe the electromagnetic behavior of the faulty machine. In addition, it is found that the multiphase Clarke transformation can be used to simplify the proposed fault model with the inductances calculated analytically or numerically using finite element analysis. With the latter, both linear and nonlinear inductances can be obtained, and the non-linear inductances are used for the fault modelling of large power rating machines due to larger electrical loading and heavier magnetic saturation. With the developed fault model, studies of scaling effects (different power ratings such as 3 kW, 500 kW and 3 MW) and the influence of fault location on the electromagnetic performance of SPM generators with series-parallel coil connections have been carried out. The simulation results show that large-power SPM wind generators are vulnerable to ITSC faults when a relatively small number of turns are short-circuited and a single-turn short-circuit fault at the top of the slot is found to be the worst case. [ABSTRACT FROM AUTHOR]

This paper proposes a novel torque ripple model of V-Shape interior permanent magnet (IPM) synchronous machine based on the general field modulation theory (GAFMT). Firstly, the magnetic field modulation behavior of a 12-stator-slot/8-rotor-pole (12/8) IPM machine is discussed, where the expressions of permanent-magnet-excited (PM-excited) and armature fields are derived. Secondly, the total torque ripple is divided into three components, namely, the PM-excited cogging torque, the armature cogging torque, and the modulation torque ripple. Additionally, the relationship between the field harmonics and the torque ripple is discussed based on the GAFMT. Then, a finite element analysis (FEA)-assisted dual fast Fourier transformation (FFT) method is proposed to obtain the accurate value of the field amplitude for torque ripple calculation. The field analysis results based on the GAFMT and the proposed torque ripple are then validated by comparing their results with those obtained from the FEA simulations, and a good agreement is observed, demonstrating the effectiveness of the field analysis and the proposed torque ripple model. Finally, experiments on a prototype 12/8 IPM machine demonstrate the validity of the torque ripple model, providing an effective method for torque ripple suppression of IPM machines. [ABSTRACT FROM AUTHOR]

Permanent magnet synchronous machines (PMSM) are competitive motors for in-wheel traction systems of electric vehicles. A new tangentially magnetized permanent magnets machine with outer rotor and unequal stator teeth for in-wheel motor application is proposed in this paper. The analytical calculations of the proposed topology are presented by determining the magnetic flux densities and the iron losses in all parts of the machine. The machine design is optimized using three state-of-the-art multiobjective algorithms which are AbYSS, MOCell and NMOPSO algorithms. Moreover, the optimization procedure is carried out according to three objectives: the maximization of the machine efficiency and the minimization of the mass and ripple torque. The optimization results showed that all the algorithms can find a set of optimal solutions and that the NMPSO algorithm outperforms the other two techniques. The finite element method (FEM) is used to investigate the optimization results. It is observed some magnetic saturation in the rotor yoke and the magnet's extremes. The value of the induction in these machine regions is about 1.9 T. The comparison between the FEM and optimization results proved the rationality of the proposed optimization procedure. [ABSTRACT FROM AUTHOR]