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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]

This paper aims to investigate the dynamic characteristics of vacuum metal vapor arcs under rotating and traditional direct contact separation modes. Non-symmetrical pure copper electrodes with an anode radius of 7.5 mm and a cathode radius of 22.5 mm are employed in the experiments. The permanent magnet actuator provides an average opening speed of 1.0 m/s for cathode direct separation and 1–3 deg/ms for rotation. Results show that electrode rotation significantly influences the distribution and motion speed of the arc root on the cathode surface. [ABSTRACT FROM AUTHOR]

The undulator is a key luminous component of the Shanghai high repetition rate x-ray free electron laser and extreme light facility, and the motion control system is an important part of the undulator. The main task of the motion control system is to complete the high precision adjustment of the gap and taper between the upper magnetic pole girder and lower magnetic pole girder, so as to adjust the wavelength of the radiation light. According to the development requirements of the motion control system for the U26 undulator, which is a conventional permanent magnet, this paper proposes a new motion control system with double position feedback closed-loop control, including programmable logic controller (PLC) closed-loop control based on position feedback by a linear absolute encoder (LAE) and driver closed-loop control based on position feedback by a rotary absolute encoder (RAE) of a servo motor. Multiple motion tests of the U26 undulator have shown that the repeatability accuracy of the gap is ±50 nm and the gap drive can reach 0.1 µm step size, the error of which is about ±20 nm according to the feedback of the LAE. The conclusion can be drawn that the motion step size and repeatability accuracy of the motion control system for the U26 undulator are improved by one order of magnitude on the basis of meeting all technical requirements. At the same time, motor torque protection, motor temperature protection, and redundant position protection with RAE can further improve the reliability and safety of the motion control system for the U26 undulator. [ABSTRACT FROM AUTHOR]

Despite continuous effort to minimize torque ripple, the reduction of vibration has not been yet achieved due to the lack of link between these two performances. The difficulty of investigating the relationship stems from the fact that torque is solely influenced by tangential force whereas vibration is directly tied to radial force. In this paper, the correlation between torque ripple and vibration in an IPMSM (Interior Permanent Magnet Synchronous Motor) is established by examining the air-gap flux density in both radial and tangential directions. Its temporal and spatial harmonics are analyzed. A six-pole nine-slot IPMSM is used as a base configuration, and the air-gap flux density is varied by changing the height of a stator tooth tip. In the previous study, the same approach has been done to observe how to reduce torque ripple effectively. In this study, however, it is found that the trend of torque ripple is not the same as that of vibration with respect to the height of a pole tip, and the relation between the two is thoroughly observed and explained. [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]

Variable flux memory machines (VFMMs) have become a research hotspot due to their adjustable air-gap flux with the employment of low coercive force (LCF) permanent magnets (PMs). Series hybrid magnet VFMMs (SHM-VFMMs) utilizing series-magnetic-circuit high coercive force (HCF) and LCF PMs are extensively investigated due to their excellent unintentional demagnetization (UD) withstand capability. Nevertheless, the existing researches still focus on the UD of LCF PMs under heavy load operation, and the remagnetization issue remains unreported. Therefore, in this paper, the over-load unintentional remagnetization (UR) effect of the a dual-layer-SHM-VFMM (DLSHM-VFMM) is first revealed, and its mechanism is investigated and analyzed in depth based on finite element (FE) analyses. A DLSHM-VFMM prototype is manufactured and tested to verify the effectiveness of the theoretical analyses. [ABSTRACT FROM AUTHOR]

In this paper, in order to further reduce torque ripple and improve power factor, a new vernier permanent magnet motor is proposed, in which the design concept of dual-winding hybrid-tooth configuration is incorporated. In order to clarify motor torque ripple and power factor, the winding-magnetomotive-force-based design and analysis method is proposed, in which harmonic characteristics are considered as key factors during the magnetic field modulation process. The relationship between harmonics generated by winding MMF, torque ripple, and power factor are investigated. In addition, the split-tooth vernier permanent magnet motor is also investigated as a referenced motor. Detailed comparisons between the DWHT-VPM motor and ST-VPM motor are carried out, including air gap magnetic field, torque, and power factor. Both theoretical and simulation results verify the reasonability of the proposed DWHT-VPM motor, and the effectiveness of the proposed winding-MMF-based analysis method, which provide a new potential research path for the design and analysis of flux modulation motors. [ABSTRACT FROM AUTHOR]

With the development of electric motors, high speed and high efficiency have become the new development trend. Therefore, reducing the iron loss of motors has become the focus of academia and industry. Amorphous alloys are gradually being used in high speed motors by virtue of their low loss characteristics at high frequencies. Amorphous alloys generate large internal stresses during the manufacturing process, and annealing is usually required to eliminate the effect of internal stresses on magnetism. Amorphous transformer cores are usually annealed by applying a magnetic field in the direction of the magnetic circuit to improve the magnetic domain state, increase the saturation density in that direction, and reduce iron loss. Since the magnetic field of the motor stator teeth is pulsating, and amorphous annealed under longitudinal magnetic field (AALM) has the most performance along the direction of the annealed magnetic field. Therefore, in this paper, the magnetic properties of AALM, annealed amorphous (AA), and unannealed amorphous (UA) are tested to prove the advantages of the material, and then AALM is spliced as the tooth of the motor. The advantages of this material in the motor species are further demonstrated by designing a comparative simulation scheme in the longitudinal direction (same material with different structure) and in the transverse direction (same structure with different material). [ABSTRACT FROM AUTHOR]

With designing stator teeth by using grain oriented silicon sheets (GO) and other parts still with non-grain oriented silicon sheets (NGO), the electromagnetic performance of interior permanent magnet synchronous machine (GO-IPMSM) can be improved greatly, however its torque ripple will be increased as well. For reducing its torque ripple, optimizing its rotor barrier shape is an effective way. In this paper, the polynomial method is proposed to establish the rotor barrier shape, and the genetic algorithm (GA) method is employed for the optimization process. In case the optimized GO-IPMSM can work normally, its anti irreversible demagnetization ability is analyzed as well. As shown, with the GO is adopted for designing the stator teeth and its rotor barrier shape is optimized, though its torque ability and efficiency have been increased, its anti irreversible demagnetization risk ability is reduced, however the proposed machine can still operate safely. [ABSTRACT FROM AUTHOR]

Permanent magnet synchronous motors (PMSMs) having high power density and high efficiency are rigorously researched in various premium applications. Among PMSMs, many studies have been conducted on interior permanent magnet synchronous motors (IPMSMs) to improve torque ripple, but its accurate estimation is not straightforward. Therefore, a six-pole nine-slot (6p/9s) IPMSM is adopted as a base model due to its popularity in academia and industries, and other two pole/slot combinations (8p/12s and 10p/15s) are additionally selected to investigate the influence of a pole/slot combination on torque ripple. Torque performance is easily identified by analyzing tangential force due to their direct proportional relation. In this paper, magnetic flux densities in radial and tangential direction are systematically analyzed since tangential force is determined by the product of the two magnetic flux densities. The modification of a stator pole regarding its tip thickness is chosen as a key parameter in 6p/9s IPMSM. The thickness of a stator pole tip opposite to the direction of spin is more critical in torque ripple improvement. It is verified that the proposed method is sufficient for accurate torque prediction. [ABSTRACT FROM AUTHOR]

In this paper, a new field-modulated permanent magnet (FMPM) machine with an improved rotor is proposed and analyzed. The proposed FMPM machine enjoys the advantages of high PM utilization and better heat dissipation. For a fair comparison, the proposed FMPM machine is designed with the same geometrical parameters based on the existing FMPM machine. The electromagnetic performances of existing FMPM (E-FMPM) machine and proposed FMPM (P-FMPM) are compared and analyzed by using finite element method, verifying that the proposed FMPM machine with an improved rotor can obtain high torque density and high PM utilization. [ABSTRACT FROM AUTHOR]

In this paper, based on the conventional flux-switching permanent magnet (PM) (FSPM) machine, a novel dual-three-phase dual-rotor FSPM machine with PMs of NS layout (NS-DRFSPM) is proposed. The stator of the proposed NS-DRFSPM machine is equipped with dual PMs and dual armature windings to operate in a variety of operating modes and to handle the case of PMs or armature windings failure. Firstly, the topological structure and eight fault operating states of the NS-DRFSPM machine are introduced, and the key design parameters of the NS-DRFSPM machine are optimized by genetic algorithm (GA) optimization and finite element analysis (FEA). Then, the operation principle of the NS-DRFSPM machine is analyzed in detail. Finally, the finite element method is used to analyze the performances of the NS-DRFSPM machine under eight fault operating states, which is mainly analyzed from two aspects: no-load performance and torque performance. The results show that the NS-DRFSPM machine has good electromagnetic performance under different fault conditions, including large back-electromotive force (EMF) amplitude, sinusoidal EMF waveform, high average torque, small torque ripple, and strong anti-saturation ability. [ABSTRACT FROM AUTHOR]

The magnetic levitation system of a high-temperature superconductor (HTSC) has nonlinear vibration under external excitation, in which the HTSC is subjected to a sizable electromagnetic force. The high-temperature superconducting block is a brittle material, which will crack when subject to heavy pressure. Microfracture of superconductors is inevitable, especially in superconducting magnetic levitation systems. Our paper studies the fracture behavior of a YBaCuO superconducting magnetic levitation system under a large electromagnetic force based on nonlinear bifurcated motions. The E − J constitutive model and the current vector T method are applied to obtain the electromagnetic force of the bulk superconductor during vibration. We analyze the effects of five lengths of the central crack on vibration displacements, the electric field distribution, and the electromagnetic force of superconductors. Without damages, the system does not have apparent bifurcation motion. For the inner cracks, the system has obvious bifurcation motions. The results show that the cracks have a meaningful influence on the nonlinear vibration of the superconducting magnetic levitation system. The displacement of the suspended permanent magnet in bifurcation motion increases with the increase in the crack length, and the collision occurs when the crack length reaches 15 mm. [ABSTRACT FROM AUTHOR]

The TM14RE2B-based phases (TM = transition metal, RE = rare earth metal; hereafter called 14:2:1) enable permanent magnets with outstanding magnetic properties. Novel chemical compositions that represent new 14:2:1 phases necessitate that they do not demagnetize at application-specific operating temperatures. Therefore, an accurate knowledge of the Curie temperature (Tc) is important. For magnetic 14:2:1 phases, we present a machine learning model that predicts Tc by using merely chemical compositional features. Hyperparameter tuning on bagging and boosting models, as well as averaging predictions from individual models using the voting regressor, enables a low mean-absolute-error of 16 K on an unseen test set. The training set and a test set have been constructed by randomly splitting, in an 80:20 ratio, of a database that contains 449 phases (270 compositionally unique) mapped with their Tc, taken from distinct publications. The model correctly identifies the relative importance of key substitutional elements that influence Tc, especially in an Fe base such as Co, Mn, and Al. This paper is expected to serve as a basis for accurate Curie temperature predictions in the sought-after 14:2:1 permanent magnet family, particularly for transition metal substitution of within 20% in an Fe or Co base. [ABSTRACT FROM AUTHOR]

To increase the airgap flux density, this paper proposes a new magnetic-field-modulated permanent magnet (FMPM) machine. The proposed FMPM machine has the compound magnets in the rotor, which is composited by the spoke PMs (SPM) and Halbach PMs (HPM). The proposed SH-FMPM machine facilitates better use of space for armature winding and PMs and combines the benefits of high torque density and high torque/loss. The formation process, operation principle, and electromagnetic performance of the SH-FMPM machine are introduced. It is demonstrated that the SH-FMPM machine has the high torque density and low torque ripple compared to the S-FMPM machine and the H-FMPM machine. [ABSTRACT FROM AUTHOR]

Variable flux memory machines (VFMMs) with series hybrid magnets using both low coercive force (LCF) and high coercive force (HCF) permanent magnets (PMs) have been recognized as a viable candidate for wide-speed-range industrial applications due to the advantages of high torque density and wide speed range. Nevertheless, the adverse effects of LCF PM on the HCF PM in series-type VFMM under different magnetization states (MSs) are still unreported. In this paper, the flux barrier effect (FBE) of the LCF PM existing in series hybrid magnet VFMM is first revealed, and its causes are discussed as well as analyzed in depth on the basis of the equivalent magnetic circuit method and finite-element (FE) analyses. A topology of VFMM with dual-layer PMs is further developed to alleviate the FBE induced from LCF PMs. It can be found that the FBE can be effectively suppressed by employing the dual-layer (DL) PM arrangement and additional leakage flux paths. A prototype of the proposed design is built, and the theoretical and FE results are experimentally verified. [ABSTRACT FROM AUTHOR]

Magnetic microspheres have been widely applied in DNA determination, bacterial analysis, and information coding. Magnetic microspheres screening is important, as the sizes of the obtained microspheres vary with different manufacturing methods, causing considerable impact on subsequent applications. In this paper, a co-simulation method based on MATLAB and COMSOL was presented to design the magnetic microfluidic chip, which was utilized to separate the magnetic micro-spheres of different sizes efficiently. In order to complete the separation and screening of magnetic microspheres in the microchannel, a movable permanent magnet device was adopted to adjust the magnetic interactions in the separation area, allowing the microspheres to deviate from different distances. A batch analysis of chip model was performed with this method, and an optimal design that showed high efficiency in separating microspheres of different sizes and magnetic properties was also revealed. Moreover, detailed analysis focused on the influence of flow rate, magnetism and arrangement of magnets on the separation effect of the chip. The presented simulation method will not only shorten the chip design time but also have a better understanding of the factors that can affect the separation of particles. This study has shown its potential in the computer-aided design of microfluidic chips for magnetic microspheres screening. [ABSTRACT FROM AUTHOR]

Losses during the operation of electrical machines heat up permanent magnets which in turn changes their demagnetization behavior. An elevation of permanent magnet's temperature usually correlates to a decreasing remanence and coercivity. The relation between them may become nonlinear. Existing material models either lack of accuracy or are parameterized with a high number of variables. This paper presents a novel semi-physical material model for permanent magnets with a reduced number, physically based independent variables, which enables a transition between a description of linear and nonlinear demagnetization behavior efficiently. [ABSTRACT FROM AUTHOR]

This paper presents an analytical model for the computation of the electromagnetic performance in interior permanent magnet (IPM) machines that accounts for the stator and the complex rotor structure. Using the subdomain method, we propose a simplified analytical model that considers the magnetic properties of the IPM machine. The analytical solutions are derived by solving the field-governing equations in each simple and regular subdomain, i.e., magnet, barrier, air gap, slot opening, and slot, and then applying the boundary conditions to the interfaces between these subdomains. The analytical model accurately accounts for the influence of the interaction between the slots, the relative recoil permeability of the magnets, and the boundary conditions. The magnetic field and electromagnetic performance obtained using the analytical method are compared with those obtained using finite element analysis. Finally, the analytical predictions are compared with the measured data in order to confirm the validity of the methods proposed in this paper. [ABSTRACT FROM AUTHOR]

This paper presents the magnetic flux density and torque calculation of coaxial magnetic gear. We obtained analytical magnetic field solutions produced by permanent magnets based on subdomain method and super position method. Then, the analytical solutions for torque characteristics were obtained. All analytical results were validated with two-dimensional finite element analysis and experimental results. [ABSTRACT FROM AUTHOR]

To solve the problem of mode competition in high-order working modes, this paper presents a fast design method based on the TM31-2π mode for the dumbbell shaped extended interaction cavity. Based on the equivalent circuit theory, the high-frequency characteristics of the structure are studied. In addition, we propose a W-band continuous wave sheet beam extended interaction klystron high-frequency circuit. The circuit was driven by a 20 kV and 0.85 A sheet electron beam, with a 3.2 × 0.3 mm2 section. The beam was focused by a 0.8 T permanent magnet system. The high-frequency system adopts five dumbbell shaped five-gap cavities, and the output system adopts a symmetrical output waveguide. The 3D particle-in-cell simulation shows that more than 1.5 kW power can be obtained at an input power of 0.12 W, and the electron efficiency and gain are 9.2% and 41.2 dB, respectively. [ABSTRACT FROM AUTHOR]

This paper proposes a new type of dual-armature alternating pole bearingless magnetic flux reverse permanent magnet machine, which combines the advantages of the alternating pole structure and the dual-armature structure. This machine shows the advantages of high torque density and good fault tolerance, which can not only reduce the number of permanent magnets but also further improve the machine's torque. It is suitable for use in wind power, aerospace, and other applications. The dual-armature alternating pole bearingless magnetic flux reverse permanent magnet machine is used to improve the torque performance and suspension force. Based on the dual-armature alternating pole magnetic flux reverse machine, by adding an additional set of stator teeth to suspended windings, a new type of dual-armature alternating pole bearingless magnetic flux reverse permanent magnet machine is obtained. The number of permanent magnets is halved, and each permanent magnet has the same polarity. The ferromagnetic pole piece next to the permanent magnet automatically acts as the other pole. Based on the introduction of its related structure, the stator flux, rotor flux, stator back electromotive force, cogging torque, electromagnetic torque, etc., are analyzed. This new machine can reduce the number of permanent magnets and has a higher torque conferring advantages of output capacity and low torque ripple. [ABSTRACT FROM AUTHOR]

This paper introduces the detailed design scheme of a multi-beam electron gun applied to an S-band high power multi-beam klystron. The multi-beam gun adopts a coaxial cavity arrangement, and the total number of electron beams are 40 (19 in the inner layer and 21 in the outer layer). The working voltage of the electron gun is 60 kV, the total current is 300 A (evenly distributed on 40 electron beams), and the single beam perveance is 0.51 μP. The total perveance is 20.4 μP. The cathode loading of the gun is 12 A/cm2, which can meet the requirements of cathode operational lifetime. The beam focusing system uses a periodic reversal permanent magnet to realize miniaturization of the klystron. [ABSTRACT FROM AUTHOR]

A cryogenic motor with active magnetic bearings (AMBs) which works in liquid nitrogen is discussed in this paper. The cryogenic motor is composed of two AMBs, four displacement sensors, a permanent magnet (PM) motor, etc. In order to check the stability for the rotor, FFT (fast Fourier transform) analysis for the levitated rotor in the radial direction is performed. Displacement of rotor in the axial direction is studied during rotation. [ABSTRACT FROM AUTHOR]

Low-field NMR (LF-NMR) relaxation analyzers have been more and more widely used in food science, biomedicine, and petroleum exploration in recent years. An LF-NMR device analyzes various interactions between sample molecules through spin relaxation, diffusion, flow, and imaging experiments. However, temporal field fluctuations in the magnet limit the scope of application. A stable magnetic field is the basic guarantee for detecting weak signals with shorter relaxation time. This paper presents an approach involving a field-frequency lock for a 21.3-MHz high-performance NMR bipolar permanent magnet. The diameter spherical volume (DSV) of the magnet is only 60 mm. The field-frequency lock system uses 19F in a micro coil integrated into the main probe as a lock detector. The required magnetic field compensation can be calculated from the lock free induction decay (FID) signal frequency, which is measured by lock spectroscopy. The compensation coils used to produce the magnetic field were designed based on Helmholtz coils. The system determines the signal frequency by detecting the lock FID signal and calculates the required compensation-coil current to stabilize the main magnetic field of the analyzer. The results of practical locking experiments in a 21.3-MHz high-performance NMR relaxation analyzer showed that this new approach helps to reduce magnetic field fluctuations from 11 ppm/3h (11 × 10–6) to 0.4 ppm/3h (0.4 × 10–6), which meets the application requirements. This approach is especially viable and effective for a permanent magnet with large field fluctuations. This paper also provides observations of the effect of these fluctuations on NMR measurements before and after installation of the field-frequency lock system. [ABSTRACT FROM AUTHOR]

A bearingless flux-switching permanent magnet memory machine (BFSPMMM) is proposed, which demonstrates the advantages of good suspension performance and wide-ranging speed regulation. The bias magnetic field of the radial force generated by the motor is provided by the permanent magnet, which can flexibly decide whether to adopt a single-phase or two-phase mode of conduction according to the needs of radial levitation force in the X- and Y-directions, so as to ensure the tracking of radial levitation forces therein. This paper introduces its structure, which lays a foundation for the subsequent establishment of an accurate mathematical model of a BFSPMMM. [ABSTRACT FROM AUTHOR]

Within the area of permanent magnet electrical machines, there is an ongoing focus on replacing the rare earth permanent magnets with alternatives. An option is hard ferrites, commonly used in other applications. The relatively low coercive field strength of the ferrite magnets makes irreversible demagnetization an area that should not be neglected. In this paper, a methodology is proposed for the optimization of a slow-moving linear generator simulated in a finite element environment. The no-load phase voltage is maximized while accounting for iron saturation and permanent magnet irreversible demagnetization. This demagnetization is considered when the translator is alongside either the stator or air. The inclination angle between magnetization and magnetic field strength is accounted for by adjusting the intrinsic coercivity for each element of the permanent magnets. Characteristics for the magnet grades Y30 and Y40 are used in the optimization process. The velocity of the translator is set to resemble a speed common to wave power applications. Commercial finite element software is used together with two optimization algorithms: the genetic algorithm and the particle swarm optimization. The results of these optimization algorithms reach similar optimal solutions for the considered objective function, assuring a result close to a global maximum. The results also show a great difference in the optimal geometry for the two magnet grades and highlight the need to account for irreversible demagnetization when designing generators with ferrite magnets. [ABSTRACT FROM AUTHOR]

The Electrical Vehicle industry has developed rapidly in recent years, and the demand for new energy-driven motor systems has also increased. Permanent Magnet Synchronous Machine (PMSM) are high performance drive motors. In this paper, a new type of GO silicon steel material assembled stator core is proposed, compared with conventional Non Grain-Oriented (NGO) silicon steel stator, and the magnetic properties of the motor are analyzed. The method of assembling the stator core is given, in which the GO silicon steel sheets are stacked as the teeth of the stator core. GO silicon steel has low iron loss and large saturation magnetic density, which is more conducive to improving motor efficiency. The teeth of the stator core tend to have higher magnetic density and are more prone to sustain a higher iron loss. This research ensures the reliability of the test results through simulation analysis and physical test verification. [ABSTRACT FROM AUTHOR]

Conventional diesel railway vehicles produce many air pollutants. In order to solve this problem, railway vehicles using eco-friendly hydrogen fuel cells are emerging. The main difference from the conventional traction motor is that it does not control the phase back electromotive force (phase-BEMF) separately at the maximum speed. Because of this, it should reduce the use of permanent magnets yet increase their size due to necessary high current. This paper performs the interior permanent magnet synchronous motor (IPMSM) design to meet the harsh electrical and mechanical constraints. Although the basic design is carried out to satisfy the design constraints, structural problems occur. These are resolved through the optimization process to attain the optimal design of a 314kW-class IPMSM for railway vehicles using hydrogen fuel cells. [ABSTRACT FROM AUTHOR]

This paper investigates the magnetization characteristics of variable flux permanent magnet (VF-PM) by using a simplified C-core magnetizer device with AlNiCo PMs. A combined methodology with magnetic circuit model, finite element analysis and Fourier series fitting hysteresis model is proposed. By means of the magnetic circuit analysis, the basic sizing parameters of the device are designed for the prototype manufacturing. A simple experimental setup including a device prototype, a Gaussmeter and H-bridge-converter-based magnetizing circuit is established. Then several experimental schemes are conducted to research the magnetization characteristics. According to the experimental results, a new numerical hysteresis model of AlNiCo PMs is proposed based on Fourier-fitting functions, which can be employed to correct the hysteresis model parameters used in finite element (FE) simulation. Finally, the correctness of the proposed Fourier-fitting hysteresis model (FFHM) is experimentally verified by the test results. [ABSTRACT FROM AUTHOR]

The magnetic pendulum array (MPA) is a novel mechanical antenna for efficient and portable ultra-low-frequency transmission. Its natural frequency is affected by the magnetic field of its rectangular permanent magnets. In this work, the influence of the magnetization of a permanent magnet on the demagnetizing field and the magnetic field of other permanent magnets is analyzed to accurately calculate the natural frequency, and a magnetic field model of the rectangular permanent magnets in an MPA is established to improve the calculation accuracy. The consistency of the theoretical model results is verified through experiments and simulations. Finally, the effect of sizes and distances of the permanent magnets on the natural frequency of an MPA is analyzed, providing theoretical guidance for the dynamic analysis of "A Mechanically Based Antenna (AMEBA)." This research has significance and practical application value in the optimization of the magnetic field characteristics and natural frequency calculation methods for AMEBA. [ABSTRACT FROM AUTHOR]

Dual rotor permanent magnet (DRPM) wind power generator using ferrite magnets has the advantages of low cost, high efficiency, and high torque density. How to further improve the performance and reduce the cost of the machine by proper choice of pole number and slot number is an important problem to be solved when performing preliminarily design a DRPM wind generator. This paper presents a comprehensive performance comparison of a DRPM wind generator using ferrite magnets with different slot and pole number combinations. The main winding factors are calculated by means of the star of slots. Under the same machine volume and ferrite consumption, the flux linkage, back-electromotive force (EMF), cogging torque, output torque, torque pulsation, and losses are investigated and compared using finite element analysis (FEA). The results showthat the slot and pole number combinations have an important impact on the generator properties. [ABSTRACT FROM AUTHOR]

In this paper, a W-band multi-beam extended interaction klystron operating in the coaxial high order mode (HOM) is proposed. The HOM coaxial cavity with large transverse dimensions is suitable for accommodating multiple electron beams, promising to achieve high output power in the millimeter-wave frequency band. However, the operating method also brings lower characteristic impedance and a higher risk of mode competition. Based on the angular boundary condition of the coaxial HOM electric field, we propose a coaxial multi-gap cavity with a ridge structure to solve these problems. The TM51-2π mode is selected as the operating mode, of which the characteristic impedance can overwhelm that of the competing mode. The corresponding five-beam gun with a total current of 7 A (5 × 1.4 A) at a voltage of 25 kV is focused by a 0.65 T permanent magnet system. To demonstrate the capability of the device, the 3D particle-in-cell simulation predicts an output power of up to 30 kW at 94.4 GHz. The gain and electric efficiency are 54.8 dB and 17.2%, respectively. [ABSTRACT FROM AUTHOR]

A novel Ku-band coaxial transit-time oscillator (TTO) with Pierce-like cathode is proposed in this paper. TTO has the characteristics of low space-charge effect and short interaction distance. Combining with these features, we design a novel Pierce-like cathode to lower the demand for the guiding magnetic field. The guiding magnetic field intensity is reduced to about 0.32T by loading the Pierce-like cathode, but the magnetic field intensity is not a stable value, it fluctuates at 0.32T because of the properties of permanent magnet. To achieve the light and small goals of TTO, we design a novel permanent magnet structure with NdFeB. Based on the research, the typical simulation result is that when the diode voltage is 440kV, the beam current is 11kA, the guiding magnetic field is about 0.32T, the device can output 1.46GW microwave pulse at 14.2GHz. The power conversion efficiency is about 30%. [ABSTRACT FROM AUTHOR]

In this paper, methods for finding the demagnetization factor, specifically for permanent magnets, are considered and compared. Widely applied and cited literature expressions are compared to high resolution numerical modeling in order to establish the applicability of the expressions. Overall, the expressions are found to be very closely correlated with the modeling results. In the second part, a simple geometrically based method to find the demagnetization factor is proposed and compared to the numerical modeling results. Fairly good correspondence is found, indicating the applicability of this simple method. [ABSTRACT FROM AUTHOR]

This paper presents an improved flux intensifying permanent magnet embedded salient pole wind generator (FI-PMESPWG) with mirror symmetrical magnetizing directions permanent magnet (PM) for improving generator’s performances. The air-gap flux densities, the output voltage, the cogging torque and the d- and q-axis inductances of FI-PMESPWG are all calculated and analyzed by using the finite element method (FEM). To highlight the advantages of the proposed FI-PMESPWG, an original permanent magnet embedded salient pole wind generator (PMESPWG) model is adopted for comparison under the same operating conditions. The calculating results show that the air-gap flux densities of FI-PMESPWG are intensified with the same magnet amounts because the PMs are set in a form of V shape in each pole. The difference between d-axis inductance and q-axis inductance of the proposed FI-PMESPWG is reduced. Thus, the output power of the proposed FI-PMESPWG reaches a higher value than that of the original PMESPWG at the same current phase angle. The cogging torque is diminished because the flux path is changed. All the analysis results indicate that the electromagnetic characteristics of the proposed FI-PMESPWG are significantly better than that of the original PMESPWG. [ABSTRACT FROM AUTHOR]

This paper presents analytical torque calculation and experimental verification of synchronous permanent magnet couplings (SPMCs) with Halbach arrays. A Halbach array is composed of various numbers of segments per pole; we calculate and compare the magnetic torques for 2, 3, and 4 segments. Firstly, based on the magnetic vector potential, and using a 2D polar coordinate system, we obtain analytical solutions for the magnetic field. Next, through a series of processes, we perform magnetic torque calculations using the derived solutions and a Maxwell stress tensor. Finally, the analytical results are verified by comparison with the results of 2D and 3D finite element analysis and the results of an experiment. [ABSTRACT FROM AUTHOR]

This paper presents the design for a high-speed permanent magnet synchronous machine (PMSMs) considering the demagnetization and mechanical characteristics of rare-earth magnets based on the operating temperature. The TRV equation and plane stress analytical method are considered for the temperature, the rotor size is derived from the analysis results of the sleeve thickness, and the stator is designed on the basis of the results of the electromagnetic analysis method. The B–H curve of the permanent magnet (PM) changes with its operating temperature; thus, a thermal demagnetization analysis is conducted to verify the irreversible demagnetization caused by the operating temperature and armature reaction field using electromagnetic finite element method (FEM). It is necessary to consider the irreversible demagnetization with the operating temperature because it can decrease the electromagnetic performance. Therefore, the electromagnetic characteristics of high-speed machines using rare-earth PMs are analyzed to confirm irreversible demagnetization. The validity of the proposed design is confirmed via comparative verifications with the measured results from prototype models. [ABSTRACT FROM AUTHOR]

Rotational permanent magnet eddy current couplers are promising devices for torque and speed transmission without any mechanical contact. In this study, flux-concentration disk-type permanent magnet eddy current couplers with double conductor rotor are investigated. Given the drawback of the accurate three-dimensional finite element method, this paper proposes a mixed two-dimensional analytical modeling approach. Based on this approach, the closed-form expressions of magnetic field, eddy current, electromagnetic force and torque for such devices are obtained. Finally, a three-dimensional finite element method is employed to validate the analytical results. Besides, a prototype is manufactured and tested for the torque-speed characteristic. [ABSTRACT FROM AUTHOR]

In order to realize the low vibration design, variable leakage flux permanent magnet (VLF-PM) motor is investigated and purposefully optimized. Firstly, the variable flux characteristics of the VLF-PM motor are studied in detail. Then the electromagnetic vibration characteristics of the VLF-PM motor under different operating conditions are analyzed. On this basis, key electromagnetic force harmonics caused by the vibration at typical operating conditions and torque performances are selected to be optimized. By the adoption of multi-objective optimization, low radial electromagnetic force (REF) and high output torque can be achieved. Both simulation and experimental results verify the effectiveness of the reduced vibration design of LCF-PM motors, which provides a potential research path for the low vibration design of PM motors, especially multi-mode PM motors. [ABSTRACT FROM AUTHOR]

High entropy alloys (HEA) contain multiple principal alloying elements, and possess unique properties due to the high configurational entropy and lattice strain in the system. Ferromagnetic FeCoNi-based HEAs exhibit dramatic changes in crystal structure and the type of magnetism expressed when adding non-magnetic elements such as Al, Cr, Ga, Ti, etc. Interestingly, Alnico permanent magnets also contain multiple principal alloying elements, such as Fe, Co, Ni, and Al, along with other minor additions. This well-studied system is similar in concept to high entropy alloys (HEAs). In this paper, we investigate the hard magnetic properties of FeCoNiAl-based HEAs with additions of Cu/Ti. The addition of Cu/Ti to an equimolar FeCoNiAl alloy is effective at enhancing coercivity, due to spinodal decomposition, but at the expense of saturation magnetization. By varying the ratio of Fe and Co, however, with respect to the other alloying elements, the saturation magnetization is increased, while generally retaining or improving the coercivity. In particular, the Fe2CoNiAlCu0.4Ti0.4 HEA shows promising hard magnetic properties as an isotropic cast magnet, with an HC of 1,078 Oe and (BH)max of 2.06 MGOe, slightly better than the performance of isotropic cast Alnico 2 magnets. The thermal stability is also sufficient for use at elevated temperatures over 200 °C. There was also an interesting increase in high temperature coercivity observed at temperatures from ∼650-800 °C, where these alloys often exhibited higher coercivity than that measured at RT. [ABSTRACT FROM AUTHOR]

In this paper, a new dual stator linear permanent-magnet (PM) vernier (LPMV) machine with toroidal winding is proposed and analyzed. The proposed machine enjoys the advantages of less copper usage and copper loss without sacrificing the thrust force performance. For a fair comparison, the proposed machine is designed with the same geometrical parameters based on the conventional dual stator LPMV machine with concentrated winding. Finally, the electromagnetic performances of the proposed machine and the conventional one are compared and analyzed by using finite element method, verifying that the proposed machine with the low copper loss can obtain high force density. [ABSTRACT FROM AUTHOR]

In this paper, a novel 12/10 stator/rotor pole bearingless flux-switching permanent magnet (BFSPM) motor is proposed to overcome the drawbacks of rotor permanent magnet type bearingless motors. The basic motor configuration, including motor configuration and winding configuration, is introduced firstly. Then, based on the principle of reverse direction magnetization for symmetrical rotor teeth, the radial suspension forces generation principle is analyzed in detail. Finally, decoupling performances between suspension force windings and torque windings are investigated. The results show that the proposed BFSPM not only ensures the merits of high torque output capability compared with conventional 12/10 stator/rotor pole FSPM motor, but also achieves stable radial suspension forces which have little mutual effect with torque. The validity of the proposed structure has been verified by finite element analysis (FEA). [ABSTRACT FROM AUTHOR]

In this paper, firstly a novel 6-stator-coil/17-rotor-pole (6/17) flux-switching permanent magnet (FSPM) machine with V-shaped magnets, deduced from conventional 12/17 FSPM machines is proposed to achieve more symmetrical phase back-electromotive force (back-EMF), and smaller torque ripple by comparing with an existing 6/10 V-shaped FSPM machine. Then, to obtain larger electromagnetic torque, less torque ripple, and easier mechanical processing, two improved variants based on the original 6/17 V-shaped topology are proposed. For the first variant, the separate stator-core segments located on the stator yoke are connected into a united stator yoke, while for the second variant the stator core is a whole entity by adding magnetic bridges at the ends of permanent magnets (PMs). Consequently, the performances of the three 6/17 V-shaped FSPM machines, namely, the original one and the two variants, are conducted by finite element analysis (FEA). The results reveal that the first variant exhibits significantly larger torque and considerably improved torque per magnet volume, i.e., the magnet utilization ratio than the original one, and the second variant exhibits the smallest torque ripple, least total harmonic distribution (THD) of phase back-EMF, and easiest mechanical processing for manufacturing. [ABSTRACT FROM AUTHOR]

An experimental study on the effect of permanent magnet tolerances on the performances of a Tubular Linear Ferrite Motor is presented in this paper. The performances that have been investigated are: cogging force, end effect cogging force and generated thrust. It is demonstrated that: 1) the statistical variability of the magnets introduces harmonics in the spectrum of the cogging force; 2) the value of the end effect cogging force is directly linked to the values of then remanence field of the external magnets placed on the slider; 3) the generated thrust and its statistical distribution depend on the remanence field of the magnets placed on the translator. [ABSTRACT FROM AUTHOR]

This paper proposed an analytical method, based on conformal mapping (CM) method, for the accurate evaluation of magnetic field and eddy current (EC) loss in fault-tolerant permanent-magnet (FTPM) machines. The aim of modulation function, applied in CM method, is to change the open-slot structure into fully closed-slot structure, whose air-gap flux density is easy to calculate analytically. Therefore, with the help of Matlab Schwarz-Christoffel (SC) Toolbox, both the magnetic flux density and EC density of FTPM machine are obtained accurately. Finally, time-stepped transient finite-element method (FEM) is used to verify the theoretical analysis, showing that the proposed method is able to predict the magnetic flux density and EC loss precisely. [ABSTRACT FROM AUTHOR]

In this paper, the partitioned rotor flux switching permanent magnet machine with ferrite permanent magnet is proposed. By the adoption of the partitioned rotor configuration, the stator flux leakage is eliminated and the permanent magnet utilization is improved. The ferrite permanent magnet machine often suffers from irreversible demagnetization due to the inherent relatively low coercivity of ferrite permanent magnet. To mitigate the machine irreversible demagnetization risk, an improved partitioned rotor flux switching permanent magnet machine with hybrid permanent magnet topology is also proposed. Two little pieces of rare-earth permanent magnet are installed at the corners of ferrite permanent magnet, thus forming the hybrid permanent magnet topology. And the demagnetization mechanisms of both machines are clarified by the magnetic equivalent circuit method, which prove that the rare-earth permanent magnet offer magnetic protection function for the ferrite permanent magnet. Furthermore, by the 2-D finite element analysis, the demagnetization characteristics and the electromagnetic performances of the two machines are quantitively assessed, revealing that the demagnetization risk is reduced significantly. Both theoretical analysis and simulation results verify that the improved machine can not only maintain low-cost design, but also possess enhanced demagnetization withstand capability and competitive electromagnetic performances as expected. [ABSTRACT FROM AUTHOR]

Since permanent magnets (PM) are stacked between the adjacent stator teeth and there are no windings or PMs on the rotor, flux-switching permanent magnet machine (FSPMM) owns the merits of good flux concentrating and robust rotor structure. Compared with the traditional PM machines, FSPMM can provide higher torque density and better thermal dissipation ability. Combined with the soft magnetic composite (SMC) material and ferrite magnets, this paper proposes a new 3D-flux FSPMM (3DFFSPMM). The topology and operation principle are introduced. It can be found that the designed new 3DFFSPMM has many merits over than the traditional FSPMM for it can utilize the advantages of SMC material. Moreover, the PM flux of this new motor can be regulated by using the mechanical method. 3D finite element method (FEM) is used to calculate the magnetic field and parameters of the motor, such as flux density, inductance, PM flux linkage and efficiency map. The demagnetization analysis of the ferrite magnet is also addressed to ensure the safety operation of the proposed motor. [ABSTRACT FROM AUTHOR]

Vernier permanent-magnet (VPM) machine offers the advantage of high torque density. However, the existing VPM machines usually suffer from relatively low power factor. To solve the problem, this paper proposes a new high power factor faulttolerant VPM machine. Compared with the existing one, the proposed VPM machine has higher power factor and higher torque density. Also, the fault-tolerant capability is provided. The electromagnetic characteristics of the proposed machine are analyzed by using the finite element method. [ABSTRACT FROM AUTHOR]

This paper compares permanent magnet synchronous motors with rare earth permanent magnets (PM) and those with ferrite PM, and it suggests that ferrite PM can replace rare earth PM. Therefore, the two models with the same output were compared and analyzed by comparing the mechanical and electromagnetic characteristics. Finally, the study is validated experimentally. [ABSTRACT FROM AUTHOR]