Arrangement Of Permanent Magnets Research Articles

Research on Magnetic Field of Permanent Magnet Rolls Arranged Periodically in Circumferential—Axial Direction

The separation of non-magnetic non-ferrous metals such as copper and aluminum from scrapped automobiles is a critical area of research due to the increasing number of end-of-life vehicles. Traditional eddy current separation methods have limitations, particularly in handling large-sized broken copper and aluminum parts. This paper proposes a novel magnetic roller model featuring a circumferential–axial periodic arrangement of permanent magnets. This study explores the external magnetic field distribution of this new roller design by constructing an equivalent current model, solving magnetic scalar potential equations, and employing simulation tools. The findings indicate that the new magnet array enhances both the magnetic field strength and the range of the external magnetic field, leading to improved separation efficiency of large-sized metal fragments. The results provide a theoretical basis for advancing the separation technology of large-sized broken copper and aluminum parts in scrapped automobiles, offering potential improvements in the recycling of non-ferrous metals from end-of-life vehicles.

An incremental permeability detection method for yield strength of ferromagnetic materials based on permanent magnet excitation

ABSTRACT In this paper, in order to meet the engineering requirements of mechanical properties detection of materials with low power consumption, a novel incremental permeability detection system based on permanent magnet excitation is proposed to reduce system power consumption. Initially, a new incremental permeability sensor was designed to extract magnetic incremental permeability (MIP) signal. Through finite element simulation, experimental parameters were optimised, and a rational arrangement of double permanent magnets was devised to furnish an optimally strong AC bias field intensity. Subsequently, a practical detection platform was assembled to extract electromagnetic signal features. From the perspective of domain wall displacement, a characteristic value θ was proposed to predict the yield strength, with experimental results yielding a relative error of less than ±10%. These experiments have validated the capability of permanent magnet-type MIP to enable quantitative detection of the yield strength in ferromagnetic materials.

A pole-changing flux reversal permanent magnet motor

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.

Influence of cusp magnetic field configuration on plasma parameters of radio frequency driven negative ion source for CRAFT NNBI

Radio Frequency (RF) driven negative ion source is the preferred ion source for negative ion based Neutral Beam Injection system (NNBI). The plasma generator, which consists of RF driver(s) and an expansion chamber, is one of the key parts for NNBI. The distribution of cusp magnetic field which is generated by permanent magnets installed at the lateral wall of the expansion chamber is a common issue, due to the great influence on electron density, electron temperature and spatial uniformity of plasma density in the extraction area. Two kinds of configuration of cusp magnetic field (checkerboard type and symmetric type) and three types of arrangement of permanent magnets (with three, four and five rows of magnets) have been carried out with the approach of finite element and the experimental performance. On the RF negative ion source testbed, a moveable Langmuir probe has been adopted to investigate the characteristic of electron density and temperature near the extraction area. Since the symmetric type with three rows of permanent magnets generates the distribution of cusp magnetic field that contribute to extract the plasma from RF driver and improve the probability of particle collision easily, the higher electron density and the lower electron temperature was obtained via simulation. The experimental conclusion is that the symmetric type with three rows of permanent magnets leads to a higher electron density and lower electron temperature, showing a great agreement with simulation results. The results are helpful to optimize the structure and performance of high power ion source, and provide support for the development of large area RF negative ion sources with multi-driver.

Design of an L-Shaped Array Vernier Permanent Magnet Machine for Unmanned Aerial Vehicle Propulsion Using a Schwarz–Christoffel Mapping-Based Equivalent Magnetic Network Model

The Vernier permanent magnet (VPM) machines supersede conventional permanent magnet synchronous machine (PMSM) topologies in terms of torque-density and cogging torque. This paper presents a fractional-slot L-shaped magnet VPM machine, including peculiar designs for permanent magnet (PM) housing and rotor core construction for small-scale EVs such as unmanned aerial vehicles (UAVs). The idea for selecting the PM arrangement is based on combining the V-shaped and spoke-array PM topologies for achieving a higher torque-density than V-shaped PM machines and a lower cogging torque than spoke-array PM machines. The rotor core is created from non-integrated segments to form the flux-barriers in end-portions of PM housings. In this way, the leakage flux lines in the end-portion of the PMs reduce, resulting in enhanced flux linkage and power factor. A 630 W, 12-slot/8-pole motor is designed and prototyped for model validation purposes. An innovative equivalent magnetic network (EMN) model is established for analytical prediction of the performance of the machine. The Schwarz-Christoffel mapping is used to create the rotor core permeance network due to its special shaping. Two innovative pentagonal-shaped mesh cells are used in the air-gap region for more accurate capturing of flux behavior. The model is validated by comparing the results with the finite element results and experimental measurements.

Investigation of the magnetic field created by axially symmetric permanent magnet arrangements

Investigation of the magnetic field created by axially symmetric permanent magnet arrangements

Development and comparison of double-stator memory machines with parallel hybrid magnets

PurposeThis paper aims to further develop stator permanent magnet (PM) type memory machines by providing generalized design guidelines for double-stator memory machines (DSMMs) with hybrid PMs. This paper discusses the design experience of DSMMs and presents a comparative study of radial magnetization (RM) and circumferential magnetization (CM) types.Design/methodology/approachIt begins with an introduction to RM and CM operating principles and magnetization mechanisms. Then, a comparative study is conducted for one of the RM-DSMM rotor pole pairs, inner and outer stator clamping angles and low coercive force PMs thickness. Finally, the two machines’ finite element simulation performance is compared. The validity of the proposed machine structure is demonstrated.FindingsIn this paper, the double-stator structure is extended to parallel hybrid PM memory machines, and two novel DSMMs with RM and CM configurations are proposed. Two types of DSMMs have PMs and magnetizing windings on the inner stator and armature windings on the outer stator. The main difference between the two is the arrangement of PMs on the inner stator.Originality/valueConventional stator PM memory machines have geometrical space conflicts between the PM and armature windings. The proposed double-stator structure can alleviate these conflicts and increase the torque density accordingly. In addition, this paper contributes to comparing the arrangement of hybrid PMs for DSMMs.

Investigation of a Flux-Switching Machine With U-V-Array Permanent Magnet Arrangement for Traction Applications

This paper investigates a flux-switching (FS) machine with U-V-array permanent magnet (PM) arrangement, termed UV-FSPM. The key design is to construct parallel magnetic circuit by adopting U-V-array PMs. Based on the parallel magnetic circuit, the operating principle of the UV-FSPM is illustrated. To provide a deeper insight into the torque enhancement mechanism, the analytical model of the UV-FSPM is built by using the general air-gap field modulation theory. It is found that the U-V-array PMs can significantly enhance the dominant working harmonic which effectively contributes to torque enhancement of the investigated UV-FSPM. To reveal the impact of key parameters on torque performances, the parametric optimization of the UV-FSPM is conducted. The electromagnetic performances of three FSPMs are comparatively studied by finite element analysis (FEA). It is proved that the investigated UV-FSPM exhibits the highest torque density and highest PM utilization ratio within the pool. Finally, a prototype of the UV-FSPM is fabricated and tested for verification of the investigated concepts.

Programming Deformations of 3D Microstructures: Opportunities Enabled by Magnetic Alignment of Liquid Crystalline Elastomers.

Synthetic structures that undergo controlled movement are crucial building blocks for developing new technologies applicable to robotics, healthcare, and sustainable self-regulated materials. Yet, programming motion is nontrivial, and particularly at the microscale it remains a fundamental challenge. At the macroscale, movement can be controlled by conventional electric, pneumatic, or combustion-based machinery. At the nanoscale, chemistry has taken strides in enabling molecularly fueled movement. Yet in between, at the microscale, top-down fabrication becomes cumbersome and expensive, while bottom-up chemical self-assembly and amplified molecular motion does not reach the necessary sophistication. Hence, new approaches that converge top-down and bottom-up methods and enable motional complexity at the microscale are urgently needed. Synthetic anisotropic materials (e.g., liquid crystalline elastomers, LCEs) with encoded molecular anisotropy that are shaped into arbitrary geometries by top-down fabrication promise new opportunities to implement controlled actuation at the microscale. In such materials, motional complexity is directly linked to the built-in molecular anisotropy that can be "activated" by external stimuli. So far, encoding the desired patterns of molecular directionality has relied mostly on either mechanical or surface alignment techniques, which do not allow the decoupling of molecular and geometric features, severely restricting achievable material shapes and thus limiting attainable actuation patterns, unless complex multimaterial constructs are fabricated. Electromagnetic fields have recently emerged as possible alternatives to provide 3D control over local anisotropy, independent of the geometry of a given 3D object. The combination of magnetic alignment and soft lithography, in particular, provides a powerful platform for the rapid, practical, and facile production of microscale soft actuators with field-defined local anisotropy. Recent work has established the feasibility of this approach with low magnetic field strengths (in the lower mT range) and comparably simple setups used for the fabrication of the microactuators, in which magnetic fields can be engineered through arrangement of permanent magnets. This workflow gives access to microstructures with unusual spatial patterning of molecular alignment and has enabled a multitude of nontrivial deformation types that would not be possible to program by any other means at the micron scale. A range of "activating" stimuli can be used to put these structures in motion, and the type of the trigger plays a key role too: directional and dynamic stimuli (such as light) make it possible to activate the patterned anisotropic material locally and transiently, which enables one to achieve and further program motional complexity and communication in microactuators. In this Account, we will discuss recent advances in magnetic alignment of molecular anisotropy and its use in soft lithography and related fabrication approaches to create LCE microactuators. We will examine how design choices-from the molecular to the fabrication and the operational levels-control and define the achievable LCE deformations. We then address the role of stimuli in realizing the motional complexity and how one can engineer feedback within and communication between microactuator arrays fabricated by soft lithography. Overall, we outline emerging strategies that make possible a completely new approach to designing for desired sets of motions of active, microscale objects.

Experimental investigation of liquid metal droplet flow affected by a time-dependent magnetic field

Abstract The present study investigates experimentally the effects of a time-dependent and spatially inhomogeneous magnetic field on liquid metal droplet flow down an inclined substrate. The flow is solely excited by the electromagnetic interactions between the electrically conducting melt and the applied magnetic field. The metal droplet consists of the eutectic alloy GaInSn which is liquid at room temperature. The magnetic field is generated in the gap between two metallic disks that are equipped with a special geometric arrangement of permanent magnets and put into a measured rotation. During the experiments, a droplet of a measured volume is positioned on an electrically non-conducting substrate that is slightly inclined against the horizontal direction. Droplet and substrate are placed in between the two rotating magnetic disks. In our experiments, we record the electromagnetically excited flow of the droplet downwards onto the substrate using a high-speed camera system. Applying standard techniques of digital image processing, we measure both the displacement position and velocity of the droplet as a function of time. We observe that, depending on the rotation rate of the disks and angle of inclination, the magnetic field eventually triggers this spreading process. In more detail, by evaluating the recorded data, we find that the magnetic field excites capillary waves at the free surface of the droplet. These surface waves contribute to a redistribution of volume towards the contact line formed at the downward-facing end tip of the droplet. This mode of transport steepens the contact angle, allowing the droplet to move. Besides the fundamental aspect of this work, the present study may contribute to the electromagnetic control of both the production of metallic microfibers and metallurgic coating processes as well as to the non-contact electromagnetic flow measurement technique of Lorentz force velocimetry applied to liquid metal free-surface flows.

Braking force characteristics and multi-objective optimization of eddy current brake under intensive impact load

As a new type of permanent magnet arrangement in the eddy current brake (ECB), the Halbach array is gradually gaining attention thanks to its excellent magnetic field utilization. However, the absence of an accurate theoretical model causes great distress in the design phase of the ECB. To tackle this, this article establishes a subdomain model that can intuitively observe the influence of structural and material parameters on the magnetic field and eddy current braking force. The accuracy of the analytical model is verified by the finite element method (FEM). The calculation results show that the eddy current braking force is the largest when the relative velocity of the primary and secondary reaches the critical velocity value. The recoil equation of motion is introduced to analyze the change law of the braking force under intensive impact load. A small prototype impact test platform was set up to analyze the change of braking characteristics of the ECB under the impact load. To reduce the weight of the ECB, the multi-objective optimization of the ECB parameters is carried out. The vital structural mass of the ECB is reduced by 19.44% while meeting the recoil requirements.

Influences of Magnet Arrangements on Air-Gap Field Modulation Effects in Interior Consequent-Pole PM Machines

This article comprehensively investigates and compares the influences of permanent magnet (PM) arrangements on air-gap field modulation effects (AFMEs) in interior consequent-pole PM (ICPM) machines. Four typical single-layer PM structures, i.e., flat-type, spoke-type, U-shaped, and V-shaped magnet designs, are exemplified in order to identify how different rotor structures perform AFMEs due to a double-side slotting and affect the torque behavior. The contributed torque components and corresponding torque proportions of the main air-gap flux density working harmonics are quantificationally distinguished by adopting the Maxwell stress tensor (MST) method. It shows and confirms a fact that the flat-type and V-shaped ICPM cases present the lowest and the highest torque proportions due to their AFMEs, respectively. In addition, the influences of rotor PM parameters on AFMEs of the four single-layer ICPM machines are subsequently studied. Finally, the prototype of the ICPM machine with V-shaped PM structure is manufactured. The corresponding experimental results are conducted to validate the theoretical and finite element (FE) analyses.

Design and Evaluation of Reduced-Rare-Earth Interior Consequent-Pole Permanent Magnet Machines for Automotive Applications

This article investigates the feasibility of interior consequent-pole permanent magnet (ICPM) machines with reduced rare-earth magnet consumption for automotive applications. A new ICPM machine with a double-layer V-shaped permanent magnet (PM) arrangement is proposed and compared with a commercial Nissan Leaf interior PM (IPM) machine. Their basic electromagnetic performances and rotor mechanical strength are evaluated by finite-element (FE) simulation. It shows that the proposed ICPM machine exhibits comparable torque capability, similar high-efficiency region, and significantly improved PM utilization ratio compared with traditional Nissan Leaf IPM case. Besides, to verify the universality of ICPM designs with reduced-rare-earth consumption, two typical ICPM machines with different magnet configurations (single- and double-layer V-shaped) and power levels (80 kW and 2 kW) are, respectively, investigated and compared with their corresponding traditional IPM counterparts. Finally, some tested results on an ICPM machine prototype with V-shaped magnets are carried out to validate the FE analysis.

Transmission Performance of Halbach Array Cylindrical Permanent Magnet Governor

A novel cylinder permanent magnet governor (CPMG) with Halbach segmentation is proposed in this paper. In order to improve the transmission performance of the CPMG, different permanent magnet (PM) arrangement methods are adopted. To achieve a fair comparison result, all the PMs are of the same size. The main magnetic fluxes are considered to obtain a comprehensive equivalent magnetic circuit model of the CPMG with Halbach array and analytical output torque that is calculated. The analytical method of transmitted torque for CPMG is then presented. Additionally, the effect of the average output torque of CPMG under parameters of the thickness of the copper rings, the slip rate and the effective coupling of the copper rings are investigated. Finally, the prototype platform is ready for testing on the field. The results were consistent with the results of the simulation, and the error was kept within the range of 5%. This research can provide a theoretical and practical reference for the optimal design of the transmission characteristic of CPMG.

Investigation of the Influence of Skewed Slots and Degmagnetization Effects to Line Start Permanent Magnet Assistance Synchronous Reluctance Motors

A permanent magnet assistance synchronous reluctance motor can start directly with a net voltage or a power converter via a torque control method. However, this motor has usually a higher irreversible demagnetization level in comparison with interior permanent magnet motors, due to the fewer permanent magnets in rotor slots. In order to cope with this disadvantage, different arrangements of permanent magnets in the rotor of the line-start permanent magnet assistance synchronous reluctance motor are proposed in this paper. The V magnet shape taking skewed slots and demagnetization effect into account with the short circuit current are investigated by the finite element approach. The efficiency, torque, and output power of the proposed model have been also improved. Finally, the rotor with 3V layered magnets is prototyped to verify the efficiency of the proposed motor.

Analysis of flux barrier effect of LCF PM in series hybrid magnet variable flux memory machine

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.

Comparative Study of Yokeless Stator Axial-Flux PM Machines Having Fractional Slot Concentrated and Integral Slot Distributed Windings for Electric Vehicle Traction Applications

Due to the high-power density and compact structure, axial-flux permanent magnet (AFPM) machines have gradually received much attention with a view to researching breakthroughs in the next generation electric drive technology for electric vehicles in the recent decades. The AFPM machines with factional slot concentrated winding (FSCW) and yokeless stator, namely yokeless, and segmented armature (YASA) motors, have drawn much attention for its high-power density and potential manufacturability due to the concentrated winding and modular stator core configuration. However, the significant rotor loss resulting from the abundant armature reaction harmonics in FSCW machines imposes a great challenge to the rotor heat dissipation, especially when the pursuit of higher speed has become the trend for electric vehicle applications. On the other hand, distributed winding is widely used in high speed radial flux permanent magnet (PM) machines due to its low armature reaction harmonics. In order to figure out the advantages and disadvantages of various winding arrangement and rotor configuration of AFPM for electric vehicle applications, the comparative study of four AFPM machines with various winding configurations and rotor PM arrangements are comprehensively conducted in this article. First, the design and primary optimization of the four AFPM machines are conducted for the electric vehicle requirement specifications. Then, a comprehensive three-dimensional finite-element analysis (FEA) is employed to compare the electromagnetic performance including torque/power density, efficiency, and flux-weakening capacity. Furthermore, the guideline of winding selection of AFPM machines for electrical vehicle is given. Finally, a yokeless stator AFPM prototype with ISDW configuration is manufactured and tested to verify the validity of the FEA results, as well as confirm the comparison conclusion.

Design of a non‐ferromagnetic spoke array Vernier permanent magnet generator with iron‐bar based on enhanced equivalent magnetic network model

AbstractThe spoke‐type arrangement of permanent magnets (PMs) in rotor of Vernier PM (VPM) machines was first introduced in a dual‐stator topology to overcome low‐power drawback of VPM machines. However, this structure is mostly applicable for high‐power motor drives. A non‐ferromagnetic spoke array VPM generator with a special rotor structure for small‐scale wind turbine generator is presented. The leakage flux lines tend to be aligned with the main flux routes due to a special design of flux barriers in end portion of PM housings. High torque‐density, low weight, torque‐speed curve with a wide constant torque region, promising efficiency, and power factor are the advantages of the proposed machine. An Equivalent‐Magnetic‐Network (EMN) model is established for predicting the complex behaviour of flux lines and operating quantities of the proposed structure with reasonable accuracy. The contribution of the modelling method includes a special mesh cell for the air‐gap permeance network to more accurately capture the flux routes, continuous positioning method for omitting spikes on post‐processing waveforms due to numerical errors, and a stable solving flowchart with a high convergence rate. The validity of the EMN model is validated by comparing the operating waveforms of the machine with the corresponding waveforms obtained by the finite element and experiments.The cover image is based on the Research Article Design of a non‐ferromagnetic spoke array Vernier permanent magnet generator with iron‐bar based on enhanced equivalent magnetic network model by Mehrage Ghods et al., https://doi.org/10.1049/elp2.12272.

영구자석 배열이 사각 공동 내부 자성나노유체의 열유동 특성에 미치는 영향

Various researches have been performed to cool the device. However, dealing with cooling problems through structural design changes becomes increasingly difficult. Therefore, more research on new cooling media and methods to increase heat transfer efficiency is necessary. Particularly, ferrofluid is composed of nanoscale particles of magnetite, hematite, or some others. And it has superior thermal properties compared with conventional heat transfer fluids due to the nanoparticles dispersed in the base liquid. In addition, the heat dissipation method using ferrofluid is effective for local heat transfer because the flow can be controlled through a magnetic field. In this study, flow and heat transfer characteristics of the ferrofluid in a rectangular cavity, which vary depending on the arrangement of permanent magnets were investigated through computational fluid dynamics(CFD). As a result, the enhancement of heat transfer due to the magnet arrangements was verified. The time-averaged Nusselt number at the heat source surface was increased up to 9.6 %.

Low-cost variable-speed wind turbines design by recycling small electrical machines. Arrangement of permanent magnets in the rotor

This paper describes the design of low-cost variablespeed wind turbines by recycling small electrical machines. In this way, electrical machines such as automobile claw-pole alternators, induction motors for domestic applications, or simply electric motors for some industrial applications are studied, considering their reuse as permanent magnet synchronous generators (PMSG) in small wind turbines or hydro-power turbines. The main purpose is the integration of hybrid energy conversion systems (wind and hydraulic turbines) in small stand-alone microgrids within the rural environment. Likewise, in order to optimize the design, the arrangement of the permanent magnets in the rotor is analyzed. The analysis has been carried out using the FluxMotor simulation software, which is based on the 2D finite element method. At the same time, the FEM software provides a lot of information about the optimization of the electrical machine and its multiple design options and topologies. Suggested designs have similar performance as well as a similar size and weight. The purpose has been to explore different topologies and select the most efficient designs. In this way, it is shown that it is possible to reuse an electrical generator easily, without losing much of the general performance.