Radial Magnet Research Articles

Laser and thermal control over structure and magnetic properties of PrDy-FeCo-B microwires

Magnetic microcombs are necessary in microrobotics, MEMS technologies, actuator and magnetic flow analyzer industries. Usually, magnetic microcombs are artificial linear magnets of periodic shape. We propose another type of microcombs based of microwires, where periodicity of magnetization is caused by equidistant alternation of natural domains. We have demonstrated the presence of quasi-periodic radial magnetization and the effect of temperature and magnetic field on magnetic relief in PrDyFeCoB microwires. Accurate analysis of chemical, phase and structural composition of the microwires allowed us to reveal necessary conditions for the creation of periodical magnetic relief. Annealing affects magnetic relief and changes structure of initially amorphous microwires. Crystal structure of inclusions enriched with Fe and Co instead of Dy and Pr is body-centered cubic (BCC), while the bulk of the microwire has tetragonal structure. We have found laser stimulated amorphization of surface of PrDy-FeCo-B microwires. Partial restoration of the amorphous structure in polycrystalline microwires under single laser pulse of irradiation of 1mJ power and 120 ns duration has been found in 1–2 μm depth.

Design and analysis of double-permanent-magnet enhanced hybrid stepping machine with tangential and radial magnetization

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

Modeling and Study of Different Magnet Topologies in Rotor of Low Rating IPMSMs

A study and performance analysis of magnet positions in different topology on the surface of rotor in permanent magnet synchronous motors (PMSMs) based on finite element method is observed here. A 3-phase interior PMSM is numerically simulated with ANSYS Maxwell 2018.1. Differently positioned permanent magnets improve the performance of PMSMs. Apart from handling nonlinear equations, FEM is used for simulation. ANSYS is used to analyze PMSM performance under variable conditions. This proposal examines a three-phase, 0.55 kW PMSM at 220 V, 50 Hz. Here rotor topologies of five types, namely, (i) spoke/tangential, (ii) saturable bridge / u-shape, (iii) V-shape, (iv) radial, and (v) segmented bridge permanent magnet rotor are taken for observation. The motive of this study is to analyze the performance of PMSMs in different rotor designs with different magnet positions. All topologies have been modeled and simulated with ANSYS. Each topology is compared in terms of electromagnetic and mechanical parameters. The 2D model is used to model the distribution of magnetic fields and the performance of operating parameters under transient and steady-state conditions. Magnetic flux, and efficiency are heavily influenced by the rotor shape with the volume of magnet. A study of radial force distribution and mechanical stress across rotor surface is also discussed. Motor performance is affected by the design of PMs.

Calculating torque, back-EMF, inductance, and unbalanced magnetic force for a hybrid electrical vehicle by in-wheel drive application

To use a Hybrid Excitation Synchronous Machine (HESM) in a hybrid electrical vehicle (HEV), its performance indicators such as back-EMF, inductance and unbalanced magnetic force should be computed preferably by an analytical method. First, the back-EMF is calculated by considering alternate-teeth and all-teeth non-overlapping and overlapping windings. The effects of three types of magnetization patterns including the radial, parallel and Halbach magnetizations on the back-EMF waveform have also been investigated. Then, the self-inductance of the stator and rotor windings, the mutual inductance between the stator and rotor windings, and the mutual inductance between the stator phases are computed. Next, the components of the unbalanced magnetic force (UMF) in the direction of the x and y axes and its amplitude are computed. Moreover, the effects of the magnetization patterns on those magnetic pulls are investigated. To minimize the UMFs, symmetry must be implemented in the excitation sources; therefore, first the stator winding then the permanent magnet and rotor winding are modified in such a way that the UMFs are reduced. Increasing the temperature leads to a weakening of the magnet’s residual flux density, which strongly affects the performance characteristics of the electric machine such as Back-EMF and UMF. Finally, the ratio of the permanent magnet flux to the rotor flux is determined in such a way that the average torque is maximized. In this section, the effects of three magnetization patterns will be investigated.

The Magnetic Field from Cylindrical Arc Coils and Magnets: A Compendium with New Analytic Solutions for Radial Magnetization and Azimuthal Current

AbstractThis study provides analytic solutions for the magnetic field of coils and magnets that have a non‐axisymmetric cylindrical geometry with a rectangular cross‐section. New analytic solutions are provided for radially magnetized permanent magnet arcs, thin coil disc sectors, and thick coil sectors. If components of the 3D field are not representable in closed‐form or as canonical Legendre elliptic integrals, the exact solution is given in terms of a series of regularized beta functions. The limit and hence spatial convergence is found to these series, giving a well‐defined and fast solving algorithm for computation. The equations can be readily applied to find the magnetostatic field in linear or non‐linear systems that contain a large set of elements. Example applications are provided to demonstrate how the field can be used to calculate forces and benchmark computational efficiency of the equations. A thorough review of the preceding literature and background theory is provided before a detailed methodology obtaining the analytic solutions contained in this compendium, and further related geometries in cylindrical or spherical coordinates. This is the first study to comprehensively solve the field equations for this collection of electromagnetic geometries.

Research on Cogging Torque Reduction of Direct-Drive Type Dual-Rotor Radial Flux Permanent Magnet Synchronous Motor for Electric Propulsion Aircraft

The direct-drive type high-torque-density motor is one of the most promising solutions of electric propulsion for aircraft. The cogging torque of the direct-drive motor causes torque ripple, vibration, and noise, which seriously affect the stability and reliability of the electric propulsion system for aircraft. In this paper, a novel direct-drive type high-torque-density dual-rotor radial flux permanent magnet synchronous motor (DRPMSM) is proposed, and its cogging torque is weakened by permanent magnet shape design and pole-arc coefficient combination. An eccentric and chamfered permanent magnet shape is proposed, and the influence of eccentric distance and chamfer angle on cogging torque is clarified. Through the pole-arc coefficient combination design of the inner and outer rotors of the DRPMSM, the cogging torques of the inner and outer rotor are phase reversed, thus further reducing the total cogging torque of the DRPMSM. By employing the response surface method, a mathematical model is established for the cogging torque of the DRPMSM in relation to the pole-arc coefficients, chamfer angle, and eccentric distance of the permanent magnets. The parameters that minimize the cogging torque of the DRPMSM are obtained using a genetic algorithm. A prototype is manufactured according to the optimized parameters, and experimental results validate the correctness of the theoretical analysis and the effectiveness of the optimization design method.

Equivalent Analytical Model of Magnetic Field in Parallel Magnetic Circuit Axial Flux Permanent Magnet Machines

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.

Novel Halbach Permanent Magnet Solenoid Design using Finite Element Method

To generate the high axial field usually Electromagnetic Coils solenoid is used but it consumes large DC power supplies and cooling system and is not compact. The PM (Permanent Magnet) solenoid on the contrary can give fixed axial field profiles that are very compact and do not require any energy source as they are themselves energy sources. PM solenoids are usually designed using large radial and axial magnetized magnets. The drawback of such a design is using large radial magnets which are often unavailable with assembly problems. The paper discusses the novel Halbach solenoid configuration design and uses ref1 solenoid results to verify it. The finite element magneto static method is used to analyze the two models. The FEM magneto static analysis was done in Magnet Infolytica FEM magneto static analysis package.

Small wind in urban sectors: Review of literature and dynamic model implementation

Large industry is focusing on off-shore wind generation solutions which permit extra large turbine dimensions. In an economically recessing situation it may be sensible to underline the good results observed in distributed and local generation. Attending to consumer proximity, cities and urban areas are to be studied. These locations present renewable resource scarcity in general. However, several authors, following the evolution of regulations in countries like UK, present the advantages of small wind. From the point of view of generator concept options experimental comparative analysis’ results are included. Finally, a mathematical model for small radial flux permanent magnet synchronous generators (RF-PMSG) is included and verified by means of a contrasted simulator in Matlab Simulink. The implemented simulator will permit more accurate and analytical comparatives between small wind generator solutions.

Miniature water flow energy harvester based on savonius-type microturbine: an experimental study

In this experimental study, a miniature turbine-based water flow energy harvester designed for the purpose of providing power to wireless sensors within water pipes is reported. The device comprises a Savonius-type turbine and a radial flux permanent magnet electromagnetic generator. The two are magnetically coupled so that, while the turbine is submerged in the water flow, the generator operates in air. The device is cylindrical with a diameter of 0.8 cm and a length of 7.2 cm and, when inserted through a hole in a pipe wall so that only the turbine protrudes into the flow, it presents a cross-sectional area to the flow of only 1.25 cm2. Manufacturing was achieved through a blend of conventional machining methods, laser cutting, rapid prototyping, and the utilization of flexible printed circuit board technology for the generator stator. To ensure low friction and minimize cut in speed, ceramic ball bearings were employed. The prototype can function effectively at water velocities as low as 0.5 m s−1, generating electrical power within the range of 125 µW–5.1 mW when subjected to flow speeds between 0.5 and 2 m s−1. A maximum overall efficiency of 2.2% is achieved, when the water speed is 0.8 m s−1. Performance curves derived from experimental testing of the turbine for a range of rotor designs, obtained on a water flow rig, are presented and discussed.

Design and Optimization of Halbach Magnetic Gear

This article proposes a new structure to enhance the torque and torque density of permanent magnet gears. The outer magnet is designed with a dual-layer permanent magnet configuration, where the first layer adopts a Halbach array, and the other layer utilizes a conventional radial magnetization structure. With the optimization objectives defined as maximum torque and torque density, and guided by parameter sensitivity, optimization analysis was conducted using response surface method and multi-objective genetic algorithm. The optimized parameters were determined, and finite element simulations were performed to validate the optimization results. The result indicate a 22.22% increase in torque and a 27.42% increase in torque density compared to the previous the traditional magnet gear. The performance of the proposed new structure of magnetic gear has shown significant improvement.

Dynamic investigation of 650 W roof-top horizontal wind turbine rotor system supported by radial permanent magnet bearings

Dynamic investigation of 650 W roof-top horizontal wind turbine rotor system supported by radial permanent magnet bearings

A Review: Various Designs of Radial Flux Permanent Magnet Generator Technologies

In a renewable energy system, the amount of power generated by a renewable energy source constantly evolves. Furthermore, with the smart energy approach, small distributed renewable energy can be included into an industrialized network, enabling real-time optimization, and enabling communication with other facilities. A magnetic generator is one of the renewable energies that use the permanent magnet. As a result, this generator generated magnetic flux power by using the permanent magnetic field. An overview of the radial flux permanent magnet generator for small industry is provided in this study. First, a categorization and in-depth description of radial permanent magnet generators are reviewed. The important features of the permanent magnets are presented, along with their advantages and disadvantages. Additionally, an overview of the most recent machine developments is also presented. Lastly, an overview of the conventional radial flux permanent magnet generator designs that have been used in the development of small-scale generators is as follows.

Cogging torque reduction for permanent magnet structure of radial flux permanent magnet generator

Recently, Permanent Magnet Generator has been widely used due to its ability of having simple structure yet high efficiency. A radial flux permanent magnet generator’s (RFPM) cogging torque leads to the decrease in output power. Generally, cogging torque is affected from the size of permanent magnet. This paper presents the techniques for cogging torque reduction and low torque ripple of RFPM design. This research used two methods to reduce the cogging torque which is the permanent magnet pole-arc ratio and also the permanent magnet structure. The cogging torque has been successfully reduced by increasing the permanent magnet pole-arc ratio and reducing the permanent magnet structure The best design configuration that can reduced the cogging torque by using pole-arc ratio is 0.49 pole-arc ratio which can reduce the cogging torque to 0.6986Nm. Moreover, for PM structure method 0.25 PM structure has been chosen as the best configuration since it can reduce the cogging torque to 0.2366Nm. This method able to reduce the cogging torque by 69.88%. Hence, both of these techniques are successfully reduced the cogging torque.

Design and Optimization of Coaxial Magnetic Gear With Double-Layer PMs and Spoke Structure for Tidal Power Generation

A coaxial magnetic gear (CMG) with double-layer permanent magnets (PMs) and Spoke structure is proposed to replace the mechanical gearbox in tidal power generation system. For the inner rotor PMs, the distributions of PMs are the spoke structure with different sizes, and the magnetization direction is Halbach array. The outer rotor PMs have two layers, one is Halbach array, and the other is radial magnetization. According to the sensitivity of parameters, the response surface method and multiobjective genetic algorithm are used for optimization analysis to determine the optimal structural dimension parameters of CMG. A CMG topology with 4 inner poles and 17 outer poles is established. Compared with the conventional CMG, the output torque of the proposed CMG is increased by 33.42%. Finally, a prototype was made and a test platform was built. The experimental results show that the transmission ratio of the proposed model is consistent with the theoretical value, the no-load loss is relatively small, and the efficiency is high.

Slot-pole structure investigation for radial flux permanent magnet generator

Recently, Radial Flux Permanent Magnet Generator (RF-PMG) has been applied in various applications of generator. The configuration of the radial flux permanent magnet is the magnetic rotor arranged in a circle rotation while the inner core attached to the rotor’s center. However, various sizes and structure of RF-PMG can produce different output power levels, cogging torque and generator’s flux regulation capability. By investigating the output voltage and cogging torque value, this paper showed the suitable slot-pole combinations that can influence the output performance of the generator by using 2D-Finite Element Analysis. This investigation shows the comparison of the slot-pole that resulting the least cogging torque value and high output voltage, 0.1739Nm and 180.81V respectively. Hence, 36slots-30poles indicates as the best slot-pole combinations.

Analytical Model of Air‐Gap Magnetic Field for Eccentric Harmonic Magnetic Gear with Halbach Array

The eccentric harmonic magnetic gear (EHMG) has the characteristics of high torque density, high transmission ratio and high efficiency. The EHMG with Halbach array has better performance than the EHMG with traditional radial magnetization. Accurate calculation of its air‐gap magnetic field is of great significance for design and optimization. Based on the boundary perturbation method, a 2D analytical model of the air‐gap magnetic field of EHMG with Halbach array is established in this paper. The eccentric air‐gap magnetic field is calculated due to the permanent magnets of the eccentric rotor and the stator acting alone, and then the air‐gap magnetic field of the EHMG is obtained according to the superposition principle. The results of the air‐gap magnetic field are compared and evaluated by the regression evaluation indexes. The analytical results are consistent with the finite element results, which verifies the validity and accuracy of the analytical model. Comparing the EHMG with Halbach array and radial magnetization, the maximum static and dynamic electromagnetic torques of EHMG with Halbach array are increased by 59.1% and 55.6% compared with the EHMG with radial magnetization, which verifies the superior performance of EHMG with Halbach array. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

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.

Cold-Spray Additive Manufacturing of a Petal-Shaped Surface Permanent Magnet Traction Motor

Several applications require low torque pulsations as they can lead to mechanical vibrations and acoustic noise in the electric motor. Optimization of the rotor permanent magnet (PM) shape is one of the effective methods for reducing torque pulsations. Unfortunately, the low versatility of the magnet fabrication technologies limits the development of new motor geometries. Cold spray additive manufacturing can be used for shaping permanent magnets for the direct fabrication of motor parts without the need for additional assembly steps. This fabrication technique allows an increase in the design flexibility of electric machine geometries targeting improved performance. This paper investigates the performance of permanent magnet rotors fabricated using a cold spray additive manufacturing technique for radial flux surface permanent magnet synchronous machines (SPMSM). The permanent magnet rotors considered are conventional rectangular-shaped with unskewed magnets (Model A), skewed magnets (Model B), and sinusoidal-petal shaped magnets (Model C) along the axial direction. The magnitude of magnetization current pulse required to magnetize these rotors is calculated and an impulse magnetizer setup is designed for in-situ magnetization. The performance of the shaped cold sprayed permanent magnet rotors and their effects on back EMF, electromagnetic torque, and cogging torque are analyzed experimentally and comparisons are made between the different rotor designs.

Quantitative comparison of low-cost electrical machines with soft magnetic composite and ferrite magnet materials

Because of its special structure and manufacturing process, the soft magnetic composite (SMC) material has shown its advantages over silicon sheets, including magnetic and thermal isotropy, low high-frequency core loss, low material wastes during its manufacturing process, etc.. Considering the price of SMC raw material can be very cheap in the future, it is an ideal material for developing the low-cost electrical machine. Combined with SMC cores and low-cost ferrite magnets, some electrical machines with SMC and ferrite magnets for low-cost applications were developed in the past decades, which include the transverse flux flux switched permanent magnet motor (TFFSPMM), axial flux claw pole permanent magnet motor (AFCPM), axial flux vernier motor (AFVM), dual rotor axial flux permanent magnet motor (DRAFM) and axial radial flux permanent magnet motor (RAFM). To better utilize SMC material, all these machines are designed following the design guidelines of SMC machines. Though both of them with good performance for low-cost applications, it is necessary to know the main advantages of each machine. The main target of this paper is to compare these machines quantitatively. For obtaining the comparison results fairly all these machines are optimized by using the sequential robust Taguchi method. Finally, it can be seen that the AFVM and TFFSPMM are with relatively high torque ability and the DRAFM is with high efficiency and power factor ability.