Halbach Permanent Magnet Array Research Articles

Modeling and analyzing of magnetic field in unequal segmented Halbach array permanent magnet machine

Permanent magnet machine adopting Halbach array has more sinusoidal air-gap flux density distribution and higher air-gap flux density magnitude. Compared with the equal segmented Halbach array, the fundamental magnitude of air gap flux density can be higher and distortion rate can be lower by reasonably designing each segment width in unequal segmented Halbach array. Thus, in this paper, the permanent magnet machine adopting unequal segmented Halbach array is researched. Firstly, an analytical model is established for PM machine adopting Halbach array to improve the calculation efficiency. This analytical model can be applied to the Halbach array having arbitrary pole pair number, arbitrary number of segments per pole, arbitrary segment width and arbitrary gap width between segments. Further, the calculation results for air gap flux density between analytical model and finite element method are compared to verify the analytical model. In addition, the method to determine each segment width in the unequal segmented Halbach array is proposed firstly in this paper. On this basis, effects of the gap width between segments and each segment width under one pole on air gap flux density are researched. The research conclusions will provide guidance for the design and fabrication of unequal segmented Halbach array.

A new HTS dual stator linear permanent magnet Vernier machine with Halbach array for wave energy conversion

In this paper, a high-temperature superconductor-dual stator linear permanent magnet Vernier machine (HTS-DSLPMVM) with Halbach array has been proposed for wave energy conversion. In order to better investigate, this machine has been compared to the prototype double stator linear permanent magnet Vernier machine (DSLPMVM). Both of the machines operate based on magnetic gear effect. At lower speeds they have the ability to produce a high thrust force. DSLPMVM and HTS-DSLPMVM have the same structure. So that, DSLPMVM and HTS-DSLPMVM consist of two stators and one translator with a three-phase concentrated winding. Each phase has been located independently on the translator. Also, permanent magnet (PM) Halbach array with appropriate magnetic direction mounted among the slot of the translator. The innovation of the proposed machine is that HTS-Bulk is located between the slot of the stators to shield the leakage flux. The operation of the two machines has been compared and analysed using the finite element method (FEM). Results show that, HTS-Bulk makes back-EMF, air gap flux density, power factor and thrust force to increase significantly and inductance to decrease, which effectively improves the machine operation.

Analysis of end effect in ironless stator AFPM machine via MEC model

The Halbach-array permanent magnet (PM) rotors can achieve higher air-gap flux density due to magnetic flux gathering effect, which contributes to the higher-torque density improvement of the ironless stator axial flux PM (AFPM) machine. However, the end leakage fluxes of the ironless stator AFPM machine are serious due to the large magnetic resistance of the main flux loop in ironless stator machines. Circular arc straight line permeance model is adopted to calculate magnet-to-magnet and magnet-to-rotor end leakage fluxes based on the analysis of the relationship between end leakage fluxes and coils. A magnetic equivalent circuit (MEC) model is established considering end leakage fluxes. The leakage coefficients representing the ratio of end leakage fluxes to main flux and radial coefficients representing effective radial lengths of end leakage fluxes are analysed via the MEC model. The coefficients vary with machine parameters including PM thickness, rotor yoke thickness and air-gap length. On the basis of the analysis results, the influence factors of end leakage fluxes are summarised and the 50 kW ironless stator AFPM machine is optimised. Finally, a 50 kW ironless stator AFPM machine with Halbach-array PM rotors is prototyped to verify the results of the finite element analysis and MEC model.

Design and Analysis of Coaxial Magnetic Gear Mechanism with Halbach Permanent-Magnet Array

The disadvantages of mechanical gear can be replaced by the advantages of magnetic gear related to transferring torque without mechanical touch, no gear lubrication, low mechanical loss, low vibration, and intrinsic overload protection. From the types of magnetic gear, coaxial magnetic gear is the most developed type. Halbach permanent-magnet arrangement in coaxial magnetic gear mechanism can offer higher on transmitted torque and also capable of increasing the magnetic field compared to radially magnetized. Then this paper aims to carry out the characteristic of coaxial magnetic gear with Halbach magnetized in steady-state condition. Furthermore, magnetic field and transmitted torque were investigated by commercial software ANSYS/Maxwell. Finally, by using 2D finite element method, the result shows the maximum torque with 2150.76 Nm.

Design and Optimization of Halbach-Array PM Rotor for High-Speed Axial-Flux Permanent Magnet Machine With Ironless Stator

In this article, a high-speed Halbach-array permanent magnet (PM) rotor for ironless stator axial-flux permanent magnet (AFPM) machine is proposed and researched with consideration of the multiphysics constraints, including the electromagnetic characteristics, mechanical strength, and rotor dynamics. Considering the severity of attractive force between twin rotors, the complex repulsive force among PM segments of Halbach-array and centrifugal force, the new hybrid sleeve, and PM fixation method are proposed to improve the rotor mechanical strength. Then, the rotor stress is analyzed by numerical analysis and three-dimensional (3-D) finite-element analysis (FEA). Furtherly, the sleeve thickness and interference fit are optimized by 3-D FEA. The rotor dynamics and bearing arrangement are analyzed to validate the effectiveness of the high-speed Halbach-array PM rotor. A 50-kW, 9000 r/min ironless stator AFPM machine prototype with Halbach-array PM rotor is manufactured and tested. The measured results show that the output power is up to 53.8 kW at 9000 r/min. The feasibility of high-speed Halbach-array PM rotor and accuracy of analysis method are validated by both simulated and measured results.

RETRACTED: Electromagnetic performance analysis of the novel dual-mechanical-port electrical machine with Halbach permanent magnet array

The dual-mechanical-port electrical machine (DMPEM) is a new kind of power coupling device for hybrid electric vehicles. In this paper, the structure of the DMPEM is improved, and the planetary gea...

Thermal Modeling and Analysis of a Novel Transverse Flux HAPM Generator for Small-Scale Wind Turbine Application

This article focuses on a Transverse Flux Permanent Magnet generator which benefits from Halbach-array permanent magnets. In this topology, a sinusoidal air-gap flux is achieved and thus, lower THD content and cogging torque is resulted. The Transverse flux generators can be a proper choice for direct drive, low speed, and high torque density applications such as wind turbines. Regarding the available small scale turbines in the market, an operating point is chosen for the proposed machine. The problem of a high torque density generator is thermal stresses which should be taken into consideration in the design and modeling process. Precise thermal modeling at the design stage can take the risk of the increase in machine temperature. Using an active component meshed model by considering the localized losses along with a lumped parameter circuit for the unmeshed parts is proposed for the understudy machine. A 3 kW, 320 rpm generator is designed and analyzed by considering the electromagnetic and thermal properties. It is shown that the magnetic-thermal modeling of the proposed machine is highly consistent with the experimental results.

Modeling of a Halbach Array Voice Coil Actuator via Fourier Analysis Based on Equivalent Structure

This paper presents the magnetic field analysis for the double layer Halbach array voice coil actuator (VCA). This VCA is composed of a stator and a mover supported by the flexure-based bearings. The mover gets three coils winded on the skeleton. The stator comprises the closed yoke and the double layer Halbach array permanent magnets (PMs). The boundary condition of the quadrangularly surrounded yoke and the aperiodic distribution of the Halbach array PMs complicate the magnetic analysis process. An equivalent VCA structure that has almost identical air-gap flux distribution to the original one is, therefore, proposed. For the equivalent structure, the boundary condition is simple and the Halbach array PMs is periodically distributed, thus the analysis process of air-gap flux density distribution via Fourier analysis is simplified. The equivalence between these two structures is validated by finite-element analysis (FEA). The analytical model is built by adopting Fourier analysis. The results of the FEA and experiments confirm the correctness of the developed model and prove the feasibility of the analytic method with the equivalent structure.

Design and experiment of noncontact eddy current damping module in air bearing–guided linear motion system

As a method for reducing the friction of high-precision system, air bearings have been widely used for various industrial applications. However, their small damping leads to poor in-position stability and therefore systems are susceptible to residual vibration and disturbance. In this study, a linear motion stage which is guided by air bearing for a noncontact eddy current damping module is proposed. The eddy current damping module consists of a Halbach array of permanent magnets and a fixed conductor plate. An eddy current is generated in the conductor in the direction opposing the change in the magnetic field when the magnets move, after which the resistivity in the conductor dissipates the kinetic energy of the moving part; therefore, the module has a damping effect without contact and system is shown good in-position stability. In order to specify the damping effect, the motion of the moving part was experimentally analyzed. The step response confirmed that the eddy current damping module can improve the performance of the positioning system: the settling time decreased by 36.8% and the resolution improved by 59.4%. These improvements verify that eddy current damping is a suitable method for application in precision industries.

Voltage regulation Rate and THD optimization analysis of coreless axial flux PM synchronous generator for wind power generation

The basic design and characteristic analysis of the coreless axial flux permanent magnet synchronous generator (AFPMSG) for small wind power generation are carried out. The prototype is manufactured and tested to verify the designed generator. In addition, to reduce the voltage regulation rate and harmonic content of the generator, the optimal design is carried out on the basis of the original generator. The voltage regulation rate and THD of a coreless AFPMSG using the Halbach permanent magnet array are studied. The effects of different generator parameters such as pole arc coefficient, air gap length, permanent magnet thickness, and number of turns in series per phase on the voltage regulation rate and THD are analyzed when the generator is loaded with pure resistance. Because the various parameters of the generator are affected each other, the Taguchi algorithm was adopted for multi‐objective optimization. The influence proportion of different generator parameters on the voltage regulation rate and THD was analyzed. According to the results, the parameters are reasonably selected to design the generator and improve the performance of the generator. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Analytical Model of Magnetic Field of a Permanent Magnet Synchronous Motor With a Trapezoidal Halbach Permanent Magnet Array

This paper presents an analytical model of magnetic field of a permanent magnet synchronous motor (PMSM) with a trapezoidal Halbach permanent magnet array (THPMA). Compared with conventional Halbach array, the shape of each magnet in THPMA is transformed from rectangle to trapezium in polar coordinates. The THPMA is delaminated indefinitely radially and each layer is approximately considered to be a conventional Halbach array. The air-gap magnetic field of each layer is analyzed with the scalar magnetic potential. Then, the air-gap magnetic field of the THPMA is obtained by superposing magnetic fields of all layers. The validity of the analytical model is verified by a finite-element model (FEM). The air-gap flux density is optimized by adjusting the center angle coefficients of the THPMA, and a no-load phase back electromotive force (EMF) with the harmonic distortion rate (THD) of 0.75% is obtained by FEM. The back EMF is basically consistent with the measured result of a prototype motor.

Demagnetization research on PMs in the Halbach magnetized pulsed alternator

Demagnetization behavior of Halbach magnetized compensated pulsed alternator (CPA) is studied by using finite element method (FEM) under the different demagnetization factors in this paper. The effect of armature reaction magnetic field and thermal rise on demagnetization of PMs is analyzed. This paper investigates the effect of different demagnetization factors on magnetic field distribution, load current, and no-load phase voltage. A series of dynamic demagnetization points in Halbach array permanent magnet (PM) are evaluated to search the worst working point. Partial demagnetization risk can be represented by the worst working point, and the global demagnetization of the PM is represented by the no-load phase voltage characteristics after discharge. The research results demonstrated that the compensation shield with a certain thickness can increase the discharge current and weaken the demagnetization influence of armature reaction. The demagnetization effect of armature reaction on PMs at high temperatures will be strengthened.

Spectrum Analysis and Optimization of the Axial Magnetic Gear with Halbach Permanent Magnet Arrays

In order to study the contribution of each harmonic to the output torque and axial torque of the axial magnetic gear with Halbach permanent magnet arrays (HAMG), torque and axial force calculation formulas of the HAMG are proposed based on the air-gap flux density distribution of the HAMG. Because of the difference of the air-gap flux densities at different radii, two simplified torque and axial force calculation formulas are proposed and compared. To improve the torque capability of the HAMG, parametric analysis of eight dimensional parameters is firstly conducted. By parametric analysis, six parameters such as the inner radius have been found to have obvious impact on the output torque and output torque density of the HAMG. The optimization using Maxwell software is then executed for maximizing the output torque density of the HAMG. The output torque density of the optimized HAMG is improved from 78.1 kNm/m3 to 93.3 kNm/m3 with an increase of 19%. Furthermore, spectrum analysis is also presented to illustrate the significant output torque improvement based on the torque calculation formulas.

Linear consequent pole Halbach array flux reversal machine

This paper presents a linear variable reluctance permanent magnet (LVRPM) machine where the armature winding and inset Halbach array permanent magnets (PMs) are mounted on E-core stators. The Halbach array consists of a vertically magnetised PM pole and a salient ferromagnetic iron pole (split tooth) sandwiched between two horizontal PMs. The translator consists solely of laminations with salient iron poles. As a variable reluctance machine, it exhibits inherent magnetic gearing and a higher force and power density than the conventional synchronous PM machines. Finite element analysis (FEA) has been used to investigate the effect of machine parameters. The logical development of the LVRPM from the more conventional Vernier Hybrid machine is presented, including a near 50% reduction in magnetic flux leakage and a higher flux per unit magnet mass.

Analytical design of the integrated motor used in a hubless rim‐driven propulsor

The rim-driven integrated motor propulsor (IMP) has received much attention in recent years, owing to its superiority in flexibility, reliability, and space occupation. For this propulsion system, radially thin motors with high torque and large air gaps are essential. Two-segment Halbach array permanent magnets with unequal segment-arc are adopted to enable a thin rotor and a large air gap. The general analytical solution of the magnetic field is presented. Based on the analytical calculation of the Halbach motor performance, the necessity of the rotor core was discussed, and the Halbach array was optimised with an analytical method to maximise the electromagnetic torque. This study also tried and compared three designs of the integrated motor stator to further reduce the radial thickness, and the slotted stator proved more reasonable. The fabrication of an IMP prototype was completed, and the experimental data of the integrated motor are presented and compared with the calculated results. This study also conducted the water tunnel experiment of the IMP prototype to test the integrated motor performance in the overall IMP system. The measured rotational speed and output thrust are less than expected, so the friction loss in the IMP gap flow field is calculated and analysed.

Design of a PCB stator coreless axial flux permanent magnet synchronous motor based on a novel topology Halbach array

A novel topology Halbach permanent magnet array is proposed and applied to the design of a printed circuit board (PCB) axial flux permanent magnet (AFPM) motor. Compared with the traditional coreless AFPM motor, this novel topology for a Halbach permanent magnet array PCB stator AFPM motor has larger air-gap magnetic flux density and air-gap flux per pole. The magnetic flux leakage is effectively reduced, and the air-gap magnetic density is close to the sine wave. Results of the finite element analysis and prototype experiments verify the feasibility and effectiveness of the novel Halbach permanent magnet array PCB stator motor. A reference basis and practical value for the design of the PCB AFPM motor are provided.

Assessment of three different gadolinium-based regenerators in a rotary-type magnetic refrigerator

Room-temperature magnetic refrigeration is a recently developed, environment-friendly refrigeration technology. A rotary-type magnetic refrigerator has been built with a modified double Halbach permanent magnet array, which can provide an average magnetic field varying from 0.04 T to 1.50 T at a length of 100 mm. To evaluate the performance of AMRs with geometries, active magnetic regenerators (AMR) filled with gadolinium plates, spheres and flakes were respectively tested and compared. System performance such as temperature span, cooling power and pressure drop were investigated at different utilization factors and operating frequencies. The results revealed three AMRs performed quite differently. With larger specific heat transfer areas and smaller hydraulic diameters, AMRs filled with flakes/spheres provided better cooling performance. A maximum no-load temperature span of 14.8 K was obtained by flake-AMR with largest specific heat transfer areas and least filled mass. Sphere-AMR achieved a maximum temperature span of 10.8 K at a cooling power of 10 W among AMRs. With the same porosity and filled mass, sphere-AMR performed much better than plate-AMR, although the latter had a smaller pressure drop and associated pumping work.

A Novel 3-D Analytical Modeling Method of Trapezoidal Shape Permanent Magnet Halbach Array for Multi-objective Optimization

In this paper, a novel three-dimension magnetic flux density analytical model of linear permanent magnet (PM) Halbach arrays with trapezoidal shape PMs, is established based on the theory of magnetic charge. The proposed analytical model is numerically efficient and can be utilized to evaluate the effects on motor performance caused by varying their configurations. Furthermore, the configurations of PMs for both single and double-sided structures are optimized exploiting a surrogate model assisted by a multi-objective optimization algorithm, where the surrogated model is constructed by the kriging method with expected improvement utility function. The validity and accuracy of this proposed analytical model is verified via finite element modeling, the optimization results with different schemes of weight distribution show the further improvement of magnetic flux density distribution.

Penetrating particle ANalyzer (PAN)

PAN is a scientific instrument suitable for deep space and interplanetary missions. It can precisely measure and monitor the flux, composition, and direction of highly penetrating particles (>∼100 MeV/nucleon) in deep space, over at least one full solar cycle (11 years). The science program of PAN is multi- and cross-disciplinary, covering cosmic ray physics, solar physics, space weather and space travel. PAN will fill an observation gap of galactic cosmic rays in the GeV region, and provide precise information of the spectrum, composition and emission time of energetic particle originated from the Sun. The precise measurement and monitoring of the energetic particles is also a unique contribution to space weather studies. PAN will map the flux and composition of penetrating particles, which cannot be shielded effectively, precisely and continuously, providing valuable input for the assessment of the related health risk, and for the development of an adequate mitigation strategy. PAN has the potential to become a standard on-board instrument for deep space human travel.PAN is based on the proven detection principle of a magnetic spectrometer, but with novel layout and detection concept. It will adopt advanced particle detection technologies and industrial processes optimized for deep space application. The device will require limited mass (20 kg) and power (20 W) budget. Dipole magnet sectors built from high field permanent magnet Halbach arrays, instrumented in a modular fashion with high resolution silicon strip detectors, allow to reach an energy resolution better than 10% for nuclei from H to Fe at 1 GeV/n. The charge of the particle, from 1 (proton) to 26 (Iron), can be determined by scintillating detectors and silicon strip detectors, with readout ASICs of large dynamic range. Silicon pixel detectors used in a low power setting will maintain the detection capabilities for even the strongest solar events. A fast scintillator with silicon photomultiplier (SiPM) readout will provide timing information to determine the entering direction of the particle, as well as a high rate particle counter. Low noise, low power and high density ASIC will be developed to satisfy the stringent requirement of the position resolution and the power consumption of the tracker.

Magnetic Field Calculation and Dynamics Simulation of a Permanent Magnetic Hybrid Driven 3-DOF Motor

In view of the poor precision of existing deflection movement control and low speed of multi-degree-of-freedom motor rotation speed, a novel type of permanent magnet type 3-DOF hybrid driven motor is proposed, the motor contains two part named lateral rotation module and internal deflection modules. By using Halbach permanent magnet array, the magnetic field shielding and optimization of two modules inside and outside the motor are realized, and the magnetic field characteristics of the motor are improved. Using the analytical and finite element methods, the magnetic field characteristics and distribution of the permanent magnet of the motor are analyzed and proved. The dynamic model of the motor is established and analyzed. The back EMF of the physical motor is tested and verifies the accuracy of the finite element model. The results provide a new theoretical basis for the follow-up optimization of this kind of motors.