Halbach Permanent Magnet Array Research Articles

Tapered helical undulator system for high efficiency energy extraction from a high brightness electron beam

In this paper we discuss the design choices and construction strategy of the tapered undulator system designed for a high energy extraction efficiency experiment in the ultraviolet region of the electromagnetic spectrum planned for installation at the Argonne National Laboratory Linac Extension Area (LEA) beamline. The undulator is comprised of 4 sections pure permanent magnet Halbach array separated by short break sections, each one of them housing a focusing quadrupole doublet and a phase shifter. The quadrupoles use a novel hybrid design which allows one to vary the gradient and match the beam transversely. The undulator tapering profile is optimized to maximize the energy conversion efficiency from a 343 MeV 1 kA beam into coherent 257.5 nm radiation taking into account the longitudinal current profile generated by the linac.

A Novel Axial-Flux Dual-Stator Toothless Permanent Magnet Machine for Flywheel Energy Storage

This paper presents an alternative system called the axial-flux dual-stator toothless permanent magnet machine (AFDSTPMM) system for flywheel energy storage. This system lowers self-dissipation by producing less core loss than existing structures; a permanent magnet (PM) array is put forward to enhance the air–gap flux density of the symmetrical air gap on both sides. Moreover, its vertical stability is strengthened through the adoption of an axial-flux machine, so expensive active magnetic bearings can be replaced. The symmetry configuration of the AFDSTPMM system is shown in this paper. Then, several parts of the AFDSTPMM system are optimized thoroughly, including stator windings, number of pole pairs and the PM parameters. Further, the performance of the proposed PM array, including back-EMFs, air–gap flux density, average torque, torque ripple and over-load capacity, are compared with the Halbach PM array and spoke PM array, showing the superiority of proposed configuration. Finally, 3D simulations were made to testify for the 2D analyses.

Continuously Variable Valve Mechanism for Spark Ignition Engines Using Linear Actuator

In order to achieve higher performance in spark-ignition engines, it is required to control the intake and exhaust valves in stepless manner according to the engine speed. Our research group has been continuously studying the electromagnetic drive valve system using a linear actuator. In this report, we have designed a linear actuator with a dual Halbach array of permanent magnets in the stator to further increase the thrust of the linear actuator. The thrust characteristics of the proposed model were investigated using electromagnetic field analysis based on the finite element method. The analysis confirmed that the Halbach array concentrates the magnetic flux on the coil side, which generates Lorentz force.

Control-oriented modeling for the electrodynamic levitation with permanent magnet Halbach array

Poor stability of the permanent magnet electrodynamic levitation hinders its application in the maglev field. Therefore, building a control-oriented model to improve its stability is most challenging. However, intractable electromagnetic models leading to an implicit relationship between levitation force and gap, yields a barrier for model-based controller design. To solve the above-mentioned problem, this paper develops a control-oriented model by two stages. Specifically, the first stage is to show an explicit formula of the levitation force with regard to the levitation gap by neglecting end effect; meanwhile the “maximum–minimum rectification” method is put forward to evaluating an accurate levitation force. The second stage is to bring forth the control-oriented model on basis of the estimated levitation force. Although the paper focus mainly on the development of the control-oriented model, an example of PD controller is provided to verify its validation. Experiment results demonstrate the estimated levitation force is highly consistent with the real one. Simulation results show that the control-oriented model is sufficiently reliable. The research bridges the gap between the physical model and the model-based controller for the electrodynamic levitation with permanent magnet Halbach array.

Design and Optimization of a Novel HTS Flux-Modulated Linear Motor Using Halbach Permanent Magnet Arrays

For rope-less elevator applications, a novel high temperature superconducting (HTS) flux modulation linear motor (LM) using Halbach permanent magnet (PM) arrays is investigated in this paper. The flux modulation structure with iron segments can serve simultaneously and regulate the magnetic field. The HTS bulks are filled between the iron segments to further improve the flux modulation effect based on the Meissner effect. Compared with conventional counterparts, the force density of the proposed LM with HTS fillers is apparently higher. Furthermore, the mover with Halbach PM arrays is used to reduce the force ripple and increase the output force. The electromagnetic performances of the flux-modulated LM are researched by transient finite element analyses (FEA) to prove the effectiveness of the proposed structure. Finally, the parameters of the motor structural are optimized and analyzed by the combination of FEA and genetic algorithm (GA).

Design and Optimization of Halbach Permanent Magnet Array with Rectangle Section and Trapezoid Section

A novel Halbach permanent magnet array with rectangle section and trapezoid section is proposed and optimized in this paper. The analytical model of the premanent magnet segment is established based on the surface current method, which is numerically efficient and can be utilized to evaluate the magnetic field closely with the premanent magnet segment’s configurations. The analytical model of the Halbach array is acquired based on the superposition principle and coordinate transformation. The fundamental component of the magnetic flux density and the sinusoidal distortion rate are chosen as the optimization object. And the optimization is executed on the Halbach array with one specific set of dimensions by the genetic algorithm in global scale. The effectiveness of the optimization is validated by the finite element analysis. Compared to the traditional Halbach array with rectangle section, the magnetic field created by the optimized proposed Halbach array in this paper owns better performance.

Efficiency Improvement of Permanent Magnet BLDC Motors for Electric Vehicles

A permanent magnet Brushless DC (BLDC) motor has been designed with different rotor configurations based on the arrangement of the permanent magnets. Rotor configurations strongly affect the torque and efficiency performance of permanent magnet electric motors. In this paper, different rotor configurations of the permanent magnet BLDC motor with parallel the Halbach array permanent magnet were compared and evaluated. Many applications of electric drives or air-crafts have recently preferred the surface-mounted permanent magnet design due to its ease of construction and maintenance. The finite element technique has been used for the analysis and comparison of different geometry parameters and rotor magnet configurations to improve efficiency and torque performance. A comprehensive design of a three-phase permanent magnet BLDC 35kW motor is presented and simulations were conducted to evaluate its design. The skewing rotor and Halbach magnet array are applied to the permanent surface-mounted magnet on the BLDC motor for eliminating torque ripples. In order to observe the skewing rotor effect, the rotor lamination layers were skewed with different angles and Halbach sinusoidal arrays. The determined skewing angle, the eliminated theoretically cogging torque, and the back electromotive force harmonics were also analyzed.

Magnetic FEA Direct Optimization of High-Power Density, Halbach Array Permanent Magnet Electric Motors

Hybrid electric aero-propulsion requires high power-density electric motors. The use of a constrained optimization method with the finite element analysis (FEA) is the best way to design these motors and to find the best solutions which maximize the power density. This makes it possible to take into account all the details of the geometry as well as the non-linear characteristics of magnetic materials, the conductive material and the current control strategy. Simulations were performed with a time stepping magnetodynamic solver while taking account the rotor movement and the stator winding was connected by an external electrical circuit. This study describes the magnetic FEA direct optimization approach for the design of Halbach array permanent magnet synchronous motors (PMSMs) and its advantages. An acceptable compromise between precision and computation time to estimate the electromagnetic torque, iron losses and eddy current losses was found. The finite element simulation was paired with analytical models to compute stress on the retaining sleeve, aerodynamic losses, and copper losses. This type of design procedure can be used to find the best machine configurations and establish design rules based on the specifications and materials selected. As an example, optimization results of PM motors minimizing total losses for a 150-kW application are presented for given speeds in the 2000 rpm to 50,000 rpm range. We compare different numbers of poles and power density between 5 kW/kg and 30 kW/kg. The choice of the number of poles is discussed in the function of the motor nominal speed and targeted power density as well as the compromise between iron losses and copper losses. In addition, the interest of having the current-control strategy as an optimization variable to generate a small amount of flux weakening is clearly shown.

Stability control of permanent magnet and electromagnetic hybrid Halbach array electrodynamic suspension system

Purpose The purpose of the paper is to study the stability control of permanent magnet (PM) and electromagnetic hybrid Halbach array electrodynamic suspension (EDS) system because of the poor suspension stability caused by the well-known under-damped nature of PM EDS system. The adjustment control is realized by PM and electromagnetic hybrid Halbach array, which is composed by winding active normal conductor coils on PM surface. Design/methodology/approach The three-dimensional (3-D) electromagnetic force analytical expression of PM and electromagnetic hybrid Halbach array EDS system for a nonmagnetic conductive plate is derived. And the accuracy of the derived equations is verified by a 3-D finite-element model (FEM). Basing on the 3-D levitation force expression, an acceleration feedback suspension controller is designed to suppress the vibration of PM EDS system, and the suspension stability of the system under the track and load disturbance was simulated and analyzed. Findings The 3-D electromagnetic force comparison of analytical model and FEM are in good agreement, which verifies the correctness of the analytical expression. The simulation results show that the acceleration feedback suspension controller can make the system have good suspension stability under the external disturbance. So it proved that the PM and electromagnetic hybrid Halbach array EDS system can overcome the poor suspension stability caused by the under-damped nature of PM EDS system through the designed acceleration feedback suspension controller. Originality/value This paper designed an acceleration feedback suspension controller to suppress the vibration of PM and electromagnetic hybrid Halbach array EDS system under external disturbance, basing on the derived levitation force analytical expression. And the simulation results show that the acceleration feedback suspension controller can make the system have good suspension stability under the external disturbance.

Analytical Optimization of Electrodynamic Suspension for Ultrahigh-Speed Ground Transportation

Electrodynamic suspension with a permanent magnet Halbach array is suitable for ultrahigh-speed vacuum pipeline transportation. The optimization of a Halbach array is helpful to save cost and increase carrying capacity. Intricate analytical expressions of electromagnetic forces or time-consuming numerical simulation show inherent defects in the structural optimization. To solve the abovementioned problem, this article develops an analytical optimization by two stages. First, a brief approximate analytical expression of electromagnetic forces is established by omitting high-order harmonic components for both the scalar magnetic potential and vector magnetic potential. Second, the lift-to-weight ratio is taken as the optimization index, and the optimal wavelength-to-gap ratio and thickness-to-gap ratios are put forward by seeking extreme values. The numerical simulation is conducted to verify the validation of the analytical optimization, and the result shows that the optimal structural parameters are highly reliable. An experimental rotatory device for electrodynamic suspension with optimal sizes for a Halbach array is built to verify the validation of the analytical expressions of electromagnetic forces.

Frozen image analysis of a superconducting magnetic levitation system consisting of multi-surface superconductor and Halbach array permanent magnet configuration

Levitation strength provided by high temperature superconductors are limited for device applications. Although superconducting material properties are continuously improving, there is still strong necessity of efficient design mechanisms for the superconducting magnetic levitation systems. Studies in the last decades have shown that combining multi-surface superconductor and permanent magnet components in optimum configurations has improved the levitation forces. In this respect, Halbach arraying permanent magnets interacting with multi-surface superconductors has become one of the most utilized methods. This paper investigates frozen image modeling of the levitation and guidance forces on a particular levitation system, which consists of a permanent magnet guideway and high temperature superconductor car body. The levitation enhancement is investigated for three configurations according to force interactions between the guideway and car body. These configurations are based on the use of single permanent magnet-single superconductor, Halbach array permanent magnets-single superconductor and Halbach array permanent magnets-multi-surface superconductors. The vertical and guidance forces for the present configurations were calculated in terms of field cooling and zero field cooling conditions by using frozen image model with magnetic dipole approximation. The predicted force calculations are analyzed in terms of vertical and lateral traverses of the car body respect to guideway for particular measurement distances. The force analysis provided by frozen image model qualitatively agree with the previously obtained experimental data.

Design and Analysis of a Novel Axial-Radial Flux Permanent Magnet Machine with Halbach-Array Permanent Magnets

Electric machines with high torque density are needed in many applications, such as electric vehicles, electric robotics, electric ships, electric aircraft, etc. and they can avoid planetary gears thus reducing manufacturing costs. This paper presents a novel axial-radial flux permanent magnet (ARFPM) machine with high torque density. The proposed ARFPM machine integrates both axial-flux and radial-flux machine topologies in a compact space, which effectively improves the copper utilization of the machine. First, the radial rotor can balance the large axial forces on axial rotors and prevent them from deforming due to the forces. On the other hand, the machine adopts Halbach-array permanent magnets (PMs) on the rotors to suppress air-gap flux density harmonics. Also, the Halbach-array PMs can reduce the total attracted force on axial rotors. The operational principle of the ARFPM machine was investigated and analyzed. Then, 3D finite-element analysis (FEA) was conducted to show the merits of the ARFPM machine. Demonstration results with different parameters are compared to obtain an optimal structure. These indicated that the proposed ARFPM machine with Halbach-array PMs can achieve a more sinusoidal back electromotive force (EMF). In addition, a comparative analysis was conducted for the proposed ARFPM machine. The machine was compared with a conventional axial-flux permanent magnet (AFPM) machine and a radial-flux permanent magnet (RFPM) machine based on the same dimensions. This showed that the proposed ARFPM machine had the highest torque density and relatively small torque ripple.

Partitioned Stator Hybrid Excitation Doubly Salient Machine With Slot Halbach PM Arrays

A new partitioned stator (PS) hybrid excitation (HE) machine with slot Halbach permanent magnet (PM) arrays is proposed in this paper. Due to the adoption of PS structure, its armature winding (AW) is located in the outer stator, and the PMs and the field winding (FW) are housed in the inner stator, thus the space utilization is significantly enhanced. The key difference of proposed machine is that Halbach PM arrays are employed in the inner stator slot openings, so that the parallel magnetic circuit between PM field and wound field is performed and the ratio of PM field short-circuited in the inner stator is effectively reduced. Thus a wider speed regulation region and a higher torque/power density can be achieved. Firstly, the configuration of proposed machine is described, based on which its operating principle is discussed. Then the electromagnetic performances are calculated and compared based on 2-dimensional finite element analysis (FEA). The results show that the torque can be improved by 76% with a similar magnetic field regulation ratio compared with an existing PS-HE machine with slot PMs. Finally, a prototype machine is built and tested to verify the analysis and FEA results.

Analytical field model of segmented Halbach array permanent magnet machines considering iron nonlinearity

The permeability of the iron is usually assumed to be infinite by the linear subdomain technique, leading to the neglect of magnet saturation. This study presents an analytical model of a segmented Halbach array permanent magnet machine by considering the iron B-H curve and saturation effects. Firstly, the entire field problem is divided into six regions in the radial direction according to the excitation source. Then, Poisson's and Laplace's equations are solved in each region to obtain the magnetic vector potential. Specifically, in our approach, the teeth and slots' permeability variation is solved by Cauchy's product theorem. An iterative algorithm incorporates the nonlinearity of the iron. Subsequently, the electromagnetic performance, such as air-gap magnetic flux density, electromagnetic torque, and unbalanced magnetic force, is predicted by the analytical method. The analytical results are shown in line with those obtained from finite element analysis, and a prototype was fabricated to further verify the accuracy of the analytical method. Besides, the proposed method can also be used to evaluate the performance of the Halbach array machines with any number of segmented magnets.

Design Study of a High Loading Superconducting Magnetically Levitated Planar Motor

Magnetically levitated planar motor (MLPM) with moving-magnet has the advantages of no electric cable interference and no cooling for moving part. In this paper a novel superconducting magnetic levitation planar motor (SMLPM) whose stator uses high-temperature superconducting coils is proposed. Based on the traditional design, the cooling system and thermal shield are added. The copper coil used in the traditional magnetic levitation planar motor cannot provide large current density and have very low force-to-mass ratio. As superconducting technology has the advantages of low energy consumption and high current density, SMLPM could provide greater driving force and torque. Based on the new system, an analytical model was used to calculate the electromagnetic force/torque acting on the Halbach permanent magnet array. The heat load to the cryogenic system is calculated. The finite element method (FEM) for full model has been used to benchmark the magnetic field and force of the theoretical result.

Magnetic levitation planar motor and its adaptive contraction backstepping control for logistics system

Magnetic levitation planar motor has the characteristics of no friction loss, fast dynamic response, and real-time change of transportation track according to the demand. Therefore, a kind of magnetic levitation planar motor based on logistics transportation system is designed, which can meet the transportation needs of the logistics system through any combination of unit modules. Firstly, based on the mechanical model of magnetic levitation float in Halbach permanent magnet array magnetic field, establishing the thrust and torque model of maglev float. Secondly, according to the force/current relationship, considering the influence of uncertain parameters and load disturbance on the system, the decoupling control model of six degree of freedom motion system of magnetic levitation planar motor is established. Thirdly the adaptive contraction backstepping (ACB) controller is derived that can eliminate the uncertain disturbance of the nonlinear model and realize the real-time control of the system. The simulation and experimental results demonstrate that the method has expected response speed, strong robustness, and good dynamic tracking performance. Applying it to the logistics transportation system described in this article and has a good control effect.

Dynamic analysis of Halbach coaxial magnetic gears based on magnetic equivalent circuit modelling

Halbach permanent magnet arrays (HPMAs) are an attractive configuration that can be applied in PM electric machines such as magnetic gears. These arrays have some merits, namely near-sinusoidal distribution of flux density along air gap, low torque ripple and iron losses. This article proposes a two-dimensional magnetic equivalent circuit method to determine the magnetic field distribution of HPMA based on coaxial magnetic gears (HCMG). Furthermore, regarding the proposed model, distribution of radial and tangential components of flux densities is extracted within outer and inner rotors. Moreover, the dynamic model of HCMG is extracted and its pull-out torque and output speed are calculated using it. Finally, in order to validate the effectiveness of the proposed model, the obtained results for a sample HCMG are compared with finite element analysis method results.

Research on torque of based hydraulic rotary hole cleaning tool on Halbach permanent magnet array

The hydraulic rotary hole cleaning tool does not require a drill string to provide torque, so it is compatible with downhole motors in the sliding phase of directional drilling. It facilitates efficient cutting cleaning, especially in the directional interval and horizontal interval. The magnet array structure must be optimized to enhance the magnetic torque transmission capacity and thus increase the output power of this tool. Magnetic field analysis was conducted in this study using Laplace and Poisson equations. A mathematical model was established to calculate the magnetic torque transmitted by the hydraulic rotary hole cleaning tool. The effects of various magnetic field and tool design parameters on the magnetic torque transmission capacity were compared among different permanent magnet array structures. The negative-positive Halbach magnet array structure shows enhanced magnetic torque transmission capacity compared to the traditional radial magnet array structure; it achieves a better excitation magnetic field direction of the permanent magnets on the magnetic shafts and an increased magnetic flux density within the tool housing. The suggested tool housing thickness under the field operation safety requirement is 9–10 mm. The optimum tool design features include a negative-positive Halbach magnet array structure, 100% magnet field coverage within the tool housing and a permanent magnet thickness range of 9.5–10.5 mm. The maximum magnet torque transmission capacity can be obtained within these parameters. The proposed magnetic torque transmission capacity model was compared against laboratory experiment data to prove that it is reliable and precise enough to optimize existing hydraulic rotary hole cleaning tools with the negative-positive Halbach magnet array structures.

2-D and 3-D Analytical Calculation of the Magnetic Field and Levitation Force Between Two Halbach Permanent Magnet Arrays

As we know, the analytical calculation of magnetic field and magnetic force has important guiding significance for the optimal design of the size and structure of a magnet. At present, the magnetic field and magnetic force between two permanent magnet (PM) monomers have been described by effective analytical models. However, the magnetic field strength and magnetic force generated by two PM monomers are limited and cannot meet the requirements of a PM levitation system with high magnetic field strength and large levitation force. To this end, this article establishes analytical calculation models of magnetic field and levitation force between two Halbach PM arrays. First, on the basis of Ampere molecular circulation hypothesis, the 2-D analytical model of magnetic field was established based on the surface current method; on the basis of magnetic charge theory, the 3-D analytical model of magnetic field was established based on the magnetic charge method. Second, based on the analytical models of magnetic field, the 2-D and 3-D analytic models of levitation force were derived by virtual work method, respectively. Numerically, the results of two analytical models of magnetic field and two analytical models of levitation force have been compared to verify the accuracy of the models. At the same time, the 2-D and 3-D finite element simulation models of magnetic field and levitation force were established, respectively, and the accuracy of the analytical models were verified again. The results show that the analytical models established in this article is effective and can be used to guide the design and optimization of the magnet composed of two Halbach arrays.

Design of coaxial magnetic gear utilising a novel permanent magnet Halbach array structure

Mechanical gears are constrained due to wear and tear and call for lubrication. A magnetic gear, utilising permanent magnet (PM) arrays, facilitates the mechanical gear roles. It can withstand high-speeds and large loads with zero friction. The magnetic gear is more efficacious on account of the least noise, performance, overload protection, and physical isolation between parts than conventional mechanical gears. The quantity of PMs in magnetic structures plays a principal role in its total price, which necessitates optimal arrangements for PMs. Halbach array provides a bigger torque density according to its one-sided flux. In this research, proposing a novel Halbach array structure, leads to intensification in the one-sided flux in a much sinusoidally waveform that consequently increases the magnetic torque. These all lead to gain higher torques in constant volumes of magnets. Besides, the magnetic torque ripple and the modulators’ losses are decremented. The new model is based on the variation of the magnetisation angles of the adjacent permanent magnet blocks, in the array. Various states of the magnetisation angles in the array are optimised based on a heuristic method. This is studied in the whole trigonometric range for magnetisation angles characteristics. The prototype is fabricated based on the optimised magnetic gear design and complies with the results.