3D Magnetic Flux Research Articles

On the Origin of Solar Hemispheric Helicity Rules: Rise of 3D Magnetic Flux Concentrations through a Background Magnetic Field

Sunspots and active regions observed on the solar surface are widely believed to be manifestations of compact predominantly toroidal magnetic field structures (“flux tubes”) that emerge by magnetic buoyancy from the deeper interior of the Sun. Much work has examined the evolution of such magnetic structures, typically considering them as idealized isolated magnetic entities and not as more realistic magnetic concentrations in a volume-filling background magnetic field. Here, we report results that explore the buoyant rise dynamics of magnetic concentrations in a volume-filling field in the full three dimensions. Earlier 2.5D work in this series established the remarkable fact that the twist orientation of a flux concentration relative to the background field affected its likelihood to rise and emerge, regardless of whether the buoyant rise took place in the absence or presence of convection. The contrasting dynamics between structures with differing orientations lead to a selection mechanism that reproduces characteristics of the “solar hemispheric helicity rule(s)” observations strikingly well. Here, we show that this two-dimensional selection mechanism persists in the face of the added complexity of three-dimensional dynamics. Arching of the magnetic structure in the third dimension, as might be expected in the solar application, is introduced. The role of tension force leading to this selection mechanism is elucidated and subtle differences that arise due to the three-dimensional geometry are discussed.

Analysis and Compensation of Lorentz Force Magnetic Bearing Magnetic Flux Density Uniformity Error.

Aiming at the influence of the magnetic flux density uniformity error (MFDUE) of the Lorentz force magnetic bearing (LFMB) on the sensitivity accuracy of magnetically suspended control and sensing gyroscopes (MSCSGs) on the angular rate of a spacecraft, a high precision measurement method of the angular rate of a spacecraft based on the MFDUE compensation of LFMB is proposed. Firstly, the structure of MSCSG and the sensitivity principle of MSCSG to the spacecraft angular rate are introduced. The mechanism influencing the accuracy of MSCSG to spacecraft angular rate sensitivity is deduced based on the definition of magnetic flux density uniformity. Secondly, the 3D magnetic flux distribution of LFMB is analyzed using ANSYS. The relationship between the rotor tilt angle, tilt angular rate, and magnetic flux density is established. The induced current calculation model due to MFDUE is proposed, and the LFMB magnetic flux density error compensation is realized. Finally, the simulation results show that the estimation accuracy of the induced current by the proposed method can reach 96%, and the simulation and the experiment show that the error compensation method can improve the accuracy of MSCSG in measuring the spacecraft angular rate by 12.5%.

A Magnet Splicing Method for Constructing a Three-Dimensional Self-Decoupled Magnetic Tactile Sensor

Tactile sensory organs for three-dimensional (3D) force perception are essential for most living organisms and enable them to perform complex and sophisticated tasks to survive and evolve. Magnetic-based tactile sensors have been developed rapidly in recent years due to the exploitability of 3D force decoupling. Here, a method of magnet splicing is introduced, which can be applied to a magnetic tactile sensor to realize 3D self-decoupling of magnets’ displacements. This method enables the magnets to produce a completely consistent magnetic field distribution as the ideal magnetization model within a certain working range, eliminating the compensation and correction of the 3D magnetic flux density signal. This method carves out a new way for the practical application of 3D decoupling theory, showcasing the great potential in the fields of magnetic sensors and magnetic actuators.

3D magnetic flux density measurement with reduced sampling and high accuracy using visual localization and adaptive mesh generation

3D magnetic flux density measurement with reduced sampling and high accuracy using visual localization and adaptive mesh generation

Evaluation of microstructure, mechanical and magnetic properties of laser powder bed fused Fe-Si alloy for 3D magnetic flux motor application

Since their high power-to-volume property, electric machines with 3D magnetic flux (3D-flux) structure are of great current interest. In them, the flux path is typically achieved by utilizing a soft magnetic composite (SMC) material to minimize the eddy current losses. Here, laser powder bed fusion (LPBF) technique is employed to manufacture a soft magnetic core (Fe-3.5 wt%Si alloy) with the following advantages: i) the (001) texture of Fe-Si alloy is well aligned with the Z direction of the 3D-flux path, which is the easiest magnetization direction in the cubic system; ii) the strength and ductility of the annealed alloy are far superior to those of SMCs. The alternating-current ring method was employed to measure the magnetic properties and a simulation of the 3D-flux electric machine was conducted. The results illustrated that the rotary torque generated with the additively manufactured alloy is 19.1% higher than that of SMCs in the weak magnetic field excited by ferrite at the 50 Hz frequency. However, it is important to note that the additively manufactured alloy also exhibited higher total iron loss in strong magnetic field and high electric frequency, indicating a need for further research to optimize the microstructure and reduce losses for medium/high frequency applications.

Hall effect on the magnetic reconnections during the evolution of a three-dimensional magnetic flux rope

We present a novel Hall magnetohydrodynamics (HMHD) numerical simulation of a three-dimensional (3D) magnetic flux rope (MFR)—generated by magnetic reconnections from an initial 3D bipolar sheared field. Magnetic reconnections during the HMHD evolution are compared with the MHD. In both simulations, the MFRs generate as a consequence of the magnetic reconnection at null points which has not been realized in contemporary simulations. Interestingly, the evolution is faster and more intricate in the HMHD simulation. Repetitive development of the twisted magnetic field lines (MFLs) in the vicinity of 3D nulls (reconnection site) is unique to the HMHD evolution of the MFR. The dynamical evolution of magnetic field lines around the reconnection site being affected by the Hall forcing correspondingly affects the large-scale structures.

Geometrical control of eddy currents in additively manufactured Fe-Si

Additive manufacturing has enabled the processing of high silicon electrical steels which have excellent soft magnetic properties. In bulk form, core losses as a result of eddy currents would be too large to allow their use in high-frequency electrical machines, therefore strategies are needed to reduce eddy currents. Additive manufacturing affords high part complexity and provides the opportunity for cross sectional patterns within the material to limit eddy current generation. This study investigates several designs, including a novel hexagonal pattern which is shown to have the lowest eddy current loss coefficient of 0.0005, less than 25% of the bulk material which has an eddy current loss coefficient of 0.0021. Heat treatment is shown to increase the eddy current losses, demonstrating that for high-frequency machines, it may be beneficial to use the material in the as-built state. Physical samples were compared to their intended geometries, showing there are defects in these complex cross sections causing increased eddy currents when compared to simulations, but that geometrical accuracy can be improved by alternative design methodology which experimentally experiences smaller losses. These novel cross sectional designs may be implemented into an electric machine that has a 3D magnetic flux pathway enabled by additive manufacturing, affording more flexibility for electrical engineers to design new motor architectures in the pursuit of higher power density machines.

Loss performance of an additively manufactured axial flux machine stator with an eddy-current limiting structure

AC electrical machines have mostly been limited to 2D magnetic circuits due to the use of electrical-steel laminations, however, in recent years advances in non-traditional motor architectures such as axial flux show promise for increased torque and power densities. 3D magnetic circuits as required by axial flux motors are difficult to manufacture using laminations, and for other architectures impossible. Soft magnetic composites enable 3D flux pathways but at the expense of magnetic properties. In this study, an axial flux stator is fabricated from high-silicon electrical steel (Fe-6.5 wt%Si) using additive manufacturing with Hilbert cross-sectional geometry to limit eddy current losses and compared with electrical steel laminations of 0.127 mm and 0.35 mm. This shows comparable performance between the additively manufactured Hilbert stator and 0.35 mm laminations below 500 Hz. A torque loss of approximately 20% was observed due to 34% less magnetic material in the Hilbert stator than 0.127 mm laminations, but improved torque density for the stator by 13%. By designing for additive manufacturing, tooth area could be scaled up providing an electrical machine with 3D magnetic flux pathways with acceptable loss behaviour and good magnetic circuit properties, enabling further flexibility to electrical engineers in their pursuit of higher torque and power density.

A Review of Electric Motors with Soft Magnetic Composite Cores for Electric Drives

Electric motors play a crucial role in modern industrial and domestic applications. With the trend of more and more electric drives, such as electric vehicles (EVs), the requirements for electric motors become higher and higher, e.g., high power density with good thermal dissipation and high reliability in harsh environments. Many efforts have been made to develop high performance electric motors, such as the application of advanced novel electromagnetic materials, modern control algorithms, advanced mathematical modeling, numerical computation, and artificial intelligence based optimization design techniques. Among many advanced magnetic materials, soft magnetic composite (SMC) appears very promising for developing novel electric motors, thanks to its many unique properties, such as magnetic and thermal isotropies, very low eddy current loss, and the prospect of low-cost mass production. This paper aims to present a comprehensive review about the application of SMC for developing various electric motors for electric drives, with emphasis on those with three-dimensional (3D) magnetic flux paths. The major techniques developed for designing the 3D flux SMC motors are also summarized, such as vectorial magnetic property characterization and system-level multi-discipline robust design optimization. Major challenges and possible future work in this area are also discussed.

Experimental study of grain oriented electrical steel laminations under 3D magnetic flux excitation

The magnetic behavior of a lamination stack made of grain-oriented electrical steel (GOES) is investigated under non-conventional 3D magnetic flux excitations. An experimental demonstrator has been designed to study a normal orientation of the magnetic flux path, with regard to the lamination plane, combined with different in-plane orientations of the easy magnetization axis of the lamination stack. The results in terms of the magnetic flux distribution and the iron losses are presented and discussed.

Magnetic Flux Switching Type Permanent Magnet Generator for Bicycles: Modelling and an Experimental Study

Abstract The article introduces two new designs of flux switching permanent magnet alternators with a radial and an axial arrangement of the inductor relative to the magnetic flux switch. The study presents the results of 3D magnetic flux modelling along with the outcomes of physical experiments. In the course of laboratory experiments, the results of theoretical estimations are compared with actual physical performance parameters. The results are presented in the form of power and output voltage curves in relation to the frequency and load current. The study proposes the practical application of the alternators based on the magnetic flux switching principle in the development of a bicycle generator. Laboratory test models are made of a laminated steel using a waste-free technology.

Investigation of a 3D-Magnetic Flux PMSM With High Torque Density for Electric Vehicles

This paper presentsan investigation of a 3D-magnetic flux permanent magnet synchronous motor (3D-MF PMSM) used for electric vehicle applications. The investigated 3D-MF PMSM consists of an integrated radial-flux and axial-flux structure. It has two radial-flux air-gaps and two axial-flux air-gaps, as well as a toroidal winding wound stator. The integrated structure helps to concentrate all the flux within the motor to maximize torque production. Moreover, there are no end-windings in this motor and all the stator windings effectively are used in torque production. A comprehensive performance evaluation, in terms of the back-electromotive force, average output torque, cogging torque, torque ripple, flux-weakening capability, etc., of the investigated 3D-MF PMSM is conducted. An interior PMSM is purposely included as a benchmark for comparison. The results show that compared to the benchmark interior PMSM, the original 3D-MF PMSM exhibits significantly improved torque density, higher power factor, and higher efficiency, but suffers from serious cogging torque and torque ripple. Accordingly, a skewed arrangement is introduced to the 3D-MF PMSM. As a result, the cogging torque and torque ripple are significantly reduced.

Analysis and Methods for HTS DC Cables

High-temperature superconducting (HTS) DC cables with the merits of light weight, large capacity and low loss provide a novel power transmission method for future utility grid. In this paper, the electromagnetic characteristics of unipolar and bipolar coaxial HTS DC cables are compared by finite element simulation. Besides, the 3D magnetic flux density distribution characteristics of HTS DC cable are obtained. The method to investigate the influence of winding angle on HTS DC cable magnetic flux density is also applied to 3D HTS DC analysis.

Analysis and design optimization of a low-cost axial flux Vernier machine with SMC cores and ferrite magnets

In this paper, a low-cost high-performance axial flux Vernier machine (AFVM) with soft magnetic composite (SMC) cores and ferrite magnet is proposed, analyzed and optimized. By cooperating with spoke magnet rotor configuration and 3D magnetic flux stator structure, the proposed AFVM can output higher torque compared with the traditional permanent magnet machine though low-cost low-energy-density ferrite magnet and low-permeability SMC material are adopted. The main electromagnetic topology and operation principle of the proposed AFVM are introduced; then, its main dimensions are investigated and optimized by using sequential optimization method. Moreover, a new multilevel Taguchi design optimization which is an improvement of multilevel optimization is proposed for the torque and power factor optimization. Lastly, its main performance of AFVM optimized by the sequential optimization method and multilevel Taguchi design optimization method has been compared with a normal axial flux machine in terms of torque ability, power factor and efficiency based on 3D finite element method.

A Novel Flux Reversal Claw Pole Machine With Soft Magnetic Composite Cores

This paper proposes a novel flux reversal claw pole machine (FRCPM) with soft magnetic composite (SMC) cores, the proposed FRCPM has both the advantages of flux reversal permanent magnet machine (FRPMM) and claw pole machine (CPM). Specifically, with the permanent magnets (PMs) are surface mounted on the surface of stator claw pole teeth with a determined pattern, the FRCPM can operate based on flux reversal principle. As the adopted winding is global ring winding and 3D magnetic flux stator core structure is similar to the CPM's, the FRCPM is operated based on magnetic flux characteristic of the CPM as well. Therefore, the FRCPM can be operated under relatively high rotate speed since there is no winding or PMs on rotor, and the weak PMs, ring winding and SMC stator cores are encapsulated together as a whole part. Moreover the adopted 3D magnetic flux path can bring FRCPM with relatively high torque ability, and the adopted SMC cores can bring FRCPM with low core loss at the high speed operation. The operation principle of FRCPM is explained, the power equation is deduced for obtaining the initial design, and the main dimensions are optimized to ensure the developed FRCPM can have good performance. The main electromagnetic parameters and performance of FRCPM are obtained based on using the 3D finite element method (FEM).

Influence of inhomogeneous stress on biaxial 3D magnetic flux leakage signals

Magnetic memory method (MMM) is a newly developed passive nondestructive testing method, mainly used to detect the ferromagnetic materials. Because of the faster testing speed and the more convenient testing equipment, MMM has attracted many scholars’ attention. This paper designed wide plate tensile specimens without and with a defect to study the influence of stress distributions on magnetic-flux-leakage (MFL) signals. The three-dimensional (3D) MFL signals on the specimen surface along the directions parallel (x-axis) and vertical (y-axis) to the loading direction were measured. Finite element method (FEM) simulation and digital image correlation (DIC) testing were performed as comparison. Then a theoretical model was applied in finite element method (FEM) software to calculate the MFL signals. The experimental results are essentially in agreement with the calculated results. It is shown that the MFL signals on the measuring lines both parallel and vertical to the loading direction are capable of describing the load magnitude and stress inhomogeneity. Besides, the MFL gradient is in agreement with the equivalent stress distribution along the loading direction. The magnitude of MFL gradient vector developed in this paper shows a good correlation with the equivalent stress distribution vertical to the loading direction. Finally, five characterization parameters were extracted to evaluate the stress inhomogeneity.

Observation of ring–shaped pulsed DC discharge plasma source using single pole magnet setups for material processing

ABSTRACTA pulsed direct current (DC) discharge ring–shaped plasma source has been proposed using single pole magnet arrangements, including a center magnet, with magnets in the setups (a): one circle, (b): two circles, and (c): three circles. The three-dimensional (3D) magnetic flux lines profiles, gyro–radii and Hall parameters of the electrons and ions, the electrical discharge characteristics, the temporal evolutions of the ion saturation currents were investigated to characterize the proposed plasma source. The calculated electron gyro–radii, re were 0.17, 1.64, 5.82 mm for setups (a), (b), and (c), respectively. The strong ring–shaped plasma discharges was observed for all setups. The typical discharge voltages were 1.0, 0.6, and 0.6 kV for setups (a), (b), and (c), respectively. The ion saturation currents, Iisat were 1.44, 2.88, and 2.2 mA for setups (a), (b), and (c), respectively at r = 45 mm and t = +10 μs. The Iisat of setup (b) is less fluctuating, whereas Iisat of setup (a) and (c) is highly variable in all positions, so that setup (b) has the best profile among the setups.

Varying driver velocity fields in photospheric MHD wave simulations

Torsional motions are ubiquitous in the solar atmosphere. In this work, we perform 3D numerical simulations which mimic a vortex-type photospheric driver with a Gaussian spatial profile. This driver is implemented to excite MHD waves in an axially symmetric, 3D magnetic flux tube embedded in a realistic solar atmosphere. The Gaussian width of the driver is varied and the resulting perturbations are compared. Velocity vectors were decomposed into parallel, perpendicular and azimuthal components with respect to pre-defined magnetic flux surfaces. These components correspond broadly to the fast, slow and Alfven modes, respectively. From these velocities the corresponding wave energy fluxes are calculated, allowing us to estimate the contribution of each mode to the energy flux. For the narrowest driver ($0.15$ Mm) the parallel component accounts for $\sim 55 - 65\%$ of the flux. This contribution increases smoothly with driver width up to nearly $90\%$ for the widest driver ($0.35$ Mm). The relative importance of the perpendicular and azimuthal components decrease at similar rates. The azimuthal energy flux varied between $\sim 35\%$ for the narrowest driver and $< 10\%$ for the widest one. Similarly, the perpendicular flux was $\sim 25 - 10\%$. We also demonstrate that the fast mode corresponds to the sausage wave in our simulations. Our results therefore show that the fast sausage wave is easily excited by this driver and that it carries the majority of the energy transported. For this vortex-type driver the Alfven wave does not contribute a significant amount of energy.

Inhibiting the amine flotation of magnetite through aggregation with uniform low magnetic fields and no chemical depressants

The depression of magnetite in cationic flotation has been investigated using external 3D uniform low magnetic flux densities up to 0.015 T, in a laboratory Jameson-type flotation cell and in the absence of chemical depressants. In addition, the magnetic susceptibility and agglomeration of pure magnetite particles have been evaluated. The motion, size and morphology of magnetite aggregates and bubbles-magnetite aggregates in the flotation cell have been monitored by video microscopy. The cationic collector dodecyl amine and an iron concentrate with 65.1% total Fe, mainly as magnetite, were used for the flotation studies. In the absence of a magnetic field, the magnetite particles were fully dispersed and the iron flotation recovery linearly increased with the amine concentration. The 3D uniform magnetic flux density led to aggregation of magnetite particles as chains and chain columns whose sizes increased as the magnetic flux density increased. These magnetite aggregates rapidly settled by the action of the gravitational force and were removed easily from the flotation cell as tailings. The high amine flotation recovery of iron was significantly impaired by the magnetic field. Magnetite depression was associated with the large mass of the magnetite aggregates, which could not be floated by attached air bubbles so that they passed out as tailings.

Optimal design of a linear transverse‐flux machine with mutually coupled windings for force ripple reduction

This study presents a design method of a linear transverse-flux machine with mutually coupled windings aiming at the force ripple optimisation. Considering the three-dimensional (3D) magnetic flux in the proposed machine, a mathematic model based on Maxwell stress tensors is developed to facilitate the optimisation, so that the objectives depending on the selected design parameters can be analytically calculated. In order to reduce the optimisation time of the complex machine, mostly influential design parameters are evaluated by the Taguchi method first. Furthermore, the selected parameters are optimised with the human group optimisation algorithm. The main purpose of the algorithm is to attain the desired electromagnetic force with the minimum force ripple coefficient under the restriction of the overall volume. The proposed optimisation has been applied for a case study, and the final design is compared with that optimised by the genetic algorithm. The results show that the optimal machine design obtained by the proposed method has the lower force ripple coefficient, which is also verified by the 3D finite-element method and experiments.