Magnetic Flux Distribution Research Articles

Design and Dynamic Stiffness Evaluation of Magnetorheological Elastomer Bushing using FEMM and Dynamic Testing Machine

This research presents a simulation study on electromagnetic behaviour of magnetic flux density distribution in a magnetorheological elastomer (MRE) bushing. The design concept of MRE bushing is based on the design of the bushing used in the conventional car, only the natural rubber is being replaced by the MRE compound. Furthermore, the electromagnetic simulations wereconducted by using Finite Element Method Magnetics (FEMM) software where the main aim is for more magnetic flux density in the MRE, which indicates better performances for MRE bushing in this study. The best configuration of the MRE bushing for this study is using single coil, magnetic material for all parts except for coil bobbin, and the thickness of ring plate of 4 mm, which yield the highest magnetic flux density of 0.205 T. By using this configuration, the dynamic stiffness of this MRE bushing is ranging from 2259.13 N/mm to 2671.06 N/mm with the applied currents of 0.5 A to 2.5 A and frequencies from 1 Hz to 15 Hz. All in all, the optimized configurations improve the performance of MRE bushing remarkably.

Investigation of biparametric resonance sensors with distributed parameters

This article describes the ways to preserve the resonant mode in biparametric circuits with distributed parameters and studies the effect of changes in the circuit parameters and power supply on the resonant mode. During the moving part’s movement of the sensor due to the influence of the distributed magnetic resistance of the steel part of the circuit, the law of change in the electrical inductance of the resonant circuit (distribution of magnetic flux in long magnetic conductors) differs from the linear one.

Analysis and Experimental Investigation of High-Frequency Magnetic Flux Distribution in Mn-Zn Ferrite Cores

This article presents a comprehensive investigation of the high-frequency magnetic flux distributions in manganese-zinc ferrite ring cores. New experimental characteristics are presented and used in the flux modeling. The flux distribution is predicted by a one-dimensional analytical model, a transmission-line model, and finite-element analysis. The models are used to investigate the high-frequency effects, such as skin depth and dimensional resonance. A complete experimental validation is presented. The nonuniform magnetic flux distributions are experimentally validated for two Mn-Zn materials: 3F36 and 3E10. The low permeability 3F36 material performance can be significantly degraded by dimensional resonance. However, the high permeability 3E10 material degrades due to the skin effect. The presented analytical methods show a very good correlation with the measurements.

IONIC WIND FLOW CHARACTERISTICS OF A MAGNETIC-FIELD-ENHANCED SOLID-STATE FAN AND ITS PERFORMANCE IN LIGHT-EMITTING DIODE COOLING APPLICATIONS

Solid-state fans (SSFs) have distinct advantages over traditional cooling fans in the thermal management of high-power electronics. In this work, a magnetic-field-enhanced SSF is proposed, and the physical model of negative corona discharge superimposed by an electromagnetic field is established. A computational model is used to calculate and analyze the effect of the magnetic field on the ionic wind distribution. The magnetic flux density and permanent magnet position distribution in the SSF are optimized experimentally, and the optimized SSF is applied to LED chip cooling. The findings show that adding a magnetic field encourages electrons to collide with neutral gas molecules and enhances the driving force of charged particles. The ionic wind velocity and mean driving force at the SSF's outlet will grow as magnetic flux density rises, and the ionic wind flow distribution will show apparent divergence. When the permanent magnet spacing is 15 mm, the highest ionic wind velocity is 2.82 m/s, and the mean driving force of SSF increases by 30.2%. The magnetic-field-enhanced SSF has a better LED-chip cooling effect, the maximum junction temperature drop is 11.6°C, and the cooling efficiency is higher. This research introduces a novel way of improving the cooling of electronics.

Probability Distribution Functions of Sunspot Magnetic Flux

We investigated the probability distributions of sunspot area and magnetic flux by using data from the Royal Greenwich Observatory and USAF/NOAA. We constructed a sample of 2995 regions with maximum-development areas ≥500 MSH (millionths of solar hemisphere), covering 146.7 yr (1874–2020). The data were fitted by a power-law distribution and four two-parameter distributions (tapered-power-law, gamma, lognormal, and Weibull distributions). The power-law model was unfavorable compared to the four models in terms of AIC, and was not acceptable according to the classical Kolmogorov–Smirnov test. The lognormal and Weibull distributions were excluded because their behavior extended to smaller regions (S ≪ 500 MSH) do not connect to previously published results. Therefore, our choices were tapered-power-law and gamma distributions. The power-law portion of the tapered-power-law and gamma distributions was found to have a power exponent of 1.35–1.9. Due to the exponential falloff of these distributions, the expected frequencies of large sunspots are low. The largest sunspot group observed had an area of 6132 MSH, and the frequency of sunspots larger than 104 MSH was estimated to be every 3–8 × 104 yr. We also estimated the distributions of the Sun-as-a-star total sunspot areas. The largest total area covered by sunspots on record was 1.67% of the visible disk, and can be up to 2.7% by artificially increasing the lifetimes of large sunspots in an area evolution model. These values are still smaller than those found on active Sun-like stars.

Роль геокосмического транспорта в крупномасштабной индустриализации космоса

Today, humanity is faced with a number of environmental problems, the solution of which depends on our continued existence. The authors propose a systematic approach to get out of this situation, which is described in detail in the EcoSpace program. The main vector of further industrial development will be space, but its implementation requires transport that has a number of unique characteristics. The authors of the article proposed the design of a general planetary vehicle (GPV), which is a self-supporting aircraft (with a length of 40,076 km, a total mass without payload of about 30 million tons), made in the form of a torus with a cross section of several meters, covering the planet in a plane, parallel to the equator. A solution to the problem of stabilization of the central position of the rotor in the channel of the stator of a general planetary vehicle (GPV) with the help of the forces of the magnetic fields of permanent magnets is proposed. The designed system compensates for external forces acting both on the rotor during takeoff preparation and on the stator during climb. The diagrams of the distribution of magnetic fluxes in the suspension, as well as under the influence of the Earth's gravity force on the rotor near its surface, are given. Thus, a general planetary vehicle, designed to move all harmful industrial production beyond the planet Earth, opens up prospects for using the conditions of weightlessness, vacuum, ultra-low and ultra-high temperatures, spatial, energy and raw materials of near space and the boundless Universe. The results of the conducted studies and their analysis demonstrate that UTS is able to provide a planetary scale and a rapid pace of practical implementation of the uSpace project.

Analytical and FEM Methods for Line Start Permanent Magnet Synchronous Motor of 2.2kW

This paper has developed electromagnetic equations based an analytical model to design a three-phase line start permanent magnet synchronous motor (LSPMSM) of 2.2 kW. In order to enhance the torque and efficiency of this machine, an optimized slot shape of rotor permanent magnet is proposed. The analytical model is first presented to evaluate the magnetic characteristics, and then analytical expressions are derived under the open circuit condition. The influence of the magnet size variables on the analytical model is considered to investigate the magnetic leakage flux and flux density distribution in air gaps. Moreover, the variation of design has a significant impact on the steady-state performance characteristics of this motor. In addition, in order to check the output results from the analytical model, a finite element method is developed to evaluate these solutions. Finally, experimental and simulation results have been compared and analyzed to validate the development of method.

Identification of asynchronous motor and transformer situations in thermal images by utilizing transfer learning-based deep learning architectures

Asynchronous motors are thoroughly preferred in industrial applications regarding their advantages in comparison with other motor types, and transformers constitute another oft-used category for the adjustment of voltage to be fed to an electrical system. Concerning the inevitable usage of these equipment, the fault diagnostics are generally fulfilled by in-depth determinations of stator current signals, magnetic flux distributions, etc. which require conventional electrical measurements. Herein, thermal image analyses arise as an easy way to identify the situations of electrical equipment in which there is no need for direct intervention to the structure. In this paper, we handle the thermal image-based analyses to distinguish the situations of asynchronous motors and transformers. For this purpose, without a pre-processing step, efficient deep learning architectures (DenseNet201, MobileNetV2, ResNet50, ShuffleNet, Xception) are examined to discriminate twenty situations formed by combining the conditions of both types of equipment. These conditions are defined as the cooling fan failure, rotor fault, short-circuit faults in different phases and in various rates inside the motor, short-circuit faults in different rates inside the transformer, no-load motor, and no-load transformer. In experiments, the hyperparameters of models are examined in a comprehensive manner to observe the highest scores of architectures that can be achieved. Herein, four phenomena (mini-batch size, learning rate, learning rate drop factor, optimizer type) are evaluated to perform the transfer learning task, not to spoil the main part of the models, and to reveal the appropriate model for thermal image classification. In trials, an 80–20% training-test split is allowed to compare the models without data augmentation. As a result, the highest performance is observed with all deep learning architectures by attaining 100% accuracy for condition discrepancy of thermal images belonging to the three phase-motor and one phase-transformer. In addition to the accuracy-based analyses, an in-depth evaluation is presented to reveal the most appropriate architecture in thermal image classification.

The large N limit of topologically twisted indices: a direct approach

We study the large N limit of the refined topologically twisted index of three-dimensional mathcal{N} = 2 gauge theories with a holographic dual, which is relevant for counting the number of microstates of rotating, magnetically charged and twisted AdS4 black holes. As a difference with previous computations, we perform a direct saddle point analysis of the relevant matrix model. Among other things we explicitly identify the distribution of gauge magnetic fluxes that contributes at large N. The index exhibits a large N factorized form in agreement with the supergravity expectations based on gravitational blocks and correctly reproduces the entropy of magnetically charged rotating AdS4× S7 black holes.

Study the dynamic performance of PM machines for different rotor topologies

<p>For hybrid and electric vehicle drive-train (automotive applications) achieving high torque and efficiency at a wide range of operating conditions can be considered an important matter. Therefore, precise structure optimization of the permanent magnet synchronous machines (PMSMs) is recommended. Consequently, the effect of the main leading design parameters (such as PM arrangement, magnet thickness, pole arc to pole pitch ratio, airgap length as well as the effect of shaft material) for a different number of rotor poles configuration of PMSM can achieve optimum design results in electric motors with economical cost and excellent performance. This paper submits a comparative analysis of different rotor topologies of (PMSM). Moreover, the dynamic performances of the suggested rotor geometry topologies are investigated based on investigation of finite element analysis (FEA). The analysis offers a piece of complete information about the magnetic flux distribution and magnetic flux density over the motor geometry. Gained results from the analysis are used to give a decision for the selection of a suitable PMSM design.</p>

Flux penetration of an HTS coated-conductor tape by an approaching permanent magnet

Interactions between inhomogeneous magnetic fields and a superconductor lie at the heart of several high-temperature superconducting (HTS) devices. An example is the situation where the magnetic field from a small permanent magnet (PM) is applied to a coated-conductor HTS tape, such that flux penetrates the superconductor. The PM field is highly spatially inhomogeneous, such that there is significant variation in the applied field magnitude and direction across the tape. This leads to a varying local critical current density, Jc(B , θ ), across the tape, and consequently different ‘shielding’ (magnetic flux penetration) behaviour than is the case for a uniform applied field. Here, we report results from measurements and numerical simulations of the penetrating magnetic field within an HTS coated-conductor tape which occur as a PM dipole approaches from a distance. Electromagnetic simulations were performed using a finite-element model based on the H -formulation, and which incorporated experimentally-measured anisotropic Jc(B , θ ) properties from a coated-conductor tape. This showed good agreement with experimental measurements. The effects of varying key modelling assumptions and parameters were then studied, including changing the widths of the PM and HTS tape and the magnitude of Jc(B , θ ). The inhomogeneity of the PM field leads to a characteristic gull-wing distribution of magnetic flux across the superconductor at elevated applied fields. Close approach of the PM to the tape suppresses Jc in the centre of the tape, and this results in the observation of a characteristic maxima for the total shielding currents circulating in the tape. A figure of merit is introduced which uses this effect to provide a threshold definition for ‘full flux penetration’ of an HTS tape by an inhomogeneous dipole field.

Revisiting the Space Weather Environment of Proxima Centauri b

Close-in planets orbiting around low-mass stars are exposed to intense energetic photon and particle radiation and harsh space weather. We have modeled such conditions for Proxima Centauri b, a rocky planet orbiting in the habitable zone of our closest neighboring star, finding a stellar wind pressure 3 orders of magnitude higher than the solar wind pressure on Earth. At that time, no Zeeman–Doppler observations of the surface magnetic field distribution of Proxima Cen were available and a proxy from a star with a similar Rossby number to Proxima was used to drive the MHD model. Recently, the first Zeeman–Doppler imaging (ZDI) observation of Proxima Cen became available. We have modeled Proxima b’s space weather using this map and compared it with the results from the proxy magnetogram. We also computed models for a high-resolution synthetic magnetogram for Proxima b generated by a state-of-the-art dynamo model. The resulting space weather conditions for these three scenarios are similar with only small differences found between the models based on the ZDI observed magnetogram and the proxy. We conclude that our proxy magnetogram prescription based on the Rossby number is valid, and provides a simple way to estimate stellar magnetic flux distributions when no direct observations are available. Comparisons with models based on the synthetic magnetogram show that the exact magnetogram details are not important for predicting global space weather conditions of planets, reinforcing earlier conclusions that the large-scale (low-order) field dominates, and that the small-scale field does not have much influence on the ambient stellar wind.

Effect of Local Annealing on Magnetic Flux Distribution and Noise in a Micro-Generator with Amorphous Shell.

This study examined micro-alternators with two different housing structures--an uncoated shell and a shell coated with an iron-based amorphous-alloy soft magnetic material. The electromagnetic power and noise characteristics of generators with these shell structures were measured and analyzed. The material used for the shell coating was the SA1 amorphous alloy. The magnetic property of the SA1 material was evaluated, including its hysteresis expansion, hysteresis-loop parameters, α-Fe crystal formation, thermogravimetric transfer, and Curie temperature. The center point of the casing was subjected to flame local-heating annealing to attain ferromagnetism and paramagnetism material characteristics. The experimental shell was between these magnetic-phase-transition properties and was used to observe the magnetic power and noise characteristics of the microgenerator. The measured magnetic flux at the center of the amorphous shell was 1.2-2.4 mT, and the magnetic flux distributed around the shell was 0.6-1.0 mT. The generator with the amorphous-alloy shell had the lowest demagnetization rate in the permanent magnet region, which was close to the bottom of the pole piece, and the magnetic flux leakage of the pole-piece side frame changed the magnetic flux path, thus affecting the demagnetization performance. For the noise experiment, the flame-annealing temperature of the local center point of the amorphous casing reached the Curie temperature, and the noise characteristics of the casing can be reduced by 15 dB compared to those of the generator without the casing. However, the overall performance of generator harmonics and power were not fully improved.

Material removal analysis during MR polishing of complex gear teeth profiles

The geometric intricacy of tiny gears makes nano-finishing difficult. In the current study, the magnetorheological (MR) polishing process is used for the nano-finishing of intricate surfaces of tiny gear components uniformly. For polishing, the technique employs a dynamic fluid recognized as magnetorheological polishing fluid (MRPF), that has the ability to stiffen in the presence of a magnetic field. Base media, iron and abrasive particles are utilized to synthesize the MRPF. Permanent magnets produce the necessary magnetic field in the finishing zone. Finite element analysis (FEA) is utilized to model the iron and abrasive particles to understand better how they would react in the external magnetic field. FEA is utilized to analyze the magnetic flux density (MFD) distributions and the amount of magnetic force exerting on gear profiles through iron particles (IPs). It has been observed that the IPs present close to the active abrasives are primarily accountable for indenting active abrasives into the workpiece surfaces. In addition, the influence of particle dimension on the stiffness of iron particle chains in MRPF has been investigated. A mathematical model for material removal is developed by utilizing normal finishing force analysis on active abrasives. Lastly, the finishing surface characteristics of gear profiles are examined using an optical profilometer, field emission scanning electron microscope (FESEM) and spectroscopic analysis. Finally, 92.68% improvement in the surface finish is observed.

Design optimization of microfabricated coils for volume-limited miniaturized broadband electromagnetic vibration energy harvester

Broadband electromagnetic vibration energy harvesters (EMVEHs) can effectively convert mechanical energy into electricity from human motions with low and random frequencies. However, such applications require a small device footprint which limits the power density of the energy harvester, making it hard to generate sufficient energy for wearable electronics. Here, we present a design of a nonresonant broadband EMVEH based on a magnet array with alternating magnetic polarities and microfabricated planar coils. To enhance the power output and power density of the EMVEH, we propose a geometric optimization method for determining the coil geometry. First, the magnetic flux density (MFD) distribution and the power output under different types of excitation motions are studied by finite element analysis and numerical simulation, respectively. Based on these results, a design of a stackable microfabricated double-sided planar coil sheet consisting of 10 coil groups is chosen. Through the optimization based on the trade-off between induced voltage and coil resistance, four coil turns in each coil group is determined as the optimal design for maximizing the output power, which proved independent of the excitation conditions. Based on the optimized design, a prototype consisting of 20 layers of coil sheets connected in series on each side is fabricated, occupying only 1.73 cm3. The device is tested to have a wide half-power bandwidth of 8 Hz, a maximum output power of 346.7 μW, and a maximum power density of 200.4 μW/cm3, when connected to a matched load of 69.46 Ω under sinusoidal excitations of 2.0 g acceleration. Furthermore, we propose a preliminary optimization methodology to determine the optimal number of stacked coil layers.

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.

Performance Analysis and Optimization of a Novel Outer Rotor Field-Excited Flux-Switching Machine with Combined Semi-Closed and Open Slots Stator

Slotting effect in electric machines reduces flux per pole that effect magnetic flux density distribution in the air gap which induces harmonics in magnetic flux density causing flux pulsation, that in turn generates dominant torque pulsation in the form of cogging torque and torque ripples. To overcome the abovesaid demerits, a novel outer rotor field-excited flux-switching machine (OR-FSFSM) with a combined semi-closed and open slots stator is proposed in this study. The developed OR-FEFSM offers a high-power factor, due to the utilization of the semi-closed slot for armature coils. The open slot stator structure was chosen for the field excitation coil, which effectively suppresses leakage reluctance that causes flux pulsation. Thus, the influence of torque ripples is reduced, and the average torque is improved. In order to investigate the effectiveness of the proposed OR-FEFSM, a detailed study of stator slot and rotor pole combinations are performed. Based on simplified mathematical formulation, 12S/7P (stator slot/rotor poles), 12S/11P, 12S/13P, and 12S/17P are the most feasible combinations. Finite Element Analysis (FEA) based on comprehensive electromagnetic performance is performed on each combination, and found that 12S/13P offers the highest average torque of 4.62 Nm, whereas 3.72 Nm, 2.72Nm, and 1.68 Nm average torque is offered by 12S/17P, 12S/7P, and 12S/11P, respectively. Based on the initial analysis, 12S/13P was considered for further analysis and optimized using JMAG built-in Genetic Algorithm (GA). Moreover, thermal analysis was performed, and the proposed design was compared with the conventional design.

Electromagnetic and Mechanical Analysis and Measurements of Interior Permanent Magnet Motors Based on Equivalent Magnetic Circuit Method

This paper is about the magnetic field analysis of an interior permanent magnet motor (IPM motor) by using the equivalent magnetic circuit method (EMC method), which requires a small amount of computation time compared with the finite element method (FEM). IPM motors have a specific shape of rotor in which the permanent magnets are embedded. Therefore, in the bridge region, the magnetic saturation is generated due to the shape of the permanent magnet, which affects the magnetic flux density distribution in the air gap and the characteristics of the IPM motor. Thus, to design an IPM motor, the magnetic saturation effects should be considered along with the rotor shape. In addition, because the rotor of the IPM rotates at a high speed directly in connection with the load, the stress generated from the rotor must be stably distributed. Consequently, according to the rotor shape characteristics of the IPM, the stress is concentrated in the thin bridge region during high-speed rotation. When the stress generated in the bridge region exceeds the yield stress of the rotor iron core material, the bridge part is destroyed. Therefore, it is important to analyze the stress that occurs in the rotor during high-speed rotation in the rotor design stage of the IPM. In this study, we analyzed the magnetic field characteristics of an IPM motor using its equivalent magnetic circuit while considering the magnetic saturation in the bridge region. The stability of the rotor was determined by presenting a safety factor based on the maximum stress generated at the rotor for each speed. We derived the stator natural frequency to evaluate the resonance possibility between the electrical frequency and the stator natural frequency. Finally, the validity of the constructed equivalent magnetic circuit was verified by comparing the results with those obtained via the FEM analysis and experiments.

The Design of the Outer-Rotor Brushless DC Motor and an Investigation of Motor Axial-Length-to-Pole-Pitch Ratio

In this study, the effects of the ratio of a motor’s axial length to its pole pitch on efficiency, magnetic flux density distribution, torque, torque/weight, and motor volume were investigated in an outer-rotor (hub) brushless direct current motor. The weight and volume of an electrical machine affects the output power, efficiency and output torque, and it is advantageous to design an electric motor at an appropriate power and high efficiency with an appropriate weight and volume. Therefore, the aim of this study was to optimize the motor’s axial length and stator outer diameter, which affects the motor volume. Initially, the axial-length-to-pole-pitch ratio of the hub BLDC motor was taken at 0.75. According to this ratio, the dimensions of the rotor outer diameter, rotor inner diameter, stator outer diameter, stator inner diameter, slot height, motor axial length, and magnet thickness were optimally determined. Then, the axial-length-to-pole-pitch ratio was considered as 1, 1.50, 2, and 3, respectively. The effects of the change in the motor’s axial-length-to-pole-pitch ratio on the efficiency, torque, speed, torque/volume, torque/weight, and cogging torque were examined in a simulation environment. According to the motor’s axial-length-to-pole-pitch ratio, the torque value in the final state was 28.65% higher than the torque value in the initial state. In the last part, the motor axial length and the stator outer diameter were defined as variables in a genetic algorithm procedure and optimized. The number of poles and the number of slots were fixed parameters. Simulation studies were carried out using the finite element method via AN-SYS/Maxwell software.

Analysis and Application of the Influence of Magnetic Material and Magnetic Gap on Electromagnetic Actuator

The impact of the actuator is examined in light of the properties of various materials. The features of the N48 material are examined when the N48 permanent magnet material is chosen. A novel magnetic steel construction for an electromagnetic actuator is built after analysis of the air gap structure. The functionality and nonlinear issues of the electromagnetic actuator are investigated in accordance with the properties of the materials and constructions. The link between electromagnetic output and current and frequency is investigated and determined using theoretical analysis, finite element analysis, and real test. The magnetic flux density distribution, electromagnetic dynamic response, current frequency relationship, and surface skin effect are derived using the electromagnetic simulation model built in COMSOL. Time domain simulation is used to determine the electromagnetic actuator’s static linearity. Simulation in a steady state is used to determine the operating linearity of an electromagnetic actuator. To confirm the accuracy of the theoretical and simulation results, the electromagnetic actuator prototype is put to the test. The simulation results demonstrate the high linearity and good performance of the electromagnetic actuator, with an average static linearity of 97.24%. To confirm the validity of the theory and simulation, an actual test is conducted on the structural prototype. The outcomes can not only serve as a guide for the best design of electromagnetic actuators but can also demonstrate the benefits and potential uses of various materials used in actuator construction.