Magnetic Flux Distribution Research Articles

Study on the Efficiency of Simultaneous Tube Compression and Expansion Electromagnetic Forming

The low efficiency of the electromagnetic forming is one of the obstacles for the advancement of this technology. Aiming at solving this issue, this paper presents a double tube-task electromagnetic forming technology method by employing a single driving coil to achieve tube compression and expansion at the same time. On the basis of electromagnetic forming principles and the law of energy conversion, this paper presents a new electromagnetic forming model for double tubes. The magnetic flux density distribution, electromagnetic force distribution and forming efficiency of the tube are analyzed and the effect of the equivalent pulse width of the driving coil current on the forming efficiency is investigated. Results show that in order to maintain the same plastic strain energy of the tube, the initial discharge energy required by the proposed double tube model is 25 kJ which is smaller than that required by a traditional single tube model (33.58kJ) and the efficiency can be improved by about 34.3%. The double tube model attains the maximum forming efficiency near the optimal current pulse width and can improve the low efficiency of traditional electromagnetic forming to a certain extent and provide more possibilities for this technological process.

Analysis of the Impact of Magnetic Materials on Cogging Torque in Brushless DC Motor

The cogging torque is the most significant issue in permanent magnet applications, since it has a negative impact on machine performance. In this article, the impact of magnetic materials on cogging torque is analyzed on brushless DC motors (BLDC). The effect of neodymium magnets (NdFeB), compression molded magnet, and samarium cobalt (SmCo) magnet on the cogging torque is analyzed to the BLDC motor designed for hybrid electric vehicle traction that has the peak power rating of 50 kW motor with 48 stator slots and 8 rotor poles. With the presence of these three magnetic materials, the cogging torque is estimated independently using multiposition simulation. The multiposition is simulated using a transient application that runs at constant speed. The results of cogging torque, rotational speed, angular position of BLDC motor, and magnetic flux density distribution have been presented. Also, the maximal, mean, minimal, rectified mean, and rms values of cogging torque were provided.

Magnetic measurement and analysis of c-type amorphous by an improved adjustable air gap tester

A novel magnetic properties tester is designed to accurately and conveniently change the air gap of the core, which can fix cores of various types. The dynamic magnetic characteristics of the amorphous core under sinusoidal excitation within 20 kHz is measured with different air gap lengths and magnetic flux density. It is found that in the case of the small air gap, the total loss decreases as the air gap increases. When the frequency is 20 kHz and the flux density is 0.1 T, the loss can even be reduced by 7%. This paper analyzes the experimental data and summarizes the influence of the air gap and magnetic flux density about the core loss. Besides, the influence of air gap on magnetic flux density distribution is illustrated and analyzed by the means of FEM (Finite Element Method). It is valuable for the design of high frequency transformer and inductor.

Optimization on Size of Halbach Array Permanent Magnets for Magnetic Levitation System for Permanent Magnet Maglev Train

A permanent magnet suspension (PMS) magnetic levitation (Maglev) system consisted of magnetic rail magnets and carriage magnets are investigated for PMS Maglev vehicle. The characteristics of magnetic flux line and magnetic flux density distribution in the suspension gap region are analyzed by using finite element method. The results show that the Halbach Array stack structure generates strong sinusoidal periodic magnetic field in the suspension gap region. The size of Halbach Array permanent magnets stacked structure model was simulated and optimized, and the optimal size factor was obtained. In addition, a levitation force model describing the relationship between magnetic levitation force, permanent magnet size and levitation height was established by molecular current method. The correctness of the levitation force model is evaluated. Finite element simulation and experiment verify the validity of the levitation force model. The results show that the optimized Halbach Array permanent magnets can generate large suspension force and good stability, which is of great significance to improve the utilization rate of permanent magnet materials and save costs, and is conducive to the further development of permanent magnet maglev train. The study is useful for analysis and design optimization of maglev train.

A new magnetic modeling method for magnetic levitation rotary table

Precision machining fields require the worktable to have a large-scale multi-degree-of-freedom motion capability. In order to provide a more accurate magnetic model for the control strategy decoupling process and the size parameter optimization design process of the maglev rotary table. This paper proposes a new magnetic modeling method based on the Two-Dimensional Harmonic method. Different from the existing harmonic method, this method simultaneously considers the tangential and radial magnetic field changes of circumferential magnetic array. And it eliminates the edge effect of the magnetic flux density distribution in the radial aperiodic direction. The magnetic force and torque are solved by the Lorenz integral formula and the Gaussian quadrature method. In order to verify the accuracy of the TDH method, the boundary element software RadiaTM is used for simulation, and a prototype is made for measurement. The experimental results shown that this method reduced the maximum error of the radial edge magnetic field from 104.19% to 3.29%. And it improved the calculation accuracy of magnetic force and torque by 60.74% and 84.39% respectively. This method does not rely on special example, and is beneficial to cross-platform applications. It is more suitable for realizing the magnetic modeling of the maglev rotary table with both rotational motion and large-stroke translational motion.

Magnetic field distribution simulation and performance experiment of a magnetic seed-metering device based on the combined magnetic system

The magnetic seed-metering method is one of the universal approaches for plug tray seeding. Conventional electromagnetic and permanent-magnetic seed-metering devices either cannot supply a desirable magnitude of magnetic force or need a seed-clearing mechanism. Thus the objective of this research was to develop a combined magnetic system (CMS) seed-metering device for generating higher magnetic forces than the electromagnetic ones without using any auxiliary seed-clearing mechanisms. Firstly, the CMS component was designed and its magnetic field distributions in both attractive and clearing states were obtained by finite element method simulations. Secondly, based on the CMS components, a magnetic seed-metering device was developed and validated by a prototype experiment. The simulation results displayed that along the axial direction of the magnetic head, the maximum magnetic flux density in the clearing state was 21.03% of that in the attractive state. In addition, along the radial direction, the proportion was 24.16%. Concerning the spatial magnetic flux density distribution, the magnetic flux density on the seeding planes of CMS components (approximately 60 mT) was higher than that of transitional space between two CMS components (nearly 0 mT). As for the seeding performance experiment, when the rotational speed of the roller was 21 r/min and the exciting current was 0.15 A, the highest single rate was acquired (90.20%). In the same condition, the reseeding rate was 5.88% and the miss-seeding rate was 3.92%. The results suggest that the magnetic field distribution and seeding performance of the developed magnetic seed-metering device are acceptable. Therefore, the developed magnetic seed-metering device can be used in practical plug tray seeding processes. Keywords: seed-metering device, magnetic field, magnetic flux density, finite element method, simulation DOI: 10.25165/j.ijabe.20211401.5852 Citation: Liu W, Hu J P, Yao M J, Zhao J, Lakhiar I A, Lu C T, et al. Magnetic field distribution simulation and performance experiment of a magnetic seed-metering device based on the combined magnetic system. Int J Agric & Biol Eng, 2021; 14(1): 108–117.

Analytical Calculation of Magnetic Field in Fractional-Slot Windings Linear Phase-Shifting Transformer Based on Exact Subdomain Model

Fractional-slot windings linear phase-shifting transformers (FW-LPSTs) are a new type of transformer that can be used as an important component of multi-rectifier and multi-inverter systems. The FW-LPSTs are proposed for the first time, and few scholars have studied their magnetic field. However, accurate calculation of magnetic field distribution of the FW-LPSTs is the premise of the optimal design of the ontology, and the establishment of an accurate analytical model which remains a challenging task is the key to solving the magnetic field distribution. In view of the limitation of traditional analytical theory in solving the magnetic field, the FW-LPST model based on the exact subdomain method is proposed to obtain the exact magnetic field distribution. Considering the influences of the permeability and the structural parameters of the slot subdomain and the interaction of all slots on the distribution of the magnetic field, the governing equations of the air gap and slot subdomains are established using magnetic vector potential as the variable. According to the boundary conditions of each subdomain, all equations of the boundary condition are listed based on the Fourier series method. Finally, the vector magnetic potential and open-circuit magnetic flux density distribution of each subdomain are solved. The model accurately analyzes the influence of the cogging effect on the magnetic field distribution. The inductances of the primary side and the induced potentials of the secondary side are solved using the magnetic flux linkage method. The accuracy of the proposed analytical model is verified by comparison of the results obtained with those obtained by the finite element method.

Proposal and Challenge of Halbach Array Type Induction Coil for Cooktop Applications

This paper proposes a new induction heating (IH) coil using Halbach-arranged coils for cooktop. In general, a control inverter is placed on the back side of the coil, but by using the Halbach array coils, magnetic flux leakage to the back of the coil can be prevented without using a ferrite cores for magnetic shielding. Further, the magnetic flux can be concentratedly linked to the pot. First, differences and advantages of the magnetic flux distribution between the conventional IH-coil and the proposed IH-coil will be described based on electromagnetic field analysis. Next, the results of verification of the effect of the Halbach array coil via the prototype for principle verification are demonstrated.

Simulation of a Grid Multi-Layer Shield to Reduce the Magnetic Field of Power Lines

Seeing the harmful effects of the magnetic field on human health, the task of reducing the magnetic flux density in places of people long-term stays near power lines is actual. One of the ways to solve this problem is a passive shielding.Analyze of shielding efficiency was performed by computer simulation using COMSOL Multiphysics software. It was created a 2D model of a three-phase 330 kV overhead power transmission line and the research area, which is a conventional residential building located outside the security zone.The magnetic field was simulated and the value of magnetic flux density in the research area was determined for cases of using a passive grid electromagnetic screen of different configurations. The efficiency comparison of different shields was performed qualitatively on the color and contour maps of the magnetic flux density distribution in the research area and quantitatively on the average value of the shielding factor.The efficiency of a single layer vertical shield, located on the building wall closest to the power line, and a horizontal shield, located at the average height of the building, were compared. It is shown that with the same metal content (the same diameter of the shield conductors and the same number of them) the vertical shield is more efficient than the horizontal, but it also cannot always provide a safe level of magnetic flux density.The configuration of the multilayer shield, which can be placed in overlapping between floors of the building, is presented. It is shown that with the same metal content such shield can provide better reducing of the magnetic field than a single-layer, and it is able, under the same conditions, to decrease the magnetic flux density to a safe level. But this configuration has one disadvantage. In the part of the building closer to the power line (approximately 4 m from the wall) the value of magnetic flux density exceeds the safe level. It is possible to reduce the width of such zone due to a denser placement of shield conductors. It was also found that the placement of the shield horizontal layers on each floor is more effective, i.e. as evenly as possible over the research area.In addition, a research the dependence of the shielding factor of the multilayer shield on the conductor’s diameter and the distance between them. It is shown that such shield allows reducing the average value of magnetic flux density in the research area hundreds of times, although with a fairly large metal content.

Analysis, Design, and Implementation of a Spatially Nested Magnetic Integration Method for Inductive Power Transfer Systems

Inductive power transfer (IPT) technology uses large resonant inductors as compensation components. In this article, a spatially nested magnetic integration method is proposed to integrate discrete inductors into an IPT transformer structure. Unipolar transformer coils are employed and are decoupled orthogonally from a nested solenoidal inductance coil for various misalignment cases. The variations of the coupling coefficients and the magnetic flux density distribution are presented with the three-dimensional finite-element modeling tool. An LCC series compensation circuit is selected to implement the proposed method with an optimal efficiency design. A 4-kW prototype with a 160 mm airgap is implemented to demonstrate the validity of the proposed method. The experimental results show that the compact structure retains the outstanding performance and avoids significant cross coupling for lateral, vertical, and axial misalignment. The maximum conversion efficiency of the proposed system is 96.7% at full output power and stays above 91.6% throughout the misalignment range.

Two-Step Method for the Calculation of Eddy Current Losses in an Open-Core Transformer

In order to minimize eddy current losses in an open-core type of transformer, a lower width-to-thickness ratio of lamination sheets and even varying lamination stacking direction than in the case of standard transformers are used. Consequently, narrow eddy current loops must be considered as a 2-D phenomenon, i.e., edge effects and irregular current density distributions cannot be neglected. A two-step method for the calculation of eddy currents and eddy current losses in an open-core transformer is presented. In the first step, using the anisotropic surrogate material, the magnetic flux density distribution within the bulk core model is calculated. In the second step, the magnetic flux density obtained in the first step is used as input to calculate eddy currents in a sufficient number of densely meshed 2-D slices of the laminated core. Numerical simulation of the method is carried out, and the results are compared with those obtained using a homogenization method and the brute force approach. The results show good agreement and indicate the importance of taking edge effects into account.

2D Analytical Model of Armature Reaction Magnetic Field Distribution in Slotless Permanent-Magnet Linear Tubular Machines

This paper presents a 2D analytical model for predicting the magnetic flux density distribution in slotless permanent-magnet (PM) linear tubular (PMLT) motors due to armature reaction effects based on the sub-domain method. According to this method, the machine cross-section is divided into the six sub-regions and Maxwell partial differential equations (PDEs) are formed in each sub-region. Solving these PDEs leads to defining the magnetic vector potential in each sub-region and applying curl on the calculated magnetic vector potential results in determining the magnetic flux density components. Eventually, the extracted results are compared with those of the finite-element method (FEM) to confirm the accuracy of the described analytical model. The results reveal that the presented analytical model is a suitable candidate for predicting the magnetic flux density components of the slotless PMLT motors in a shorter time.

THE INVESTIGATION OF DISTRIBUTION OF THE MAGNETIC FLUX DENSITY OF OPERATING TWO-CIRCUIT POWER LINE 110 KV «CHTPP-CHERNIHIV-330» IN THE RESIDENTIAL AREA AND METHODS OF ITS DECREASING TO A SAFE LEVEL

Purpose. The problem of evaluation and analysis of magnetic flux density of overhead power lines is very relevant now, since the magnetic field of industrial frequency can have a negative effect on human health. The analysis of the magnetic field of the operating double-circuit overhead transmission line was made in this work. This overhead line is in the residential area of Chernihiv, Ukraine. The purpose of this work is to determine safe habitation conditions as a function of the magnetic flux density along the route of two-circuit power line with the voltage 110 kV «ChTPP-Chernihiv-330». Real modes of operation are taken into account. Recommendations are given for reducing the magnetic flux density level in the residential area to a value that will not exceed the standard value. Methodology. Methods of electromagnetic field theory were used to calculate the magnetic field of power lines. The location of the phase wires on different types of supports of the existing power transmission line and the minimum distance between the conductors and the ground were taken into account. The current value of the current in the phases of the transmission line was taken from the Company «Chernihivoblenergo». Also, the calculation of the magnetic flux density was made for the perspective loads of the transmission line. Estimation of the value of the magnetic flux density was made for the zone of one-story and multi-story buildings near power lines. The option of uniform loading of two power transmission lines was considered and the case where the entire load is transferred along one circuit was also considered. Results. In this work, the distribution of magnetic flux density at a height of 1.8 m in the direction perpendicular to the power transmission line for the sections built on supports of the U110-2 and PB110-2 types was obtained. The graphs show that the magnitude of the magnetic flux density at the boundary of the protection zone of the transmission line will be exceed twice the standard value 0.5 μT for the existing and perspective loads. This problem is relevant in the case of transmission lines in single-circuit mode. The graphs of distribution of magnetic flux density on the facade of an apartment building, located at a distance of 20 m from the axis of symmetry of the transmission line, were constructed. As a result, it is shown that at a height of 11 m from the earth's surface, magnetic flux density will be 1.5-2 μT. Practical value. It is determined that safe habitation along the route of two-circuit power line with the voltage 110 kV «ChTPP-Chernihiv-330» can be achieved when facades of an apartment building are removed from the axis of symmetry of the transmission line at a distance of 33 m for high-rise buildings and at a distance of 27 m for one-storey buildings. Recommendations for reducing the magnetic flux density of this power transmission line have been developed.

Torque Characterization of T-shaped Magnetorheological Brake Featuring Serpentine Magnetic Flux

Recently, T-shaped Magnetorheological Brake (MRB) usually utilize more than one wire coil electromagnetic to maximize magnetic flux reaching all Magnetorheological Fluid (MRF) gaps. This research was focused on the usage of a single wire coil on MRB with uniformly magnetic flux distribution. To achieve the goal, the serpentine magnetic flux profile was adopted to maximize all MRF gaps that only use a single coil. Firstly, the magnetic circuit which implementing serpentine magnetic flux was design in a two-dimensional model. It was then followed by magnetostatic simulation using Finite Element Method Magnetics (FEMM) to determine the amount of magnetic flux density. The data were then employed to calculate the braking torque. After having the final dimension and completing the workshop drawing, an MRB prototype was fabricated. Thus, the prototype was characterized using the braking test apparatus to figure out the torque profiles. Moreover, the experimental results were compared to the simulation results. This process justified the validity of the proposed mathematical model of the T-shaped MRB. It was investigated that the maximum braking torque from simulations and experimental works were 1.51 Nm and 1.91 Nm at 1 A, respectively. Overall the between differences of simulations and experimental works were about 10%. It is therefore, the mathematical model can be used for further application in the actuator control system.

Dış Kafesinde Kırık Bar Arızası Olan Çift Kafesli Asenkron Motorun Performans Analizi

Induction motors are one of the most commonly used motor in the industry. For this reason, a fault (electrical or mechanical) inside or outside of the motor can cause the motor to go out of power and even cause the production losses inside the factory. Although there are many studies on single-cage induction motor failures in the literature, double cage motor failures are not a frequent subject of study. Therefore, in this study, it was investigated how the outer cage slot faults in a double cage induction motor affect the motor performance. Analyses were performed using Finite Element Method (FEM). 1, 2, 3 and 4 outer cage broken bars in the rotor slot were investigated. Rotor currents, magnetic vector potential values, magnetic flux distributions, current densities, radial forces and torque-speed graphs of the motor models were obtained and compared for both healthy and failure motors. The results show that as the number of broken bar in the rotor increased, a significant reduction was observed in all three torque (starting, maximum and nominal) values. It has been observed that the starting torque decreased by 13.77% for the 4 broken outer cage rotor bars motor according to the healthy motor.

Analysis of a New Partitioned-Primary Flux-Reversal Hybrid-Excited Linear Motor

A new partitioned-primary flux-reversal hybrid-excited linear motor is proposed and investigated in this article, which features an asymmetrical double-sided primary structure. The novelty of this motor lies in the adoption of a partitioned-primary structure by moving the field excitation winding to an additional primary, thus it benefits from improved space utilization ratio since both armature and field windings can be separately mounted. First, the topology, feasible slot/pole combinations, and operating principles of the proposed machine are introduced. The magnetic flux density distributions in two air-gap regions are comparatively studied from the perspective of magnetic gearing effect. Then, global optimization of the proposed motor with different slot/pole combinations is performed to maximize both the output thrust force and flux-adjusting range based on 2-D finite-element analysis (FEA). In addition, the electromagnetic performance of the motors including flux-adjusting capability, thrust force, detent force, and force ripple with different slot/pole combinations are comparatively investigated. Finally, a 6-slot/7-pole prototype is manufactured and tested to verify the FEA and calculations. It is shown that the proposed motor, benefiting from a partitioned-primary topology, exhibits very good flux-adjusting capability and overloading capacity. Thus, it has good prospect in applications that require flexible speed control.

On the temperature analysis of magnetic abrasive finishing of aluminum 6060 using finite element method

Magnetic abrasive finishing (MAF) process is the superfinishing process used to enhance the surface quality of metallic and nonmetallic materials such as alloys, composites and ceramics etc. This process erodes material from a workpiece surface in the form of micro-chips with the help of flexible magnetic abrasive brush (FMAB) in working gap with the presence of a magnetic field. This process generates heat due to rubbing action that produced by FMAB between the interface surface of FMAB-workpiece. Thermal stability of the finishing surface of workpiece is vital during finishing of MAF process because it affects the surface texture and surface integrity. Measuring surface temperature at the interface of FMAB-workpiece during finishing is very tough in MAF process. In the present study, finite element analysis (FEA) is used for simulation of magnetic flux distribution and surface temperature distribution of interface surface of aluminum 6060 workpiece-FMAB of MAF process. FEA predicts the magnetic flux density in between 0.429 T and 1.263 T for current between 3.0 A and 6.0 A) and surface temperature distribution in the range of 27.33 ºC–34.92 ºC for different processing conditions of process parameters. FEA simulated results are validated by comparing with experimental finding and estimated error between simulated and experimental results are in the range of 4.94%–10.26%. Finally, the present developed FEA is employed on the mild steel workpiece to cross-examine the simulated behavior of magnetic flux density and surface temperature at the finished interface surface of mild steel.

Novel design of hydrodynamic–magnetic compound support for cylinder block–valve plate in axial piston pump

An innovative hydrodynamic–magnetic compound support (HMCS) is proposed for the cylinder block–valve plate pair of the axial piston pump. Compared with the traditional design method, the magnetic structure provides a fixed magnetic torque to balance the residual torque, which causes eccentric wear on the valve plate and keeps the compression coefficient constant. First, the structure and principle of the HMCS are introduced, the magnetic model is established together with relative hydraulic models, and the influence of the permanent magnet length on the magnetic force is obtained. By studying the magnetic moment, the optimal structure of the magnetic pole is determined. Next, the 3D finite element method is used to simulate the magnetic forces under different pole gaps. After that, a reasonable magnetic pole gap and flux density distribution are determined. To obtain the influence mechanism of the HMCS on the cylinder block, the changing law of the track radii of hydraulic forces and average difference in the track radii are analyzed. Finally, the trend of the resultant torque of the cylinder block under multiple working conditions is analyzed. The results show that the HMCS can balance the residual torque acting on the valve plate, which is beneficial in preventing the occurrence of eccentric wear of the valve plate.

Simulation Analysis of Vibration and Noise Characteristics of High Voltage Shunt Reactor Based on Multi-physical Field Coupling

In order to study the vibration characteristics of the high-voltage shunt reactor, a finite element model of the single-phase reactor was established based on the analysis of the vibration mechanism of the reactor body, by using COMSOL multi-physical field coupling simulation software. The magnetic flux density distribution of reactor core, windings, stress distribution and vibration displacement of iron core were analysed by simulation. The sound pressure distribution of the iron core was analysed based on the pressure sound field model. The results indicate that the magnetostrictive effect of the iron core reactor, the electromagnetic attraction between the iron core cakes and the ampere force on the winding are the main factors for its vibration. In addition, the reactor vibration to be mainly concentrated at the core air gap. The results obtained by multi-physics simulation are basically consistent with the measured data, which verifies the effectiveness of the simulation method. The conclusions can provide theoretical basis for the analysis and monitoring of reactor vibration and noise.

Novel design of a coreless axial‐flux permanent‐magnet generator with three‐layer winding coil for small wind turbines

This study presents a novel design of the three-layer winding coil sets of a coreless axial-flux permanent-magnet generator applied to small wind turbines. The proposed generator design consists of two rotors and an integrated stator with flattened winding coil sets of three-phase three layers connected using a wye configuration. An analytical model of the inductance and resistance of the coil set is described to analyse the influence of the coil shape variation due to winding imperfection. The air gap magnetic flux distribution analysis shows the advantage of the integrated flatten coil sets compared with a typical stack up three layers stator. An experimental design is conducted for the parameter design of geometric variables to optimise the output power of the proposed axial-flux permanent-magnet design. A prototype generator is then constructed to compare with a benchmark generator that has a rated output power of 300 W at 800 rpm. The proposed design outperforms the benchmark generator by 26.5% in terms of generated power at a typical driving rotation velocity of 500 rpm for a small wind turbine, and demonstrates a superior performance at a lower driving speed range, which is particularly important in a small wind turbine application.