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This paper proposes an innovated approach to model an electromagnetic force which is an ideal control force without plume and light pollution for optical imaging system. The main scope is modeling the 3-axis coupled electromagnetic force using dual quaternion for its advantages in describing spiral motion with translation and rotation motion simultaneously. The derivation procedure relies on a far field model of the electromagnetic force, and also, the force is re-formulized. Final equations show the dual quaternion dynamics can express the relative motion caused by the electromagnetic force acting on the position and attitude integrally. A new mission concept of diffraction imaging system in GEO is discussed as application scenario of the new dynamics model. Two cases with different mass were simulated to verify the new model, and the results display the electromagnetic force is significant for a small mass spacecraft in GEO. • The electromagnetic force is expressed by dual quaternion. • A novel dynamics model is derived to describe GEO electromagnetic collocated satellite. • The motion of diffraction imaging system is modelled using dual quaternion. [ABSTRACT FROM AUTHOR]

This paper presents a detailed analysis of the electromagnetic force and vibration behavior of an axial flux permanent magnet synchronous machine (AFPMSM). First, the AFPMSM configuration and two types of dual three-phase winding are introduced. Subsequently, the electromagnetic force of the double-stator inner-rotor AFPMSM is investigated. Its spatial and temporal characteristics are derived analytically and validated through two-dimensional Fourier decomposition. A multiphysics model is established to calculate the vibration of the AFPMSM, which includes control, electromagnetic, structural, and vibration model. The accuracy of this multiphysics model is verified by the modal and vibration test. Furthermore, the vibration of the AFPMSM with three winding types considering current harmonics are calculated based on the multiphysics model. The vibration performance of the AFPMSM with three different winding types are compared and the mechanism of vibration is discussed. It was concluded that the novel detached winding could mitigate the vibration of dual three-phase AFPMSMs. Finally, the vibration test is carried out to validate the theoretical analysis and the experimental results agree well-with the simulation results. This paper provides an effective method for double-stator permanent magnet synchronous machine (PMSMs) to reduce vibration. [ABSTRACT FROM AUTHOR]

Copyright of Journal of South China University of Technology (Natural Science Edition) is the property of South China University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The nature and behavior of forces acting on the arc are important factors for the design of furnaces, management and automation of their work. The effect of electromagnetic arc blowing has a negative effect on the technical and economic parameters of the furnace, since the arc is removed from the recess in the metal and slag, while its radiation on the walls and arch increases, and the effective power absorbed by the metal decreases. To solve this problem and a number of other problems, it is necessary to know the dynamic behavior of the arc, which is largely determined by the instantaneous values ​​and directions of individual forces and the resulting force. The electromagnetic force behavior acting on the arc column from currents flowing through liquid metal and currents flowing through other parallel arcs and graphitized electrodes in a three-phase AC arc furnace is considered. It is assumed that arcs burn perpendicular to the metal bath's surface (their axes coincide with the electrode axes) and the effective value of the linear currents in different phases is the same. A mathematical model for calculating the instantaneous values ​​and directions of the main electromagnetic forces acting on arcs in a three-phase arc furnace is proposed. This model reveals the dynamic behavior nature of arcs. A computer simulation has been created to visualize the behavior of the hodograph of forces acting on an arc. Thus, the resulting force is an even harmonic function with a frequency two times higher than the industrial current frequency. The hodographs of the forces acting on the arc from the side of the currents, flowing through the melt, and the resulting force are ellipses lying in the horizontal plane. It is established that the resulting force deflecting the arc is an even harmonic function with a frequency two times higher than industrial current frequency. Its hodograph is an ellipse lying in the horizontal plane, the semi-major axis of which makes an angle of 20°–80° with a line connecting the decay center of the electrodes and the electrode axis. [ABSTRACT FROM AUTHOR]

ComforTone is a noise reduction technology used in magnetic resonance imaging (MRI) systems; it suppresses acoustic noise by modifying pulse sequences, which appropriately changes the magnetic field gradient waveforms. Although ComforTone can be used to solve the acoustic noise problems that affect patients who are exposed to acoustic noise from MRI, to the best of our knowledge, the associated technical details have not been published and its effects on acoustic noise reduction remain unclear. To evaluate the efficacy of acoustic noise reduction and the impact of acoustic noise reduction technology involving magnetic field gradient waveform control on image quality. The study included 18 healthy volunteers (11 males and 7 females; median age, 34 years; age range, 24–51 years). 1.5 T Philips Ingenia using a SENSE head–spine coil. The sound pressure level (SPL) and 1/3 octave spectra of MRI acoustic noise with the human head positioned in the iso-center of the MRI system were measured for five different pulse sequences used in clinical MRI. This subjective evaluation of noise included 18 healthy volunteers. The degree of discomfort experienced by the subjects was measured using a visual analog scale. The image quality was assessed objectively and subjectively. For objective assessment, signal-to-noise ratio (SNR) and contrast-to -noise ratio (CNR) of diffusion-weighted images were measured; for subjective assessment, visual evaluation was performed by two radiologists. Data were analyzed using Welch's t -test, and a p value <0.05 defined significance. ComforTone could recognize a decrease in sound pressure, and the sound pressure of the acute high-frequency portion of the auditory characteristics was reduced. As reported by the subjects, discomfort caused by the sound pressure was significantly alleviated with ComforTone (p < 0.01). The sound pressure reduction in the high-frequency region with high audibility characteristics was recognized by ComforTone. The visual evaluation of the image quality of the diffusion-weighted images revealed that although there was no difference between SNR and CNR, the image quality was reduced by distortion artifacts. ComforTone reduced the SPL in the frequency range where auditory characteristics were sensitive, suggesting that ComforTone was useful for auditory protection and alleviation of discomfort in patients undergoing MRI. However, because magnetic field gradient waveform control is involved, such noise-reducing techniques should be used by considering their possible influence on the image quality. [ABSTRACT FROM AUTHOR]

The arc ablation properties of Ti 3 SiC 2 material are systematically studied. The breakdown current increases with increasing load voltage from 3 kV to 10 kV. The results from an energy dispersive spectroscope, the Raman spectra, and X-ray photoelectron spectroscopy show that Ti 3 SiC 2 is decomposed and oxidized to TiO 2 and SiO 2 by electric arcs. The breakdown strength first decreases, and then increases with breakdown times, arising from more and more oxides formed on the Ti 3 SiC 2 surface. By means of field-emission scanning electron microscopy and a three-dimensional laser scanning confocal microscope, cracks, pores and pits are observed on the ablated Ti 3 SiC 2 surface. The characteristics of element distributions are attributed to gravity, plasma forces and to the electromagnetic force, which is affected by the value of breakdown current. [ABSTRACT FROM AUTHOR]

The solenoid is one of the key components of a fuel injection system. It plays an important role in controlling the valve opening time of an injector, as well as in deciding engine combustion performance. The purpose of this study is to research and develop a high-performance solenoid that can be used for natural gas injector. Operation of the solenoid is described based on mathematical models. The solenoid is modeled and simulated using Maxwell and Simplorer software, in which its simulation parameters are based on the specifications of a real solenoid injector. In addition, effects of key parameters, such as thickness of cut-off of sleeve, cross-sectional shape of the coil and the relative position between the coil and plunger on the operating characteristics of the solenoid injector are investigated. The various thickness of cut-off of sleeve, coil's cross-sectional shape and relative position with respect to the plunger are found to have a significant influence on the electromagnetic force of the solenoid injector. In other words, a large electromagnetic force along with an optimized response time can be easily obtained by changing the coil's cross-sectional shape and relative position to the plunger. [ABSTRACT FROM AUTHOR]

In conventional electromagnetic tube expansion (EMTE), the wall thickness of the tube decreases significantly because the electromagnetic force is mainly in the radial direction. To solve this problem, this paper proposes a new method named electromagnetic tube expansion with axial compression (EMTEAC). Besides the driving coil, we introduce a coil at each end of the tube to generate axial electromagnetic force on the tube. We use the finite element method to analyze the distribution of the magnetic flux density and the electromagnetic force generated by the three coils in series. The simulation results show that the axial electromagnetic force generated by EMTEAC is about 7 times that generated by conventional electromagnetic tube expansion, which enhances material flow when the tube is expanding. The effectiveness of the method is verified by a series of experiments. The experimental results show that EMTEAC reduces the decrease in wall thickness from 27 to 19%. [ABSTRACT FROM AUTHOR]

• Composition of the divertor assembly 1 in ASDEX Upgrade. • Measurement of displacements of the divertor assemblies over an experimental campaign. • Results of full 3D electromagnetic simulations regarding forces and torques on the assembly. • Measurement of friction coefficient between stainless steel and silicon nitride. • Results of transient structural analysis regarding displacements. The divertor serves as the main power exhaust of tokamaks. Hence the target tiles in the divertor must be carefully aligned to prevent leading edges which would result in higher power deposition and subsequent melting. The outer strike line in the lower divertor of ASDEX Upgrade is located on the assembly 1, which consists of the target tiles, the cooling plates and the support structure. Since the transition to the tungsten optimized divertor design of the divertor in 2014, it has been observed that the assembly 1 and the underlying frame are displaced over the course of an experimental campaign. The attachment of the assembly has been modified several times to prevent this displacement. However, a complete suppression of the movement was not achieved. The reason for the displacement is suspected to be due to induced currents and the resulting jxB forces during disruptions. This was investigated using a full 3D transient model of the ASDEX Upgrade coil system and a model of the assembly 1 with frame and vacuum vessel. The different assembly modifications and several current quench times were simulated, resulting in forces of up to 5.5 kN and torques up to 6.3 kN m. These forces were then used in a 3D transient structural model of the assembly to investigate the resulting displacements. It was found that displacements occur in all cases but they vary between 0.25 mm and 0.75 mm. [ABSTRACT FROM AUTHOR]

The solenoid valve used on the hydraulic roof support in the coal mine is an intrinsically safe solenoid. It requires the solenoid valve to achieve large electromagnetic force at low current. The load can not be driven if the current is too low, while a large temperature rise and energy loss would occur in the form of heat if the current is too high. In order to solve this contradictory problem, the load force of the solenoid valve was analyzed first. Then the ANSYS models of the solenoid were established to carry out the simulation jobs. The effects of the three parameters, the sleeve length, the seat length and the boss height, on the electromagnetic forces and magnetic fields were researched so as to optimize the three parameters. The static and dynamic characteristics of the optimized solenoid valve were also studied. An experimental setup was established to verify the simulation results finally. Results show that the simulation values are in good agreement with the experimental values. The peak value of starting current and holding current is small and the solenoid responses rapidly. This study proves the accuracy and reliability of the simulation models and the methods. It also provides valuable references for the design and optimization of the intrinsically safe solenoid valve. [ABSTRACT FROM AUTHOR]

• A novel friction damper is presented for seismic response control of buildings. • The damper force can be controlled by an electromagnetic mechanism. • A semi-active controller is proposed to smooth the hysteretic behavior of the damper. • A current driver is designed to modify the control current, reducing the time delay. • Numerical results demonstrate the energy dissipation capability of the damper. This paper studies the use of a smart/semi-active electromagnetic friction damper (SEMFD) for the control of seismic response of multi-story base-isolated buildings. The SEMFD consists of a ferromagnetic plate and two similar arrays of thick rectangular ferromagnetic-core coils (FCs) connected in series. The FCs are attached to the two sides of the ferromagnetic plate through two non-magnetic friction pads. The force in the damper is developed because of the friction between the friction pads and the ferromagnetic plate when the FCs moves relative to ferromagnetic plate. The normal force between the friction pad and the ferromagnetic plate is caused by the attractive magnetic interactions between the FCs arrays and the ferromagnetic plate. The magnitude of this force is controlled by a proposed semi-active controller that is capable of varying the current flowing through the FCs in such a way that it is able to avoid stick-slip motion by smoothing the nonlinear hysteretic behavior of the SEMFD. The capability of the SEMFD and the proposed semi-active controller to control the seismic response of base-isolated buildings is demonstrated by implementing them into the dynamic model of a six-story base-isolated building supported on lead-rubber bearings (LRBs). The numerical results show that the SEMFD and its semi-active controller are capable of limiting the displacement of the base floor without noticeably increasing the inter-story drifts and absolute accelerations of the floors. It is demonstrated that the parallel actions of the LRBs and the SEMFD in the base floor create a smart base isolation system that is capable of fully protecting a multi-story building from ground motions with intensities at a level as that of the ASCE 7–10 Maximum Considered Earthquake (MCE). [ABSTRACT FROM AUTHOR]

The optimal trigger position of the induction coil launcher is difficult to determine, which can affect the design efficiency of the induction coil launcher. Accordingly, the characteristics of the induction current and the reverse point of electromagnetic force for an armature are analyzed based on the electromagnetic force equation and the electromagnetic induction law. Then, the relative position of the electromagnetic force and the discharge current curves are analyzed, and the intrinsic characteristic of the optimal trigger position is obtained. After that, the determination method for the optimal trigger position and the calculation equation are given based on the reverse point of the electromagnetic force. At last, taking the armature whose initial velocity is 200 m/s, for instance, the validity of the determination method for the optimal trigger position is verified by calculation instance and numerical simulations. Meanwhile, the determination method is also verified by experimental results. One can draw the conclusion that the essence of the optimal trigger position is to make the peak zone of the discharge current located just in the acceleration zone of the electromagnetic force, which can improve the launching efficiency of the coil launcher. Furthermore, the optimal trigger position of the driving coil can be determined rapidly when the curve of the electromagnetic force for the armature at a certain initial velocity is obtained. Thus, it is unnecessary to obtain the optimal trigger position by a large number of simulations and experiments, which can improve the efficiency of the simulation and the experiment for the coil launcher. [ABSTRACT FROM AUTHOR]

Copyright of Rare Metal Materials & Engineering is the property of Northwest Institute for Nonferrous Metal Research and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The fast mechanical switch is one of the key devices for high-voltage direct-current circuit breakers (DCCB), and the mechanical contacts separation time determines the operating time of hybrid mechanical circuit breakers. With the increasing of the voltage and power levels of DC system, numerous technical challenges begin to emerge. For high-voltage system, the new research and the series arrangements of very fast mechanical switches include designing new drive unit to satisfy larger load mass and longer travel stroke. Aimed to reducing the peak value of electric force, a novel drive unit by using modular double capacitors has been proposed here. Based on the equivalent circuit method (ECM), the mathematical model of Thomson coil (TC) actuator which is the drive unit in fast mechanical switch is established. First, the time sequence of capacitance discharge is studied. Then, the electromagnetic force can be divided into five types in different time sequences, and the characteristics of the electromagnetic force are analysed. Finally, it is concluded that using a combination electromagnetic force with three approximate peaks can reduce the impact of the metal plate, which improve the reliability of the fast switch. [ABSTRACT FROM AUTHOR]

Synchronous induction coilgun (SICG) has attracted more and more attention due to its advantages of simple manufacturing and no physical contact between armature and barrel. The armature, as an important component of SICG, will directly affect the launch speed and energy conversion efficiency. According to the distribution characteristics of eddy current and electromagnetic force, a new structural armature is proposed in this paper. The proposed inner conical armature is characterized by the maximum thickness at the tail end and the minimum thickness at the front end, with a gradual decrease in the thickness along the axial direction. The simulation results reveal that the proposed armature not only increases the mutual inductance between the armature and the drive coil but also enhances the electromagnetic force and weakens the armature capture effect. The experimental results verify that, compared with a traditional armature weighing 56.5 g, the new structure armature weighing 58.0 g enables higher muzzle velocities using the same set of pulsed power supply and drive coil, providing higher efficiency. [ABSTRACT FROM AUTHOR]

The effect of harmonic magnetic field (HMF), pulse magnetic field (PMF), differential phase harmonic magnetic field (DHMF), and differential phase pulse magnetic field (DPMF) on liquid and mushy zones of crystallizing metal was investigated by numerical simulation referring to electromagnetic DC (direct chill) casting process. Firstly, the experimental pulse current for electromagnetic casting was obtained by a digital oscilloscope. The physical and finite element models of Φ300-mm cylindrical crystallization for the electromagnetic field simulation were established. Then, the distribution of magnetic flux density (B) and electromagnetic forces (FMAG) generated by the four types of magnetic fields were obtained in a period (T). Actions of HMF, PMF, DHMF, and DPMF on molten melt were discussed based on radial and axial electromagnetic forces. Finally, the effects of electromagnetic parameters (current intensity, frequency, and duty cycle) on electromagnetic forces under PMF and DPMF were studied. The effect of electromagnetic forces on metal flow has been discussed. The results indicate that compared with harmonic current, the pulse current can generate a stronger magnetic field with the same conditions. Single-coil magnetic field can easily cause the molten metal radial vibration. The differential phase magnetic field can not only cause radial vibration but also produce axial convection, while the vibration effect is weaker. The electromagnetic forces increase with the increase of current intensity and duty cycle under PMF and DPMF. Moreover, the electromagnetic force has low sensitivity to frequency under DPMF. [ABSTRACT FROM AUTHOR]

This paper proposes a new cableless transportation system that associates a magnetic actuator with the piping system in which it travels. To achieve high-speed transport within the pipe, the proposed actuator must show excellent movement characteristics. An aluminum pipe was cut in half longitudinally, and an alternating current was passed through the cut piping. The proposed cableless actuator powered by an electric current supplied by an electric brush was demonstrated to be capable of high-speed movement in a curved pipe. A scheme of attaching a cargo container to a nodal point of the actuator using a flexible rod was also proposed. The experimental results show that the actuator can be driven through the pipe even when the curved pipe is nearly U-shaped. Furthermore, the cableless actuator transporting a cargo mass of 30 g can be driven at a speed of 87.9 cm/s in a curved aluminum pipe with a curvature angle of 22.5°. The method established in this paper is considered to be applicable to the high-speed transport of lightweight reagents, bacteria, and microfluidic chips. [ABSTRACT FROM AUTHOR]

The paper presents the electromagnetic method for control the solidification of the pure Al99.99%. For experiments, the treatments using (1) the flow of an alternating current of 500 A and (2) the simultaneous action of a DC magnetic field (0.035 or 0.07 T) and an alternating current of 500 A were applied. The as-cast aluminum structure obtained under only an alternating current action was formed with the coarse crystallites being the shape of a plate with a thickness of 5 mm and a transverse dimension from 3 to 30 mm. The simultaneous action of a DC magnetic field and an alternating current resulted in grain refinement. Under a magnetic field of 0.035 T, the surface layer of the 0.8 mm thickness made up of the equiaxed grains with a size from 300 to 400 µm, and the target's central zone formed with crystallites being of a size from 500 µm to 1.2 mm were observed. Under magnetic field of 0.07 T, the structure was formed with the fine equiaxed grains of 20-80 µm. The theoretical analysis was carried out to identify the processes involved in control of the solidification process of Al99.99 under the electromagnetic method. [ABSTRACT FROM AUTHOR]

In this paper, a novel electromagnetic blank holding system (EBHS) for a conventional drawing process is proposed. The system is created to substitute mechanical or hydraulic blank holder force (BHF) with mutually attractive electromagnetic force (EMF). The winding type of electromagnetic coils is determined as a single-coil through numerical simulation. For avoiding the fluctuation of the magnitude of BHF, direct current is chosen to generate BHF. Corresponding magnetic circuit model of the electromagnetic blank holding device (EBHD) has been established to find the mathematical relationship between EMF and input voltage. Besides, several groups of EMF testing data are measured to prove the correction of deduced expression. To validate the feasibility of the novel system, corresponding numerical simulation and experiment have been carried out. It is worth to mention that the cylindrical parts created by simulation and experiment at different BHF agree well with each other. Additionally, the thickness reduction rate of drawn part is controlled at a reasonable level with the application of EBHS, which well validates the effectiveness of the EBHS. [ABSTRACT FROM AUTHOR]

The current density and electromagnetic force distribution of the armature directly affect the performance of electromagnetic railgun. In this paper, the electromagnetic thrust, electromagnetic pressure, and current density of the C-shaped armature and H-shaped armature are calculated, respectively, by the finite-element method under different Armature–rail contact modes (different contact areas and positions), and the calculation results under different contact modes are compared. The calculation results show that the maximum current density of the armature head is independent of the contact mode, and the position of the maximum current density of the armature tail moves with the advance of the contact position. The separation of the rear part of the armature tail and rail will result in a sharp decrease in electromagnetic pressure, so the armature tail and rail need to maintain contact to ensure a stable current transfer. At the same time, only the head and the rear part of the armature tail are in contact with the rail, the electrical performance of the armature in complete contact with the rail can be achieved. Therefore, the armature adopts the structural design scheme of interference at both ends, which is more conducive to electromagnetic emission and greatly reduces the difficulty of the armature structural design. [ABSTRACT FROM AUTHOR]

Abstract The uniform droplets of gallium based eutectic alloys have been widely used to develop the electronic packaging. Therefore, a droplet generator has been designed for formation uniform droplets in a controlled way, which entails important technological advantages over existing techniques. The results indicated that, the uniform droplets could be produced by continuous-ink-printing and drop-on-demand based on the mode of pulse electromagnetic force; compared with the droplets generator using one elastic diaphragm for producing water droplets by continuous-ink-printing, the metal droplets could be produced without using elastic diaphragm. Therefore, this work provides a useful parameter-selection approach for droplets production. Highlights • The droplets were produced by DOD and CIJ based on the mode of electromagnetic force. • The metal droplets were produced by CIJ without using elastic diaphragm. • The gas pressure and frequency had a important effect on droplets formation by CIJ. [ABSTRACT FROM AUTHOR]

Copyright of Technical Electrodynamics / Tekhnichna Elektrodynamika is the property of National Academy of Sciences of Ukraine, Institute of Electrodynamics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We review the geometric evolution of a linearly polarized light wave coupling into an optical fiber and the rotation of the polarization plane in the three dimensional semi-Riemannian manifold. The optical fiber is assumed to be a one-dimensional object imbedded in a 3D semi-Riemannian manifold along the paper. Thus, in the 3D semi-Riemannian manifold, we demonstrate that the evolution of a linearly polarized light wave is associated with the Berry phase or more commonly known as the geometric phase. The ordinary condition for parallel transportation is defined by the Fermi-Walker parallelism law. We define other Fermi-Walker parallel transportation laws and connect them with the famous Rytov parallel transportation law for an electric field , which is considered as the direction of the state of the linearly polarized light wave in the optical fiber in the 3D semi-Riemannian manifold. Later, we define a special class of magnetic curves called by Bishop electromagnetic curves (–curves), which are generated by the electric field along the linearly polarized monochromatic light wave propagating in the optical fiber. In this way, not only we define a special class of linearly polarized point-particles corresponding to –curves of the electromagnetic field along with the optical fiber in the 3D semi-Riemannian manifold, but we also calculate, both numerically and analytically, the electromagnetic force, Poynting vector, energy-exchanges rate, optical angular and linear momentum, and optical magnetic-torque experienced by the linearly polarizable point-particles along with the optical fiber in the 3D semi-Riemannian manifold. [ABSTRACT FROM AUTHOR]

The Active Magnetic Bearing (AMB) is used in the main helium blower in the High Temperature Reactor-Pebble-bed Modules (HTR-PM) which is being constructed in Shandong province, China. The axial AMB is very large and works under extreme conditions. The calculation deviation of the electromagnetic force of the axial AMB was studied experimentally. Through measuring B-H curve of the material in large range of magnetic field intensity, considering flux leakage in calculation, and considering residual magnetism and the change of the gas gap in measurement, the calculation deviation reduces to 10%, with most values less than 5%. The material selection method of the axial AMB working under extreme conditions was studied experimentally. Through measuring the electromagnetic force when the stator and the thrust disc are made of different materials, it's found that the force mostly depends on the stator. Combined with the analysis of the stress distribution of the stator and the thrust disc under working condition, the dual material selection method is proposed. That is, the stator material should have good magnetic properties and its mechanical properties are not very important, however, the thrust disc material should have good mechanical properties, and its magnetic properties are not very important. [ABSTRACT FROM AUTHOR]

In this paper, the control of turbulent channel flow by space-dependent electromagnetic force and the mechanism of drag reduction are investigated with the direct numerical simulation (DNS) methods for different Reynolds numbers. A formulation is derived to express the relation between the drag and the Reynolds shear stress. With the application of optimal electromagnetic force, the in-depth relations among characteristic structures in the flow field, mean Reynolds shear stress, and the effect of drag reduction for different Reynolds numbers are discussed. The results indicate that the maximum drag reductions can be obtained with an optimal combination of parameters for each case of different Reynolds numbers. The regular quasi-streamwise vortex structures, which appear in the flow field, have the same period with that of the electromagnetic force. These structures suppress the random velocity fluctuations, which leads to the absolute value of mean Reynolds shear stress decreasing and the distribution of that moving away from the wall. Moreover, the wave number of optimal electromagnetic force increases, and the scale of the regular quasi-streamwise vortex structures decreases as the Reynolds number increases. Therefore, the rate of drag reduction decreases with the increase in the Reynolds number since the scale of the regular quasi-streamwise vortex structures decreases. [ABSTRACT FROM AUTHOR]

The arc welding has been used in various welding methods because it is inexpensive and high in strength after welding. However, it is a problem that accidents such as collapse of the bridge occur because of the welding defects. The welding of low cost and high productivity is required without the welding defects. The pulsed TIG welding is inexpensive and capable of high‐quality welding. The electromagnetic force contributing to penetration changes because the transient response of arc temperature and iron vapor generated from anode occurs. However, the analysis of pulsed TIG welding with metal vapor has been elucidated only metal vapor concentration near anode with transient phenomenon and heat flux. Thus, the theoretical elucidation of penetration depth with control factor has not been researched. In this paper, the contribution of metal vapor mass at the periphery part of pulsed arc to the electromagnetic force in the weld pool is elucidated. As a result, the iron vapor mass at periphery part decreased with increasing the frequency. The iron vapor was stagnated at axial center within one cycle. The electromagnetic force to the penetration depth direction in weld pool increased at axial center. Therefore, the metal vapor mass at periphery part plays an important role for the electromagnetic force increment at axial center. [ABSTRACT FROM AUTHOR]

The power transformer is the major electrical equipment in the power system and should be able to resist the damage that caused by the abnormal conditions, like the influence of the inrush current and the electromagnetic force. However, the residual flux, which is the most common influence factor of the inrush, can result in large current magnitude. This paper is to analyse inrush current and the electromagnetic force that as the result of inrush current for the impact of the safe operation of the large power transformer. The research of the inrush current under various factors has practical significance. In order to study the electromechanical forces influenced by the residual flux, the inrush current was analysed by Jiles-Atherton (J-A) hysteresis model. During transient switching process, electromechanical forces under the different residual fluxes were calculated, using the finite-element method coupled to the external circuit. The studies presented in this paper would be used in the design of the power transformer and power network protection. [ABSTRACT FROM AUTHOR]

Abstract The flow of a weakly conductive fluid (i.e. seawater) can be controlled by electromagnetic forces, which holds promising applications in the drag reduction. In this paper, a fully developed weakly conductive turbulent flow controlled by a space-dependent electromagnetic force is investigated with direct numerical simulation (DNS) methods for different Reynolds numbers. With the application of electromagnetic force, the in-depth relations among characteristic structures in the flow field, mean Reynolds shear stress and the effect of drag reduction for different Reynolds numbers are discussed. The numerical results indicate that the well-organized quasi-streamwise vortex structures induced by electromagnetic force are generated with the optimal values of the amplitude and the wave number. The Reynolds shear stress is suppressed and the maximum of drag reduction is obtained with the effect of these structures. However, with the increase of Reynolds number, the wave number of optimal electromagnetic force increases, resulting in the decrease of scale of the well-organized quasi-streamwise vortex structures, which leads to the decrease of the height of these vortex structures. Therefore, the maximum rate of drag reduction decreases due to the decrease of the effective depth with the increase of Reynolds number. [ABSTRACT FROM AUTHOR]

Accurate calculation of electromagnetic parameters in electromagnetic forming (EMF) process is crucial for predicting the deformation behavior of metallic workpieces. Previous theoretical and numerical studies for EMF process with a die have assumed that the die near the workpiece is non-conductive. However, the simplified treatment could be invalid for the cases with a conductive die since an eddy current would also be induced in the die under transient magnetic fields, thus resulting in the change of electromagnetic force acting on the workpiece. In this work, a coupled finite element method and circuit simulation approach with an improved circuit model for analyzing the workpiece deformation is presented, in which the mechanical analysis of the workpiece is done using ANSYS, while the circuit analysis is performed using an improved current filament model. Numerical simulations have been carried out for two types of EMF process, revealing the potential effects of an electrically conductive die on the electromagnetic force distribution and workpeice deformation. The coupled modeling method and simulation results could be useful for better understanding EMF process and designing EMF systems. [ABSTRACT FROM AUTHOR]

Interturn fault detection is a challenging issue in power transformer protection. In this paper, interturn faults of distribution transformer are studied and a new online detection method based on vibration analysis is proposed. Transformer electromagnetic forces are analyzed by time stepping finite element (TSFE) modeling of interturn fault. Since the vibration associated with inter-turn faults is caused by electromagnetic forces, axial and radial electromagnetic forces for various interturn faults are studied. Transformer winding vibration under interturn faults is studied through an equivalent mathematical model combined with electromagnetic force analysis. The results show that it is feasible to predict the interturn winding faults of transformer windings with the transformer vibration analysis method. Simulation and experimentation studies are carried out on 20/0.4 kV, 50 kVA distribution transformer. The results confirm the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

An electromagnetic launcher can be used as an accelerator for yarn attached to a ferromagnetic projectile. As a result, yarn endures a specific amount of tension. In addition to the yarn variables and the type of weft insertion system, the parameters of the weft yarn accelerator strongly affect the weft yarn velocity, its tension, and consequently the fabric quality. An applicable model that can represent the relationship between input and output parameters of this weft insertion system is very useful for predicting the strike of the projectile. Therefore, in this research a 3D imitating launching model was developed by the finite element method. A coil electromagnetic launcher was employed. An experimental methodology using an image-processing technique was also utilized to measure the projectile velocity. Numerical results were compared with experimental results to verify the numerical procedure. A validated model can be a reliable tool to investigate the effects of many process parameters on the strike of the projectile and to optimize them. Therefore, the system parameters can be scientifically defined by this model to insert a weft yarn. [ABSTRACT FROM AUTHOR]

Aiming at the fail to open problem of the solenoid operated pilot valve of the MSIV in TNPS,the spring force of the pilot valve,the electromagnetic force of the electromagnetic actuator and other factors were researched. The relationship between the electromagnetic force and the working air gap of the electromagnetic actuator was obtained through the static characteristics of direct-acting electromagnet test,and some improvement work performance impact tests were done,combined with the mechanical stroke of the pilot valve and the adjust method of the working air gap of electromagnetic actuator,the temperature rise characteristics and the ambient temperature affect to the performance of the electromagnetic actuator,the temperature rise test and operation test under rated condition were done after the improvement. The results indicate that the opening reliability of the electromagnetic pilot valve can be greatly improved by reducing the air gap of electromagnetic actuator and the operating temperature of electromagnetic actuator,the improved electromagnetic pilot valve has not been unable to open or accidentally shut down after a period of time. [ABSTRACT FROM AUTHOR]

Electromagnetic force due to induced eddy current during plasma disruptions is one of the key design-driving issues for the first wall (FW) in the Tokamak device. In this paper, a method to evaluate the electromagnetic force in the FW is proposed based on inversion of the measured magnetic field. An inversion scheme for reconstruction of eddy current from measured magnetic field is developed based on a newly proposed algorithm that can eliminate the effect of plasma current. To solve this inverse problem, the conjugate gradient (CG) algorithm is adopted in addition with an efficient parameterization strategy of eddy current distribution. To demonstrate the efficiency of the method, a simplified FW plate and plasma current model is considered with the magnetic field simulated with a numerical code of the reduced magnetic vector potential (Ar) formulation. The numerical results show that proper eddy current and electromagnetic force distribution can be predicted even for case of unknown plasma current, which reveals that the proposed method has good potential to be applied to the electromagnetic force evaluation of practical Tokamak problem. [ABSTRACT FROM AUTHOR]

The permanent magnet synchronous motors (PMSMs) with space vector pulsewidth modulation (SVPWM) technique will inevitably introduce sideband current harmonic components around the carrier frequency. The armature reaction field caused by the sideband current interacts with the permanent magnet field, generating sideband electromagnetic force and resulting in high-frequency noise. This paper provides a comparative study of the sideband electromagnetic force in internal and external rotor PMSMs with SVPWM technique. First, the analytical model of the electromagnetic force in internal and external rotor PMSMs is established based on the Maxwell tensor method. The source, spatial order, and frequency of the electromagnetic force is obtained. Then, the spatial and temporal characteristics of the sideband force in internal and external rotor PMSMs with different pole and slot combinations are derived and investigated. The results show that the frequency characteristics of the zeroth order sideband force in internal and external rotor PMSMs introduced by SVPWM are identical. However, the frequency characteristics demonstrate significant differences for the nonzeroth order sideband force. Finally, the theoretical analysis is validated through the finite element and experimental results, respectively. This study is benefit for the source identification and reduction of high-frequency acoustic noise for PMSMs. [ABSTRACT FROM AUTHOR]

• For superconductor REBa 2 Cu 3 O 7-x (REBCO, RE = rare earth) tapes. • A randomly distributed multi-edge crack model was established based on the H -formulation and the J-integral method. • The interaction effect of multiple edge cracks was investigated by the comparison of various edge crack models. • Numerical results indicate that geometrical parameter randomness is essential for the fracture damage of REBCO tapes. It is often necessary to narrow wide tapes through a slitting process in applications of the second-generation high-temperature superconductor REBa 2 Cu 3 O 7-x (REBCO, RE = rare earth) tapes. However, this results in some random length edge cracks appearing on the slit edge and extending at certain angles towards the center of the tape. In this paper, we proposed a randomly distributed multiple-edge crack model to investigate the fracture mechanism of the superconducting tape under electromagnetic force due to high magnetic fields and current density (∼10 T and ∼ 1010A/m2). The electromagnetic body force distributions within the superconducting tape, incorporating multiple edge cracks, are simulated based on the H-formulation. Then a fracture analysis is conducted under the combined loading of tensile and electromagnetic forces, with the numerical calculation of stress intensity factors (SIFs) using the J-integral method. To validate the model's accuracy, we compare the body force distribution caused by an edge crack and the SIFs of edge cracks under uniform tension with existing results. Detailed analyses are undertaken to explore the impacts of electromagnetic body force non-uniformity, interactions between neighboring cracks, and the stochastic nature of geometrical parameters (length, angle, and spacing) on the fracture behavior under an alternating magnetic field. Numerical results indicate that non-uniform electromagnetic body forces arising from defects are a critical factor in crack propagation. Furthermore, the randomness of the geometrical parameters amplifies the interactions between some of the neighboring cracks, causing the tendency of the tape containing random edge cracks to fracture. Therefore, it is advisable to avoid random cracks with substantial length, angle, and spacing during the mechanical slitting process. [ABSTRACT FROM AUTHOR]

The uneven distribution of renewable energy supply and demand promotes the development of high-voltage direct current transmission. As the critical reactive power compensation equipment for high voltage direct current transmission, the synchronous condenser must have a strong overload capability. One of the critical factors limiting the improvement of its overload capacity is the reliability of the end winding, which depends on the magnitude of the force on end windings during dynamic large reactive power output. Therefore, this paper proposes a coupling model of transient electromagnetic force for the high voltage direct current transmission system and the end zone of the synchronous condenser. The transient response of the synchronous condenser under different fault degrees is calculated, analyzed, and verified by experiments. Based on the current response of the synchronous condenser, the transient electromagnetic force on end windings is calculated. The distribution law of the force on end windings of the synchronous condenser under different degrees of dynamic reactive power compensation process is revealed. Further, the regions on end windings with larger force during strong overload are indicated. The optimizing fixation scheme for end windings is proposed according to the distribution features of the force, which can improve the operational reliability of end windings. • Force on end windings under dynamic large reactive power output is important. • Propose transient force coupling model of end winding under large reactive power. • Reveal the law of the force on end winding during dynamic reactive power process. • Indicate the regions with a larger force under large reactive power. • Propose an optimized fixing scheme to enhance the reliability of the end windings. [ABSTRACT FROM AUTHOR]

Vibration and noise reduction are very important in electric vehicle driving motors. In this study, topology optimization of housing was performed to reduce vibration in a specific frequency caused by electromagnetic force generated by a permanent magnet synchronous motor (PMSM). The vibration induced by the electromagnetic force of the motor was calculated using electromagnetic-structural coupled analysis. Then, the magnitude of the acceleration for a specific frequency at which peak occurs in the rectangular and circular shape housing concept design model was reduced by using the topology optimization method. As a result, the rectangular and circular shape housing design reduced 92.9% and 96.0%, respectively. Finally, the vibration was effectively reduced while maintaining the electromagnetic characteristics of the motor, for which topology optimization was conducted while not changing the rotor or stator shape design (electromagnetic design factor) but by changing the motor housing shape design (mechanical and structural design factor).