In this paper, the boundary value problem (BVP) of 3 D transient eddy current field in the end region in the case that the generator is affected by impact load is specified. Besides, ways to implement discrete method...In this paper, the boundary value problem (BVP) of 3 D transient eddy current field in the end region in the case that the generator is affected by impact load is specified. Besides, ways to implement discrete methods in both time domain and space domain during the solution of the problem are investigated. The Crank Nicolson scheme is utilized to attain the iterative format of time differential, after taking factors that can ensure both computation precision and stability into consideration. In this paper, the magnetic distribution in the end region of a turbogenerator in the case that the generator is affected by impact load is specified. As a result, it provides foundation for further study of electromagnetic force and electromagnetic vibration in the end region of the turbogenerator.展开更多
The fracture behavior of superconducting tapes with central and edge oblique cracks subject to electromagnetic forces is investigated. Maxwell's equations and the critical state-Bean model are used to analytically...The fracture behavior of superconducting tapes with central and edge oblique cracks subject to electromagnetic forces is investigated. Maxwell's equations and the critical state-Bean model are used to analytically determine the magnetic flux density and electromagnetic force distributions in superconducting tapes containing central and edge oblique cracks. The distributed dislocation technique(DDT) transforms the mixed boundary value problem into a Cauchy singular integral equation, which is then solved by the Gauss-Chebyshev quadrature method to determine the stress intensity factors(SIFs).The model's accuracy is validated by comparing the calculated electromagnetic force distribution for the edge oblique crack and the SIFs for both crack types with the existing results. The findings indicate that the current and electromagnetic forces are significantly affected by the crack length and oblique angle. Specifically, for central oblique cracks, a smaller oblique angle enhances the risk of crack propagation, and a higher initial magnetization intensity poses greater danger under field cooling(FC) excitation. In contrast, for edge oblique cracks, a larger angle increases the likelihood of tape fractures. This study provides important insights into the fracture behavior and mechanical failure mechanisms of superconducting tapes with oblique cracks.展开更多
A new apparatus was designed to measure the electromagnetic force and a computational study of the traveling magnetic field(TMF)and its application to the Ga-In-Sn melt(with low melting point),then the forces on Al,Mg...A new apparatus was designed to measure the electromagnetic force and a computational study of the traveling magnetic field(TMF)and its application to the Ga-In-Sn melt(with low melting point),then the forces on Al,Mg,and Li melt,were simulated. The result show that the electromagnetic force on the melt increases linearly with the increasing length of the melt in the TMF.The TMF-induced Lorentz force increases with increasing frequency,and then decreases.The maximum value is obtained when the current frequency is 160 Hz,over that frequency the force decreases rapidly.When the iron-core is activated,the force increases when the melt closes to the iron-core.The Lorentz forces have inversely-proportional relationships with the electrical resistivity,the dfx/dρdecreases and the dfy/dρincreases with the increasing electrical resistivity(df/dρis the slope of the Lorentz force profile).展开更多
Because of the different conductivities between the primary phase (low electric conduc tivity) and the metal melt, electromagnetic force scarcely acts on the primary phase. Thus, an electromagnetic repulsive force ap...Because of the different conductivities between the primary phase (low electric conduc tivity) and the metal melt, electromagnetic force scarcely acts on the primary phase. Thus, an electromagnetic repulsive force applied by the metal melt exerts on the pri mary phase when the movement of the melt in the direction of electromagnetic force is limited. As a result, the repulsive force exerts on the primary phase to push them to move in the direction opposite to that of the electromagnetic force when the metal melt with primary phase solidifies under an electromagnetic force field. Based on this, a new method for production of in situ surface composite and gradient material by electromagnetic force is proposed. An in situ primary Si reinforced surface composite of Al-15wt%Si alloy and gradient material of Al-l9wt%Si alloy were produced by this method. The microhardness of the primary Si is HV1320. The reinforced phase size is in the range from 40μm to 100μm. The wear resistance of Al-Si alloy gradient material can be more greatly increased than that of their matrix material.展开更多
The standard k-ε model was adopted to simulate the flow field of molten metal in three aluminum electrolysis cells with different anode risers. The Hartman number, Reynolds number and the turbulent Reynolds number of...The standard k-ε model was adopted to simulate the flow field of molten metal in three aluminum electrolysis cells with different anode risers. The Hartman number, Reynolds number and the turbulent Reynolds number of molten metal were calculated quantitatively. The turbulent Reynolds number is in the order of 103 , and Reynolds number is in the order of 104 if taking the depth of molten metal as the characteristic length. The results show that the molten metal flow is the turbulence of high Reynolds number, the turbulent Reynolds number is more appropriate than Reynolds number to be used to describe the turbulent characteristic of molten metal, and Hartman number displays very well that electromagnetic force inhibits turbulent motion of molten metal.展开更多
Based on the commercial computational fluid dynamics software CFX-4.3, electrolyte flow fields in a 156 kA pre-baked anode aluminum electrolysis cell were investigated in three different cases where the electrolyte me...Based on the commercial computational fluid dynamics software CFX-4.3, electrolyte flow fields in a 156 kA pre-baked anode aluminum electrolysis cell were investigated in three different cases where the electrolyte melt was driven by different kinds of force, i.e. electromagnetic force only, the anode gas drag force only and both of the former two forces. The results show that when electromagnetic force was introduced only, most of the electrolyte moves horizontally; when anode gas drag force was introduced only, the electrolyte flows mainly around each anode with small circulation; when electromagnetic force and anode gas drag force were both introduced together, the structure of the electrolyte flow fields and the velocity of electrolyte are similar to that of the case where only anode gas drag force is used. The electrolyte flow fields are mainly determined by the anode gas drag force.展开更多
The conductor on round core(CORC)cables are fabricated with multilayer high-temperature superconductor tapes,which are helically wound around a circular central former.The large Lorentz force will be generated by the ...The conductor on round core(CORC)cables are fabricated with multilayer high-temperature superconductor tapes,which are helically wound around a circular central former.The large Lorentz force will be generated by the transport current in CORC cables under high magnetic field,which will affect the stress and strain distributions of tapes in the cables and the performance of superconducting tape.This paper establishes a two-dimensional axisymmetric model to analyze the mechanical response of CORC cables subjected to the Lorentz force and analyzes the influence of air gaps on stress and strain distributions inside the cables.The T-A method is used to calculate the distributions of current density,magnetic field and the Lorentz force in CORC cables.The mechanical response of CORC cables is analyzed by applying the Lorentz force as an external load in the mechanical model.The direction of electromagnetic force is analyzed in CORC cables with and without shielding current,and the results show that the shielding current can lead to the concentration of electromagnetic force.The maximum stress and strain occur on both sides of the superconducting tapes in the cables with shielding current.Reducing the size of air gaps can reduce the stress and strain in the superconducting layers.The analysis of mechanical response of CORC cables can play an important role in optimizing the design of CORC cables and improving transmission performance.展开更多
This paper introduces a novel method for fast calculating the electromagnetic forces in interior permanent magnet synchronous machines(IPMSMs)under pulse width modulation(PWM)voltage source inverter(VSI)supply based o...This paper introduces a novel method for fast calculating the electromagnetic forces in interior permanent magnet synchronous machines(IPMSMs)under pulse width modulation(PWM)voltage source inverter(VSI)supply based on the small-signal time-harmonic finite element analysis(THFEA),which has been successfully utilized for fast calculating the PWMinduced losses in silicon steel sheets and permanent magnets.Based on the small-signal THFEA,the functional relationships between high-frequency harmonic voltages(HFHVs)and corresponding airgap flux densities are established,which are used for calculating the flux density spectra caused by each HFHV in the PWM voltage spectra.Then,the superposition principle is applied for calculating the flux density spectra caused by fundamental currents and all HFHVs,which are converted to the electromagnetic force spectra at last.The relative errors between the force density spectra calculated with the proposed method and those obtained from traditional time-stepping finite element analysis(TSFEA)using PWM voltages as input are within 3.1%,while the proposed method is 24 times faster than the traditional TSFEA.展开更多
All-position welding is an important technology in energy sources, chemical, shipbuilding and other industries. When welding current is larger than 200 A, the molten metal tends to flow down due to the force of gravit...All-position welding is an important technology in energy sources, chemical, shipbuilding and other industries. When welding current is larger than 200 A, the molten metal tends to flow down due to the force of gravity. In order to ＂push＂ the molten metal into the weld, a new kind of U-frame excitation model, which could produce electromagnetic force to balance the gravity of the molten pool, was designed. The related parameters of the excitation model were simulated by Maxwell 3D, and the relationships between the parameters and the magnetic induction intensity were analyzed. Finally, the electromagnetic force in the molten pool was calculated, and the appropriate parameters of the U-frame excitation model were determined. The results of the simulation verify the feasibility of the all-position welding excitation model.展开更多
Magnetic field was introduced in laser melting deposition to reduce the pores in workpieces.Finite 3-D model of the coil-deposition layer-substrate was established.Simulation results show that the electromagnetic forc...Magnetic field was introduced in laser melting deposition to reduce the pores in workpieces.Finite 3-D model of the coil-deposition layer-substrate was established.Simulation results show that the electromagnetic force in deposition layer mainly concentrates in the projection area of the coil.Axial electromagnetic force shows repulsion in one cycle.The experimental results indicate that the magnetic field is beneficial for grain refinement,microhardness increasement and decline of quantities and average sizes of pores.展开更多
Contact force is related to the mechanical response of superconducting strands under a large electromagnetic body force,which is important for the safety of the international t hermonuclear experimen tai reac tor(ITER...Contact force is related to the mechanical response of superconducting strands under a large electromagnetic body force,which is important for the safety of the international t hermonuclear experimen tai reac tor(ITER)magne t struc ture.Due to the complex st rue ture of the cable-in-conduit conductor(CICC),the component unit of the ITER magnet,and the extreme operating environment,the research on the strand contact force caused by the electromagnetic force has been progressing slowly.In this study,a two-dimensional(2D)theoretical model based on the granular elemen t method is construe ted to compute the contac t forces among some opaque and non-photoelastic ferromagnetic particles which are placed in a non-uniform magnetic field.In the experiment,the contact deformations of these particles may be obtained by the digital image correlation method.We also propose a method,which is similar to the least-squares method,to calculate the electromagnetic body forces of different particles.Subsequently,the distributional and statistical characteristics of the contac t force chains and contact angles are presen ted.It is considered that the method proposed in this paper is suitable for the contact force analysis of the cross section of superconducting strands in the ITER CICC that is subjected to a transverse elec-tromagnetic force.In the end,this 2D theoretical model is generalized to the three-dimensional(3D)case,and the concise mathematical framework is presented.展开更多
In modern processing of conducting materials, such as steel,the time-varying electromagnetic field plays a key role in obtaining the desired microstructure or eliminating solidification defects such as porosity and se...In modern processing of conducting materials, such as steel,the time-varying electromagnetic field plays a key role in obtaining the desired microstructure or eliminating solidification defects such as porosity and segregation in cast billets. Up to now,few studies on the induced electromagnetic force （also called the Lorentz force） field in liquid metal have been reported. Compared with the magnetic field, the induced force field is the real and only direct cause for flow control. The electromagnetic force is comprised of two components. One is time-independent and the other is time- dependent. The time-dependent component varies with time in both amplitude and direction. When it reaches the extreme value,it can be one dozen times larger than the time-independent component. In this paper, a new method to quantitatively describe the induced electromagnetic force in liquid metal under a harmonic electromagnetic field,including both its time- independent and dependent components, was proposed based on the formula derivation from the data of amplitude and phase angle. Through this method ,the features of the time-dependent component were discussed, including the directions of rotation and the long axis. As a result, the force pattern was described. With two example calculations, the method was explained in detail. The results of both examples show that the force field in liquid metal can be divided into several regions with different force features. Example 1 shows the effect of coil position on the evolution of the force field pattern in liquid metal. Example 2 is a kind of stirring by the travelling magnetic field ,whose results present the sub-structures in metal and show that most of them have almost the same rotating direction.展开更多
A method of producing rotating radial electromagnetic force with a separable structure is proposed, and an experimental model was designed on which open loop vibration control experiments were carried out. Experimenta...A method of producing rotating radial electromagnetic force with a separable structure is proposed, and an experimental model was designed on which open loop vibration control experiments were carried out. Experimental results prove that the electromagnetic force designed has a constant magnitude and an uniform speed, and the idea of using an electromagnetic force as an active control in automatic balancing is correct in principle, and practicable in engineering.展开更多
The particle migrating behavior at solidifying front is discussed in theory with the application of electromagnetic force field(EMFF), on the basis of foregone analysis of force upon particle ahead of solidifying fron...The particle migrating behavior at solidifying front is discussed in theory with the application of electromagnetic force field(EMFF), on the basis of foregone analysis of force upon particle ahead of solidifying front without electromagnetic force field. The critical solidification velocities of particle pushing/engulfment transition ahead of horizontal and vertical interface are derived respectively when a certain EMFF is applied. And the critical electromagnetic forces of particle pushing/engulfment transition ahead of horizontal and vertical interface are also derived separately when a certain solidifying velocity is given.展开更多
This paper compares the estimated electromagnetic forces due to short circuits in power transformers using two computational models. The first model is based on approximate analytical expressions of the electromagneti...This paper compares the estimated electromagnetic forces due to short circuits in power transformers using two computational models. The first model is based on approximate analytical expressions of the electromagnetic lbrces as they have been compiled in earlier versions of the IEC standard 60076-5. The second model is based on a finite element model of the transformer using the software FEMM （Finite Element Method Magnetics）. The paper shows how valid the analytical model is for design purposes. Results have been obtained and compared from both models in a number of actual power distribution transformers. It is possible to conclude that the analytical formulation provides satisfactory results for the design of power transformers compared to detailed finite element models. A tool has been designed for this purpose and the main features of it will be described in the paper.展开更多
Heavy eddy currents exist in oil tanks during the normal operation of high-voltage and large-capacity transformers.Therefore,considerable vibration and noise are produced.Electromagnetic interference is studied in det...Heavy eddy currents exist in oil tanks during the normal operation of high-voltage and large-capacity transformers.Therefore,considerable vibration and noise are produced.Electromagnetic interference is studied in detail.The calculation of electromagnetic force in oil tanks due to the eddy current and related vibration noise is studied.A 334-MVA singlephase oil-immersed transformer is considered,and the leakage magnetic field,eddy current,and the electromagnetic force of the oil tank are calculated using the finite element method.The distribution characteristics of electromagnetic force are analyzed.The corresponding three-dimensional finite element model of vibration is established based on the stiffness characteristics of the transformer.The frequency characteristics of oil tank vibration caused by the electromagnetic force are analyzed using harmonic response analysis.A simulation model of noise caused by the vibration of oil tank is established.The fundamental frequency noise and high-frequency noise are calculated.The spectral characteristics of noise are obtained.The influence of load change on the electromagnetic force,vibration,and noise caused by the oil tank is investigated.The mathematical relationship between vibration noise and load is analyzed.The above study can provide reference and design basis for the safety design and noise prediction of large-capacity power transformers.展开更多
The application of dry-type on-board traction transformers(D-OBTTs)aims to achieve lightweight electric multiple units(EMUs)and support the approach for carbon neutrality.However,the production of large capacity D-OBT...The application of dry-type on-board traction transformers(D-OBTTs)aims to achieve lightweight electric multiple units(EMUs)and support the approach for carbon neutrality.However,the production of large capacity D-OBTTs are limited due to the defects in insulation materials under the impact of short-circuit electromagnetic force.This paper is dedicated to enhancing the mechanical performance of the high-capacity D-OBTT under the influence of short-circuit electromagnetic force.It establishes and validates an electromagnetic force coupling model,while also analysing how the traditional structure leads to defects in the insulation material.To satisfy the requirements of safe and stable operation during the service life of the large capacity D-OBTT and minimise the weight,this paper proposes a comprehensive improvement of the mechanical performance under short-circuit electromagnetic force through material modification and structural optimisation.The improvement effect is verified through experiments and simulations.After comprehensive improvement,the tensile strength of the insulation material is 43%higher than the maximum principal stress on the contact surface of the insulation material,which meets the standard requirement and ensures long-term safe and stable operation of the D-OBTT during its service life.展开更多
Superconducting electrodynamic suspension(EDS)systems generate the required propulsion,levitation,and guidance forces for vehicle motion through electromagnetic interactions between ground coils and onboard supercondu...Superconducting electrodynamic suspension(EDS)systems generate the required propulsion,levitation,and guidance forces for vehicle motion through electromagnetic interactions between ground coils and onboard superconducting coils.The propulsion coils(providing propulsion force)and the null-flux coils(providing levitation and guidance forces)are typically installed separately.In the 1980s,an integrated Propulsion-Levitation-Guidance(PLG)coil was proposed to reduce the number of ground coils and lower system costs,combining all three functional requirements into a single coil design.Visually resembling conventional null-flux coils in appearance,the PLG coils are distinguished by their active three-phase alternating current(AC)exci-tation.However,extensive research and experimental studies revealed that PLG coils exhibit significant pro-pulsion force fluctuations,which not only increase control complexity in the propulsion system but also adversely affect the maintenance of the superconducting state of the superconducting coils.This paper presents an improved PLG system design featuring a double-layer coil configuration,which achieves significant reduction in propulsion force fluctuations without increasing material costs.A comprehensive theoretical model is developed for the fully coupled dynamic circuit,explicitly incorporating mutual inductance coupling between adjacent PLG coils.The model’s validity is rigorously verified through comparison with experimental data ob-tained from the Miyazaki test line.Based on the structural parameters of the PLG coils in the Miyazaki test line,this paper presents the structural parameters of the double-layer PLG coils.Through comparative analysis of the theoretical electromagnetic force characteristics between the two kinds of coil structures,the superior perfor-mance of the double-layer PLG coils is confirmed.展开更多
Satellite formation keeping through inter-satellite electromagnetic force provides an attractive alternative for future space missions due to its distinct advantages of no propellant consumption or plume contamination...Satellite formation keeping through inter-satellite electromagnetic force provides an attractive alternative for future space missions due to its distinct advantages of no propellant consumption or plume contamination as compared to conventional approaches.However,the internal force nature as well as the high nonlinearity and coupling of electromagnetic force brings new control challenges for this novel technique.In this paper,analysis on the dynamics characteristics and special control issues in the presence of electromagnetic force is carried out on the basis of the derived relatively translational dynamics.Considering the model uncertainties,external disturbances and sensor noise,a combined nonlinear control scheme involving feed-forward and feedback control components is proposed for electromagnetic-force-based formation keeping.The feed-forward component is directly obtained through desired configuration and dynamics under nominal conditions while the feedback component is realized utilizing active disturbance rejection control methodology with some reasonable improvement.Numerical simulation is presented to verify the feasibility and validity of the combined control scheme.展开更多
A new method to produce mono dispersed silicon balls is proposed.In this method,mono dispersed droplets are formed directly from a capillary jet of molten silicon.The silicon droplets fall down in a cooling tower and ...A new method to produce mono dispersed silicon balls is proposed.In this method,mono dispersed droplets are formed directly from a capillary jet of molten silicon.The silicon droplets fall down in a cooling tower and they are solidified into mono dispersed balls.An electromagnetic pinch force is applied intermittently to the jet of molten silicon in order to generate fluctuations of equal interval on the surface of the jet.As the fluctuations grow,the molten silicon jet is broken up into droplets according to a frequency of the pinch force,if the frequency is lower than a critical value derived by a liner instability theory.Numerical simulation of the breakup of the capillary jet is carried out by a multiphase fluid flow analysis with an electromagnetic force analysis.The simulation results are compared with model experiments and the agreement between the two is good.展开更多
文摘In this paper, the boundary value problem (BVP) of 3 D transient eddy current field in the end region in the case that the generator is affected by impact load is specified. Besides, ways to implement discrete methods in both time domain and space domain during the solution of the problem are investigated. The Crank Nicolson scheme is utilized to attain the iterative format of time differential, after taking factors that can ensure both computation precision and stability into consideration. In this paper, the magnetic distribution in the end region of a turbogenerator in the case that the generator is affected by impact load is specified. As a result, it provides foundation for further study of electromagnetic force and electromagnetic vibration in the end region of the turbogenerator.
基金Project supported by the National Natural Science Foundation of China (Nos. 12232005 and 12072101)the Ningxia Natural Science Foundation of China (No. 2024AAC04004)。
文摘The fracture behavior of superconducting tapes with central and edge oblique cracks subject to electromagnetic forces is investigated. Maxwell's equations and the critical state-Bean model are used to analytically determine the magnetic flux density and electromagnetic force distributions in superconducting tapes containing central and edge oblique cracks. The distributed dislocation technique(DDT) transforms the mixed boundary value problem into a Cauchy singular integral equation, which is then solved by the Gauss-Chebyshev quadrature method to determine the stress intensity factors(SIFs).The model's accuracy is validated by comparing the calculated electromagnetic force distribution for the edge oblique crack and the SIFs for both crack types with the existing results. The findings indicate that the current and electromagnetic forces are significantly affected by the crack length and oblique angle. Specifically, for central oblique cracks, a smaller oblique angle enhances the risk of crack propagation, and a higher initial magnetization intensity poses greater danger under field cooling(FC) excitation. In contrast, for edge oblique cracks, a larger angle increases the likelihood of tape fractures. This study provides important insights into the fracture behavior and mechanical failure mechanisms of superconducting tapes with oblique cracks.
基金Project supported by the Program of Excellent Team in Harbin Institute of Technology,China
文摘A new apparatus was designed to measure the electromagnetic force and a computational study of the traveling magnetic field(TMF)and its application to the Ga-In-Sn melt(with low melting point),then the forces on Al,Mg,and Li melt,were simulated. The result show that the electromagnetic force on the melt increases linearly with the increasing length of the melt in the TMF.The TMF-induced Lorentz force increases with increasing frequency,and then decreases.The maximum value is obtained when the current frequency is 160 Hz,over that frequency the force decreases rapidly.When the iron-core is activated,the force increases when the melt closes to the iron-core.The Lorentz forces have inversely-proportional relationships with the electrical resistivity,the dfx/dρdecreases and the dfy/dρincreases with the increasing electrical resistivity(df/dρis the slope of the Lorentz force profile).
基金supported by the National Natural Science Foundation of China(Grant No.50001008)the China Postdoctoral Science Foundation.
文摘Because of the different conductivities between the primary phase (low electric conduc tivity) and the metal melt, electromagnetic force scarcely acts on the primary phase. Thus, an electromagnetic repulsive force applied by the metal melt exerts on the pri mary phase when the movement of the melt in the direction of electromagnetic force is limited. As a result, the repulsive force exerts on the primary phase to push them to move in the direction opposite to that of the electromagnetic force when the metal melt with primary phase solidifies under an electromagnetic force field. Based on this, a new method for production of in situ surface composite and gradient material by electromagnetic force is proposed. An in situ primary Si reinforced surface composite of Al-15wt%Si alloy and gradient material of Al-l9wt%Si alloy were produced by this method. The microhardness of the primary Si is HV1320. The reinforced phase size is in the range from 40μm to 100μm. The wear resistance of Al-Si alloy gradient material can be more greatly increased than that of their matrix material.
文摘The standard k-ε model was adopted to simulate the flow field of molten metal in three aluminum electrolysis cells with different anode risers. The Hartman number, Reynolds number and the turbulent Reynolds number of molten metal were calculated quantitatively. The turbulent Reynolds number is in the order of 103 , and Reynolds number is in the order of 104 if taking the depth of molten metal as the characteristic length. The results show that the molten metal flow is the turbulence of high Reynolds number, the turbulent Reynolds number is more appropriate than Reynolds number to be used to describe the turbulent characteristic of molten metal, and Hartman number displays very well that electromagnetic force inhibits turbulent motion of molten metal.
基金Project (G1999064903) supported by the National Key Fundamental Research and Development Programof China
文摘Based on the commercial computational fluid dynamics software CFX-4.3, electrolyte flow fields in a 156 kA pre-baked anode aluminum electrolysis cell were investigated in three different cases where the electrolyte melt was driven by different kinds of force, i.e. electromagnetic force only, the anode gas drag force only and both of the former two forces. The results show that when electromagnetic force was introduced only, most of the electrolyte moves horizontally; when anode gas drag force was introduced only, the electrolyte flows mainly around each anode with small circulation; when electromagnetic force and anode gas drag force were both introduced together, the structure of the electrolyte flow fields and the velocity of electrolyte are similar to that of the case where only anode gas drag force is used. The electrolyte flow fields are mainly determined by the anode gas drag force.
基金support from the National Natural Science Foundation of China(Nos.U2241267,11872195 and 12172155)Fundamental Research Funds for the Central Universities(No.lzujbky-2022-48).
文摘The conductor on round core(CORC)cables are fabricated with multilayer high-temperature superconductor tapes,which are helically wound around a circular central former.The large Lorentz force will be generated by the transport current in CORC cables under high magnetic field,which will affect the stress and strain distributions of tapes in the cables and the performance of superconducting tape.This paper establishes a two-dimensional axisymmetric model to analyze the mechanical response of CORC cables subjected to the Lorentz force and analyzes the influence of air gaps on stress and strain distributions inside the cables.The T-A method is used to calculate the distributions of current density,magnetic field and the Lorentz force in CORC cables.The mechanical response of CORC cables is analyzed by applying the Lorentz force as an external load in the mechanical model.The direction of electromagnetic force is analyzed in CORC cables with and without shielding current,and the results show that the shielding current can lead to the concentration of electromagnetic force.The maximum stress and strain occur on both sides of the superconducting tapes in the cables with shielding current.Reducing the size of air gaps can reduce the stress and strain in the superconducting layers.The analysis of mechanical response of CORC cables can play an important role in optimizing the design of CORC cables and improving transmission performance.
基金supported in part by the National Natural Science Foundation of China under projects 51907053by Natural Science Foundation of Jiangsu Province of China under Project BK20190489+1 种基金by the Fundamental Research Funds for the Central Universities under grant B200202167by the China Postdoctoral Science Foundation under grant no.2019M661708。
文摘This paper introduces a novel method for fast calculating the electromagnetic forces in interior permanent magnet synchronous machines(IPMSMs)under pulse width modulation(PWM)voltage source inverter(VSI)supply based on the small-signal time-harmonic finite element analysis(THFEA),which has been successfully utilized for fast calculating the PWMinduced losses in silicon steel sheets and permanent magnets.Based on the small-signal THFEA,the functional relationships between high-frequency harmonic voltages(HFHVs)and corresponding airgap flux densities are established,which are used for calculating the flux density spectra caused by each HFHV in the PWM voltage spectra.Then,the superposition principle is applied for calculating the flux density spectra caused by fundamental currents and all HFHVs,which are converted to the electromagnetic force spectra at last.The relative errors between the force density spectra calculated with the proposed method and those obtained from traditional time-stepping finite element analysis(TSFEA)using PWM voltages as input are within 3.1%,while the proposed method is 24 times faster than the traditional TSFEA.
基金This work was supported by the National Natural Science Foundation of China （No. 51075299）.
文摘All-position welding is an important technology in energy sources, chemical, shipbuilding and other industries. When welding current is larger than 200 A, the molten metal tends to flow down due to the force of gravity. In order to ＂push＂ the molten metal into the weld, a new kind of U-frame excitation model, which could produce electromagnetic force to balance the gravity of the molten pool, was designed. The related parameters of the excitation model were simulated by Maxwell 3D, and the relationships between the parameters and the magnetic induction intensity were analyzed. Finally, the electromagnetic force in the molten pool was calculated, and the appropriate parameters of the U-frame excitation model were determined. The results of the simulation verify the feasibility of the all-position welding excitation model.
基金supported by the National Science Foundation of China(No.51475238)the Jiangsu Science and Technology Support Program(No.BE2014009-1)the Jiangsu Provincial Key Research and Development Plan (Nos.BE201561,BE201603-3)
文摘Magnetic field was introduced in laser melting deposition to reduce the pores in workpieces.Finite 3-D model of the coil-deposition layer-substrate was established.Simulation results show that the electromagnetic force in deposition layer mainly concentrates in the projection area of the coil.Axial electromagnetic force shows repulsion in one cycle.The experimental results indicate that the magnetic field is beneficial for grain refinement,microhardness increasement and decline of quantities and average sizes of pores.
基金This work is supported by the fund of Natural Science Foundation of China(Nos.11872196,11902130).
文摘Contact force is related to the mechanical response of superconducting strands under a large electromagnetic body force,which is important for the safety of the international t hermonuclear experimen tai reac tor(ITER)magne t struc ture.Due to the complex st rue ture of the cable-in-conduit conductor(CICC),the component unit of the ITER magnet,and the extreme operating environment,the research on the strand contact force caused by the electromagnetic force has been progressing slowly.In this study,a two-dimensional(2D)theoretical model based on the granular elemen t method is construe ted to compute the contac t forces among some opaque and non-photoelastic ferromagnetic particles which are placed in a non-uniform magnetic field.In the experiment,the contact deformations of these particles may be obtained by the digital image correlation method.We also propose a method,which is similar to the least-squares method,to calculate the electromagnetic body forces of different particles.Subsequently,the distributional and statistical characteristics of the contac t force chains and contact angles are presen ted.It is considered that the method proposed in this paper is suitable for the contact force analysis of the cross section of superconducting strands in the ITER CICC that is subjected to a transverse elec-tromagnetic force.In the end,this 2D theoretical model is generalized to the three-dimensional(3D)case,and the concise mathematical framework is presented.
文摘In modern processing of conducting materials, such as steel,the time-varying electromagnetic field plays a key role in obtaining the desired microstructure or eliminating solidification defects such as porosity and segregation in cast billets. Up to now,few studies on the induced electromagnetic force （also called the Lorentz force） field in liquid metal have been reported. Compared with the magnetic field, the induced force field is the real and only direct cause for flow control. The electromagnetic force is comprised of two components. One is time-independent and the other is time- dependent. The time-dependent component varies with time in both amplitude and direction. When it reaches the extreme value,it can be one dozen times larger than the time-independent component. In this paper, a new method to quantitatively describe the induced electromagnetic force in liquid metal under a harmonic electromagnetic field,including both its time- independent and dependent components, was proposed based on the formula derivation from the data of amplitude and phase angle. Through this method ,the features of the time-dependent component were discussed, including the directions of rotation and the long axis. As a result, the force pattern was described. With two example calculations, the method was explained in detail. The results of both examples show that the force field in liquid metal can be divided into several regions with different force features. Example 1 shows the effect of coil position on the evolution of the force field pattern in liquid metal. Example 2 is a kind of stirring by the travelling magnetic field ,whose results present the sub-structures in metal and show that most of them have almost the same rotating direction.
文摘A method of producing rotating radial electromagnetic force with a separable structure is proposed, and an experimental model was designed on which open loop vibration control experiments were carried out. Experimental results prove that the electromagnetic force designed has a constant magnitude and an uniform speed, and the idea of using an electromagnetic force as an active control in automatic balancing is correct in principle, and practicable in engineering.
基金Supported by the Science Foundation of Shanghai Municipal Commission of Scienceand Technology!( 97JC1 41 0 7)
文摘The particle migrating behavior at solidifying front is discussed in theory with the application of electromagnetic force field(EMFF), on the basis of foregone analysis of force upon particle ahead of solidifying front without electromagnetic force field. The critical solidification velocities of particle pushing/engulfment transition ahead of horizontal and vertical interface are derived respectively when a certain EMFF is applied. And the critical electromagnetic forces of particle pushing/engulfment transition ahead of horizontal and vertical interface are also derived separately when a certain solidifying velocity is given.
文摘This paper compares the estimated electromagnetic forces due to short circuits in power transformers using two computational models. The first model is based on approximate analytical expressions of the electromagnetic lbrces as they have been compiled in earlier versions of the IEC standard 60076-5. The second model is based on a finite element model of the transformer using the software FEMM （Finite Element Method Magnetics）. The paper shows how valid the analytical model is for design purposes. Results have been obtained and compared from both models in a number of actual power distribution transformers. It is possible to conclude that the analytical formulation provides satisfactory results for the design of power transformers compared to detailed finite element models. A tool has been designed for this purpose and the main features of it will be described in the paper.
基金supported by the National Natural Science Foundation of China(51807061).
文摘Heavy eddy currents exist in oil tanks during the normal operation of high-voltage and large-capacity transformers.Therefore,considerable vibration and noise are produced.Electromagnetic interference is studied in detail.The calculation of electromagnetic force in oil tanks due to the eddy current and related vibration noise is studied.A 334-MVA singlephase oil-immersed transformer is considered,and the leakage magnetic field,eddy current,and the electromagnetic force of the oil tank are calculated using the finite element method.The distribution characteristics of electromagnetic force are analyzed.The corresponding three-dimensional finite element model of vibration is established based on the stiffness characteristics of the transformer.The frequency characteristics of oil tank vibration caused by the electromagnetic force are analyzed using harmonic response analysis.A simulation model of noise caused by the vibration of oil tank is established.The fundamental frequency noise and high-frequency noise are calculated.The spectral characteristics of noise are obtained.The influence of load change on the electromagnetic force,vibration,and noise caused by the oil tank is investigated.The mathematical relationship between vibration noise and load is analyzed.The above study can provide reference and design basis for the safety design and noise prediction of large-capacity power transformers.
基金supported by National Natural Science Foundation of China(Grant/Award U1834203)Natural Science Foundation of Sichuan Province(Grants/Award 2024NSFSC0020 and 2023NSFSC0828).
文摘The application of dry-type on-board traction transformers(D-OBTTs)aims to achieve lightweight electric multiple units(EMUs)and support the approach for carbon neutrality.However,the production of large capacity D-OBTTs are limited due to the defects in insulation materials under the impact of short-circuit electromagnetic force.This paper is dedicated to enhancing the mechanical performance of the high-capacity D-OBTT under the influence of short-circuit electromagnetic force.It establishes and validates an electromagnetic force coupling model,while also analysing how the traditional structure leads to defects in the insulation material.To satisfy the requirements of safe and stable operation during the service life of the large capacity D-OBTT and minimise the weight,this paper proposes a comprehensive improvement of the mechanical performance under short-circuit electromagnetic force through material modification and structural optimisation.The improvement effect is verified through experiments and simulations.After comprehensive improvement,the tensile strength of the insulation material is 43%higher than the maximum principal stress on the contact surface of the insulation material,which meets the standard requirement and ensures long-term safe and stable operation of the D-OBTT during its service life.
基金supported in part by the National Key Research and Development Program of China under Grant 2016YFB1200601in part by the Major Project of Advanced Manufacturing and Automation of Changsha Science and Technology Bureau under Grant kq1804037+1 种基金in part by the Youth Independent Innovation Science Fund of National University of Defense Technology under Grant ZN2019-009in part by the Key Project of the National Natural Science Foundation of China under Grant 52241103.
文摘Superconducting electrodynamic suspension(EDS)systems generate the required propulsion,levitation,and guidance forces for vehicle motion through electromagnetic interactions between ground coils and onboard superconducting coils.The propulsion coils(providing propulsion force)and the null-flux coils(providing levitation and guidance forces)are typically installed separately.In the 1980s,an integrated Propulsion-Levitation-Guidance(PLG)coil was proposed to reduce the number of ground coils and lower system costs,combining all three functional requirements into a single coil design.Visually resembling conventional null-flux coils in appearance,the PLG coils are distinguished by their active three-phase alternating current(AC)exci-tation.However,extensive research and experimental studies revealed that PLG coils exhibit significant pro-pulsion force fluctuations,which not only increase control complexity in the propulsion system but also adversely affect the maintenance of the superconducting state of the superconducting coils.This paper presents an improved PLG system design featuring a double-layer coil configuration,which achieves significant reduction in propulsion force fluctuations without increasing material costs.A comprehensive theoretical model is developed for the fully coupled dynamic circuit,explicitly incorporating mutual inductance coupling between adjacent PLG coils.The model’s validity is rigorously verified through comparison with experimental data ob-tained from the Miyazaki test line.Based on the structural parameters of the PLG coils in the Miyazaki test line,this paper presents the structural parameters of the double-layer PLG coils.Through comparative analysis of the theoretical electromagnetic force characteristics between the two kinds of coil structures,the superior perfor-mance of the double-layer PLG coils is confirmed.
基金supported by the National Natural Science Foundation of China(Grant No.11172322)
文摘Satellite formation keeping through inter-satellite electromagnetic force provides an attractive alternative for future space missions due to its distinct advantages of no propellant consumption or plume contamination as compared to conventional approaches.However,the internal force nature as well as the high nonlinearity and coupling of electromagnetic force brings new control challenges for this novel technique.In this paper,analysis on the dynamics characteristics and special control issues in the presence of electromagnetic force is carried out on the basis of the derived relatively translational dynamics.Considering the model uncertainties,external disturbances and sensor noise,a combined nonlinear control scheme involving feed-forward and feedback control components is proposed for electromagnetic-force-based formation keeping.The feed-forward component is directly obtained through desired configuration and dynamics under nominal conditions while the feedback component is realized utilizing active disturbance rejection control methodology with some reasonable improvement.Numerical simulation is presented to verify the feasibility and validity of the combined control scheme.
文摘A new method to produce mono dispersed silicon balls is proposed.In this method,mono dispersed droplets are formed directly from a capillary jet of molten silicon.The silicon droplets fall down in a cooling tower and they are solidified into mono dispersed balls.An electromagnetic pinch force is applied intermittently to the jet of molten silicon in order to generate fluctuations of equal interval on the surface of the jet.As the fluctuations grow,the molten silicon jet is broken up into droplets according to a frequency of the pinch force,if the frequency is lower than a critical value derived by a liner instability theory.Numerical simulation of the breakup of the capillary jet is carried out by a multiphase fluid flow analysis with an electromagnetic force analysis.The simulation results are compared with model experiments and the agreement between the two is good.
