Evaporation erosion of the contacts is one of the fundamental failure mechanisms for relays. In this paper, the evaporation erosion characteristics are investigated for the copper contact pair breaking a resistive dir...Evaporation erosion of the contacts is one of the fundamental failure mechanisms for relays. In this paper, the evaporation erosion characteristics are investigated for the copper contact pair breaking a resistive direct current （dc） 30 V/10 A circuit in the air. Molten pool simulation of the contacts is coupled with the gas dynamics to calculate the evaporation rate. A simplified arc model is constructed to obtain the contact voltage and current variations with time for the prediction of the current density and the heat flux distributions flowing from the arc into the contacts. The evaporation rate and mass variations with time during the breaking process are presented. Experiments are carried out to verify the simulation results.展开更多
An arc model in SiO2 current-limiting fuse has been put forward. Through taking into account the comprehensive effects such as: fundamental action process among particles of arc column, geometrical and external circui...An arc model in SiO2 current-limiting fuse has been put forward. Through taking into account the comprehensive effects such as: fundamental action process among particles of arc column, geometrical and external circuit characteristics of arc column, physical procedure in arc column and in cathode and anode, and power equilibrium in arc column plasma et al., parameters such as the temperature, length, volumn, pressure, arc voltage, arc current et al. in the arc column can be obtained by the model. In view of the serious nonlinearity and huge difference among parameters in the equation set of the model, via analysis on these equations, two solution methods for the equations of the model have been presented with a basic accordance between calculated results and test results.展开更多
Conventional arc models are usually used to research the interaction between switching arc and circuit. It is important to simulate the fault arc for arc flash calculations, choice of electrical equipments and power s...Conventional arc models are usually used to research the interaction between switching arc and circuit. It is important to simulate the fault arc for arc flash calculations, choice of electrical equipments and power system protection. This paper investigates several conventional arc models for calculating the fault arcing current. Simulation results show that conventional arc models can be used to simulate the fault arc if the parameters of arc models are given properly. This paper provides the parameters of 5 popular arc models and describes the simulation results of the fault arc.展开更多
To simulate the process of electrode operation, a dynamic model describing the electrode system of three-phase electric arc furnace was developed. This new model can be divided into three submodels in terms of the pra...To simulate the process of electrode operation, a dynamic model describing the electrode system of three-phase electric arc furnace was developed. This new model can be divided into three submodels in terms of the practical situation. They are the power supply system model the electric arc model and the hydraulic actuator system model. According to the basic circuit theory, the power supply system model where the high voltage transmission circuit and mutual inductances were considered, was set up. The electric arc model, which was novel for the electrode control, served as the electrical load and was connected to the power supply system model. The hydraulic actuator system model consists of the proportional valve part that is modeled to capture the dead-zone nonlinear characteristics and the hydraulic cylinder part where the impact of the load force is taken into account. By comparing simulation data and actual data, the results show that the electrode system model is proved to be accurate.展开更多
A commercial CFD （computational fluid dynamics） code FLUENT was used and modified to model an atmospheric pressure argon arc in a low cross flow by solving the fully coupled conservation equations. Numerical experim...A commercial CFD （computational fluid dynamics） code FLUENT was used and modified to model an atmospheric pressure argon arc in a low cross flow by solving the fully coupled conservation equations. Numerical experiments, with an arc current of 100 A to 200 A, an arcing distance of 3 mm to 6 mm, and a cross-flow velocity of 10 m/s to 30 m/s, were carried out. The modelling results show that the arc tends to take the shortest path to the anode when deflected by the cross flow; its anode attachment is farther downstream than the cathode one. Furthermore, due to the low input gas flow imposed in this study, the effect of electromagnetic force is important and it influences the crosscut shape of the arc significantly.展开更多
In the computational process of very fast transient over-voltage （VFTO）, it is essen-tial to find an accurate model for a gas insulated substation. The arcing model of the disconnector is particularly important. The...In the computational process of very fast transient over-voltage （VFTO）, it is essen-tial to find an accurate model for a gas insulated substation. The arcing model of the disconnector is particularly important. The general arcing model is not able to give a good description of the arc development process. In this paper, based on the physical process of arcing and existing arc models （the exponential time-varying resistance model and the segmental arcing models）, a dy- namic arcing model is proposed, which is divided into two stages before and after the zero crossing. The dynamic arcing model combines hyperbola time-varying resistance and the Mayr model to describe the dynamic process of arcing. The present paper creates an arc model blockset upon the Matlab/Simulink software platform. Moreover for a specific 1100 kV station, VFTO is simulated in detail based on different arcing models. It is demonstrated that the dynamic arcing model can describe the physical arc process precisely and is useful for improving the accuracy of VFTO simulations.展开更多
It is of great significance to model the keyhole shape and dimensions to optimize the plasma arc welding process parameters. In this study, through employing a combined volumetric heat source mode, the weld pool in ke...It is of great significance to model the keyhole shape and dimensions to optimize the plasma arc welding process parameters. In this study, through employing a combined volumetric heat source mode, the weld pool in keyhole plasma arc welding is determined firstly, and then the dynamic force-balance condition on the interface between the plasma jet and the molten metal is dealt with in describing the keyhole formation inside the weld pool. The effects of welding current on the shape and size of keyhole are numerically analyzed. The sharp transformation from a partial keyhole to a full-penetration keyhole is quantitatively demonstrated.展开更多
A three-dimensional numerical model is developed to study the behaviour of an argon-nitrogen plasma arc inside a non-transferred torch. In this model, both the entire cathode and anode nozzle are considered to simulat...A three-dimensional numerical model is developed to study the behaviour of an argon-nitrogen plasma arc inside a non-transferred torch. In this model, both the entire cathode and anode nozzle are considered to simulate the plasma arc. The argon-nitrogen plasma arc is simulated for different arc currents and gas flow rates of argon. Various combinations of arc core radius and arc length, which correspond to a given torch power, are predicted. A most feasible combination of the same, which corresponds to an actual physical situation of the arc inside the torch, is identified using the thermodynamic principle of minimum entropy production for a particular torch power. The effect of the arc current and gas flow rate on the plasma arc characteristics and torch efficiency is explained. The effect of the nitrogen content in the plasma gas on the torch power and efficiency is clearly detected. Predicted torch efficiencies are comparable to the measured ones and the effect of the arc current and gas flow rate on predicted and measured efficiencies is almost similar. The efficiency of the torch, cathode and anode losses and core temperature and velocity at the nozzle exit are reported for five different cases.展开更多
By using alternating current plasma arc welding,the influences were studied of such parameters as welding curent,arc voltage,welding speed,wire feed rate,and magnitude of ion gas flow on front melting width,wdle rei...By using alternating current plasma arc welding,the influences were studied of such parameters as welding curent,arc voltage,welding speed,wire feed rate,and magnitude of ion gas flow on front melting width,wdle reinforcement,and back melting width of LF6 aluminum alloy.Model of the formation of welding seam in alternating current plasma arc welding of aluminum was set up with the method of artificial neural neural network - BP algorithm. Qyakuty of formation was consequently predicted and evaluated.The experimental result shows that,compared with other modeling methods,artificial network model can be used to more accurately predict formation of weld,and to guide the production practice.展开更多
The prompt extinction of the secondary arc is critical to the single-phase reclosing of AC transmission lines, including half-wavelength power transmission lines. In this paper, a low- voltage physical experimental pl...The prompt extinction of the secondary arc is critical to the single-phase reclosing of AC transmission lines, including half-wavelength power transmission lines. In this paper, a low- voltage physical experimental platform was established and the motion process of the secondary arc was recorded by a high-speed camera. It was found that the arcing time of the secondary arc rendered a close relationship with its arc length. Through the input and output power energy analysis of the secondary arc, a new critical length criterion for the arcing time was proposed. The arc chain model was then adopted to calculate the arcing time with both the traditional and the proposed critical length criteria, and the simulation results were compared with the experimental data. The study showed that the arcing time calculated from the new critical length criterion gave more accurate results, which can provide a reliable criterion in term of arcing time for modeling and simulation of the secondary arc related with power transmission lines.展开更多
This paper focuses on the simulation of a fault arc in a closed tank based on the magneto-hydrodynamic （MHD） method, in which a comparative study of three radiation models, including net emission coefficients （NEC...This paper focuses on the simulation of a fault arc in a closed tank based on the magneto-hydrodynamic （MHD） method, in which a comparative study of three radiation models, including net emission coefficients （NEC）, semi-empirical model based on NEC as well as the P1 model, is developed. The pressure rise calculated by the three radiation models are compared to the measured results. Particularly when the senti-empirical model is used, the effect of different boundary temperatures of the re-absorption layer in the semi-empirical model on pressure rise is concentrated on. The results show that the re-absorption effect in the low-temperature region affects radiation transfer of fault arcs evidently, and thus the internal pressure rise. Compared with the NEC model, P1 and the semi-empirical model with 0.7 〈 α 〈 0.83 are more suitable to calculate the pressure rise of the fault arc, where is an adjusted parameter involving the boundary temperature of the re-absorption region in the semi-empirical model.展开更多
Based on the analysis of three-dimensional power conductor for DC arcfurnace, the electric arc deflection model was set up and the control system of the arc directionwas configured. According to the bus bar distributi...Based on the analysis of three-dimensional power conductor for DC arcfurnace, the electric arc deflection model was set up and the control system of the arc directionwas configured. According to the bus bar distribution at the bottom electrodes cooled by water, thearc direction control principle and its configuration were described. The simulation results showthat the control system can restrain the electric arc deflection and control the arc direction.展开更多
In the electric arc furnace （EAF） steel production processes, scrap steel is principally used as a raw material instead of iron ore. In the steelmaking process with EAF, scrap is first melted in the furnace and then...In the electric arc furnace （EAF） steel production processes, scrap steel is principally used as a raw material instead of iron ore. In the steelmaking process with EAF, scrap is first melted in the furnace and then the desired chemical composition of the steel can be obtained in a special furnace such as ladle furnace （LF）. This kind of furnace process is used for the secondary refining of alloy steel. LF furnace offers strong heating fluxes and enables precise temperature control, thereby allowing for the addition of desired amounts of various alloying elements. It also provides outstanding desulfurization at high-temperature treatment by reducing molten steel fluxes and removing deoxidation products. Elemental analysis with mass balance modeling is important to know the precise amount of required alloys for the LF input with respect to scrap composition. In present study, chemical reactions with mass conservation law in EAF and LF were modeled altogether as a whole system and chemical compositions of the final steel alloy output can be obtained precisely according to different scrap compositions, alloying elements ratios, and other input amounts. Besides, it was found that the mass efficiency for iron element in the system is 95.93%. These efficiencies are calculated for all input elements as 8. 45% for C, 30.31% for Si, 46.36% for Mn, 30.64% for P, 41.96% for S, and 69.79% for Cr, etc. These efficiencies provide valuable ideas about the amount of the input materials that are vanished or combusted for 100 kg of each of the input materials in the EAF and LF system.展开更多
基金supported by National Natural Science Foundation of China(Nos.51377038,51307030)
文摘Evaporation erosion of the contacts is one of the fundamental failure mechanisms for relays. In this paper, the evaporation erosion characteristics are investigated for the copper contact pair breaking a resistive direct current （dc） 30 V/10 A circuit in the air. Molten pool simulation of the contacts is coupled with the gas dynamics to calculate the evaporation rate. A simplified arc model is constructed to obtain the contact voltage and current variations with time for the prediction of the current density and the heat flux distributions flowing from the arc into the contacts. The evaporation rate and mass variations with time during the breaking process are presented. Experiments are carried out to verify the simulation results.
文摘An arc model in SiO2 current-limiting fuse has been put forward. Through taking into account the comprehensive effects such as: fundamental action process among particles of arc column, geometrical and external circuit characteristics of arc column, physical procedure in arc column and in cathode and anode, and power equilibrium in arc column plasma et al., parameters such as the temperature, length, volumn, pressure, arc voltage, arc current et al. in the arc column can be obtained by the model. In view of the serious nonlinearity and huge difference among parameters in the equation set of the model, via analysis on these equations, two solution methods for the equations of the model have been presented with a basic accordance between calculated results and test results.
文摘Conventional arc models are usually used to research the interaction between switching arc and circuit. It is important to simulate the fault arc for arc flash calculations, choice of electrical equipments and power system protection. This paper investigates several conventional arc models for calculating the fault arcing current. Simulation results show that conventional arc models can be used to simulate the fault arc if the parameters of arc models are given properly. This paper provides the parameters of 5 popular arc models and describes the simulation results of the fault arc.
基金Projects(2007AA04Z194, 2007AA041401) supported by the National High-Tech Research and Development Program of China
文摘To simulate the process of electrode operation, a dynamic model describing the electrode system of three-phase electric arc furnace was developed. This new model can be divided into three submodels in terms of the practical situation. They are the power supply system model the electric arc model and the hydraulic actuator system model. According to the basic circuit theory, the power supply system model where the high voltage transmission circuit and mutual inductances were considered, was set up. The electric arc model, which was novel for the electrode control, served as the electrical load and was connected to the power supply system model. The hydraulic actuator system model consists of the proportional valve part that is modeled to capture the dead-zone nonlinear characteristics and the hydraulic cylinder part where the impact of the load force is taken into account. By comparing simulation data and actual data, the results show that the electrode system model is proved to be accurate.
基金supported by National Natural Science Foundation of China (Nos.10375065,10675122)
文摘A commercial CFD （computational fluid dynamics） code FLUENT was used and modified to model an atmospheric pressure argon arc in a low cross flow by solving the fully coupled conservation equations. Numerical experiments, with an arc current of 100 A to 200 A, an arcing distance of 3 mm to 6 mm, and a cross-flow velocity of 10 m/s to 30 m/s, were carried out. The modelling results show that the arc tends to take the shortest path to the anode when deflected by the cross flow; its anode attachment is farther downstream than the cathode one. Furthermore, due to the low input gas flow imposed in this study, the effect of electromagnetic force is important and it influences the crosscut shape of the arc significantly.
基金supported by Special Research Fund for Doctoral Program of Education Ministry of China (No. 20092102110001)Natural Science Foundation of Liaoning Province of China (No. 201102169)National Natural Science Foundation of China (No. 51277123)
文摘In the computational process of very fast transient over-voltage （VFTO）, it is essen-tial to find an accurate model for a gas insulated substation. The arcing model of the disconnector is particularly important. The general arcing model is not able to give a good description of the arc development process. In this paper, based on the physical process of arcing and existing arc models （the exponential time-varying resistance model and the segmental arcing models）, a dy- namic arcing model is proposed, which is divided into two stages before and after the zero crossing. The dynamic arcing model combines hyperbola time-varying resistance and the Mayr model to describe the dynamic process of arcing. The present paper creates an arc model blockset upon the Matlab/Simulink software platform. Moreover for a specific 1100 kV station, VFTO is simulated in detail based on different arcing models. It is demonstrated that the dynamic arcing model can describe the physical arc process precisely and is useful for improving the accuracy of VFTO simulations.
文摘It is of great significance to model the keyhole shape and dimensions to optimize the plasma arc welding process parameters. In this study, through employing a combined volumetric heat source mode, the weld pool in keyhole plasma arc welding is determined firstly, and then the dynamic force-balance condition on the interface between the plasma jet and the molten metal is dealt with in describing the keyhole formation inside the weld pool. The effects of welding current on the shape and size of keyhole are numerically analyzed. The sharp transformation from a partial keyhole to a full-penetration keyhole is quantitatively demonstrated.
文摘A three-dimensional numerical model is developed to study the behaviour of an argon-nitrogen plasma arc inside a non-transferred torch. In this model, both the entire cathode and anode nozzle are considered to simulate the plasma arc. The argon-nitrogen plasma arc is simulated for different arc currents and gas flow rates of argon. Various combinations of arc core radius and arc length, which correspond to a given torch power, are predicted. A most feasible combination of the same, which corresponds to an actual physical situation of the arc inside the torch, is identified using the thermodynamic principle of minimum entropy production for a particular torch power. The effect of the arc current and gas flow rate on the plasma arc characteristics and torch efficiency is explained. The effect of the nitrogen content in the plasma gas on the torch power and efficiency is clearly detected. Predicted torch efficiencies are comparable to the measured ones and the effect of the arc current and gas flow rate on predicted and measured efficiencies is almost similar. The efficiency of the torch, cathode and anode losses and core temperature and velocity at the nozzle exit are reported for five different cases.
文摘By using alternating current plasma arc welding,the influences were studied of such parameters as welding curent,arc voltage,welding speed,wire feed rate,and magnitude of ion gas flow on front melting width,wdle reinforcement,and back melting width of LF6 aluminum alloy.Model of the formation of welding seam in alternating current plasma arc welding of aluminum was set up with the method of artificial neural neural network - BP algorithm. Qyakuty of formation was consequently predicted and evaluated.The experimental result shows that,compared with other modeling methods,artificial network model can be used to more accurately predict formation of weld,and to guide the production practice.
基金supported by National Natural Science Foundation of China(Nos.51277061 and 51420105011)
文摘The prompt extinction of the secondary arc is critical to the single-phase reclosing of AC transmission lines, including half-wavelength power transmission lines. In this paper, a low- voltage physical experimental platform was established and the motion process of the secondary arc was recorded by a high-speed camera. It was found that the arcing time of the secondary arc rendered a close relationship with its arc length. Through the input and output power energy analysis of the secondary arc, a new critical length criterion for the arcing time was proposed. The arc chain model was then adopted to calculate the arcing time with both the traditional and the proposed critical length criteria, and the simulation results were compared with the experimental data. The study showed that the arcing time calculated from the new critical length criterion gave more accurate results, which can provide a reliable criterion in term of arcing time for modeling and simulation of the secondary arc related with power transmission lines.
基金supported by National Key Basic Research Program of China(973 Program)(No.2015CB251002)National Natural Science Foundation of China(Nos.51221005,51177124)+2 种基金the Fundamental Research Funds for the Central Universitiesthe Program for New Century Excellent Talents in UniversityShaanxi Province Natural Science Foundation of China(No.2013JM-7010)
文摘This paper focuses on the simulation of a fault arc in a closed tank based on the magneto-hydrodynamic （MHD） method, in which a comparative study of three radiation models, including net emission coefficients （NEC）, semi-empirical model based on NEC as well as the P1 model, is developed. The pressure rise calculated by the three radiation models are compared to the measured results. Particularly when the senti-empirical model is used, the effect of different boundary temperatures of the re-absorption layer in the semi-empirical model on pressure rise is concentrated on. The results show that the re-absorption effect in the low-temperature region affects radiation transfer of fault arcs evidently, and thus the internal pressure rise. Compared with the NEC model, P1 and the semi-empirical model with 0.7 〈 α 〈 0.83 are more suitable to calculate the pressure rise of the fault arc, where is an adjusted parameter involving the boundary temperature of the re-absorption region in the semi-empirical model.
文摘Based on the analysis of three-dimensional power conductor for DC arcfurnace, the electric arc deflection model was set up and the control system of the arc directionwas configured. According to the bus bar distribution at the bottom electrodes cooled by water, thearc direction control principle and its configuration were described. The simulation results showthat the control system can restrain the electric arc deflection and control the arc direction.
文摘In the electric arc furnace （EAF） steel production processes, scrap steel is principally used as a raw material instead of iron ore. In the steelmaking process with EAF, scrap is first melted in the furnace and then the desired chemical composition of the steel can be obtained in a special furnace such as ladle furnace （LF）. This kind of furnace process is used for the secondary refining of alloy steel. LF furnace offers strong heating fluxes and enables precise temperature control, thereby allowing for the addition of desired amounts of various alloying elements. It also provides outstanding desulfurization at high-temperature treatment by reducing molten steel fluxes and removing deoxidation products. Elemental analysis with mass balance modeling is important to know the precise amount of required alloys for the LF input with respect to scrap composition. In present study, chemical reactions with mass conservation law in EAF and LF were modeled altogether as a whole system and chemical compositions of the final steel alloy output can be obtained precisely according to different scrap compositions, alloying elements ratios, and other input amounts. Besides, it was found that the mass efficiency for iron element in the system is 95.93%. These efficiencies are calculated for all input elements as 8. 45% for C, 30.31% for Si, 46.36% for Mn, 30.64% for P, 41.96% for S, and 69.79% for Cr, etc. These efficiencies provide valuable ideas about the amount of the input materials that are vanished or combusted for 100 kg of each of the input materials in the EAF and LF system.
