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
The use of time-frequency entropy to quantitatively assess the stability of submerged arc welding process considering the distribution features of arc energy is reported in this paper. Time-frequency entropy is employ...The use of time-frequency entropy to quantitatively assess the stability of submerged arc welding process considering the distribution features of arc energy is reported in this paper. Time-frequency entropy is employed to calculate and analyze the stationary current signals, non-stationary current and voltage signals in the submerged arc welding process. It is obtained that time-frequency entropy of arc signal can be used as arc stability judgment criteria of submerged arc welding. Experimental results are provided to confirm the effectiveness of this approach.展开更多
Numerical analysis of keyhole shape and keyhole establishment time is of great significance for selection and optimization of the process parameters in keyhole plasma arc welding. In this paper, a three-dimensional tr...Numerical analysis of keyhole shape and keyhole establishment time is of great significance for selection and optimization of the process parameters in keyhole plasma arc welding. In this paper, a three-dimensional transient model is developed to analyze the evolutions of keyhole shape and keyhole establishment time in continuous current plasma arc welding process. Firstly, a combined volumetric heat source model is used to simulate the transient variation of temperature field. And then the surface deformation equation is adopted to calculate dynamic features of the keyhole shape and keyhole establishment time inside weld pool, in which the force action on weld pool surface is considered. Experiment is cond^ted to validate the numerical simulation results. The predicted keyhole size and keyhole establishment time are in agreement with the experimental measurement. And the calculated fusion zone geometry is consistent with the measured one.展开更多
In 2005 year, SWIP carded through a general engineering and physics experiment of ECRH on HL-2A tokamak. The ECRH protection system is studied and set up to insure the security of ECRH system, and the work is normal. ...In 2005 year, SWIP carded through a general engineering and physics experiment of ECRH on HL-2A tokamak. The ECRH protection system is studied and set up to insure the security of ECRH system, and the work is normal. The main protection object of all ECRH system is the gyrotron, and the arc protection for it is more important in the protection system.展开更多
A digital arc welding power supply was designed with the advanced reduced instruction set computer machine （ARM） and embedded real-time multi-task operating system micro C/OS- Ⅱ. The ARM, with its powerful calculat...A digital arc welding power supply was designed with the advanced reduced instruction set computer machine （ARM） and embedded real-time multi-task operating system micro C/OS- Ⅱ. The ARM, with its powerful calculating speed and complete peripheral equipments, is very suitable to work as the controller of the digital power supply. The micro C/OS- Ⅱ transplanted in ARM, helps to improve the respondent speed against various welding signals, as well as the reliability of the controlling software. The welding process consists of nine tasks. The tasks of great significance on reliability of the welder, for example, the A/D conversion of current and voltage, enjoy top priority. To avoid simultaneous-sharing on A/D converter and LCD module, two semaphores are introduced in to ensure the smooth performance of the welding power supply. Proven by experiments ,the ARM and the micro C/OS- Ⅱ can greatly improve both the respondent speed and the reliability of the digital welder.展开更多
Twin wire submerged arc welding （SAW） is widely used in oil or gas line pipe fabrication because of its high productivity. To investigate the strength and toughness of the heat-affected zone （HAZ） in twin wire SAW...Twin wire submerged arc welding （SAW） is widely used in oil or gas line pipe fabrication because of its high productivity. To investigate the strength and toughness of the heat-affected zone （HAZ） in twin wire SAW, the cooling time t8/5 of the coarse grained zone must be studied. The authors presented a method of predicting the cooling time in twin wire SAW of intermediate thickness plate. Based on Rosenthal analytical solutions, an energy factor was introduced to describe the energy contribution of the two wires, equations of thermal cycle and cooling time in twin wire SAW of both thick, and thin, plates were developed. Weighting factors determined by actual thickness and critical thickness were adopted to represent the thermal cycle and cooling time of intermediate thickness plate through linear interpolation with thick, and thin, plate solutions. The predicted cooling time for an intermediate thickness plate was verified experimentally, and the predicted results agreed therewith.展开更多
It is of great significance to develop an intelligent monitoring system for weld penetration defects such as incomplete penetration and burn-through in real-time during robotic arc welding process. In this paper, robo...It is of great significance to develop an intelligent monitoring system for weld penetration defects such as incomplete penetration and burn-through in real-time during robotic arc welding process. In this paper, robotic gas metal arc welding experiments are carried out on the mild steel test pieces with Vee-type groove. Through-the-arc sensing method is used to capture the transient values of the welding voltage and current. The raw data of the captured welding current and voltage are processed statistically, and the feature vector SIO is extracted to correlate the welding conditions to the weld penetration information. It lays foundation for intelligent monitoring of weld quality in robotic arc welding.展开更多
The initial shape of the secondary arc considerably influences its subsequent shape.To establish the model for the arcing time of the secondary arc and modify the single-phase reclosing sequence,theoretical and experi...The initial shape of the secondary arc considerably influences its subsequent shape.To establish the model for the arcing time of the secondary arc and modify the single-phase reclosing sequence,theoretical and experimental analysis of the evolution process of the short-circuit arc to the secondary arc is critical.In this study,an improved charge simulation method was used to develop the internal-space electric-field model of the short-circuit arc.The intensity of the electric field was used as an independent variable to describe the initial shape of the secondary arc.A secondary arc evolution model was developed based on this model.Moreover,the accuracy of the model was evaluated by comparison with physical experimental results.When the secondary arc current increased,the arcing time and dispersion increased.There is an overall trend of increasing arc length with increasing arcing time.Nevertheless,there is a reduction in arc length during arc ignition due to short circuits between the arc columns.Furthermore,the arcing time decreased in the range of 0°-90°as the angle between the wind direction and the x-axis increased.This work investigated the method by which short-circuit arcs evolve into secondary arcs.The results can be used to develop the secondary arc evolution model and to provide both a technical and theoretical basis for secondary arc suppression.展开更多
1 Introduction A series of engineering tests and physical experiments,including ECRH[1],was carried out on the HL-2A tokamak in 2005.A fast arcing protection system[2] was developed to ensure operating of ECRH facilit...1 Introduction A series of engineering tests and physical experiments,including ECRH[1],was carried out on the HL-2A tokamak in 2005.A fast arcing protection system[2] was developed to ensure operating of ECRH facilities[3],especially the gyrotron,against arcing in the transmission line.展开更多
We consider the skew Brownian motion as a solution of some stochastic differential equation. We prove for the skew Brownian motion the analogues of the arc-sine laws for Wiener process. Unlike of existing results, we ...We consider the skew Brownian motion as a solution of some stochastic differential equation. We prove for the skew Brownian motion the analogues of the arc-sine laws for Wiener process. Unlike of existing results, we are forced to consider a stochastic differential equation with discontinuous diffusion coefficient. Possible interpretations of obtained results are suggested.展开更多
To promote the accuracy and application of arcing time measurement for SF_6 circuit breaker in substation,five measurement methods are investigated by two cases experimentally. First,the test results of the five metho...To promote the accuracy and application of arcing time measurement for SF_6 circuit breaker in substation,five measurement methods are investigated by two cases experimentally. First,the test results of the five methods for a circuit breaker in different stages of wear and a circuit breaker with a component failure were presented. Then,the time error is analyzed by simulation.Finally,the advantage and disadvantage of these methods are discussed.展开更多
Manual monitoring and seam tracking through watching weld pool images in real-time, by naked eyes or by industrial TV, are experience-depended, subjective, labor intensive, and sometimes biased. So it is necessary to ...Manual monitoring and seam tracking through watching weld pool images in real-time, by naked eyes or by industrial TV, are experience-depended, subjective, labor intensive, and sometimes biased. So it is necessary to realize the automation of computer-aided seam tracking. A PAW (plasma arc welding) seam tracking system was developed, which senses the molten pool and the seam in one frame by a vision sensor, and then detects the seam deviation to adjust the work piece motion adaptively to the seam position sensed by vision sensor. A novel molten pool area image-processing algorithm based on machine vision was proposed. The algorithm processes each image at the speed of 20 frames/second in real-time to extract three feature variables to get the seam deviation. It is proved experimentally that the algorithm is very fast and effective. Issues related to the algorithm are also discussed.展开更多
Presents penetration control by weld pool resonance which occurs when the natural frequency of weld pool is equal to the frequency of sine wave current while the weld pool is excited into oscillation by superimposing ...Presents penetration control by weld pool resonance which occurs when the natural frequency of weld pool is equal to the frequency of sine wave current while the weld pool is excited into oscillation by superimposing sine wave current with definite frequency or regular frequency on DC current, and experiments carried out on detecting resonance signals during both stationary and travelling arc welding with variant frequency pulse current, and concludes with experimental results that penetration control can be realized by weld pool resonance when welding speed is lower than 80mm/min, and this control method is applicable to welding thin (0.5～3.0 mm) plates of carbon steel, low alloy steel, high strength steel and superhigh strength steel, and suitable for alternating polarity welding of stainless steel, titanium alloy steel and aluminum alloy.展开更多
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.
文摘The use of time-frequency entropy to quantitatively assess the stability of submerged arc welding process considering the distribution features of arc energy is reported in this paper. Time-frequency entropy is employed to calculate and analyze the stationary current signals, non-stationary current and voltage signals in the submerged arc welding process. It is obtained that time-frequency entropy of arc signal can be used as arc stability judgment criteria of submerged arc welding. Experimental results are provided to confirm the effectiveness of this approach.
文摘Numerical analysis of keyhole shape and keyhole establishment time is of great significance for selection and optimization of the process parameters in keyhole plasma arc welding. In this paper, a three-dimensional transient model is developed to analyze the evolutions of keyhole shape and keyhole establishment time in continuous current plasma arc welding process. Firstly, a combined volumetric heat source model is used to simulate the transient variation of temperature field. And then the surface deformation equation is adopted to calculate dynamic features of the keyhole shape and keyhole establishment time inside weld pool, in which the force action on weld pool surface is considered. Experiment is cond^ted to validate the numerical simulation results. The predicted keyhole size and keyhole establishment time are in agreement with the experimental measurement. And the calculated fusion zone geometry is consistent with the measured one.
文摘In 2005 year, SWIP carded through a general engineering and physics experiment of ECRH on HL-2A tokamak. The ECRH protection system is studied and set up to insure the security of ECRH system, and the work is normal. The main protection object of all ECRH system is the gyrotron, and the arc protection for it is more important in the protection system.
基金Supported by the National Natural Science Foundation of China under Grant No 50575074by the Scientific and TechnologicalProject of Guangdong Province, China, under Grant No 2003A1040310
文摘A digital arc welding power supply was designed with the advanced reduced instruction set computer machine （ARM） and embedded real-time multi-task operating system micro C/OS- Ⅱ. The ARM, with its powerful calculating speed and complete peripheral equipments, is very suitable to work as the controller of the digital power supply. The micro C/OS- Ⅱ transplanted in ARM, helps to improve the respondent speed against various welding signals, as well as the reliability of the controlling software. The welding process consists of nine tasks. The tasks of great significance on reliability of the welder, for example, the A/D conversion of current and voltage, enjoy top priority. To avoid simultaneous-sharing on A/D converter and LCD module, two semaphores are introduced in to ensure the smooth performance of the welding power supply. Proven by experiments ,the ARM and the micro C/OS- Ⅱ can greatly improve both the respondent speed and the reliability of the digital welder.
文摘Twin wire submerged arc welding （SAW） is widely used in oil or gas line pipe fabrication because of its high productivity. To investigate the strength and toughness of the heat-affected zone （HAZ） in twin wire SAW, the cooling time t8/5 of the coarse grained zone must be studied. The authors presented a method of predicting the cooling time in twin wire SAW of intermediate thickness plate. Based on Rosenthal analytical solutions, an energy factor was introduced to describe the energy contribution of the two wires, equations of thermal cycle and cooling time in twin wire SAW of both thick, and thin, plates were developed. Weighting factors determined by actual thickness and critical thickness were adopted to represent the thermal cycle and cooling time of intermediate thickness plate through linear interpolation with thick, and thin, plate solutions. The predicted cooling time for an intermediate thickness plate was verified experimentally, and the predicted results agreed therewith.
文摘It is of great significance to develop an intelligent monitoring system for weld penetration defects such as incomplete penetration and burn-through in real-time during robotic arc welding process. In this paper, robotic gas metal arc welding experiments are carried out on the mild steel test pieces with Vee-type groove. Through-the-arc sensing method is used to capture the transient values of the welding voltage and current. The raw data of the captured welding current and voltage are processed statistically, and the feature vector SIO is extracted to correlate the welding conditions to the weld penetration information. It lays foundation for intelligent monitoring of weld quality in robotic arc welding.
基金supported by National Natural Science Foundation of China(Nos.92066108 and 51277061)。
文摘The initial shape of the secondary arc considerably influences its subsequent shape.To establish the model for the arcing time of the secondary arc and modify the single-phase reclosing sequence,theoretical and experimental analysis of the evolution process of the short-circuit arc to the secondary arc is critical.In this study,an improved charge simulation method was used to develop the internal-space electric-field model of the short-circuit arc.The intensity of the electric field was used as an independent variable to describe the initial shape of the secondary arc.A secondary arc evolution model was developed based on this model.Moreover,the accuracy of the model was evaluated by comparison with physical experimental results.When the secondary arc current increased,the arcing time and dispersion increased.There is an overall trend of increasing arc length with increasing arcing time.Nevertheless,there is a reduction in arc length during arc ignition due to short circuits between the arc columns.Furthermore,the arcing time decreased in the range of 0°-90°as the angle between the wind direction and the x-axis increased.This work investigated the method by which short-circuit arcs evolve into secondary arcs.The results can be used to develop the secondary arc evolution model and to provide both a technical and theoretical basis for secondary arc suppression.
文摘1 Introduction A series of engineering tests and physical experiments,including ECRH[1],was carried out on the HL-2A tokamak in 2005.A fast arcing protection system[2] was developed to ensure operating of ECRH facilities[3],especially the gyrotron,against arcing in the transmission line.
文摘We consider the skew Brownian motion as a solution of some stochastic differential equation. We prove for the skew Brownian motion the analogues of the arc-sine laws for Wiener process. Unlike of existing results, we are forced to consider a stochastic differential equation with discontinuous diffusion coefficient. Possible interpretations of obtained results are suggested.
基金Project Supported by the Technique Project of China Southern Power Grid Co.,Ltd.(20142001342)
文摘To promote the accuracy and application of arcing time measurement for SF_6 circuit breaker in substation,five measurement methods are investigated by two cases experimentally. First,the test results of the five methods for a circuit breaker in different stages of wear and a circuit breaker with a component failure were presented. Then,the time error is analyzed by simulation.Finally,the advantage and disadvantage of these methods are discussed.
文摘Manual monitoring and seam tracking through watching weld pool images in real-time, by naked eyes or by industrial TV, are experience-depended, subjective, labor intensive, and sometimes biased. So it is necessary to realize the automation of computer-aided seam tracking. A PAW (plasma arc welding) seam tracking system was developed, which senses the molten pool and the seam in one frame by a vision sensor, and then detects the seam deviation to adjust the work piece motion adaptively to the seam position sensed by vision sensor. A novel molten pool area image-processing algorithm based on machine vision was proposed. The algorithm processes each image at the speed of 20 frames/second in real-time to extract three feature variables to get the seam deviation. It is proved experimentally that the algorithm is very fast and effective. Issues related to the algorithm are also discussed.
文摘Presents penetration control by weld pool resonance which occurs when the natural frequency of weld pool is equal to the frequency of sine wave current while the weld pool is excited into oscillation by superimposing sine wave current with definite frequency or regular frequency on DC current, and experiments carried out on detecting resonance signals during both stationary and travelling arc welding with variant frequency pulse current, and concludes with experimental results that penetration control can be realized by weld pool resonance when welding speed is lower than 80mm/min, and this control method is applicable to welding thin (0.5～3.0 mm) plates of carbon steel, low alloy steel, high strength steel and superhigh strength steel, and suitable for alternating polarity welding of stainless steel, titanium alloy steel and aluminum alloy.
