Mathematical Formula to Determine Geometrical Dimensions of Electrode Metal Droplets Transferred with Short Circuits

2018 ◽  
Vol 938 ◽  
pp. 1-6
Author(s):  
D.P. Il’yashchenko ◽  
D.A. Chinakhov ◽  
K.Yu. Kirichenko ◽  
V.N. Sydorets
Keyword(s):  
Chemical Elements ◽  
Short Circuit ◽  
Power Source ◽  
Mathematical Formula ◽  
Metal Parts ◽  
Energy Impact ◽  
Short Circuits ◽  
Electrode Metal ◽  
Geometrical Dimensions ◽  
Metal Droplets

A method is described to determine geometrical dimensions of electrode metal droplets depending on short circuit duration. It provides a quantitative evaluation of the electrode metal transfer and the energy impact on metal parts being welded. It is proved that using inverter power source decreases the size of droplets transferred to the welding pool by 24% in average if compared with a diode power source. It also reduces overheating of the droplets which improves efficiency of transferring chemical elements from the electrode to the weld metal.

scholarly journals Regularities of Control of Mechanized Pulse-Arc Welding Process for Ensuring its Stability

2019 ◽  
pp. 65-76
Author(s):  
S. Yu. Maksymov ◽  
L. S. Shlapak ◽  
А. А. Havryliuk ◽  
І. М. Semianyk ◽  
V. А. Onyskiv
Keyword(s):  
Arc Welding ◽  
Low Voltage ◽  
Short Circuit ◽  
Welding Current ◽  
Short Circuit Current ◽  
Average Frequency ◽  
Maximum Value ◽  
Current Growth ◽  
Short Circuits ◽  
Electrode Metal

Mechanized arc welding in protective gases with short circuits (s.c.) is performed at moderate values of the welding current (up to 180 ... 220 A) and at the relatively low voltage (18 ... 24 V) on the arc. The main disadvantage of the process is spattering when melting an electrode metal and when transferring it to a weld bath. The elimination of disadvantages is possible through the implementation of a controlled transfer of molten electrode metal to a welding bath - due to the pulsed nature of arc burning.  At pulse-arc welding (PAW), one of the main methods of increasing the efficiency of the process is to limit the maximum value of the short-circuit current Imax s.c. by increasing the inductive resistance L in the arc-welding circuit. Proceeding from the features of mechanized arc welding, the purpose of the research is to specify the influence of the velocity of the growth of the welding current vс during the s.c. on the arc stability. The implementation of experimental work presupposes surfacing on a plate with the programming of the operating mode of the inverter at different values (9, 12, 15, 18, 21, 24, 27, 30) with the frequency f = 25 Hz and a pulse ratio C = 2. While analyzing oscillograms of welding current and processing their records, it was established that a decrease of the velocity of the welding current growth leads to a significant limitation of the maximum value of the short-circuit current. The statistical processing of the momentary values of the welding current shows that the increase in the velocity of current growth vс starting with vс = 1.23 kA / s to vс = 50 kA / s makes the average short-circuit duration 10 times shorter. At the same time, the average frequency of short circuits grows more than twice. The increase of vс leads to the destabilization of the pulse process and this is reflected in the 30-times increase of the average frequency of arc break. The increase of the energy indexes of the PAW to the Iav. = 220 ... 225 A, Uav. = 24.5 ... 25.9 V, Q ≈ 7.9 ... 8.0 kJ / cm led to the changes in the parameters which characterize the process of pulsed welding with short circuits. There is a sharp decrease in the average frequency of short circuits (2 ... 3 times as rarely) and the average duration of s.c. (twice shorter).

scholarly journals Optimization-Based Formulations for Short-Circuit Studies with Inverter-Interfaced Generation in PowerModelsProtection.jl

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2160
Author(s):  
Arthur K. Barnes ◽  
Jose E. Tabarez ◽  
Adam Mate ◽  
Russell W. Bent
Keyword(s):  
Optimization Problem ◽  
Short Circuit ◽  
Problem Formulation ◽  
Power Delivery ◽  
Fault Current ◽  
Protective Device ◽  
Protective Relaying ◽  
Overcurrent Protection ◽  
Short Circuits ◽  
Optimization Problem Formulation

Protecting inverter-interfaced microgrids is challenging as conventional time-overcurrent protection becomes unusable due to the lack of fault current. There is a great need for novel protective relaying methods that enable the application of protection coordination on microgrids, thereby allowing for microgrids with larger areas and numbers of loads while not compromising reliable power delivery. Tools for modeling and analyzing such microgrids under fault conditions are necessary in order to help design such protective relaying and operate microgrids in a configuration that can be protected, though there is currently a lack of tools applicable to inverter-interfaced microgrids. This paper introduces the concept of applying an optimization problem formulation to the topic of inverter-interfaced microgrid fault modeling, and discusses how it can be employed both for simulating short-circuits and as a set of constraints for optimal microgrid operation to ensure protective device coordination.

Identification of Electrical Fire Melted Marks of Copper Wires by Electron Backscattered Diffraction (EBSD)

2014 ◽  
Vol 513-517 ◽  
pp. 281-285
Author(s):  
Cheng Sun ◽  
Min Ju Ding ◽  
Yong Feng Zhang ◽  
Xun Tan ◽  
Peng Wang ◽  
...  
Keyword(s):  
Copper Wire ◽  
Short Circuit ◽  
Testing Methods ◽  
Electron Backscattered Diffraction ◽  
Qualitative And Quantitative ◽  
Metallographic Method ◽  
Short Circuits ◽  
In Fire ◽  
Misorientation Of Grains ◽  
Electrical Apparatus

A variety of electrical apparatus used in daily life can cause fires because of internal or external factors. During cause identification of an electrical fire, the first short circuit melted marks of copper wire have been considered highly important because they are direct proofs. Additionally, overloaded short circuit caused by the overload of current due to excessive electrical usage can give rise to an electrical fire. Despite extensive research on the first short circuit in fire scenes, the overloaded short circuit remains difficult to be distinguished because of the limitation of commonly used testing methods. Conventional metallographic method is intuitionistic and simple, but may not provide detailed data of crystals such as misorientation of grains. Here a new method (electron backscattered diffraction, EBSD) is applied for identification of the first and overloaded short-circuited melted marks of copper wires in electrical fire scenes. Results show obvious morphological distinctions in melted marks of copper wires between the first and overloaded short circuits. Qualitative and Quantitative differences obtained from the contrast of the above two short circuit situations may assist for cause identification of electrical fires in the future.

Analysis of Nonlinear Variation Accumulation in Auto-Body Assembly Process

Manufacturing ◽  
2002 ◽  
Author(s):  
Jun Lian ◽  
Zhongqin Lin ◽  
Fusheng Yao ◽  
Xinmin Lai
Keyword(s):  
Sheet Metal ◽  
State Equation ◽  
Assembly Process ◽  
Transformation Mechanism ◽  
Metal Parts ◽  
Sheet Metal Parts ◽  
Accumulation Mechanism ◽  
Auto Body ◽  
Non Gaussian ◽  
Geometrical Dimensions

In the assembly process of auto-body, variations in the geometrical dimensions of sheet metal parts and fixtures are inevitable. These variations accumulate through the multi-station assembly process to form the dimensional variations of the final products. Compared with the assembly of rigid parts, the assembly process of the elastic parts is more complex because the variation accumulation patterns rely much on the variations of fixture, jointing methods and mechanical deformation. This paper aims at analyzing the variation transformation mechanism and accumulation characteristics for the assembly of sheet metal parts based on the analysis of dimensional coordination relations among parts and fixtures. Finite element method (FEM) and Monte-Carlo Simulation (MCS) were used to analyze the effect of jointing contact on variation transformation, while a state equation was developed to describe the variation accumulation mechanism. The result of the analysis indicates that the main characteristics of elastic assembly jointing are the overlap jointing methods and elastic contacts action. The fact that the variation transform coefficients (VTC) are variable makes the assembly variation distribution Non-Gaussian even if the dimension variation of parts is Gaussian distribution. The analysis conclusions have potential value for more reasonable tolerance synthesis of elastic parts assembly.

scholarly journals Performance of Parallel Connected SiC MOSFETs under Short Circuits Conditions

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6834
Author(s):  
Ruizhu Wu ◽  
Simon Mendy ◽  
Nereus Agbo ◽  
Jose Ortiz Gonzalez ◽  
Saeed Jahdi ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
Short Circuit ◽  
Critical Factor ◽  
Charge Trapping ◽  
Parallel Connection ◽  
Bias Temperature Instability ◽  
Test Methodology ◽  
Threshold Voltages ◽  
Short Circuits ◽  
The Impact

This paper investigates the impact of parameter variation between parallel connected SiC MOSFETs on short circuit (SC) performance. SC tests are performed on parallel connected devices with different switching rates, junction temperatures and threshold voltages (VTH). The results show that VTH variation is the most critical factor affecting reduced robustness of parallel devices under SC. The SC current conducted per device is shown to increase under parallel connection compared to single device measurements. VTH shift from bias–temperature–instability (BTI) is known to occur in SiC MOSFETs, hence this paper combines BTI and SC tests. The results show that a positive VGS stress on the gate before the SC measurement reduces the peak SC current by a magnitude that is proportional to VGS stress time. Repeating the measurements at elevated temperatures reduces the time dependency of the VTH shift, thereby indicating thermal acceleration of negative charge trapping. VTH recovery is also observed using SC measurements. Similar measurements are performed on Si IGBTs with no observable impact of VGS stress on SC measurements. In conclusion, a test methodology for investigating the impact of BTI on SC characteristics is presented along with key results showing the electrothermal dynamics of parallel devices under SC conditions.

scholarly journals ANALYSIS OF MONI SIS OF MONITORING OF THE A ORING OF THE AT-3 AUTOTRANSFORM TRANSFORMATOR IN T OR IN TashTES MODE

2019 ◽  
Vol 2019 (1) ◽  
pp. 209-217
Author(s):  
F Isakov
Keyword(s):  
Cooling System ◽  
Power Transformer ◽  
Short Circuit ◽  
Operation Mode ◽  
Wear And Tear ◽  
Basic Parameters ◽  
Short Circuits ◽  
One Year ◽  
Insulation Breakdown ◽  
Winding Insulation

The article considers the results of the analysis of autotransformers operation mode monitoring. The time diagram of active load current and oil temperature of autotransformer TashTES AT-3 is established and during one year changes of these variables and basic parameters of autotransformer were observed. Technical faults of the power transformer and high power autotransformer are established and methods of their elimination are determined. Damage of transformers and autotransformers with voltage of 110-500 kV of about 30% of the total number of outages which were accompanied by internal short-circuits and two main causes of damage were determined. The main causes of technological failures, which were not accompanied by internal short-circuits, are as follows: 20% of failures in operation of the onload tap-changer, 16% of oil leaks from the bushings, 13% of oil leaks and lowering of oil from the transformer due to violation of welded joints and rubber seals, 4% of engine damage to oil pumps of the cooling system, 3% of pressure increase in high-voltage hermetic bushings, 2% of film protection shell damage. The main reasons of technological violations accompanied by internal short-circuit in the transformer are as follows: breakdown of internal insulation of highvoltage bushings, insufficient short-circuit resistance, wear and tear of winding insulation, breakdown of insulation.

ENGINEERING ANALYSIS OF THE THREE-PHASE SHORT CIRCUIT MODE IN THE 10 KV ELECTRIC NETWORK TAKING INTO ACCOUNT THE INFLUENCE OF LOAD CURRENTS

2021 ◽  
pp. 74-83
Author(s):  
YURI D. VOLCHKOV ◽  
Keyword(s):  
Remote Monitoring ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Load Current ◽  
Electric Network ◽  
Operating Modes ◽  
Three Phase ◽  
Feed Network ◽  
Short Circuits ◽  
Switching Devices

Abstract. The load current aff ects the value of the short-circuit current in the electric network and, consequently, the voltage value. In some cases, this infl uence must be taken into account for the correct choice of switching devices, remote monitoring the operating modes of electric networks, and determining the modes. It is possible to disconnect loads connected through magnetic starters and contactors. Failure to consider the infl uence of the load current can lead to an incorrect interpretation of the identifi ed grid operating modes during remote monitoring and, as a result, incorrect dispatcher’s decisions. In addition, it is also insuffi cient to specify the choice of switching devices in the 10 kV feed network. The article describes a method for analyzing the three-phase short circuit mode in a 10 kV feed network, taking into account the infl uence of load currents. The method is exemplifi ed by the case of an actual electric network – the 10 kV ring feed network containing reclosers and receiving power from diff erent sections of lowvoltage buses of the “Kulikovskaya” 110/35/10 kV substation, belonging to the Branch of PJSC «DGC of Center”-“Orelenergo.” For this network, the values of the three-phase short-circuit currents at points with diff erent distances from the substation buses have been determined. The authors have fi guredout the values of the load currents and their shares in the total short-circuit current. The voltage values at different points of the network in the case of short circuits have also been determined. The research proves that the effect of the load current on the total short-circuit current should be taken into account for the case of remote short circuits.

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