Wyniki wyszukiwania - Biblioteka Nauki

1

Influence of Harmonics on the Working Efficiency of a 6/1.2 kV Transformer in a Pit Mine

100%

Ngo X. C. , Do N. Y.

Inżynieria Mineralna

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2021

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tom no. 2

149--156

EN

Explosion-proof transformers 6/1.2 kV is important electrical equipment responsible for supplying electricity in underground mine electrical networks. A failure of this transformer will cause an interruption in the power supply and loss of safety in underground mining. Usually, explosion-proof transformers in underground mine electrical networks are designed and manufactured to work with ideal parameters such as sinusoidal currents, and the network structure is symmetrical. However, today in underground mine electric networks, many power electronics are connected to the network, such as inverters and soft starters. As a result, a current flowing through the transformer is non-sinusoidal, overloading the transformer even by working with the design specifications. This paper studies the influence of harmonics on the working efficiency of a 6/1.2 kV transformer in a pit mine. Research results suggest reasonable solutions for transformer operation to ensure longevity and not cause damage to the transformer.

2

Influence of Single-Phase Voltage Loss and Load Carrying Mode on Mine Drainage Pump Motor in Vietnam

100%

Do N. Y. , Ngo X. C.

Inżynieria Mineralna

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2021

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tom no. 2

341--352

EN

Mine drainage pump is the most important load in mining which requires high reliability when operating. Currently, the power supply of a mine drainage pump is connected to the same power line with many nonlinear loads, and is equipped with power electronic converters, which makes the power supply nonsinusoidal. During the working process of a mine drainage pump, the load-carrying factor often changes, and many types of failures occur, among which single-phase voltage loss is the most common problem. In the case of a nonsinusoidal power supply, if a single-phase voltage loss occurs in different load modes, it will greatly affect the working mode of the mine drainage pump leading to influences on the working efficiency, the life of the pump, and sometimes it is necessary to recalculate the protection parameters. This paper studies the influence of single-phase voltage loss and load carrying mode on the working mode of mine drainage pump motor in case the of nonsinusoidal power supply. Research results show that, in the case of nonsinusoidal power supplied with single-phase voltage loss, copper losses in the rotor and stator circuits increase with increases in voltage total harmonic distortion (THD) and load-carrying factor, 5th order reverse harmonic increases copper loss in asynchronous motor the most, and higher harmonic components have less effect on copper loss in the motor. At the same time, the speed ripple decreases with the increase of the motor load factor and decreases in the presence of the 5th order negative sequence harmonic, and increases significantly in the presence of the 7th order positive sequence harmonic. 5th order negative sequence harmonic increases, the torque ripple increases, while the 7th order positive sequence harmonic reduces the torque ripple in the case of single-phase voltage loss. The results of the paper will help improve the operational efficiency of the mine drainage pump in Vietnam's mines.

3

The Influence of Voltage Quality on Asynchronous Motor Performance of EKG Excavator in Open Pit Mines – Vinacomin

80%

Ngo X. C. , Do N. Y. , Tran Q. H.

Inżynieria Mineralna

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2020

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tom no. 2, vol. 1

139--145

EN

At present, in open-pit mining, the main and most important electrical load is the electric excavator, and currently using a variety of EKG excavators. 6kV electrical network in open pit mining has the characteristics such as long outgoing lines, use high-powered equipment, multiple branches, and increasing use of power electronics on the grid, this reduces the quality of the power supplied to the excavators EKG, resulting in an increase in power losses thereby greatly affecting the performance of the excavators. Previous studies on the quality of the power supplied to the excavator often only mentioned voltage deviations, in addition to this factor, the performance of the excavator is also greatly affected by nonsinusoidal voltage waveforms of the excavator power supply. This paper analyzes the influence of the nonsinusoidal of voltage on the power loss of electric motors used in EKG electric excavators in open pit mining based on the method of electromagnetic analysis and verification on simulation software.

PL

Obecnie, EKG są powszechne koparki stosowane w kopalnictwie odkrywkowym Wietnamu. Sieć elektryczna 6kV w kopalniach odkrywkowych ma takie cechy, jak długie linie wychodzące, zastosowanie sprzętu o dużej mocy, wiele odgałęzień co obniża jakość energii dostarczanej do koparek EKG, skutkując wzrost strat mocy, co znacząco wpływa na wydajność koparek. Dotychczasowe badania jakości energii dostarczanej do koparki często wskazywały tylko na odchylenia napięcia. W artykule, przeanalizowano wpływ napięcia niesinusoidalnego na straty mocy silników elektrycznych stosowanych w koparkach elektrycznych EKG w górnictwie odkrywkowym w oparciu o metodę analizy elektromagnetycznej i weryfikacji w oprogramowaniu symulacyjnym.

4

Effect of Power Quality on the Performance of Explosion-Proof Transformers in Mining in Vietnam

80%

Do N. Y. , Ngo X. C. , Nguyen T. H.

Inżynieria Mineralna

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2023

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tom no. 2, vol. 1

65--69

EN

When meeting customer demand, utility companies must consider power quality. Currently, the industrial power network in general and the underground mine power network in particular have long feeder lines, supplying power to many nonlinear loads and power electronic converters, which reduces power quality. Poor power quality can damage sensitive equipment and lead to costly repairs, leading to lost time, data corruption, and lower productivity. In this paper, a fuzzy system is developed to determine the power quality of the power network for different operating conditions and study its influence on the performance of the explosion-proof transformer in the underground mine power network in Vietnam. The simulations and calculations were performed on Matlab-Simulink software for a three-phase, 630-kVA, 6/1.2 kV explosion-proof transformer in power networks with variable power quality. A fuzzy system is developed with four measurable inputs, including frequency deviation, voltage unbalance factor, total harmonic distortion of supply voltage, total harmonic distortion of current, and an output variable, power quality. The simulation results show that the explosion-proof transformer's performance decreases when the power quality degrades, and the proposed fuzzy system can accurately diagnose this.