• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.4
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• pp.158-163
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• 2002

The pulsed Power system has been widely used to many applications, such as E/P(Electrostatic Precipitator), DeNOx/DeSOx power system, often generator, etc. In this paper, we study EMTP analysis and characteristics of critical voltage and load in impedance on various electrode length of pulse corona. To obtain a stable pulse voltage, we designed a compact pulse generator switched MOSFET and tested their characteristics by adjusting electrode length and pulse repetition. As a re sult, critical voltage of pulse corona and load impedance on increasing electrode length were decreased. These results indicate we can control critical voltage of pulse corona and suppress arc discharging between two electrodes.

• Journal of Biosystems Engineering
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• v.13 no.3
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• pp.32-43
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• 1988

This study was attempted to investigate the pneumatic separation on separating unit of a combine harvester. The aerodynamic characteristics of threshed materials were analyzed by experiments. The air velocity distribution within the separation chamber was measured for various speeds of the winnower and suction fans to find out the operational and design conditions of the separating unit which would serve for reducing the grain loss from chaff outlet. The results of study arc summarized as follows: 1. Based on the separation curve of threshed materials analyzed, it was shown that three different kind. of materials-kernels, straw chaff, and leaf chaff were as a whole able to be separated pneumatically, regardless of varieties. However, a small amount of the separation grain loss may be expected to occur if the complete separation between kernels and straw chaff would be undertaken because some portion of their separation curve were overlapping. 2. The analysis of air velocity distribution showed that the separation chamber may be divided into two regions, the discharging and separating. The air velocity of the discharging region was 5-15 m/s and that of the separating region 2-5 m/s. 3. The air movement of the separation chamber may be a turbulence flow, being its speed became greater as it moves from the left to the right section of the separation chamber. The equi-speed line. of air flow had a steep gradient in between the discharging and the separation regions. The air velocity in the discharging region was much higher than the terminal velocity of kernels, because of which those kernels appearing in the region could be possibly exhausted as the grain loss from the chaff outlet. 4. The motion trajectory of threshed material in the separating region was dominantly affected by the winnower fan, on the other hand, its motion in the discharging region was affected by suction fan. 5. The grain loss from the chaff outlet was affected greatly by the winnower fan and the trace of kernel movement. It was observed that the optimum working speed to give minimum grain loss from chaff outlet for the combine tested should be maintained at 950~1,150 rpm for the winnower fan and 1,850 rpm for the suction fan. 6. It was shown that a large portion of grain loss from chaff outlet may occur when the kernels may bump against a portion of separation chamber wall and those kernels thus scattered into the discharging region were sucked by the suction fan. It was accordingly recommended that a new design of the wall of separation chamber so as to bump down kernels may be necessary to reduce grain loss from the chaff outlet.

• Journal of Welding and Joining
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• v.18 no.2
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• pp.196-196
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• 2000

Formation of the weld defect, such as a blowhole and a pit in lap-jointed fillet arc welds has been a serious problem in arc welding of Zn-coated steel sheet. In this study, the relationship among welding conditions, welding materials and defect formation was investigated in order to minimize these defects in the CO₂ welds. In addition, the arc stability of the commercial welding wires was evaluated for revealing their effects on defect formation. Main conclusions obtained are as follows:1) There was no difference between shear tensile strength of the sound welds and that of the welds with blowholes whose diameters are less than 0.5mm. However, the welds with blowholes whose diameters are equal or larger than 0.5mm and pits exhibited tensile strength 10~20% and 30~40% lower than that of the sound welds respectively.2) The optimum welding condition to effectively prevent or reduce the weld defects formation are as follows:- The welding variables of 220A-23V-100cm/min and 120A-190V-30cm/min were recommended for minimizing the weld defects.- The gap between the two sheets at the lap-joint should be controlled to more than 0.2mm- Solid wire was less susceptible to the formation of the weld defects than the flux-cored wire.- The low welding current condition produced less weld defects than the hihg welding current condition.3) One of the reason why the amount of the defect was reduced at the low welding current was the gas discharging by the active agitation of the molten pool, due to an increasing in the number of the short circuit. (Received September 27, 1999)

• Journal of Welding and Joining
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• v.18 no.2
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• pp.69-76
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• 2000

Formation of the weld defect, such as a blowhole and a pit in lap-jointed fillet arc welds has been a serious problem in arc welding Zn-coated steel sheet. In this study, the relationship among welding conditions, welding materials and defect formation was investigated in order to minimize these defects in the CO₂welds. In addition, the arc stability of the commercial welding wires was evaluated for revealing their effects on defect formation. Main conclusions obtained are as follows: 1) There was no difference between shear tensile strength of the sound welds and that of the welds with blowholes whose diameters are less than 0.5mm. However, the welds with blowholes whose diameters are equal or large than 0.5mm and pits exhibited tensile strength 10∼ 20% and 30∼40% lower than that of the sound welds respectively. 2) The optimum welding condition to effectively prevent or reduce the weld defects formation are as follows: -The welding variables of 220A-23V-100cm/min and 120A-19V-30cm/min were recommended for minimizing the weld defects. -The gap between the two sheets at the lap-joint should be controlled to more than 0.2mm. -Solid wire was less susceptible to the formation of the weld defects than the flux-cored wire. -The low welding current condition produced less weld defects than the high welding current condition. 3) One of the reason why the amount of the defect was reduced at the low welding current was the gas discharging by the active agitation of the molten pool, due to an increasing in the number of the short circuit.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.6
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• pp.593-600
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• 2013

The asymmetric pulsed DC reactive magnetron sputtering system is widely used for the high quality plasma sputtering process such as a thin film deposition. In asymmetric pulsed DC power supply a reverse voltage is applied to the target periodically to minimize arc discharging effect. When sputtering in the mid-frequency range (20-350 kHz), the periodic target voltage reversals suppress arc formation at the target and provide long-term process stability. Thus, high quality, defect-free coatings of these materials can now be deposited at competitive rates. In this paper, a new style asymmetric pulsed DC power supply including mid-transformer is presented. In the proposed, an energy recovery circuit is adopted to reduce the mutual inductance of the transformer. As a result, the system dynamics of the voltage control loop is increased highly and the non-linear voltage boosting effect of the conventional system is removed. This work was proved through simulation and laboratory based experimental study.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1997.05a
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• pp.67-75
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• 1997

To establish testing method for ignition energy of explosive powders caused by electrostatic discharge, one testing method using a very small quantity of tested powders ( Frima ) was proposed, and the influence of discharge - limiting resistance connected in series into a capacitive discharge circuit on ignition energies of explosive powders was investigated using, as tested powders. As a result the minimum ignition energy was 9 mJ when discharge-limiting resistance was 300 k$\Omega$. The reason for the dependence of ignition energy on discharge-limiting resistance was thought to the difference in the type of electrostatic discharge, such as arc or glow discharge, from the observation of discharging wave forms.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1850-1852
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• 2002

In this paper, we studies EMTP analysis and characteristics of critical voltage of pulse corona and load impedance on variable electrode length. To obtain a stable Pulse voltage, we designed a compact pulse generator switched MOSFET and tested their characteristics by adjusting electrode length and pulse repetition. As a result, critical voltage of pulse corona and load impedance on increasing electrode length were decreased. These results indicate we can control critical voltage of pulse corona and suppress arc discharging between two electrodes.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1800-1803
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• 2002

The pulsed power system was widely making use good of many industrial and environments. The pulse generator generally required for short pulse duration and high peak value was forced to consider its volume and economy. In this paper, this system is designed and fabricated which has a compact size of pulse generator with switched MOSFET. We have studied the removal of rust material using Arc discharging in pulsed power system. It have tested their characteristics by adjusting variable voltage charging and pulse repetition rate. As a result, We can eliminate rust materials with this device.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05a
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• pp.184-186
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• 2002

In this paper, we studies EMTP analysis and characteristics of critical voltage of pulse corona and load impedance on variable electrode length. To obtain a stable pulse voltage, we designed a compact pulse generator switched MOSFET and tested their characteristics by adjusting electrode length and pulse repetition. As a result, critical voltage of pulse corona and load impedance on increasing electrode length were decreased. These results indicate we can control critical voltage of pulse corona and suppress arc discharging between two electrodes.

• Transactions of the Korean hydrogen and new energy society
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• v.10 no.2
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• pp.141-149
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• 1999

Recently the Ni/MH secondary battery has been studied extensively to achieve higher energy density, longer cycle life and faster charging-discharging rate etc. In this work, the electrode properties of $(LM)Ni_{4.49}Co_{0.1}Mn_{0.205}Al_{0.205}$ alloy and $Ti_{0.6}Zr_{0.4}V_{0.6}Ni_{1.4}$ alloy with addition of Pd were investigated. These alloys did not show any change in XRD pattern by Pd addition. As Pd was added as alloy element, the activation behavior was not affected significantly in both $AB_2$ type and $AB_5$ type electrodes and, On charging and discharging in high current density, Discharge capacity with increasing of Pd content was more decreased. But cycle life was showed increasing. Especially the electrode of $Ti_{0.6}Zr_{0.4}V_{0.6}Ni_{1.4}+0.5wt%$ Pd alloy was not almost decreased discharge capacity for 400cycles.