• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.32 no.5
• /
• pp.157-163
• /
• 1983

Positive and negative coronas in point-to-plane short gap have been investigated with the variations of point radius and gap length. Mainly the onset potentials and current pulses under various conditions were measured with a 70 MHz C.R.O. and a precise-controllable D.C. power supply. In the case of negative corona, the Trichel pulse corona, glow corona and spark regions were distinguished apparently and the critical gap lengths between them were also found clearly. In the case of positive corona, there are streamer corona, spark regions and the critical gap length between them, too. The current pulse forms of Trichel pulse corona of negative and streamer pulse corona of positive are similar in rising time, peak-to-peak time and pulse width. The glow corona current shows D.C. component in form.

• Proceedings of the KIEE Conference
• /
• 1985.07a
• /
• pp.127-130
• /
• 1985

A stochastic model to predict radio interference field as caused by corona discharges on high voltage transmission lines has been developed. This model is based on corona discharge distributed randomly in time and space. A stochastic model for the corona current induced by corona discharges on power lines is proposed. On the basis of the proposed corona current model, a rigorous analysis is presented to evaluate the radio interference (RI) field caused by corona discharges on a single conductor using the stochastic method.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.29 no.11
• /
• pp.74-81
• /
• 2015

In the measurement of atmospheric static electric field, it is important to know characteristics of corona discharges caused at the tip of test electrode. This paper presents the fundamental data of DC corona discharges that occurred at the tip of a needle-shaped electrode placed in the homogeneous background electric field which simulates the atmospheric static field under thundercloud. The major characteristics of interest for this purpose are the polarity effect of corona discharges and the magnitudes and time intervals of corona current pulses. The experimental set-up consists of the plate-to-plate configuration with a needle-shaped protrusion, DC power supply, and voltage and current measuring devices. As a result of experiments, the polarity dependence of corona pulses is significantly pronounced. The time intervals between successive corona pulses in the negative polarity is much longer than those in the positive polarity. The time intervals for both polarities is drastically decreased as the applied electric field is increased. Also the magnitudes of the positive corona pulses are slightly changed with an increase in applied electric field, but those of the negative corona pulses are linearly increased with increasing the applied electric fields.

• Journal of Electrical Engineering and Technology
• /
• v.6 no.4
• /
• pp.556-562
• /
• 2011

In the present study, a simple corona-wire charger for unipolar diffusion charging of aerosol particles is designed, constructed, and characterized. Experimental characterizations of the electrostatic discharge in terms of current-voltage relationships of positive and negative coronas of the corona-wire charger are also presented and discussed. The charging current and ion concentration in the charging zone increased monotonically with corona voltage. The negative corona showed higher current than the positive corona. At the same corona voltages, the current in the discharge zone is about 600 times larger than the charging current. The ion number concentrations ranged within approximately $5.0{\times}10^{10}$ to $1.24{\times}10^{16}$ and $4.5{\times}10^{12}$ to $2{\times}10^{16}$ ions/$m^3$ in the discharge and charging zones, respectively. A numerical model is used to predict the behavior of the electric potential lines. Numerical results of ion penetration through the inner electrode are in good agreement with the experimental results.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.56 no.10
• /
• pp.1791-1795
• /
• 2007

Small ions generated at conductor corona sources remain in the atmosphere until they recombine with ions of opposite polarity, attach to aerosols, or make contact with an object. Ion current density is major factor to design conductor configuration of DC overhead transmission line. Several techniques have been used to measure the ion current of HVDC overhead transmission line. In this study, the ion current density was measured by a plate electrode made of a metal flat board at DC corona cage. The sensitivity of the plate electrode is $0.156uA/m^2/V$. To obtain an useful database on corona discharge, it is necessary to do corona test on several kinds of conductor bundles. Therefore, a number of experiments were conducted on several kinds of conductor bundles. To reliably analyze ion effects, corona cage test data were obtained over a long period of time under various weather conditions and expressed as a statistical distribution. Ion current density distribution in foul weather shows a significant increase in levels over the corresponding fair weather. Based on this results, we evaluated the environmental characteristic caused by ion flow of three candidated conductor bundles.

• Journal of Adhesion and Interface
• /
• v.17 no.3
• /
• pp.104-109
• /
• 2016

Compare AC corona and DC corona treatment effects, polyester fabrics were AC corona treated with different current intensity (5, 10, 15 A) and feeding speed (5, 10, 15 m/min) as the same DC corona treatment conditions of the preceding research. We confirmed the surface change of polyester fabrics using scanning electron microscopy (SEM) and X-ray photoelectron spectrometer (XPS), and the change of physical properties through measuring the dry and wet bonding strength. The surface changes of polyester fabrics by treating in air atmosphere with AC corona discharge are shown similar tendency with DC corona discharge. Generally dry bonding strength were increased with increasing current intensity and feeding speed, but wet bonding strength were increased with increasing current intensity and decreasing feeding speed in both AC and DC corona treatment. When the current is 20 A, carbonization occurs in DC corona discharge but carbonization does not occur in DC corona discharge.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.59 no.10
• /
• pp.1862-1868
• /
• 2010

A corona motor, as one of a powerful cooling means of microelectronic devices, has been employed because of its very simple structure of no coils and no brushes. In this paper, the effect of polarity of applied voltage and the number of blade corona electrodes on the fundamental properties of rotation of the motor was investigated. The I-V and rotation characteristics of the blade corona electrode were significantly different from the different polarities of applied voltages and the blade corona electrode numbers, due to the different space charge effect resulted by the different migration mobility of the positive and negative ions generated near the blade corona electrode tip of the rotor of the motor. The rotation speed of the motor was influenced significantly by the polarity of corona discharge, the number of blades, and mass of rotor. At the same corona current, an effective rotation can be obtained with the positive corona caused by the lower ion mobility. On the other hand, the higher rotation speed can be obtained with the negative corona resulted from its higher corona current. The highest rotation speed and energy efficiency can be obtained with the rotor having 4 blades.

• Journal of Electrical Engineering and Technology
• /
• v.5 no.1
• /
• pp.156-162
• /
• 2010

This paper describes electrical and optical characteristics of discharge developments in water under inhomogeneous fields caused by impulse voltages. Predischarge current and discharge light images were observed for different water resistivities and applied voltages between the hemispherical water tank and the needle electrode. The electrical parameters characterizing discharge developments are analyzed based on the discharge light images and voltage-current (V-I) curves, and electrical resistances derived by voltage and current waveforms. As a result, when the streamer corona is initiated at the tip of the needle electrode, the transient resistance suddenly drops and V-I curves form a 'loop'. The length of streamer propagation is increased with increasing peak value of the applied voltage, and the streamer corona extension is enlarged with increasing water resistivity. The electrical resistances before streamer corona initiation are rarely changed by different applied voltages. On the other hand, the electrical resistances after streamer corona initiation are found to be inversely proportional to the peak value of the applied voltage, and the decreasing rates for higher water resistivities are much higher than those for lower water resistivities. The time to streamer corona initiation and the time to the second current peak become shorter as the voltage increases. Finally, the calculated resistances after streamer corona initiation are almost the same trace of measured resistances, but they are smaller than the measured values.

• Journal of the Korean Society of Safety
• /
• v.7 no.2
• /
• pp.57-62
• /
• 1992

In this thesis, the electrification phenomenon was studied by measurement of charging current and discharging current in polymers when the carriers generated by corona discharge were supplied to the surface of polymers. Corona charging current of PVC, polar and noncrystalline polymer, was larger than that of nonpolar and amorphous polymers. Corona charging current on the specimen of naked upper surface (CIM) was larger than charging current on the specimen of electrode made. Carrier injection differed from interfacial phase of polymer surFace. The transfer phenomenon vaned with chemical structure of polymer and then the polar effect of PVC was remarkable because of large electron affinity of Cl. In the characteristics of discharging current of PVC, the abnormal current was observed. It was supposed that this phenomena presented the trap of injected carriers in PVC and that static electricity phenomenon was generated by trap.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.05b
• /
• pp.123-126
• /
• 2005

In this study, the Thermally Stimulated Current(TSC) of corona charged PTFE is studied and the simulation of corona charging process is also calculated by Finite Element Method. The electrets which were formed by applying high voltages (DC ${\pm}5{\sim}{\pm}8$ [kV]) to PTFE, are used to measure TSC in the temperature range of $-100{\sim}+200$ [$^{\circ}C$] and then the Finite Element Method is performed to examine corona charging process using a obtained physical constants. As a result. it is confirmed that the charging negative corona is profitable as the applications are manufactured, because the time constant of negative corona is much larger than it of positive corona. And it is attempted to estimate the corona charging process in space using simulation.