• Journal of Industrial Technology
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• v.24 no.A
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• pp.119-126
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• 2004

BLDC Motor is one of the widely utilizable motors in servo system. The accurate calculation of the power loss for the IGBT and Inverse diode with Bipolar and Unipolar switching modes the driving modes is important for the design of drives for their heat treatment. If it were not for temperature-sensors in devices, it is difficult to get direct power loss, so. Power losses may be modeled by computer modeling to obtain the Calculation of the Power loss for Inverter in BLDC Motor with switching modes which is presented in this paper. The computer modeling is carried out by Matlab simulation. The power loss consists of conduction losses Conduction losses are the source of occurrence due to The IGBT and Inverse diode currents. Switching losses are the source of occurrence due to switching on/off in the devices, and gives the dominant influence to the loss. As a result, the unipolar I mode is best in reducing the heat losses.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.368.1-368.1
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• 2014

We proposed amorphous GeSe-based ReRAM device of metal-insulator-metal (M-I-M) structure. The operation characteristics of memory device occured unipolar switching characteristics. By introducing the concepts of valance-alternation-pairs (VAPs) and chalcogen vacancies, the unipolar resistive switching operation had been explained. In addition, the current transport behavior were analyzed with space charge effect of VAPs, Schottky emission in metal/GeSe interface and P-F emission by GeSe bulk trap in mind. The GeSe ReRAM device of M-I-M structure indicated the stable memory switching characteristics. Furthermore, excellent stability, endurance and retention characteristics were also verified.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.4
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• pp.361-365
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• 2003

A unipolar-type E-chuck was fabricated for the application of holding silicon wafers in the oxide etcher. For the fabrication of the unipolar ESC, core technologies such as coating of polyimide films and anodizing treatment of aluminum surface were developed. The polyimide films were prepared on thin coated copper substrates to minimize the plasma damage during the etch processing. Thin film heater technology was also developed for new type of E-chuck.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.2
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• pp.59-64
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• 2014

Crystallographic phases of Plasma electrolytic oxidized Al alloy, A1050, were investigated. The electrolyte of PEO was $Na_2Si_2O_3$ and KOH. Unipolar pulse, $ 2000{\mu}sec$ with $400{\mu}sec+420V$ impulse, were applied for 2 min, 5 min, 15 min, and 30 min. ${\gamma}-Alumina$, as well as ${\alpha}-alumina$, was main crystal phase. ${\gamma}-Alumina$ was appeared in the beginning, then the amount of ${\alpha}-alumina$ was increased with time, but the amount of ${\gamma}-Alumina$ remained constant without any increasing. So, it is concluded that plasma gas produce ${\gamma}-Alumina$ at the first, and then ${\gamma}-Alumina$ transform ${\alpha}-alumina$ finally. During the transformation, high temperature of micro plasma gives transformation energy.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.5
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• pp.1149-1154
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• 2014

To observe the tunneling phenomenon of oxide semiconductor transistor, The Indium-gallum-zinc-oxide thin film transistors deposited on SiOC as a gate insulator was prepared. The interface characteristics between a dielectric and channel were changed in according to the properties of SiOC dielectric materials. The transfer characteristics of a drain-source current ($I_{DS}$) and gate-source voltage ($V_{GS}$) showed the ambipolar or unipolar features according to the Schottky or Ohmic contacts. The ambipolar transfer characteristics was obtained at a transistor with Schottky contact in a range of ${\pm}1V$ bias voltage. However, the unipolar transfer characteristics was shown in a transistor with Ohmic contact by the electron trapping conduction. Moreover, it was improved the on/off switching in a ambipolar transistor by the tunneling phenomenon.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.672-674
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• 2001

Axial magnetic field(AMF) type electrode can increase the interrupting capability of vacuum interrupters. But, this interrupting capability vary with design parameters such as shape of electrode, slits of contact, material of contact and so on. In this paper, shown arc characteristics of unipolar axial magnetic field type electrode for vacuum interrupter by design parameters such as shape of contact slits and diameter of contact. And, confirmed vacuum arc configuration by individual design parameter using high speed camera.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.82-84
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• 1998

LDM(Linear DC Motor) are used in high speed, high-precision position control system. Because of these advatages, LDM has already used in the motor of pen-recorder, magnetic-disk devices. Under the limited dimension, we propose the design method of LDM by magnetic circuit. In this paper, a relation between the thrust constant and size of a LDM that is moving coil type with unipolar is described, which is defined as a simple relational equation. To maximize the rate of thrust to the volume of LDM, the magnetic flux density in the yoke is adjusted to the value of magnetic equation By the magnetic field analysis(FEM), the validity of the equation is confirmed.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.1
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• pp.56-62
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• 2022

In this paper, the effect of pulse width modulation methods on thermal loadings and power losses of single-phase five-level NPC inverters for photovoltaic systems are analyzed. The pulse width modulation methods affect the power losses of the NPC inverters and thus lead to different thermal loadings of NPC inverters. To identify the reliability-critical power device with respect to thermal stress, the thermal loadings of I- and T-type NPC inverters are analyzed by applying the unipolar pulse modulation method. Then, the effect of the discontinuous pulse width modulation method on power losses and thermal loadings of power devices of I- and T-type NPC inverters are analyzed. Finally, the operation of NPC inverters applying the discontinuous pulse modulation method is confirmed by experiments. The results show that the discontinuous pulse modulation method is able to improve the reliability of NPC inverters by reducing thermal loadings of reliability-critical power devices and it is more effective for T-type NPC inverters than I-type NPC inverters.

• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.5
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• pp.196-203
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• 2005

A semi-empirical method to determine the electrostatic characteristics of a diode type corona aerosol charger based on ion current measurement and electrostatic charging theory was presented. Results from mathematical model were in agreement with those from experimental investigation of the charger. Current-voltage characteristics, $N_{i}t$ product and charge distribution against aerosol size were obtained. It was shown that the space charge was significant and must be taken into account at high ion number concentration and low flow rate. Additionally, significant particle loss was evident for particles smaller than 20 nm in diameter where their electrical mobility was high. Increase in charging efficiency may be achieved by introducing surrounding sheath flow and applying AC high voltage. Overall, the approach was found to be useful in characterizing the aerosol charger.

• Nuclear Engineering and Technology
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• v.53 no.7
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• pp.2289-2294
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• 2021

In the present study, an original spark plasma sintering-reactive synthesis (SPS-RS) method for minerallike ceramic materials based on SrAl₂Si₂O₈ feldspar-like skeleton structure was used for the first time, promising solid-state matrices for reliable immobilization of high-energy ⁹⁰Sr. The method is based on the "in-situ" reaction of a mixture of SrO, Al₂O₃ and SiO₂ oxides when heated by a unipolar pulsed current under compacting pressure. The phase and elemental composition structure were studied. The dynamics of the consolidation of the reaction mixture of oxides was studied in the range of 900-1200 ℃. The study found the temperature of the high-speed (minutes) SPS-RS formation of single-phase SrAl₂Si₂O₈ composition ceramic in the absence of intermediate reaction products with a relative density of up to 99.2% and compressive strength up to 145 MPa and a strontium leaching rate of 10^-4g/cm²·day.