• Title/Summary/Keyword: High Power Rating

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An Evaluation of Weather Model for Increasing Ampacity in KEPCO's Overhead Transmission Lines (한국전력 가공송전선의 허용전류를 증가시키기 위한 기상모델의 평가)

  • 김성덕
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.18 no.2
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    • pp.125-134
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    • 2004
  • The new deregulated economic environment in the power utility market is forcing fundamental changes in the investment and operational decisions regarding transmission lines. Hence, it has come to be an important issue to evaluate their current utility in order to increase conductor ampacity based on conservative assumptions of worst case weather conditions. Static thermal rating has born still applied in most power companies worldwide, however some of them have been done various trials such as monitoring dynamic line ratings to increase line ratings in real time. This study is an attempt to access the static line ratings in Korea Electric Power Corporation(KEPCO) transmission lines, which were specified by weather model. Several environmental performances for determining static line ratings are examined by using the past weather data of Korean Meteorological Administration. As a result, it is shown that seasonal or regional line ratings could be adopt to the KEPCO's transmission lines, and their line ratings could be more increased without refurbishing current conductors in service to new high-temperature ones.

Natural Indigo Dyeing of Hanji Fabric using Baker's Yeast: Effect of Yeast Concentration and Repeat Dyeing (효모를 사용한 한지직물의 천연인디고 염색 : 효모농도와 반복염색 효과)

  • Son, Kyunghee;Shin, Younsook;Yoo, Dong Il
    • Textile Coloration and Finishing
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    • v.33 no.4
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    • pp.191-201
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    • 2021
  • In this study, an eco-friendly indigo reduction system(scale up reduction, use of buffer solution, and pH control) using baker's yeast(Saccharomyces cerevisiae) was applied for natural indigo(Polygonum tinctorium) dyeing of Hanji fabric and Hanji-mixture fabric(Hanji/Cotton, Hanji/Silk). The effect of concentration of baker's yeast, repeat dyeing, and bath reuse was investigated in terms of dye uptake indicating reduction power. And the oxidation-reduction potential(ORP) was monitored. We also evaluated color properties and colorfastness according to the color strength. The yeast concentration did not significantly affect the maximum reduction power. However, the highest yeast concentration was effective in improving the initial dye uptake, and its the reduction retention power was the most excellent. Even on the last reduction day, the effect of increasing the dye uptake by repeat dyeing was observed. And it was confirmed that the reduction bath could be reused for up to 30 days by supplementing yeast at the end of reduction. For all the fabrics used, deeper and darker PB color were obtained by repeat dyeing. As dyeing was repeated, purplish tint got stronger on the Hanji/Silk fabric compared to other fabrics. Regardless of the composition of Hanji fabrics and color strength, washing and dry cleaning fastness were relatively good with above rating 4-5, and fastness to rubbing and light were acceptable with a rating 3-4 ~ 4-5. The eco-friendly natural indigo dyeing process using niram and baker's yeast would offer global marketability and diversity of Hanji product as a sustainable high value-added material.

Device Suitability Analysis by Comparing Performance of SiC MOSFET and GaN Transistor in Induction Heating System (유도 가열 시스템에서 SiC MOSFET과 GaN Transistor의 성능 비교를 통한 소자 적합성 분석)

  • Cha, Kwang-Hyung;Ju, Chang-Tae;Min, Sung-Soo;Kim, Rae-Young
    • The Transactions of the Korean Institute of Power Electronics
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    • v.25 no.3
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    • pp.204-212
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    • 2020
  • In this study, device suitability analysis is performed by comparing the performance of SiC MOSFET and GaN Transistor, which are WBG power semiconductor devices in the induction heating (IH) system. WBG devices have the advantages of low conduction resistance, switching losses, and fast switching due to their excellent physical properties, which can achieve high output power and efficiency in IH systems. In this study, SiC and GaN are applied to a general half-bridge series resonant converter topology to compare the conduction loss, switching loss, reverse conduction loss, and thermal performance of the device in consideration of device characteristics and circuit conditions. On this basis, device suitability in the IH system is analyzed. A half-bridge series resonant converter prototype using the SiC and GaN of a 650-V rating is constructed to verify device suitability through performance comparison and verified through an experimental comparison of power loss and thermal performance.

Input Voltage Sharing Control for Input-Series-Output-Parallel DC-DC Converters without Input Voltage Sensors

  • Guo, Zhiqiang;Sha, Deshang;Liao, Xiaozhong
    • Journal of Power Electronics
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    • v.12 no.1
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    • pp.83-87
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    • 2012
  • Input-series-output-parallel (ISOP) modular converters consisting of multiple modular DC/DC converters can enable low voltage rating switches for use in high voltage input applications. In this paper, an input voltage sharing control strategy for input-series-output-parallel (ISOP) full-bridge (FB) DC/DC converters is proposed. By sensing the difference in the input current of two modules, the system can achieve input voltage sharing for DC-DC modules. The effectiveness of the proposed control strategy is verified by simulation and experimental results obtained with a 200w-50kHz prototype.

Digital Control Strategy for Input-Series-Output-Parallel Modular DC/DC Converters

  • Sha, Deshang;Guo, Zhiqiang;Liao, Xiaozhong
    • Journal of Power Electronics
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    • v.10 no.3
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    • pp.245-250
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    • 2010
  • Input-series-output-parallel (ISOP) converters consisting of multiple modular DC/DC converters can enable low voltage rating switches to be used under high voltage input applications. This paper presents a digital control strategy, which can achieve equal sharing of input voltage for a modular ISOP system consisting of two-transistor forward DC/DC converters by forcing the input voltages of neighboring modules to be equal. The proposed scheme is analyzed using small signals analysis based on the state space average method. The performance of the proposed control strategy is verified with an experimental prototype of an ISOP converter made up of three two-switch forward converters.

Maximum Efficiency Drive of Vector-Controlled Induction Motors (벡터제어 유도전동기의 최대효율 운전)

  • Yoon, Duck-Yong;Choe, Gyu-Ha;Hong, Soon-Chan;Baek, Soo-Hyun;Lee, Eun-Woong
    • The Transactions of the Korean Institute of Power Electronics
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    • v.1 no.1
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    • pp.27-37
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    • 1996
  • This paper proposes the control algorithm for maximum efficiency drive of PWM inverter - induction motor system with high dynamic performance. If the induction motor is driven under light load with rated magnetizing current, the Iron loss is excessively large compared with the codder loss which results in doer motor efficiency. Maximum efficiency drive of an induction motor can be achieved by controlling the magnetizing current to satisfy the optimal ratio that leads the total motor loss to be a minimum value at a given speed. The proposed control algorithm essentially uses vector control technique and adopts voltage decoupling control strategy to prevent the degradation of dynamic performance due to reduced magnetizing current. To verify the proposed method, digital simulations and experiments are carried out for a squirrel-cage induction motor with the rating of 2.2[kW].

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A New Gate Driver Technique for Voltage Balancing in Series-Connected Switching Devices (직렬 연결된 SiC MOSFET의 전압 평형을 위한 새로운 능동 게이트 구동 기법)

  • Son, Myeong-Su;Cho, Young-Hoon
    • The Transactions of the Korean Institute of Power Electronics
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    • v.27 no.1
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    • pp.9-17
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    • 2022
  • The series-connected semiconductor devices structure is one way to achieve a high voltage rating. However, a problem with voltage imbalance exists in which different voltages are applied to the series-connected switches. This paper proposed a new voltage balancing technique that controls the turn-off delay time of the switch by adding one bipolar junction transistor to the gate turn-off path. The validity of the proposed method is proved through simulation and experiment. The proposed active gate driver not only enables voltage balancing across a variety of current ranges but also has a greater voltage balancing performance compared with conventional RC snubber methods.

A Study on the Harmonic Current Characteristics of Universal Motro with Speed Controller (유니버셜모터 속도제어기의 고조파전류 특성에 관한 연구)

  • 임홍우;박수강;백형래
    • The Transactions of the Korean Institute of Power Electronics
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    • v.6 no.2
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    • pp.132-140
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    • 2001
  • A universal motor is a small dc series machine motor that is designed to operate from an ac machine. The characteristics of universal motors are high no-load and staring torque. Because of the high operating speed, the size of these motors for a given hp rating is typically smaller that other fractional hp ac machine, making it ideal for hand-held tools and appliances where weight, compactness, and speed are importance factors. A phase-angle control with AC drive system gains a high popularity due to their simple implementation, but contains the disadvantage of their poor input power factor, subharmonic current. Pulse width modulation control with DC drive systems increase the power factor as without delay phase angle. This paper analyzed the subharmonic characteristics of the phase angle control system that is controlled by zero voltage crossing similar to traditional method, and the dc chopper system that is used PWM.

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Pohang City Fire Vulnerable Area Prediction and Fire Damage Rating Measurement by Administrative District (포항시 화재 취약지역 예측 및 이에 따른 행정구역별 화재 피해 등급 측정)

  • Lim, Jung-Hoon;Kim, Heon-Joo
    • The Journal of the Korea Contents Association
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    • v.21 no.4
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    • pp.166-176
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    • 2021
  • Due to urbanization and industrialization, the importance of large-scale fire prevention, management and measures is increasing day by day. However, the fire site arrival rate in Golden Time, which is a factor that can minimize large-scale fire damage, of Pohang, a large city with a population of over 500,000, is relatively low. So additional fire fighting power deployment and infrastructure investment are required. However, as budget and manpower are limited, it is necessary to selectively deploy fire fighting power and invest in infrastructure. Therefore, this study attempted to present a fire damage rating that can compare the level of fire damage, which is an index that can help selectively provide fire fighting services in Pohang and make related decisions. For the index, the OD cost matrix was used to predict fire vulnerable areas with a high probability of increasing the fire scale in the event of a fire. Also fire damage was measured by predicting the level of fire damage in the event of a fire according to population, building density, and access of fire trucks. It is expected that the fire damage rating will be able to help in various decisions related to fire fighting service deployment and services not only in Pohang city, but also in other regions.

Performance Evaluations of the Lightning Impulse Voltage Measuring System by Intercomparative Test - in case of full lightning impulse voltage - (뇌충격 측정시스템의 비교시험에 의한 성능평가 - 전파 뇌충격전압 인가시 -)

  • Kim, Ik-Soo;Kim, Young-Bae;Lee, Hyeong-Ho
    • Proceedings of the KIEE Conference
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    • 1995.07c
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    • pp.1368-1370
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    • 1995
  • Lightning impulse voltage is essential to evaluate the insulation performance of electric power apparatus. Recently international standard(IEC-60) on high voltage measurement techniques are being revised. In the draft of this standard, a new calibration method is introduced and the accuracy of most industrial measuring systems is maintained by means of comparison test against the reference measuring systems. Intercomparison tests of dividers for lightning impulse measurement were carried out by KERI. The shielded resisitive divider with 700kV rating developed by KERI were done comparison test with PTB divider with 300kV rating which have the similar charateristics as that were circulated among the laboratories. This paper reports on the comparison test results with full lightning impulse voltages from 126kV to 240kV. It is demonstrated that KERI are capable of realizing the idea in the revision of the IEC standand, that is, to establish traceability.

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