• Proceedings of the KIEE Conference
• /
• 2004.04a
• /
• pp.83-85
• /
• 2004

We proposed the bridge type fault current limiter(FCL) using switching operation of high-Tc superconducting(HTSC) thin film. The proposed bridge type FCL consists of HTSC thin film, a diode bridge and a dc reactor. The controller for the operation of an interrupter is required in the conventional bridge type FCL to prevent the continuous increase of fault current after a fault happens. On the other hand, the proposed bridge type FCL can limit the fault current without the interrupter and the controller for its operation by the resistance generated when the gradually increased fault current exceeds HTSC thin film's critical current. We calculated the time when the gradually increased fault current started to be limited by the resistance generated in HTSC thin film after a fault happened and confirmed that it could be dependent on the amplitude of source voltage. The experimental results well agreed with the calculated ones from simulation.

• Proceedings of the KIEE Conference
• /
• 1997.11a
• /
• pp.382-384
• /
• 1997

On-site partial discharge test by use of AC voltage has been considered not to be appropriate for the extruded power cable due to their large capacitance depending on their lengths. Therefore, it is proposed, in this work, to use switching impulse voltage of which the front time is set from 1ms to 10ms. This newly proposed method enables us to simulate the 1/4 period of power frequency at 60 Hz and to obtain similar effect of AC voltage test. Our tentative results show that 51 voltage is proved to be an alternative method, replacing AC voltage, by which partial discharge was well produced from the artificial defects integrated in 22.9kV distribution power cables.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.63 no.2
• /
• pp.95-101
• /
• 2014

In this paper, UPS, with a built-in instantaneous sag drop compensation features, was developed to improve performance. The improved UPS, using instantaneous moving average method, compensates by quickly measuring the voltage and series inverter of half-bridge type, using line-interactive method that links with the voltage of the battery and power source, was developed. In addition, by developing a parallel inverter that uses a high-efficiency PWM switching method, overall UPS system was enhanced. To verify the performance of the proposed algorithm, single-phase 5[kVA] UPS systems were designed and the experimental system was constructed. The low-cost type of Cortex-M3 module CPU STM32F103R8T6 (32[bit]) is attached and the switching time of mode transfer was set within 4 [ms]. THD of the linear load operates in less than 3[%], and the stability of the output voltage operates in approximately ${\pm}2[%]$ range. The superior performance of the operations was confirmed with the system set as above.

• Journal of Distribution Science
• /
• v.16 no.2
• /
• pp.25-33
• /
• 2018

Purpose - This study focused on the effect of counter-factual thinking on post-purchase behavior producing consumer regret at HMR selection and purchase. We have analyzed the factors that HMR production and distribution businesses should consider because distribution and marketing strategy reflecting consumers' demand. Research design, data, and methodology - For the purpose of carrying out this research, we conducted a direst structured questionnaire to students at 'J' college. A total of 237 valid questionnaires were collected for students and their parents at 'J' university. For the hypothesis test, exploratory factor analysis, t-test, regression and structure equation path analysis were performed. Results - The consumers who often resented HMR purchase did counter-factual thinking on post-purchase behavior were likely to do switching purchases. Counter-factual thinking on post-purchase behavior had a negative influence upon consumer's satisfaction with HMR safety and marketing characteristics. Conclusions - Consumers who had been satisfied to a certain degree might have cognitive dissonance of minor mistakes of HMR product were likely to have downward counter-factual thinking through contrast effects. Therefore, HMR producer and distribution businesses that had production, distribution and marketing strategy to satisfy consumers by raw material, freshness and safety were likely to switch to another product at one time mistake of selection, purchase and use.

• Microbiology and Biotechnology Letters
• /
• v.18 no.4
• /
• pp.394-400
• /
• 1990

Maximization of productivity of recombinant cell fermentations requires consideration of the inverse relationship between the host cell growth rate and product formation rate. The problem of maximizing a weighted performance index was solved by using optimal control theory for recombinant E. coli fermentation. Concentration of a growth inhibitor was used as a control variable to manipulate the specific growth rate, and consequently the cloned-gene expression rate. Using a simple unstructured model to describe the main characteristics of this system, theoretical analysis showed that the optimal control profile results in an initial high growth rate phase followed by a low growth rate and high product formation rate phase. Numerical calculations were done to determine optimal switching times from the growth to the production stage for two representative cases corresponding to different dependency of the product formation rate on the growth rate. For the case when product formation rate is sensitive to the specific growth rate, the optimized operation yields about 60% increase in the final product concentration compared with a simple batch fermentation.

• Proceedings of the KIPE Conference
• /
• 2003.07b
• /
• pp.499-502
• /
• 2003

This paper presents the voltage source type half bridge lossless auxiliary inductor snubber assisted series capacitor compensated resonant high frequency inverter for induction heated fixing roller in copy machines. This high-frequency inverter treated here can completely achieve zero current soft switching (ZCS) commutation for wide power regulation range under its constant frequency pulse density modulation (PDM) scheme. Its transient and steady-state operating principle is originally presented fur a constant frequency PDM control strategy under a ZCS operation commutation, together with its output effective power regulation characteristics-based on the PDM strategy. The experimental operating performances of this ZCS-PDM high frequency inverter using IGBTs are illustrated as compared with computer simulation ones. Its power losses and actual efficiency are evaluated and discussed on the basis of simulation and experimental results.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.8 no.5
• /
• pp.389-396
• /
• 2003

This paper describes a novel ac/dc power converter suitable for frequent output short-circuit faults. The output dc power of the proposed converter can be disconnected from the load within several hundred microseconds at the instant of short-circuit fault. The rising time of the dc load voltage is as small as several hundred microseconds, and there Is no overshoot of the dc voltage because the dc output fillet capacitors stay at a undischarged state. The proposed converter has the characteristics of a simplified structure, reduced cost, weight, and volume compared to the conventional power supplies for frequent output short-circuit. Analysis, simulations, and experiments are carried out to investigate the operation and usefulness of the proposed scheme.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.9 no.1
• /
• pp.65-72
• /
• 2004

This paper proposes the novel boost input type resonant AC/DC converter. Since the proposed converter is single stage topology, it controls both of the input power factor and the output voltage at the same time, and resultingly obtains the high power factor of 99% with average current mode pulse width modulation. Especially, to accomplish the zero voltage switching, the resonance between the leakage inductance and external capacitor is used. For the theoretical consideration of the proposed converter, the six operation modes divided by means of current path are discussed, and the resonance characteristics in steady state are analyzed. To verify the validity of the proposed converter, a 200[W]($120[V_AC],\; 출력\; 48[V_DC],\; 4[A]$prototype converter was built and its experimental results were presented in this paper.

• Journal of Internet Computing and Services
• /
• v.12 no.5
• /
• pp.1-9
• /
• 2011

Wireless mobile networks that exploit generalized PF scheduling can dynamically allocate network resources by using scheduling parameters. There are limitations to predict throughputs by the conventional stochastic approach in general. Moreover the limitations make it difficult to find appropriate scheduling parameters for achieving the demanded throughputs. This paper derives a prediction algorithm that predicts throughputs of the networks by using deterministic approach. A throughput adjust algorithm and a throughput switching algorithm are derived from the prediction algorithm. The performance of the throughput prediction/switching algorithms is evaluated by a simulator based on IEEE 802.16m system.

• International Journal of Aeronautical and Space Sciences
• /
• v.4 no.1
• /
• pp.75-87
• /
• 2003

The primary objective of this study is to demonstrate ground-based experiment for the attitude control of spacecraft. A two-axis rotational simulator with a flexible ann is constructed with on-off air thrusters as actuators. The simulator is also equipped with payload pointing capability by simultaneous thruster and DC servo motor actuation. The azimuth angle is controlled by on-off thruster command while the payload elevation angle is controlled by a servo-motor. A thruster modulation technique PWM(Pulse Width Modulation) employing a time-optimal switching function plus integral error control is proposed. An optical camera is used for the purpose of pointing as well as on-board rate sensor calibration. Attitude control performance based upon the new closed-loop control law is demonstrated by ground experiment. The modified switching function turns out to be effective with improved pointing performance under external disturbance. The rate sensor calibration technique by Kalman Filter algorithm led to reduction of attitude error caused by the bias in the rate sensor output.