Dong-Kurl Kwak

A study on novel buck-boost AC-DC converter of high performance by partial resonance technique

The system efficiency of the proposed buck-boost AC-DC converter is increased by soft switching method. The converter includes to merit of power factor correction (PFC) from sinusoidal control of input current. The switching behavior of control switches operates with soft switching by partial resonance technique, and then the proposed converter has high system efficiency with decrement of switching power loss. The input current waveform in proposed converter is got to be a sinusoidal form of discontinuous quasi-pulse row in proportion to magnitude of AC input voltage under the constant duty cycle switching. Therefore, the input power factor is nearly unity. The output voltage of the converter is regulated by PWM control technique. The discontinuous mode action of current flowing into inductor makes to simplify control method and control components. The proposed novel buck-boost AC-DC converter is analyzed to compare with the conventional PFC buck-boost converter. Some computer simulative results and experimental results confirm to the validity of the analytical results.

A new buck-boost dc/dc converter of high efficiency by soft switching technique

In this paper, we study on a new buck-boost dc/dc converter of high efficiency by soft switching technique. The switching devices in the proposed converter are operated by soft switching with a new partial resonant circuit. The partial resonant circuit is designed to replacement of an energy storage inductor and a snubber circuit used in a conventional buck-boost converter, and then the configuration of the proposed converter is simplified. The switching control technique of the converter is also simplified for the switches to drive in a constant switching frequency. The results are that the switching power loss is very low and system efficiency is high. In addition, the output voltage of the converter is regulated by PWM control technique, and the discontinuous current flowing into the resonant inductor of the converter makes to simplify control method and control components. In comparison with the conventional buck-boost dc/dc converter, some simulation results on computer and experimental results are confirmed the validity of analytical results of the proposed converter.

A Study on Device Development for Electrical Fire Protection on Open Phase of Three-Phase Motor

In the three-phase power system using the three-phase motor, when any one-phase is open-phase, the unbalanced current flows and the single-phase power supplied by power supply produces overcurrent to motor coil. As a result, the enormous damage and electrical fire can be given to the power system. Recently, the thermal over-current relay (THR) or electronic motor protection relay (EMPR) is mostly used as the open-phase detection device of the three-phase motor. When the over-current or overheat of electric line is generated, it detects and operates circuit breaker, but there is the defect that the sensing speed is slow, the operation can be sometimes failed, and the precision is decreased. In order to improve these problems, this paper is proposed a new control circuit topology for openphase protection using semiconductor devices. Therefore, the proposed open-phase protection device (OPPD) enhances the sensing speed and precision, and has the advantage of simple fitting in the three-phase motor control panel in the field, as it manufactures into small size and light weight. As a result, the proposed OPPD protects the three-phase motor, minimizes the electrical fire from openphase, and contributes for the stable driving of the power system. The performance and confidence of the proposed OPPD is confirmed by a great variety of the experiments of operation characteristic.

A study on isolated DC-DC converter of soft switching with discontinuous conduction mode

In this paper, we study on a new isolated DC-DC converter of soft switching with discontinuous conduction mode (DCM). The switching devices in the proposed converter are operated by soft switching technique using a new quasi-resonant circuit, and are driven with DCM according to pulse width modulation (PWM). The quasi-resonant circuit uses a step-up inductor and a loss-less snubber capacitor. The proposed converter with DCM also simplifies the requirement of control circuits and reduces the number of control components, and the switching control technique of the converter is simplified for the switches to drive in a constant switching frequency. As a result, the proposed converter exhibits low switching power loss and high power efficiency. The validity of the analytical findings is confirmed by some simulation results and experimental results.

A Study on Design and Operation Performance of Automatic Fire Detection Equipment (P-type One-class Receiver) by Bidirectional Communication

In this paper, authors will develop the quick and precise remote controller of automatic fire detection equipment (P-type one-class receiver) based on information communication technology (IT). The remote controller detects the fire and disaster in the building automatically and quickly and then activates the facilities to extinguish the fire and disaster, monitoring such situation in a real time through wire-wireless communication network. The proposed remote controller is applied a programmable logic device (PLD) micom. of one-chip type which is small size and lightweight and also has highly sensitive-precise reliabilities. The one-chip type PLD micom. analyzes digital signals from sensors, then activates fire extinguishing facilities for alarm and rapid suppression in a case of fire and disaster. The detected data is also transferred to a remote situation room through wire-wireless network of RS232c and bluetooth communication, and then the situation room sends an emergency alarm signal. The automatic fire detection equipment (AFDE) based on IT will minimize the life and wealth loss while prevents fire and disaster.

A Study on Development of Open-Phase Protector Having Leakage Current Generation and Incapable Operation Prevention at Open-Phase Accident

In the three-phase power system, when any one-phase or two-phases is open-phase, the unbalanced current flows and the single-phase power supplies to three-phase loads. Specially, motor coil and transformer coil receive over-current. As a result, great damage as well as electrical fire can occur to the power system. In order to improve these problems, this paper proposes that an open-phase detection device is designed by a new algorithm using electric potential difference between the resultant voltage of neutral point and ground, and a control circuit topology of open-phase protector is composed of highly efficient semiconductor devices. It improves response speed and reliability. The control algorithm circuit also operates the cut-off of a conventional residual current protective device (RCD) which flows an enforced leakage current to ground wire at open-phase accident. Furthermore, time delay circuit is added to prevent the incapable operation of open-phase protector about instantaneous open-phase not open-phase fault. The time delay circuit improves more reliability.

Development of Arc Fault Circuit Interrupter Using the Distorted Voltage Wave in Electric Arc Faults

The major causes of electrical fire are classified to short circuit fault, overload fault, electric leakage and electric contact failure. The principal factor of the fire is electric arc or spark accompanied with such electric faults. Earth Leakage Circuit Breaker (ELB) and Molded_case Circuit Breaker (MCCB), that is, Residual Current Protective Devices (RCDs) used on low voltage distribution lines cut off earth leakage and overload, but the RCD can not cut off electric arc or spark to be a major factor of electrical fire. As the RCDs which are applied in low voltage distribution panel are prescribed to rated breaking time about 30[ms] (KS C 4613), the RCDs can`t perceive to the periodic electric arc or spark of more short wavelength level. To improve such problems, this paper studies on an arc fault circuit interrupter (AFCI) using the distorted voltage wave in electric arc faults. The proposed voltage sensing type AFCI is an electrical fire prevention apparatus of new conception that operates a circuit breaker with sensing the instantaneous voltage drop of line voltage at electrical faults occurrence. The proposed AFCI is composed of control circuit topology using some semiconductor switching devices. Some experimental tests of the proposed AFCI confirm practicality and the validity of the analytical results.

Development of Arc Fault Interruption Control Circuit of Fault Voltage Sensing Type

본 논문은 사고전압 감지형의 아크차단 제어회로에 대한 연구로써, 전기사고 발생 시 선간전압의 순간적인 전압감쇠를감지하여 기존 차단기를 동작시키는 전압감지형 전기화재 예방장치이다. 현재 저압배전 계통에 사용중인 누전차단기, 배선용차단기 그리고 RCD 등은 전기화재의 주요 요인인 아크사고에 대해 보호능력이 없는 것으로 분석된다. 본 논문에서는 이러한 문제점들을 개선하기위하여 이전의 전류감지에 의한 아크사고 차단방식이 아닌 사고발생 시 전압파형의 왜곡을 이용한 새로운 전압감지형 아크차단 제어회로를 개발하여 전기화재를 예방하고자 한다. 제안한 아크차단 제어회로는소형·경량으로 제작되는 장점과 다양한 동작분석을 통하여 그 실용성을 검증하였다.ABSTRACTThis paper studies on an arc fault interruption control circuit (AFICC) of fault voltage sensing type. The proposed volt-age sensing type AFICC (VST_AFICC) is an electrical fire prevention apparatus that operates the existing circuit breakerwith sensing the instantaneous voltage drop of line voltage when occurs electrical faults. The existing Earth Leakage Cir-cuit Breaker (ELB), Molded_case Circuit Breaker (MCCB), and Residual Current Protective Devices (RCDs) used in lowvoltage distributing system don’t have protective capability from electric arc faults to be a major factor of electrical fire.In this paper to improve such problems, a new VST_AFICC using the distortion of voltage waveform when occurs elec-trical faults is proposed to prevent electrical fire. There is characteristic that the control method of proposed apparatus isdifferent from previous current sensing type. The proposed AFICC has merit that is manufactured by small size and lightweight. The practicality of a new VST_AFICC is also verified through various operation analysis.

The research of sensor node power management

Wireless sensor networks consist of small sensor nodes and are able to sense the environment in a distributed fashion. And embedded system is a kind of special computer system which is suitable for application system with strict requirements on the functionality, cost, size and power consumption. Hence the application of embedded systems will become increasingly important. Also the amount of data to be dealt with in the embedded system will continue to increase, so database processing technology is needed to the embedded system. In other words we need embedded database to manage large amount of data. In this paper, we present effective management method of sensor nodes are installed in various locations to collect environmental information. This method can monitor whether sensor node passes wrong environmental information or sensor node to lack of battery power. On this basis, we design sensor node power management system based on embedded system and use SQLite as database.

A Study on Development of Disaster Prevention Automation System on IT using One-chip Type PLC

This paper deals with the quick and precise disaster prevention automation system (DPAS) based on information communication technology (IT) that detects fire and disasters in the building automatically and quickly and then activates the facilities to extinguish fire and disasters, monitoring such situation in a real time through wire-wireless communication network. The proposed DPAS is applied a programmable logic controller (PLC) of one-chip type which is smallsize and lightweight and also has highly sensitive-precise reliabilities. The one-chip type PLC analyzes detected signals from sensors in a case of fire and disasters, then activates fire extinguishing facilities for rapid suppression. The detected data is also transferred to a remote situation room through wire-wireless network of RS232c and bluetooth communication. The transferred data sounds an emergency alarm signal, and operates a monitoring program. The proposed DPAS based on IT will minimize the life and wealth loss from rapid measures while prevents fire and disasters.