• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.2
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• pp.10-18
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• 2008

This paper presents the design and imelementation of an electronic ballast with a passive PFC structure from which acoustic resonance of the metal halide lamp was removed by introducing the frequency modulation(FM) method. The proposed ballast consists of an EMI filter, passive PFC circuit full-bridge inverter, LC resonance type igniter and a circuit for removing acoustic resonance. The FM method solved two problems associated with single frequency driving: variation of the acoustic resonance range according to lamp aging and the acoustic resonance range discrepancy caused by different materials sealed inside the arc tube and their pressures for arc tubes of identical sizes from different manufacturers. Performance of the prototype developed for this study of the electronic ballast for 1[kW] metal halide lamp was verified by evaluating its optical conversion efficiency, input PF, input current THD and power conversion efficiency.

• Journal of IKEEE
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• v.22 no.2
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• pp.258-265
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• 2018

This paper proposes an algorithm for reducing the starting current when the single-phase induction motor starts and analyzes its operation. Generally, the single-phase induction motors require several starters to generate the starting torque due to their structural characteristics. In this paper, a capacitor-start / capacitor-run method of the single-phase induction motor is basically adopted. This conventional method is efficient and has a large starting torque, but it generates about 5 ~ 6 times of inrush current at startup. As a result, the freezer starting device and peripheral devices are damaged and life time may be reduced. To reduce the inrush current, the current control algorithm based on the virtual dq model is presented to control the starting current. In addition, it validates the proposed algorithm through experiments to smooth transit from start-up operation to the rated operating region.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.5
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• pp.10-24
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• 2007

In the dissertation, a power conversion system for fuel cell is composed of a PWM inverter with LC filter in order to convert fuel cell voltage to a single phase 220[V]. In addition, new insulated DC-DC converters are proposed in order that fuel cell voltage is boosted to 380[V]. In this paper, it requires smaller components than existing converters, which makes easy control. The proposed DC-DC converter controls output power by the adjustment of phase-shift width using switch $S_5\;and\;S_6$ in the secondary switch which provides 93-97[%] efficiency in the wide range of output voltage. Fuel cell simulator is implemented to show similar output characteristics to actual fuel cell. Appropriate dead time td enables soft switching to the range where the peak value of excitation current in a high frequency transformer is in accordance with current in the primary circuit. Moreover, appropriate setting to serial inductance La reduces communication loss arisen at light-load generator and serge voltage arisen at a secondary switch and serial diode. Finally, TMS320C31 board and EPLD using PWM switching technique to act a single phase full-bridge inverter which is planed to make alternating current suitable for household

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.6
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• pp.456-464
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• 2007

This paper proposes a novel three-phase current-fed active clamp DC-DC converter for fuel cells. A single common active clamp branch is used to limit transient voltage across the three-phase full bridge and to realize zero-voltage switching(ZVS) in all switches. To apply for the power generation system current-fed type has been combined with the three-phase power conversion system. The proposed approach has the following advantages: an increase (by a factor of three) of input current and output voltage chopping frequencies; lower RMS current through the inverter switches with higher power transfer capability; reduction in size of reactive later components and the power conditioning system; better transformer utilization; increase of the system reliability. Therefore, the proposed three-phase current-fed active clamp DC-DC converter is appropriate for the boost type DC-DC converter for fuel cells and also applicable for the photovoltaic and battery charge system. The paper details the analysis, simulation and hardware implementation of the proposed system. Finally, experimental results with the proposed PWM strategy demonstrate the feasibility of the proposed scheme on a 500W prototype converter.

• The Journal of the Acoustical Society of Korea
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• v.41 no.5
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• pp.481-491
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• 2022

The active sonar transmission system consists of a transmitter that outputs an electrical signal and an underwater acoustic transducer that converts the amplified electrical signal into an acoustic signal. In general, the transmitter output characteristics are dependent on load impedance, and an underwater acoustic transducer, which is a transmitter load, has a characteristic that the electrical impedance varies largely according to frequency when driven. In such a variable impedance condition, the output of the active sonar transmission system may become unstable. Hence, this paper proposes a design and control technique of a sonar transmitter for transmitting a stable transmission signal even under variable impedance conditions of an underwater acoustic transducer in an active sonar transmission system. The electrical impedance characteristics of the underwater acoustic transducer are experimentally analyzed, and the sonar transmitter is composed of a single-phase full-bridge inverter, an LC filter, and a matching circuit. In this paper, the design and output control method of the sonar transmitter is proposed to protect the transmitter and transducer. It can secure stable output voltage characteristics even if it transmits the Linear Frequency Modulation (LFM) signal. The validity is verified through the simulation and the experiment.