• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.6
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• pp.413-419
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• 2002

Noise barriers are widely used to reduce the sound level propagating from highways, railways or factories to residential areas. The reduced noise level at a receiver point is then determined by the diffracted waves around the edge of the barrier as well as by the transmitted waves through the barrier. 1'or proper usage, many studies either theoretical or experimental have been made with the objective of precisely Predicting the acoustic field and improving the noise attenuating properties of barriers. In this study. a simple scattering model. a line acoustic source scattered by an infinite cylinder, is introduced to simply Investigate the sound attenuation efficiency of a sound-resonating barrier. From this model study, it is observed that the sound-resonating harrier can be used as a good sound-shielding element especially for the pure-tone noise generated from the transformer. Large sound-attenuation is achieved by applying the sound-resonating barrier to the large transformers in a substation.

• Proceedings of the KIEE Conference
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• summer
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• pp.1166-1168
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• 2004

The high frequency series resonant converter has been widely used for the non-contact power supply system with the large air gap and the increased leakage inductance of the non-contact transformer. However. the high frequency series resonant converter has the disadvantages of high voltage gain characteristics in the overall load range due to the large air gap and the circulating magnetizing current. In this paper, unit voltage gain is revealed in the proposed three-level series-parallel resonant converter. The results are verified on the simulation results and the 5kW experimental prototype.

• Journal of Power Electronics
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• v.6 no.3
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• pp.187-194
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• 2006

A new asymmetrical pulse width modulation (PWM) half bridge converter with improved ZVS performance is proposed. The ZVS operation of the proposed converter can be maintained from no load to full load conditions since the magnetizing current of the transformer contributes to the ZVS operation at light loads without considerable conduction loss of the transformer and switch. Synchronous rectification is employed to reduce the rectification loss. Operational principles, large signal modeling, ZVS analysis and design equations are presented. Experimental results demonstrate that the proposed converter can achieve a large ZVS range and significant improvement in efficiency for a 100W (5V, 20A) prototype converter.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.659-664
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• 2001

Noise barriers are widely used to reduce the sound level propagating from highways, railways or factories to residential areas. The reduced noise level at a receiver point is then determined by the diffracted waves around the edge of the barrier as well as by the transmitted waves through the barrier. For proper usage, many studies either theoretical or experimental have been made with the objective of precisely predicting the acoustic field and improving the noise attenuating properties of barriers. In this study, a simple scattering model, a line acoustic source scattered by an infinite cylinder, is introduced to simply investigate the sound attenuation efficiency of a sound-resonating barrier. From this model study, it is observed that the sound-resonating barrier can be used as a good sound-shielding element especially for the pure-tone noise generated from the transformer. Large sound-attenuation is achieved by applying the sound-resonating barrier to the large transformers in a substation.

• Journal of Power Electronics
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• v.7 no.3
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• pp.181-190
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• 2007

This paper presents a novel circuit topology of a DC bus line series switch and parallel snubbing capacitor-assisted soft-switching PWM full-bridge inverter type DC-DC power converter with a high frequency planar transformer link, which is newly developed for high performance arc welding machines in industry. The proposed DC-DC power converter circuit is based upon a voltage source-fed H type full-bridge soft-switching PWM inverter with a high frequency transformer. This DC-DC power converter has a single power semiconductor switching device in series with an input DC low side rail and loss less snubbing capacitor in parallel with the inverter bridge legs. All the active power switches in the full-bridge arms and DC bus line can achieve ZCS turn-on and ZVS turn-off transition commutation. Consequently, the total switching power losses occurred at turn-off switching transition of these power semiconductor devices; IGBTs can be reduced even in higher switching frequency bands ranging from 20 kHz to 100 kHz. The switching frequency of this DC-DC power converter using IGBT power modules can be realized at 60 kHz. It is proved experimentally by power loss analysis that the more the switching frequency increases, the more the proposed DC-DC power converter can achieve a higher control response performance and size miniaturization. The practical and inherent effectiveness of the new DC-DC converter topology proposed here is actually confirmed for low voltage and large current DC-DC power supplies (32V, 300A) for TIG arc welding applications in industry.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.176-179
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• 1990

In this paper, the pheonmena of flowing electrification is experimently studied in the model transformer of a super high voltage transformer. The current of natural terminal which is flowed by the flowing electrification is increased according to oil flow, but according to the oil temperature the current is decreased and the direction of the current is changed.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.170-172
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• 1990

In a large power transformer, an insulating oil is forced to circulate for cooling the heat generated by the losses within the windings and core. When oil flows and rubs against various materials, including insulating paper and steel, electrostatic charges are separated at the interface of the oil and the solid material. This paper considers the polarity and the streaming electrification of the various materials which are used in transformer. As a result of this study, it is confirmed that the leakage current on the solid material, such as paper, is charged negative. On the other hand, the solid material, such as steel, is positively charged.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.3
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• pp.125-130
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• 2014

This paper is research result for a development of solar cell silicon ingot glowing(SCSIG) PWM converter system for 120[kW] 3[kA]. The system include 3-phase AC-DC rectifier diode converter of input voltage AC 460[V] and 60[Hz], DC-AC single phase full bridge PWM inverter of high frequency, AC-DC single-phase full wave rectifier using center-tapped of transformer for low voltage 50[V] and large current 3,000[A], carbon resistor load 0.2 [$m{\Omega}$]. PWM switching frequency for IGBT inverter control set 15KHz. The suggested researching contents are designed data sheets of power converter system, PSIM simulation, operating characteristics and analysis results of developed SCSIG system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.5
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• pp.884-891
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• 2007

Comparing with the conventional transformer without the air gap, a contact-less transformer with the large air-gap (4.8cm) between the long primary winding and the secondary winding has the increased leakage inductance and the reduced magnetizing inductance. By the increased leakage inductance and the reduced magnetizing inductance on the primary of the contact-less transformer, a good deal of the primary current circulates through magnetizing inductance, which results in a massive loss and the high voltage gain characteristics for load variations in contact-less power supply (CPS). To consider these characteristics, in this paper, the efficiency characteristics of the contact-less power supply using a series resonant converter is presented, described and verified through theoretical analysis, computer simulation and experimental test of 2.5kW prototype.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.517-519
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• 2008

A new transformer winding method is proposed in this paper. Generally, PWM ZVS topologies use a leakage inductor to achieve ZVS operation. However, the leakage inductance of the transformer is not often enough to meet ZVS condition. Therefore, an additional leakage inductor is necessary, which causes large core loss because high input voltage is applied to the additional leakage inductor during a short commutation period. In this paper, a new separated leakage inductor winding (SLW) method is proposed. With the proposed winding method, a leakage inductor and a transformer can be combined in one ferrite core. Therefore, size and core loss of the additional leakage inductor can be reduced. Experimental results demonstrate that the proposed winding method can achieve a significant efficiency improvement in a 1210.8W (12V, 100.9A) prototype converter.