• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.4B no.4
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• pp.201-205
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• 2004

The CCFL dimming control methods are generally used lamp current regulation or average current adjustment method feeding the CCFL inverter. Inverter operation frequency is higher than resonant frequency for safe operation. In this study, we design the half-bridge type series and parallel resonant converter circuit that switches at variable frequency modulation methods to control the output power. This method has advantages such as low EMI and reduced harmonics, and it is convenient for dimming control using a microprocessor. The validity of this study is confirmed from the simulation and experimental results.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.1
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• pp.66-71
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• 2001

In the air-conditioning industry, the refrigerant charging amount is one of the most important parameters affecting the energy efficiency ratio of heat pumps. An experimental study was performed on the characteristics of an inverter driven air-to-air heat pump system with a variation of compressor frequency and charging amount of refrigerant. The frequency was altered from 40Hz to 70Hz and the charging amount was changed from 1.6kg to 2.8kg in tests. The variation of performance was measured with switching of the expansion valve on each frequency and charging amount. All the tests were performed at the Korean Standard and test conditions of the air conditioners. As results, it was found that there existed the charging amount and the level of the suction gas superheat which provided the highest energy efficiency ratio at all the frequency bands.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.2
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• pp.150-159
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• 2016

This paper presents a study on the design optimization of a 5 kW plasma discharger for driving plasma reactor. The proposed study is composed of a high-frequency inverter based on the full-bridge circuit using soft switching techniques for high-frequency switching. The switching frequency in the operating region is the area of 130-200 kHz. By applying the LC resonance technique and a variable switching frequency, control technique is designed to be stable under changes in the load characteristics of the plasma reactor. This paper presents a quantitative analysis technique for design optimization. Experiments are performed according to load characteristic variations depending on the vacuum of the plasma reactor. This paper has verified the topology and design method for the 5 kW plasma discharger design.

• Journal of Power Electronics
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• v.5 no.4
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• pp.272-281
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• 2005

In this paper, a simple power control scheme for a constant frequency Class-D inverter with a variable duty cycle is proposed. It is more suitable and acceptable for high- frequency induction heating (IH) jar applications. The proposed control scheme has the advantages of not only wide power regulation range but also ease of control output power. Also it can achieve a stable and efficient Zero-Voltage-Switching (ZVS) in a whole load range. The control principles of the proposed method are described in detail and its validity is verified through simulated and experimental results on 42.8kHz IGBT for induction heating rated on 1.6kW with constant frequency variable power.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.10
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• pp.1262-1272
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• 1997

An experimental study on the frequency control of an inverter heat pump to get the desired indoor room temperature has been conducted for the performance characteristics during the steady, 4, 8, and 16 step frequency operations. The heat pump model used in this study was operated to meet the experimental conditions of ASHRAE standard. The performance of the system was tested by measuring the temperature and pressure of the refrigerant, and cooling capacity, power consumption, etc. of the system. As the controlling frequency steps increased, the running time of the compressor increased as well as the electric consumption of the system and the cooling energy due to the wall heating load. However, the average cooling COP was improved.

• Journal of Power Electronics
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• v.16 no.5
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• pp.1678-1688
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• 2016

This paper presents a capacitive power transfer (CPT) system using a Class-E resonant inverter. A Class-E resonant inverter is chosen because of its ability to perform DC-to-AC inversion efficiently while significantly reducing switching losses. The proposed CPT system consists of an efficient Class-E resonant inverter and capacitive coupling formed by two flat rectangular transmitter and receiver plates. To understand CPT behavior, we study the effects of various coupling distances on output power performance. The proposed design is verified through lab experiments with a nominal operating frequency of 1 MHz and 0.25 mm coupling gap. An efficiency of 96.3% is achieved. A simple frequency tracking unit is also proposed to tune the operating frequency in response to changes in the coupling gap. With this resonant frequency tracking unit, the efficiency of the proposed CPT system can be maintained within 96.3%-91% for the coupling gap range of 0.25-2 mm.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.1
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• pp.51-57
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• 1998

This paper proposed a novel SIT high frequency resonant inverter having drive signal phase shift control function. Phasor control type inverters using SIT can realize a power conversion on the high switching frequency with low switching loss. Especially, the high output power can be abstained by connecting the output voltage of two unit inverters In serIes. The stability of system using protection circuit for over current and the automatic follow-up control with load variation by PLL is presented. This inverter produce approximately sinusoidal waveform at a high frequency, switching frequency ranging from 180[kHz] to 220[kHz], and is applied to the 2[kW] induction heating. The operating characteristics of this inverter circuit are discussed from a theoretical point of view and compared with experimental results. results.

• Journal of Power Electronics
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• v.14 no.2
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• pp.292-301
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• 2014

This paper presents a new configuration for a three-phase multilevel voltage source inverter. The main bridge is built from a classical three-phase two-level inverter and three bidirectional switches. A variable DC-link employing two unequal DC voltage supplies and four switches is connected to the main circuit in such a way that the proposed inverter produces four levels in the output voltage waveform. In order to obtain the desired switching gate signals, the fundamental frequency staircase modulation technique is successfully implemented. Furthermore, the proposed structure is extended and compared with other types of multilevel inverter topologies. The comparison shows that the proposed inverter requires a smaller number of power components. For a given number of voltage steps N, the proposed inverter requires N/2 DC voltage supplies and N+12 switches connected with N+7 gate driver circuits, while diode clamped or flying capacitor inverters require N-1 DC voltage supplies and 6(N-1) switches connected with 6(N-1) gate driver circuits. A prototype of the introduced configuration has been manufactured and the obtained simulation and experimental results ensure the feasibility of the proposed topology and the validity of the implemented modulation technique.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.2
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• pp.149-156
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• 2007

The number of transformer and the size of transformer in inverter using 3-phase transformer could be reduced compare with a multi-level inverter using single phase transformer. but still the 3-phase transformer inverter needs many switches. In this study, we proposed the isolated multi-level inverter using 3-phase transformers and common arm, in this paper. Also, using phase angle control method with switching frequency equal to output fundamental frequency, harmonics component of output voltage and switching loss can be reduced. Finally, We tested multi-level inverter to clarify electric circuit md reasonableness through Matlab simulation and experiment by using prototype inverter.

• Proceedings of the KIPE Conference
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• 1997.07a
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• pp.370-373
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• 1997

In this paper, we compose of the stepdown chopper and the current source inverter. Because dc side current of the current source inverter pulse with twice frequency of utility, we control that modulation factor of chopper is pulsed twice frequency. Therefore if voltage across the dc reactor equal to zero, it tis decreased. And we control modulation factor of the chopper to operate at maximum power point around of solar cell.