• Progress in Superconductivity and Cryogenics
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• v.12 no.3
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• pp.21-24
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• 2010

A cryogenic insulation technique for a high voltage and a large current capacity of a conductor are now two big issues in a field of recent R&D projects of superconducting power devices, especially a superconducting power transformer. For the large rated currents of the power transformer, it is well known that lots of 2nd generation superconducting conductor, so called coated conductor, should be stacked together with transpositions in order to get an even distributions of the currents. We had come up with an idea of a CTCC (Continuously Transposed Coated Conductor) as a conductor for a large power superconducting transformer, and keep trying to verify the usefulness of the conductor. As one of the efforts of verifying, we prepared and tested a sample CTCC with insulations for high voltage, which includes the epoxy coating and Nomex$^{(R)}$ wrapping. This paper contains the insulation process and dielectric breakdown test results. We expect the results obtained from this experiment to improve an insulation technique for high voltages in various cryogenic environments[1,2].

• Proceedings of the KIEE Conference
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• 2001.11a
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• pp.270-273
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• 2001

In this paper, some of optical current transformers and optical potential transformers for extra high voltage system are introduced. The optical current transformer and optical potential transformer will be adopted in the near future, because of increasing demands of high accuracy and good reliability of current transformer and potential transformer. The application cases of optical current transformers and optical potential transformers are also introduced.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.280-282
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• 2007

기존 PDP 전원 시스템은 일반적으로 두 개의 절연형 Transformer 를 사용하여 유지전원($V_S$)과 어드레스 전원($V_A$), Multi단 전원($V_M$) 으로 구성된다. 이들 각 전력 변환 회로에 Transformer 및 제어 IC 가 사용되므로, 효율 저감 및 원가 상승, 소자 스트레스 등의 단점을 가지고 있다. 본 논문에서는 절연형 Transformer 한 개로 PDP 전원시스템을 구동하는 방식에 대해 제안한다. 제안된 방식은 DC/DC 전력단의 고효율 동작 및 신뢰성 개선은 물론 부피, 크기를 줄여 원가 저감에 기여한다. 또한, 제안된 방식은 PDP 구동 방식의 하나인 Address Display Separation Method (ADSM) 에 적합하다. 기존 방식과 제안된 방식을 비교하고 이론적 분석과 실험을 통해 제안된 방식의 우수성을 확인 하였다.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.701-708
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• 1998

This paper presents a novel non-resonant PWM DC-DC converter for X-ray high-voltage power generator using the parasitic impedances of the high-voltage high-frequency link transformer with its output high-voltage control scheme and steady-state characteristics compared to the conventional series-parallel resonant DC-DC converter. The key point of this approach is to evaluate effectiveness of reduction of the turn ratio of the high-voltage high-frequency transformer on improvements in power conversion efficiency and the power factor applying a boost AC-DC converter as DC voltage source, especially in the long exposure term and light output load ranges.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1297-1300
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• 2008

A conventional linear accelerator system requires a flat-topped pulse with less than ${\pm}$ 0.5% ripple to meet the beam energy spread requirements and to improve pulse efficiency of RF systems. A pulse transformer is one of main determinants on the output pulse voltage shape. The pulse transformer was investigated and analyzed with the pulse response characteristics using a simplified equivalent circuit model. The damping factor ${\sigma}$ must be >0.86 to limit the overshoot to less than 0.5% during the flat-top phase. The low leakage inductance and distributed capacitance are often limiting factors to obtain a fast rise time. These parameters are largely controlled by the physical geometry and winding configuration of the transformer. A rise time can be improved by reducing the number of turns, but it produces larger pulse droop and requires a larger core size. By tradeoffs among these parameters, the high-voltage pulse transformer with a pulse width of 10 ${\mu}s$, a rise time of 0.84 ${\mu}s$, and a pulse droop of 2.9% has been designed and fabricated to drive a klystron which has an output voltage of 284 kV, 30-MW peak and 60-kW average RF output power. This paper describes design optimization of a high-voltage pulse transformer for high-power pulsed applications. The experimental results were analyzed and compared with the design. The design and optimal tuning parameter of the system was identified using the model simulation.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.4
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• pp.210-220
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• 2002

We analysised the effect of harmonics on electric machines of substation power system barred on quantitatively measured harmonics and proposed the methods for prevention of harmonics through checking on transformer, rectifier and cable's capacities against harmonics with reference to KEPCO's electricity service standard. In order to analysis harmoninics of silicon rectifier that is power source in DC substation, computer simulations for a substation with TR of high voltage distribution switchboard are performed. Simulation results show that the total harmonic distortion factor becomes smaller for TR primary and receiving points in order rather than silicon rectifier which is harmonic generation source so that the harmonics generated frets each rectifier are outflowed to power supply and high voltage distribution switchboard The result of higher distortion factors of voltage and current for rectifier with 100% load than those with 50 % and 30% indicates that the waveform of voltage and current for the real substation power system at the office-going and the closing hours with heavy loads might be more distorted. As proposed methods for harmonic reduction, the conventional 6 pulse-type for substation is required to be replaced by 12 pulse-type for reduction of 5th and 7th harmonics. The active filter rather than the passive filter is more effective due to severe variance of rectifier loads, but the high cost is price to be paid. In view of installation area and costs, the use of 12 pulse-type transformer is desirable and then the parallel transformer and the rectifier within the substation must be replaced at the same time. Other substations with parallel feeder can use 6 pulse-type transformer.

• Journal of Environmental Impact Assessment
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• v.14 no.4
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• pp.195-202
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• 2005

The health risks from the magnetic fields exposure have been brought out difficulties in the construction of transformer substation. According to several epidemiologic studies and the relevant international organizations, magnetic fields should not exceed the exposure limits of 3mG for the people living near electric power lines. The rigid regulation of the exposure levels for the elementary school and residental areas has been established already in Switzerland and Italy. Since 1998, the environmental impact assessment system in Korea has been reviewed for power-frequency magnetic field by precautionary policies. In this study, the possible application of Prior Environmental Performance Review System for the transformer substation was reviewed from the points of the properties of the powerfrequency magnetic fields. The ranges and survey methods of the assessment for the transformer substation were proposed. The ranges of magnetic fields was between 300m to 500m for the 345kV transformer substation. It is necessary to develop further specific assessment methods for various high-voltage transformer substations.

• Journal of Power Electronics
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• v.9 no.2
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• pp.180-187
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• 2009

When converters operate in megahertz range, the passive components and magnetic devices generate high losses. However, the eddy current issues and choices of magnetic cores significantly affect on the design stage. Apart from that, the components' reduction, miniaturization technique and frequency scaling are required as well as improvement in thermal capability, integration technique, circuit topologies and PCB layout optimization. In transformer design, the winding and core losses give great attention to the design stage. From simulation work, it is found that E-25066 material manufactured by AVX could be the most suitable core for high frequency transformer design. By employing planar geometry topology, the material can generate significant power loss savings of more than 67% compared to other materials studied in this work. Furthermore, young researchers can use this information to develop new approaches based on concepts, issues and methodology in the design of magnetic components for high frequency applications.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.2027-2029
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• 1998

We have developed a compact high frequency switch mode converter (HFSMC) power supply with DC 50 kV output voltage and 10 kW output power. Since the inverter circuit uses 25 kHz rescharging scheme, the current is flowing with t kHz. For the efficient output voltage transform performed a simple design process using the transformer principle and the commercial specification. For the DC 50 kV output, we employed 7 pa windings of secondary coils for the series stac connection of the output with full-bridge rectifi In this paper the design detail and the test re the high frequency transformer together with HFSMC power supply are presented.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.32-33
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• 2006

Processing and properties of high power piezoelectric transformer (PT) fabricated by PIM with nano-sized piezoelectric powders are demonstrated. The high power characteristics of a PMed dome-shaped PT were examined by the lighting test for a 55watt PL lamp. The 55watt PL lamp was successfully driven by the PIMed PT with sustaining efficiency higher than 98%. The transformer with ring/dot area ratio of 2.1 exhibited the maximum properties in terms of output power, efficiency and temperature stability.