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Jonggi Hong,Seyong Choi,Mi-Sook Won,Hyoungku Kang Institute of Electrical and Electronics Engineers 2015 IEEE transactions on applied superconductivity Vol.25 No.3
<P>The current lead for a high-voltage superconducting fault-current limiter is made of copper or brass, and the cryostat chamber is often composed of a nonmagnetic material, such as stainless steel. Therefore, sparkover breakdown may occur at the current lead or the superconducting coil of such a superconducting coil system. The measurement of sparkover and partial discharge inception voltages is considered an important technique for diagnosing the dielectric conditions of a high-voltage superconducting instrument. In this paper, the sparkover voltage and the partial discharge inception voltage with respect to the electrode material were examined under an alternating-current voltage. Sphere-to-plane electrode systems made of stainless steel, copper, brass, and iron were tested in dielectric experiments to verify the sparkover and partial discharge inception voltages. It is observed that the sparkover and partial discharge inception voltages in gaseous nitrogen (GN<SUB>2</SUB>) were strongly dependent on the electrode material. In addition, it is found that the sparkover and partial discharge inception characteristics of GN<SUB>2</SUB> conform to the work function of the electrode material.</P>
Hong Jonggi,Park Jin Yong,Kim Sung Jun,Ok Jung-Woo,Choi Seyong 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.5
The BIBA (Busan Ion Beam Accelerator) is a compact linear accelerator facility using the 28 GHz ECRIS (Electron Cyclotron Resonance Ion Source) at the KBSI (Korea Basic Science Institute). The superconducting magnets of the 28 GHz ECRIS produce high magnetic fields for strong confinement of plasmas in an ion source chamber. For stable operation of the superconducting magnets, performance of cryostat system is very essential. However, the cryostat system produces significant quantities of the heating due to conduction from room temperature. In addition, part of the X-ray radiation produced by the collisions of the electrons within the ion source chamber is absorbed by the cold mass of the superconducting magnet, leading to an additional heat load in the cryostat system. In this paper, a study on the performance of the cryostat system for 28 GHz ECRIS is performed to improve the cooling efficiency of the cryostat system.
Jonggi Hong,Jin Yong Park,Sung Jun Kim,Jung-Woo Ok,Byoung-Seob Lee,Sangsu Jeon,Hyoungku Kang 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.73 No.8
Currently, the 28 GHz ECRIS (electron cyclotron resonance ion source) was developed to produce a high-current heavy-ion beam at the KBSI (Korea Basic Science Institute). The high-voltage platform of the 28 GHz ECRIS is essential to deliver an ion beam to the next acceleration stage. The high-voltage platform was designed considering dielectric characteristics in order to ensure electrical safety. In this paper, a study on the dielectric characteristics of GFRP (glass- fiber-reinforced plastic) is performed to determine the thickness of the GFRP cylindrical shell located between the plasma chamber and the warm bore of the superconducting magnet cryostat. The dielectric experiments on a GFRP cylindrical shell were conducted under a DC voltage. Sphere-to-plane electrode systems were used to examine the dielectric characteristics. Also, the relationship between the dielectric characteristics of the GFRP cylindrical shell and the distribution of the electric field intensity was calculated and analyzed by using FEM (Finite Elements Method) simulations.
비용 효율이 높은 24kV급 고압배전반 개발을 위한 Bus Bar 사이즈에 따른 전·자기 손실 특성 분석
홍종기(Jonggi Hong),허정일(Jeong Il Heo),남석호(Seokho Nam),강형구(Hyoungku Kang) 대한전기학회 2012 전기학회논문지 P Vol.61 No.4
The analysis on the bus bar effect is conducted to develop a cost effective 24kV/2,000A switchgear. The temperature enclosures and bus bars could rise due to several heat sources such as eddy current losses and copper losses. Therefore, a study on the characteristics of the electric field intensity and electromagnetic loss according to the bus bar size in a bus bar compartment is essential to design a electrically reliable high voltage switchgear. It is investigated that the electromagnetic influence to the temperature rising and the dielectric stability according to various bus bar sizes by using finite element method(FEM). The electric field intensity and electromagnetic loss according to various bus bar sizes are calculated to design a reliable and a high voltage switchgear. As results, it is found that the electromagnetic loss and the dielectric stability of bus bar could be determined by a bus bar size. It means that a cost effective 24kV/2,000A high voltage switchgear could be developed by selecting the proper size of a bus bar. Also, it is recognized that the electromagnetic characteristics according to various bus bar sizes in order to design an electrically stable high voltage switchgear when the enclosure size is determined as a fixed value. Futhermore, studies on the various nominal voltage class and bus bar sizes will be conducted to develop a cost effective high voltage switchgear.