• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1771-1773
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• 2001

This paper deals with the numerical estimation of the bubble behavior and the partial discharge(PD) initiation voltage basis of electric field calculation with the coaxial coil layer-to-cylindrical electrode system for the simulation of high temperature superconducting coils. The theoretical results of bubble behavior and the PD initiation voltages showed fairly good agreements with the experimental results.

• Proceedings of the KIEE Conference
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• 1998.07a
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• pp.250-253
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• 1998

This paper has proposed a method to analyze a 30 KVA superconducting generator using 3-dimensional FEM program. 3 kinds of 3D formulation methods are employed such as scalar potential in core region, reduced scalar potential in air region and T-${\omega}$ formulation in stator coil region. As results of the simulation, various parameters of the generator have been analyzed like air gap flux density, induced voltage, inductance, etc.

• Progress in Superconductivity and Cryogenics
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• v.16 no.2
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• pp.54-58
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• 2014

High-temperature superconducting (HTS) rotating machines always require an electric current of from several hundreds to several thousand amperes to be led from outside into cold region of the field coil. Heat losses through the current leads then assume tremendous importance. Consequently, it is necessary to acquire optimal design for the leads which would achieve minimum heat loss during operation of machines for a given electrical current. In this paper, conduction cooled current lead type of 10 MW-Class HTS rotating machine will be chosen, a conceptual design will be discussed and performed relied on the least heat lost estimation between conventional metal lead and partially HTS lead. In addition, steady-state thermal characteristic of each one also is considered and illustrated.

• Progress in Superconductivity and Cryogenics
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• v.10 no.4
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• pp.13-17
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• 2008

This paper presents experimental and characteristic analysis of hgh-$T_c$ eater-triggered witch using coated conductor (CC) in liquid and gas helium. The high temperature superconducting insert coil which can be installed in a low temperature superconducting (LTS) magnet has been proposed and researched to generate higher magnetic field for MR. Since CC could be an attractive option for HTS insert, it is important to research he characteristics of heater-triggered switch employing CC. We performed the heater test and constructed simulation model using finite element method (FEM.) We performed a protection test and observed normal zone propagation (NZP) signals to evaluate the witch with protection of magnet.

• Progress in Superconductivity and Cryogenics
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• v.17 no.2
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• pp.36-40
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• 2015

Electron cyclotron resonance (ECR) ion source is an essential component of heavy-ion accelerator. For a given design, the intensities of the highly charged ion beams extracted from the source can be increased by enlarging the physical volume of ECR zone [1]. Several models for ECR ion source were and will be constructed depending on their operating conditions [2-4]. In this paper three simulation models with 3, 4 and 6 solenoid system were built, but it's not considered anything else except the number of coils. Two groups of optimization analysis are presented, and the evolution strategy (ES) is adopted as an optimization tool which is a technique based on the ideas of mutation, adaptation and annealing [5]. In this research, the volume of ECR zone was calculated approximately, and optimized designs for ECR solenoid magnet system were presented. Firstly it is better to make the volume of ECR zone large to increase the intensity of ion beam under the specific confinement field conditions. At the same time the total volume of superconducting solenoids must be decreased to save material. By considering the volume of ECR zone and the total length of solenoids in each model with different number of coils, the 6 solenoid system represented the highest coil performance. By the way, a certain case, ECR zone volume itself can be essential than the cost. So the maximum ECR zone volume for each solenoid magnet system was calculated respectively with the same size of the plasma chamber and the total magnet space. By comparing the volume of ECR zone, the 6 solenoid system can be also made with the maximum ECR zone volume.

• Progress in Superconductivity and Cryogenics
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• v.11 no.2
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• pp.33-36
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• 2009

A 1 MW class HTS (High-Temperature Superconducting) synchronous motor has been developed. This motor is aimed to be utilized for industrial application such as large motors operating in large plants. The HTS field coil of the developed motor is cooled by way of neon thermo siphonmechanism and the stator (armature) coil is cooled by water through hollow copper conductor. This paper also describes evaluation of some electrical parameters from performance test results of our motor, which was conducted at steady state in generator mode and motor mode. Open and short circuit tests were conducted in generator mode while a 1.1 MW rated induction machine was rotating the HTS machine. Electrical parameters such as mutual inductance and synchronous inductance are deduced from these tests. Load test was done upto rating torque during motor mode and efficiency was measured at each load torque.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.276-279
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• 2003

The superconducting synchronous machine(S.S.M) including generator and motor has different electromagnetic structure from the conventional machine. With the help of superconductor having much higher operating current density than normal conductor, S.S.M can eliminate most of iron core filling inside of the conventional machine. This air-cored structure could be analysed and designed theoretically based on 2-dimensional(2-D) magnetic field distribution assuming that the windings are extended infinitely toward the axial direction. However the actual structure of S.S.M has the end regions interconnecting the straight parts of the same cross-section with the 2-D model. Therefore, this actual 3-D model has smaller field distribution than the 2-D model. In this paper, we consider the effect of the end regions on the output of a HTS model motor and suggest more accurate design approach through comparison of 2-D and 3-D magnetic field analysis.

• Progress in Superconductivity and Cryogenics
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• v.17 no.3
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• pp.33-36
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• 2015

A liquid nitrogen ($LN_2$) is usually used to be a coolant and insulant for a HTS coil system. HTS wires for a superconducting apparatus may be surrounded by gaseous nitrogen ($GN_2$) due to film boiling generated by a quench or voids occurred by electrical breakdown. The increased maximum electric field intensity at $GN_2$ may result in the degradation of dielectric strength of a HTS coil system. In this paper, a study on the dielectric characteristics of a composite insulation system composed of $LN_2$ and $GN_2$ is performed. A sphere-to-plane electrode system made with stainless steel is used to perform the experiments under AC and lightning impulse voltage condition. A sphere electrode is surrounded by $GN_2$ and a plane electrode is immersed into $LN_2$ to conduct dielectric experiments with a composite insulation system. The dielectric experiments are performed according to the level of $LN_2$ from the plane electrode to a sphere electrode. It is found that the dielectric characteristics of a composite insulation system are dependent on the level of $LN_2$ and the field utilization factor of an electrode system.

• Journal of Electrical Engineering and Technology
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• v.8 no.2
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• pp.326-330
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• 2013

The Korea Superconducting Tokamak Advanced Research (KSTAR) device is an advanced superconducting tokamak to establish scientific and technological bases for attractive fusion reactor. This device requires 3.5 Tesla of toroidal field (TF) for plasma confinement, and requires a strong poloidal flux swing to generate an inductive voltage to produce and sustain the tokamak plasma. KSTAR was originally designed to have 16 serially connected TF magnets for which the nominal current rating is 35.2 kA. KSTAR also has 7 pairs of poloidal field (PF) coils that are driven to 1 MA/sec for generation of the tokamak plasma according to the operation scenarios. The KSTAR Magnet Power Supply (MPS) was dedicated to the superconducting (SC) coil commissioning and $2^{nd}$ plasma experiment as a part of the system commissioning. This paper will describe key features of KSTAR MPS for the $2^{nd}$ plasma experiment, and will also report the engineering and commissioning results of the magnet power supplies.

• Progress in Superconductivity and Cryogenics
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• v.11 no.3
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• pp.26-30
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• 2009

Korea Superconducting Tokamak Advanced Research(KSTAR) device is composed of 30 superconducting magnets, magnet structure, vacuum vessel, cryostat, current feeder system, and etc. KSTAR device is operated in the cryogenic temperature and high magnetic field. We install about 800 sensors - temperature sensors, stain gages, displacement gages, hall sensors - to monitor the thermal, mechanical, electrical status of KSTAR during operation. As a tremendous numbers of sensors should be installed for monitoring the KSTAR device, the method of effective installation was developed. The sensor test was successfully carried out to check its reliability and its reproduction in the cryogenic temperature. The sensor signal is processed by PXI-based DAQ system and communicated with central control system via machine network and is shown by Operator Interface(OPI) display in the main control room. In order to safely operate the device, any violations of mechanical & superconductive characteristic of the device components were informed to its operation system & operator. If the monitored values exceed the pre-set values, the protective action should be taken against the possible damage. In this paper, the system composition, operation criteria, operation result were presented.