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Energy extraction system using dual-capacitor switching for quench protection of HTS magnet
Choi, Yojong,Lee, Woo Seung,Song, Seunghyun,Jeon, Haeryong,Kang, Hyoungku,Ko, Tae Kuk The Korea Institute of Applied Superconductivity a 2017 한국초전도저온공학회논문지 Vol.19 No.3
The superconducting magnets have a large inductance as well as high operating current. Therefore, mega-joule scale energy can be stored in the magnet. The energy stored in the magnet is sufficient to damage the magnet when a quench occurs. Quench heater and dump resistor can be used to protect the magnet. However, using quench heater to create quench resistors through heat transfer can be slower than instantly switching resistors. Also, electrical short, overheating and breakdown can occur due to quench heater. Moreover, the number of dump resistor should be limited to avoid large terminal voltage. Therefore, in this paper, we propose a quench protection method for extracting the energy stored in a magnet by charging and discharging energy through a capacitor switching without increasing resistance. The simulation results show that the proposed system has a faster current decay within the allowable voltage level.
Song, Seunghyun,Choi, Yojong,Lee, Woo Seung,Sim, Kideok,Hwang, Young Jin,Jang, Jae Young,Kang, Hyoungku,Ko, Tae Kuk Institute of Electrical and Electronics Engineers 2018 IEEE transactions on applied superconductivity Vol.28 No.3
<P>The combination of a machine's rotation cycle and the unpredictable industrial interference encountered by rotating machinery can generate a time-varying noise signal. Such signals cause difficulty while detecting the quench voltage in superconducting rotating machinery. Quench detection is more difficult in high-temperature superconductors (HTS) than in low-temperature superconductors (LTS) because the normal zone propagation (NZP) velocity of HTS is lower than that of LTS. To detect the quench signal in an HTS, signal wires are widely used for voltage taps. However, owing to the low NZP velocity, it is difficult to detect the quench signal in HTS when the voltage taps are attached at short distances from the HTS devices. Furthermore, there is a possibility of the HTS burning out when voltage taps are attached to both ends of the HTS tape, because the hot spot is scarcely dissipative and thermal runaway may occur in the normal zone. Thus, detecting the quench in HTS rotating machinery is difficult. Moreover, the signal wires used in the voltage taps become twisted when the HTS rotor coil rotates to generate magnetic flux. Therefore, in this paper, a sensitive quench-detection method that uses electromagnetically coupled coils is presented for application to HTS rotating machinery.</P>
Young Gon Kim,Geonwoo Baek,Seunghak Han,Yojong Choi,Junseong Kim,Haeryong Jeon,Tae Kuk Ko 한국초전도.저온공학회 2019 한국초전도저온공학회논문지 Vol.21 No.4
Recently, many studies have been reported on the magnetoresistance and Hall effect of REBCO thin films and bulk. The voltage interferes quench detection of high-temperature superconducting magnet and generates leakage current in no insulation hightemperature superconducting coil. Therefore, in this paper, experiments on magnetoresistance and Hall effect of commercial YBCO and GdBCO tapes have been carried out. As a result, anomalous voltages expected for the magnetoresistance and Hall effect of REBCO tapes were observed and analyzed. In addition, the voltage characteristics of REBCO have been identified, and the Hall coefficient are calculated for use in high magnetic field magnet applications.
Kim, Young Gon,Baek, Geonwoo,Han, Seunghak,Choi, Yojong,Kim, Junseong,Jeon, Haeryong,Ko, Tae Kuk The Korea Institute of Applied Superconductivity a 2019 한국초전도저온공학회논문지 Vol.21 No.4
Recently, many studies have been reported on the magnetoresistance and Hall effect of REBCO thin films and bulk. The voltage interferes quench detection of high-temperature superconducting magnet and generates leakage current in no insulation high-temperature superconducting coil. Therefore, in this paper, experiments on magnetoresistance and Hall effect of commercial YBCO and GdBCO tapes have been carried out. As a result, anomalous voltages expected for the magnetoresistance and Hall effect of REBCO tapes were observed and analyzed. In addition, the voltage characteristics of REBCO have been identified, and the Hall coefficient are calculated for use in high magnetic field magnet applications.
Jinsub Kim,Seok Chan An,Yojong Choi,Tae Kuk Ko,Yong Chu IEEE 2017 IEEE transactions on applied superconductivity Vol.27 No.4
<P>A quench detection system for Korea Superconducting Tokamak Advanced Research (KSTAR) Poloidal Field (PF) coils is indispensable against the occurrence of a normal zone due to frequently variable current operation and an enormous amount of stored energy. The co-wound conductive strips and Wheatstone bridges have been adopted in KSTAR to detect abnormal voltage signal caused from quench. Those voltage detection methods have sufficient capability to detect quench occurrence, but additional cancelling out of mutual induction by adjacent coils would improve stability and reliability of quench detection system. A new voltage detection concept, using central difference averaging (CDA) and mutual inductance compensation (MIK) simultaneously, as an advanced technique to compensate the mutual inductive voltage, has been suggested and studied for this study. The CDA and MIK methods were practically adapted to the KSTAR PF 1 coil for the feasibility study. Test results show that the inductance matrix calculated by the FEM tool should be revised because of a revealed discrepancy between measured CDA voltage and calculated MIK voltage. In this study, the inductance matrix was revised by using the “Genetic algorithm” optimization method to reduce the discrepancy between CDA and MIK effectively. The adoption of the MIK revised inductance matrix was consistent with CDA voltage; mutual inductive voltage was expected to be successfully eliminated.</P>
Lee, Jeyull,Kim, Junseong,Baek, Geonwoo,Choi, Yojong,Choi, Yoon Hyuck,Zhang, Zhan,Chung, Yoon Do,Kang, Hyoungku,Lee, Haigun,Lee, Sangjin,Ko, Tae Kuk IEEE 2018 IEEE transactions on applied superconductivity Vol.28 No.3
<P>High-temperature superconductors (HTSs) have a much larger thermal margin than low-temperature superconductors, owing to their high critical temperatures. This characteristic allows HTS magnets to tolerate extremely high heat loads that may arise from radiation. Therefore, research on the development of HTS quadrupole magnets is progressing widely. Quadrupole magnets are commonly used for focusing the transported beams of particles in accelerators. In order to focus the beam, the quadrupole magnet uses an iron yoke with a hyperbolic contour. However, the iron yoke induces nonlinear magnetic characteristics because of saturation. Therefore, an air-core HTS quadrupole magnet is proposed to improve the magnetic characteristics. In this paper, we design air-core and iron-core HTS quadrupole magnet models using a harmonic matching method. The field gradient and effective length of both magnets are 12.1 T/m and 550 mm, respectively. In order to verify the performances of the proposed air-core quadrupole magnet, the magnetic field gradient, field uniformity, and effective length are analyzed for operating currents ranging from 50 to 400 A.</P>