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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>
Voltage disturbance detection method for HTS tape using electromagnetically coupled coils
Seunghyun Song,Jiho Lee,Woo Seung Lee,Hongwoo Jin,Young Jin Hwang,Tae Kuk Ko 한국초전도저온공학회 2014 초전도와 저온공학 Vol.16 No.1
This paper represents the detection method of voltage disturbance for high temperature superconducting (HTS) tape using electromagnetically coupled coils. In order to detect the voltage as the superconductor transits from the superconducting state to the normal conduction state, voltage taps are widely used to get the voltage signal. And voltage taps are connected to data acquisition device via signal wires. However this new suggested method can detect the superconducting transition voltage without signal wires between voltage taps and data acquisition device by using electromagnetically coupled coils. This system consists of two electromagnetically coupled coils, the first coil to detect and transmit the voltage of HTS tape and the second coil to pick up the transmitted voltage from the first coil. By using this new suggested method, we can build the ‘separated voltage-detection system’. HTS tape and first coil are located under liquid nitrogen vessel and the second coil is located under room temperature condition. In this paper, experiments are performed to verify the feasibility of the proposed method. As the result of the experiment, the separated voltage-detection system using electromagnetically coupled coils can successfully observe superconducting-normal transition of HTS tapes.
Room Temperature Semiconductor-Metal Transition of MoTe<sub>2</sub> Thin Films Engineered by Strain
Song, Seunghyun,Keum, Dong Hoon,Cho, Suyeon,Perello, David,Kim, Yunseok,Lee, Young Hee American Chemical Society 2016 NANO LETTERS Vol.16 No.1
<P>We demonstrate a room temperature semiconductor-metal transition in thin film MoTe2 engineered by strain. Reduction of the 2H-1T' phase transition temperature of MoTe2 to room temperature was realized by introducing a tensile strain of 0.2%. The observed first-order SM transition improved conductance similar to 10 000 times and was made possible by an unusually large temperature-stress coefficient, which results from a large volume change and small latent heat. The demonstrated strain-modulation of the phase transition temperature is expected to be compatible with other TMDs enabling the 2D electronics utilizing polymorphism of TMDs along with the established materials.</P>
Seunghyun Song,Hyeong-Seok Kim,Hyun-Kyo Jung,Braunstein, J.,Un-Chul Moon IEEE 2006 IEEE transactions on magnetics Vol.42 No.4
<P>In this paper, an adaptive frequency sampling technique is applied to the moment method for the analysis of microstrip filters and patch antennae. The analysis of microstrip low-pass filter and patch antenna in the frequency domain has been usually done with uniform frequency step. An adaptive frequency sampling technique can significantly reduce the time taken for the analysis through the frequency range without reducing the accuracy of the results</P>
Voltage disturbance detection method for HTS tape using electromagnetically coupled coils
Song, Seunghyun,Lee, Jiho,Lee, Woo Seung,Jin, Hongwoo,Hwang, Young Jin,Ko, Tae Kuk The Korea Institute of Applied Superconductivity a 2014 한국초전도저온공학회논문지 Vol.16 No.1
This paper represents the detection method of voltage disturbance for high temperature superconducting (HTS) tape using electromagnetically coupled coils. In order to detect the voltage as the superconductor transits from the superconducting state to the normal conduction state, voltage taps are widely used to get the voltage signal. And voltage taps are connected to data acquisition device via signal wires. However this new suggested method can detect the superconducting transition voltage without signal wires between voltage taps and data acquisition device by using electromagnetically coupled coils. This system consists of two electromagnetically coupled coils, the first coil to detect and transmit the voltage of HTS tape and the second coil to pick up the transmitted voltage from the first coil. By using this new suggested method, we can build the 'separated voltage-detection system'. HTS tape and first coil are located under liquid nitrogen vessel and the second coil is located under room temperature condition. In this paper, experiments are performed to verify the feasibility of the proposed method. As the result of the experiment, the separated voltage-detection system using electromagnetically coupled coils can successfully observe superconducting-normal transition of HTS tapes.
Quench Detection Method for HTS Coils Using Electromagnetically Coupled Coils
Seunghyun Song,Jiho Lee,Woo Seung Lee,Hongwoo Jin,Jeyull Lee,Young Jin Hwang,Tae Kuk Ko Institute of Electrical and Electronics Engineers 2015 IEEE transactions on applied superconductivity Vol.25 No.3
<P>Generally, in order to detect the quench of the superconducting field coil for the superconducting rotating machine, signal wires for voltage taps are indispensably needed. However, the problem of the conventional method is wire twisting as the superconducting field coil rotates. Therefore, in this paper, authors suggest a new method to detect the quench of the superconducting field coil using electromagnetically coupled coils. The suggested method consists of two superconducting pancake and copper solenoid coils. Two superconducting pancake coils play roles of a field coil and external (alternating) field generation for the rotating machine. In addition, two copper solenoid coils are used to transmit the voltage wirelessly and receive the transmitted voltage using electromagnetic induction. In order to verify the feasibility of this method, experiments are performed according to the transporting current flowing through two superconducting pancake coils and separation distance between two copper solenoid coils. The result shows that it is expected to apply this method to the superconducting rotating machines for the detection of quench without direct connection of voltage taps.</P>
Quench Analysis of a Superconducting Magnet for RISP 28 GHz ECR Ion Source
Seunghyun Song,Tae Kuk Ko,Sukjin Choi,In Seok Hong,Hyoungku Kang,Min Cheol Ahn Institute of Electrical and Electronics Engineers 2015 IEEE transactions on applied superconductivity Vol.25 No.3
<P>This paper presents quench analysis of a superconducting magnet system for 28 GHz electron cyclotron resonance (ECR) ion source. The magnet system consists of a hexapole coil and four solenoid coils located outside of the hexapole one. All coils were wound with NbTi wire and impregnated by epoxy. To analyze the characteristic of superconducting coil when the quench occurs, a numerical code was developed. The analysis procedures are as follows. First, normal zone propagation (NZP) velocity which is as a function of magnetic field was calculated. Second, a fraction of the winding volume was obtained by transient analysis, considering longitudinal and transverse NZP velocities. Third, a generated resistance and temperature rising over time were simulated. Lastly, current trace of the coil was calculated. The current trace calculated by simulation well agrees with the test result. Also the result of hot-spot temperature is reasonable. Since simulated hot-spot temperature and experimental result are 60.32 K and 63 K when the operating current is 169 A. The normal zone resistances are also identical for 1.13 s which is the convergence time of simulation. The final resistances are about 10.2 Ω and 11.23 Ω. Therefore it is expected that the analysis code can be used to estimate the characteristic of superconducting magnet when the quench occurs.</P>