Statistical analysis for HTS coil considering inhomogeneous Ic distribution of HTS tape

Hongwoo Jin,Jiho Lee,이우승,고태국 한국초전도.저온공학회 2015 한국초전도저온공학회논문지 Vol.17 No.2

Critical current of high-temperature superconducting (HTS) coil is influenced by its own self magnetic field. Direction anddensity distribution of the magnetic field around the coil are fixed after the shape of the coil is decided. If the entire part of the HTStape has homogeneous Ic distribution characteristic, quench would be initiated in fixed location on the coil. However, the actualHTS tape has inhomogeneous Ic distribution along the length. If the Ic distribution of the HTS tape is known, we can expect the spotwithin the HTS coil that has the highest probability to initiate the quench. In this paper, Ic distribution within the HTS coil underself-field effect is simulated by MATLAB. In the simulation procedure, Ic distribution of the entire part of the HTS tape is assumed to follow Gaussian-distribution by central limit theorem. The HTS coil model is divided into several segments, and the criticalcurrent of each segment is calculated based on the-generalized Kim model. Single pancake model is simulated and self-field ofHTS coil is calculated by Biot-Savart’s law. As a result of simulation, quench-initiating spot in the actual HTS coil can bepredicted statistically. And that statistical analysis can help detect or protect the quench of the HTS coil.

Statistical analysis for HTS coil considering inhomogeneous I_c distribution of HTS tape

Jin, Hongwoo,Lee, Jiho,Lee, Woo Seung,Ko, Tae Kuk The Korea Institute of Applied Superconductivity a 2015 한국초전도저온공학회논문지 Vol.17 No.2

Critical current of high-temperature superconducting (HTS) coil is influenced by its own self magnetic field. Direction and density distribution of the magnetic field around the coil are fixed after the shape of the coil is decided. If the entire part of the HTS tape has homogeneous $I_c$ distribution characteristic, quench would be initiated in fixed location on the coil. However, the actual HTS tape has inhomogeneous $I_c$ distribution along the length. If the $I_c$ distribution of the HTS tape is known, we can expect the spot within the HTS coil that has the highest probability to initiate the quench. In this paper, $I_c$ distribution within the HTS coil under self-field effect is simulated by MATLAB. In the simulation procedure, $I_c$ distribution of the entire part of the HTS tape is assume d to follow Gaussian-distribution by central limit theorem. The HTS coil model is divided into several segments, and the critical current of each segment is calculated based on the-generalized Kim model. Single pancake model is simulated and self-field of HTS coil is calculated by Biot-Savart's law. As a result of simulation, quench-initiating spot in the actual HTS coil can be predicted statistically. And that statistical analysis can help detect or protect the quench of the HTS coil.

전투기 능동위상배열 안테나의 신뢰도 분석을 위한 송수신모듈 허용 고장 기준 설정 방안 연구

배진(Jin Bae),김종수(Chong Su Kim),박홍우(Hongwoo Park) 한국산학기술학회 2023 한국산학기술학회논문지 Vol.24 No.5

최신 전투기 개발 추세를 살펴보면 4세대 전투기 이후, 스텔스, 높은 기동성, 최신 항전 장비를 보강하는 전투기 개발로 변화가 이루어지고 있다. 특히, 전투기의 눈이라고 불리는 레이다는 4세대 전투기의 기계식 레이다에서 최신의 능동위상배열(AESA: Active Electronically Scanned Array) 레이다로 발전하고 있다. 최신 전투기에 적용되는 AESA 레이다는 반도체 송수신모듈(T/R: Transmit/Receive Module, 이하 T/R 모듈)을 이용하고 있으며, 운용 측면에서 어느 정도까지 T/R 모듈 고장이 나더라도 레이다를 운용할 수 있어서, 기계식 안테나 대비 효율적이기 때문에 최근 개발하는 전투기는 AESA 레이다를 기본적으로 고려하고 있다. 전투기 AESA 레이다 개발 단계에서 신뢰도 분석을 수행하기 위해서는 다중화 중복 구조로 되어 있는 T/R 모듈의 허용 고장률 기준 설정이 필요하다. 이러한 T/R 모듈 허용 고장은 레이다 운용 요구도를 이용하여 설정하는 방법이 적절하다. 본 연구에서는 안테나 전체 T/R 모듈 기준으로 5%에서 10% 이내 각 고장률에 따른 레이다 운용 요구성능의 기본이 되는 표적 최대 탐지 능력 만족 여부를 판단하여 최대 고장률을 설정하는 방법을 제시하였다. The latest jet fighters are mostly adopting active electronically scanned array (AESA) radars with transmit/receive modules (T/R modules) instead of mechanically scanned array (MSA) radars used for fourth-generation fighters. T/R modules have good functional characteristics that support maintaining radar operational capability until they reach a certain failure rate. Therefore, it is required to establish a random failure rate of the T/R module, which is designed for structural redundancy for reliability in the development phase of the radar. The failure rate should be determined to meet the required radar operational capability. This paper proposes a method to determine the proper random failure rate of the T/R module, in which the maximum failure rate from 5% to 10% to meet the maximum detection rate is the key factor of the required operational capability of radar.

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.

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>

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 한국초전도저온학회 (구 한국초전도저온공학회) 2014 한국초전도저온공학회논문지 Vol.16 No.1

Proof-of-Concept of a Millisecond-Scale Electromagnetic Levitator Using High-Temperature Superconducting Coils

Jiho Lee,Seokho Nam,Seunghyun Song,Hongwoo Jin,Tae Kuk Ko Institute of Electrical and Electronics Engineers 2015 IEEE transactions on applied superconductivity Vol.25 No.3

<P>This paper proposes a millisecond-scale electromagnetic levitator using high-temperature superconducting (HTS) coils. The proposed apparatus consists of an AC power supply, short-circuit switches, an aluminum plate, and two HTS coils. The HTS coils are wound in opposite directions and electrically connected in parallel. Thus, in a symmetric current distribution, the magnetic fluxes generated by the two HTS coils ideally cancel each other. However, in a sudden asymmetric current distribution created by the short-circuit switches, the magnetic fluxes are not cancelled, and the effective magnetic flux induces an eddy current in the aluminum plate placed above the HTS coils. The magnetic flux generated by the eddy current in the aluminum plate and the effective magnetic flux generated by the HTS coils together generate the repulsive force to levitate the aluminum plate. In this paper, numerical calculations and experimental verification of the repulsive force are performed. We show that this apparatus is able to provide a levitation force that we expect will be helpful for devices that need fast switching behavior of the levitation force.</P>

Analysis of the Current Charge and Discharge Characteristics of a Small-Scale Turn-to-Turn Soldered HTS Coil

Lee, Woo Seung,Lee, Jiho,Song, Seunghyun,Park, Young Gun,Jin, Hongwoo,Hahn, Seungyong,Ahn, Min Cheol,Ko, Tae Kuk Institute of Electrical and Electronics Engineers 2015 IEEE transactions on applied superconductivity Vol.25 No.3

<P>A semipersistent current-mode operation with a high-temperature superconducting (HTS) coil is very useful for some applications, including maglev. An HTS coil for semipersistent mode operation includes at least one residual joint to make a closed-loop coil. A low current decaying rate is achieved by reducing the residual joint resistance. This paper suggests a winding method with a turn-to-turn soldering process. The turn-to-turn soldering process provides a wide flow path for the charged current in the HTS coil during the semipersistent mode operation. Therefore, the total equivalent residual resistance is reduced. However, this reduced residual resistance also prevents the current from participating in the charging process. Therefore, a new current charging method for the turn-to-turn soldered HTS coil needs to be tested. In this paper, a small-scale sample HTS coil with turn-to-turn soldering method is fabricated for testing. A simple charging–discharging experiment is performed on the sample coil. The time constant of the sample coil is calculated from the experimental results. A fast current charging sequence for the turn-to-turn soldered coil is also tested and analyzed from the perspective of power and energy consumption during the current charging operation.</P>

Operational Characteristics of a Small-Scale Novel Hybrid Resistive-Type SFCL With Controlled Power Electronics

Nam, Seokho,Lee, Jiho,Lee, Woo Seung,Park, Young Gun,Song, Seunghyun,Jin, Hongwoo,Ko, Tae Kuk Institute of Electrical and Electronics Engineers 2015 IEEE transactions on applied superconductivity Vol.25 No.3

<P>As electric power systems become more complicated, the fault current experiences more frequent changes. To solve this problem, we suggest a novel hybrid-type superconducting fault current limiter (SFCL). Some issues accompany application of resistive-type SFCLs to electric power systems, including initial installation price, operation and maintenance costs, and high-current problems. To overcome these problems, <I>hybrid SFCLs </I> have been developed in some institutions. This paper presents experimental tests of a novel hybrid-type SFCL composed of a resistive superconducting coil, two thyristors, and a control circuit. The superconducting coil limits the first peak of the fault current, and the thyristors control the magnitude of the fault current other than the first peak by adjusting the firing angles. The interactions between the superconducting coil and the thyristors reduce the use of superconducting wire.</P>