• 한국초전도학회:학술대회논문집
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• v.15
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• pp.20-20
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• 2005

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.10
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• pp.537-543
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• 1999

We fabricated a resistive superconducting fault current limiter (SFCL) of a meander type based on a YBCO film with the meander cross section of 5 $\times$ $10^{-6}$$cm^2$, and performed current limitation experiments. The film was coated quench current was 9.6 Apeak at 60 Hz, and the fast quench time was 0.63 msec. The resistance of the limiter continuously increased for three cycles dut to the temperature rise in the gold layer. The temperature of the current limiting element reached the room temperature in 11 msec, $150^{\circ}C$ in 54 msec after quench, and was saturated afterwards. For $45^{\circ}$and $90^{\circ}$faults the fast quench times were 0.56 msec and 0.26 msec, respectively. The quench time is believed to be reduced because the fault occurred when the current was either increasing or at the peak value. This limiter effectively limited the fault current to about 1/5 of the potential current with no SFCL right after the fault and to about 1/8.5 in three cycles. We confirmed that the gold layer effectively carried out the role of heat dissipation as the SFCL was quenched.

• 한국초전도학회:학술대회논문집
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• v.11
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• pp.76-76
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• 2001

• 한국초전도학회:학술대회논문집
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• v.12
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• pp.9-9
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• 2002

• 한국초전도학회:학술대회논문집
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• v.15
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• pp.64-64
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• 2005

• 한국초전도학회:학술대회논문집
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• v.15
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• pp.73-73
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• 2005

• Korean Journal of Materials Research
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• v.4 no.5
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• pp.524-534
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• 1994

The effects of transformation temperature and mechanical properties by thermal cycle of CuZnAl shape memory alloy with a small of misch metal and Zr contents were investigated. The addition of misch metal and Zr was very effective for reducing the grain size. After solution treatment, the specimens were post-quench aged or step quenched at $100^{\circ}C$ to $350^{\circ}C$ for variation of Rockwell hardness value. It was found that the Rockwell hareness value was very increased at $200^{\circ}C$ and $250^{\circ}C$. The fracture strength and ductility have been significantly increased with the increase of misch metal conten when tensile tested below $M_f$ temperature. Also, the fracture strength has been more increased in the case of post quench aging treatment than that of the as-quenching treatment. Aging of the $\beta$-phase decreases the $M_s$ temperature, but that of the martensite phase increases the $A_s$ temperature. The change in $A_s$ temperature with post-quench aging can be attributed to recovery of order in the $\beta$phase. The hystersis of transformation temperature ($A_s-M_s$) has an increasing tendency by thermal cycles.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.958-960
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• 2002

High Temperature Superconducting (HTS) devices make it possible to operate with no electrical loss by resistance. If, however, the applied current is over its critical current, the phase of HTS devices is changed to normal state, so called, quench. In this case, since resistance of HTS is increased abruptly, it can not be avoidable to damage the whole apparatus. In this study, quench detector to protect HTS devices was proposed. We designed the quench detecting circuit and tested the performance of the circuit. The detecting circuit was consisted of Op-Amp and low pass filter etc, to detect very low voltage around $1{\mu}V$. The circuit detected effectively the low voltage when over current is applied to HTS tapes. At the next step, we are going to apply and test the circuit to protect the prototype HTS cable.

• Transactions of Materials Processing
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• v.23 no.6
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• pp.357-362
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• 2014

The purpose of the current study is to predict the hardness distribution in steel products after hot stamping using a quench factor analysis(QFA) coupled with FE-simulations. QFA is a method to predict properties such as hardness and tensile strength based on time-temperature-property(TTP) curves and can determine properties based on the temperature histories. The constants($K_1{\sim}K_5$) of QFA were determined using hardness data obtained after various cooling rates. In the current study, a rear side member was selected for evaluation and FE-simulations were performed to obtain the temperature histories during hot stamping. The predicted temperature data were imported into the QFA to calculate the hardness distribution of the hot stamped parts. A hot stamping experiment of the rear side member was conducted to verify the predicted hardness. The simulation results show good agreement with the experimental measurements.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.214-217
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• 1999

We investigated the quench characteristics of meander line type resistive superconducting fault current limiters based on YBCO thin films grown on 2" diameter LaAlO$_3$ substrates. A gold layer was deposited onto the 0.4 ${\mu}$ m thick YBCO film to disperse the heat generated at hot spots, prior to patterning into 1 mm wide meander lines by photolithography. The limiters were tested with simulated fault currents of various amplitudes. The quench started at 10 A and was completed within 1 msec at the fault current of 65 A$_{peak}$. The dynamic quench characteristics were explained based on the heat conduction within the film and the heat transfer between the film and the surrounding liquid nitrogen. The heat transfer coefficient per unit area was estimated to be 3.0 W/cm$^2$K.