• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.134-136
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• 1995

A superconducting parallel bifilar winding shows the phenomenon which is known as 'fast quench'. We analyzed the temperature characteristics on the winding by computer simulation, and confirmed theses by experiment. The temperature of the quenched point rose gradually as the source voltage was increased. The temperature changed radically as first, but had a gentle slope after a few milliseconds. As the source voltage was large, the initial quenched length also increased. The points in this quenched length showed almost the same temperature. but the points where initial quench had not occurred showed radical temperature gradient. We could observe that the temperature of the whole wire increased simultaneously as the fast quench occurred on the superconducting parallel bifilar winding, because a number of quenched points in that wire appeared at the same time.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.125-127
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• 1995

A superconducting parallel bifilar winding with one strand in each branch was tested and analyzed. When the superconducting parallel bifilar winding was quenched by fault current, it showed the so-called 'fast quench' and the results of experiment well explained the resistance curve. Also the experiments confirm that the current redistribution of magnetically coupled strands develops new normal zones after the initial quench, and that the size of normal zones at an early stage increases almost linearly as dI/dt increases. By these results, we could explain the resistance rise of superconducting parallel bifilar winding when it is quenched by the current above the critical value.

• Journal of Sensor Science and Technology
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• v.7 no.3
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• pp.154-162
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• 1998

A planar Bi-Sb multijunction thermal converter with high thermal sensitivity and small ac-dc transfer error has been fabricated by preparing the bifilar thin film Pt-heater and the hot junctions of thin film Bi-Sb thermopile on the $Si_{3}N_{4}/SiO_{2}/Si_{3}N_{4}$-diaphragm, which functions as a thermal isolation layer, and the cold junctions on the dielectric membrane supported with the Si-substrate, which acts as a heat sink, and its ac-dc transfer characteristics were investigated with the fast reversed dc method. The respective thermal sensitivities of the converter with single bifilar heater were about 10.1 mV/mW and 14.8 mV/mW in the air and vacuum, and those of the converter with dual bifilar heater were about 5.1 mV/mW and 7.6 mV/mW, and about 5.3 mV/mW and 7.8 mV/mW in the air and vacuum for the inputs of inside and outside heaters, indicating that the thermal sensitivities in the vacuum, where there is rarely thermal loss caused by gas, are higher than those in the air. The ac-dc voltage and current transfer difference ranges of the converter with single bifilar heater were about ${\pm}1.80\;ppm$ and ${\pm}0.58\;ppm$, and those of the converter with dual bifilar heater were about ${\pm}0.63\;ppm$ and ${\pm}0.25\;ppm$, and about ${\pm}0.53\;ppm$ and ${\pm}0.27\;ppm$, respectively, for the inputs of inside and outside heaters, in the frequency range below 10 kHz and in the air.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.6
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• pp.627-634
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• 2010

In this paper, a novel voltage-controlled oscillator(VCO) using the complimentary bifilar archimedean spiral resonator(CBASR) is presented for reducing the phase noise characteristic. A CBASR has compact dimension, a sharp skirt characteristic in stopband, a low insertion loss in passband, and a large coupling coefficient value, which makes a high Q value and improve the phase noise of VCO. The proposed VCO has the oscillation frequency of 2.396~2.502 GHz in the tuning voltage of 0~5 V, the output power of 7.5 dBm and phase noise of -119.16~-120.2 dBc/㎐ at the offset frequency of 100 kHz in tuning range.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.1
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• pp.26-34
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• 1998

In this paper, we confirm that the instanteneous phase current of the bifilar-wound hybrid stepping motor is dependent of lead angle by the experimental results. The variation of phase current with lead angle gives informations about the rotor position at the moment when phase winding coil is excited. We show that the rotor position of the bifilar-wound hybrid stepping motor for the closed-loop drives can be detected by using the instantaneous phase current measurement. We propose an instantaneous phase current equation as the function of electrical lead angle by the modeling of the bifilar-wound hybrid stepping motor. We also analyze the relationship between instantaneous phase current and rotor position by the computer simulation results. By the experimental results, we also confirm that the information about the rotor position can be obtained from the instantaneous phase current values at the instance of $\pi/2$ electrical angle of excitation pulse. pulse.

• Progress in Superconductivity and Cryogenics
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• v.9 no.1
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• pp.22-26
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• 2007

Superconductor is weak in AC condition. Bifilar geometry provides a solution to reduce AC loss. Bifialr geometry is piled up or wound with more than two layers. When a layer of superconductor abuts on other layers, AC loss is affected by not only self-field, but also magnetic field induced by adjacent layers. In this study, two superconductors are piled up as a series connection so that current flows in different directions. By this method, magnetic field is cancelled. If magnetic field is cancelled, AC loss is reduced. To compare AC loss with respect to piling method, we measured the AC loss difference between the case facing each other with substrate side and the case facing with YBCO side. Measured AC loss is compared with one-way current flow single layer AC loss. In addition, we analyzed how much AC loss was increased, or reduced. All results were compared with those calculated with Norris equation. By this experiment, we concluded that distance between two wires is the important cause of AC loss. The distance between two wires affects magnetic field reduction in YBCO and induced current flow on substrate side.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.267-268
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• 2009

Resistance standards from 1 ${\Omega}$ to 100 $k{\Omega}$, with calculable frequency dependencies of up to 1 MHz, have been developed for the calibration of commercial inductance-capacitance-resistance (LCR) meters and impedance analyzers. The resistors are designed on the basis of single bifilar loops. The typical resistance change from dc to 1 MHz is from 200 to $800\;{\mu}{\Omega}/{\Omega}$. According to the measurement results, the frequency dependencies of the resistors are severaltimes lower than the measurement uncertainty of commercial LCR meters.

• Journal of the Korean Institute of Telematics and Electronics
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• v.17 no.6
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• pp.78-85
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• 1980

A symmetrical 3-dB quadrature hybrid circuits, consisting mainly of bifilar pair of taitoted wires, is described. A cascade of two such hybrid circuits can achieve an octave bandwidth hybrid circuit with a small coupling loss. Since the proposed type is simple, compact, and low In cost 1 its applicarion may be preferred to the more common coaxial line or printed -circuit type hybrid version in the frequency region below 1 GHz. This study provides a design method for a hybrid circuit mixing two different antenna signals for the anti - ghosting of television signal.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.187-191
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• 1997

In this paper, we show that the rotor position of the bifilar-wound hybrid stepping motors for the closed-loop drives is detected by the phase current measurement. We propose an instantaneous phase current equation, which is the function of electrical angle, by the modeling of the stepping motor including motor driving circuits. We also analyze the relationship between phase current and rotor position from the computer simulation results. It is shown that the information about the rotor position is obtained from the phase current amplitude and its derivatives at the instance of ${\pi}/2$ electrical angle of excitation voltage.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.7
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• pp.1050-1060
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• 1994

This paper is a study on the computer simulation of the characteristics of the superconducting fault current limiter. Input variable parameters are apparent power, load resistance value, line resistance value and so on. Initial fault current 2 times larger than the trigger current is required to reduce the switching time of SFCL. The propagation velocity increases abruptly, the transport current is several times larger than the ciritical current. In this paper, the switching time is calculated to be 323$\mu$ sec, and the initial fault current is 19 times larger than the critical current. Because the trigger coils are bifilar winding, they have little impedance in superconducting state. After fault occurred, the limiting coil acts as a superconducting reactor and the trigger coils quench at a critical current. Without the SFCL in the circuit, fault current after the load impedence is shorted might be increased to 1100A. The fault current is, therefore, successfully limited by the superconducting limiting coil to 100A determined by the coil inductance.