• Progress in Superconductivity and Cryogenics
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• v.9 no.3
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• pp.21-25
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• 2007

Superconducting fault current limiter (SFCL) is attractive apparatus to reduce fault current in power grid. Since it is applied to the alternating current (AC) power line, the SFCL has losses in the normal operation. Recently, coated conductor (CC) is noticeable material employed for resistive bifilar winding type SFCL in many research groups. Bifilar structure is expected to have low AC loss by magnetic field offset as compared with the single tape structure in the same length. This paper reports about characteristic of bifilar pancake type coil for SFCL application in AC loss aspect. The bifilar coil is wound using CC with facing on HTS sides each other. Transport AC loss measurement and characteristic analysis of the bifilar coil using CC have been performed at 77K. The test results are compared with the Norris equations and the test results of non-inductively wound paralleled solenoid type coil which is suggested and tested in this group at present.

• Progress in Superconductivity and Cryogenics
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• v.7 no.4
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• pp.28-31
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• 2005

To verify the feasibility of bifilar winding type superconducting fault current limiter (SFCL) using BSCCO tape, two types of magnets were fabricated and tested by short-circuit in this research. Even if the FCL using high Tc superconducting (HTS) tape has zero resistance in normal state, it needs to be wound as a bifilar winding for zero inductance. Solenoid type and pancake type bifilar winding magnets are designed and fabricated with the same length of BSCCO tape. The test system consists of AC power supply, transformer, fault switch, load and bifilar winding magnet. The applied AC voltages during fault duration, 0.1s, were from 0.5V to 20V. The test results without bifilar winding magnet were compared with those with each type magnets. The test results include voltage against magnet, transport current and generated resistance curve. Thermal stability, the recovery time, was studied from the results of two type magnets. The pancake type was the most effective to limit fault current but the solenoid type was thermally the most stable. From this research, short-circuit characteristics of the two types were obtained.

• The Korean Journal of Food & Health Convergence
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• v.5 no.4
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• pp.19-23
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• 2019

In recent years, the Internet was a lot of information on the use of Tesla coils bifilar [1] in conjunction with induction cooker, for "free" electricity during power resistive load, including different incandescent lamps. With the development of scientific and technological progress, the demand for electricity in each year is increasing, and at the same time, the need to increase the capacity of electricity production, which entails large investments and, consequently, increase of prices for consumers. As before today, the search for free electric energy is an up-to-date and still open topic. The purpose of research - simplification of information on the possibility of using bifilar coils as an electric current source in conjunction with induction cooker. Consequently, it can be concluded from the above that the use of Tesla coils in combination with induction cooker has very low k.k.d. and it is not possible to obtain excessive electric energy using the Tesla coil under the connection schemes considered.

• Progress in Superconductivity and Cryogenics
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• v.7 no.2
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• pp.31-34
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• 2005

There are many kinds of high temperature superconducting (HTS) application using Bi-2223 tape which is the most commercialized HTS material. Also, resistive superconducting fault current limiters (SFCLs) have been developed using many kinds of superconducting material such as YBCO thin film, Bi-2212 bulk and so on. However, SFCL using Bi-2223 tape has never been developed. This paper deals with the feasibility study on SFCL using Bi-2223 wire. The over-current behaviors of Bi-2223 short-length sample were measured. To make the resistive SFCL, two small-scale bifilar winding modules using 7m Bi-2223 wire were fabricated; i.e. solenoid type bifilar coil and pancake type one. The short-circuit tests of the coils were successfully performed up to 16 V$_{rms}$ From these tests, the current limiting capabilities of Bi-2223 bifilar coils were confirmed and current limiting performances between two winding types were compared. In addition, the feasibility of resistive SFCL using another HTS wire, i.e. YBCO coated conductor, was also investigated.

• Korean Journal of Optics and Photonics
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• v.3 no.1
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• pp.43-49
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• 1992

A microwave free electron laser which consists of Marx generator, vacuum diode, bifilar helical wiggler, and guide solenoid was designed and constructed. The analysis of the magnetic field distributions of the bifilar helical wiggler and computer simulation of electron trajectories with the perpendicular effect of space charges led to the conclusion that the magnetic field distributions are suitable for the electron beam injection. Output frequency in a single $TE_{11}$

• Progress in Superconductivity and Cryogenics
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• v.10 no.2
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• pp.30-33
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• 2008

Several kinds of superconducting fault current limiters (SFCLs), which reduces huge fault current, have been developing by many research groups. The SFCL has no impedance during normal operation, so it dose not give any influence to electric power system. The resistive type SFCL reduces the fault current with the impedance generated in the superconducting part of the SFCL when the fault current exceeds the critical current of SFCL. In this paper, a new type resistive SFCL made of bifilar coil wound with two different high-Tc superconducting (HTS) wires in parallel. Although a bifilar coil has theoretically no inductance, the bifilar coil made in this paper could generate inductance at fault. The specifications of the used two wires were considerably different, thus current distribution between the two HTS wire was different at fault. When the fault current exceeded the critical current of one wire in the bifilar coil, the momentary sharp increase of impedance was detected. Base on the results, a new resistive type SFCL can generate not only resistance but also inductance, which can be used to control a fault current in the future.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.4
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• pp.370-374
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• 2005

AC loss of a superconducting conductor has a strong influence on the economic viability of a superconducting fault current limiter, which offers an attractive means to limit short circuit current in power systems. Therefore, the AC loss characteristics in several fault current limiting elements of a coil type have been investigated experimentally. The test result shows that AC losses measured in the fault current limiting elements depend on arrangement of a voltage lead. The AC loss of a bifilar coil is smallest among the fault current limiting elements of the coil type. The measured AC loss of the bifilar coil is much smaller than that calculated from Norris's elliptical model. However, the loss measured in a meander, which is frequently used in a resistive fault current limiter, agrees well to the theoretical one.

• Progress in Superconductivity and Cryogenics
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• v.7 no.4
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• pp.20-23
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• 2005

The Resistive Type High Temperature Superconducting Fault Current Limiter (SFCL) has been developed in many countries. Until now, materials of the resistive SFCL were Bi2212 bulk and YBCO thin film. Although YBCO coated conductor (CC) has many advantages such as high n-value and critical current for applying resistive SFCL, the resistive SFCL using CC doesn't have developed yet. The bifilar winding type SFCL was manufactured and tested rated on 30V/80A. In normal state, the SFCL using pancake type bifilar winding had very low impedance. When a fault occurred, the SFCL limited the fault current efficiently. Through these results of experiment, large-scale SFCL using CC should be developed in the future.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.6
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• pp.619-625
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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 modeling the stepping motor including motor driving circuits. We also analyze the relationship between phase current and rotor position from the computer simulation results. We show 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.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.880-882
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• 1993

In this paper, a drive circuit for a bifilar-wound hybrid step motor considering mutual inductance and back-emf is investigated. For the suppression circuit, the varition of average torque and torque ripple due to the effect of mutual inductance and back-emf is presented. In order to improve the performance of the motor, a new control scheme is also proposed.