• Progress in Superconductivity and Cryogenics
• /
• v.12 no.3
• /
• pp.16-20
• /
• 2010

For large scale power applications of HTS conductor, it is getting more important to have a stacked HTS coated conductor with low loss and large current capacity. But it was not easy to measure some electric properties. Stabilizer free YBCO CC for striated/ stacked conductors is easily burned out during the measurement of the critical current density because it has no stabilizer and it is difficult to set-up the current lead and voltage taps because it has many pieces of YBCO CC in a conductor. Instead of direct measuring the critical current of a stacked HTS coated conductor, indirect estimation from measuring a magnetization loss of HTS coated conductor could be useful for practical estimation of the critical current. The magnetization loss of a superconductor is supposed to be affected by a full penetrating magnetic field, and it tends to show an inflection point at the full penetrating magnetic field when we generate the graph of magnetization loss vs. external magnetic field. The full penetrating magnetic field depends on the shape of the conductor and its critical current density, so we can estimate the effective critical current density from measuring the magnetization loss. In this paper, to prove the effectiveness of this indirect estimation of the critical current, we prepared several different kinds of YBCO CC(coated conductor) including a stacked conductor short samples and measured the magnetization losses and the critical currents of each sample by using linked pick up coils and direct voltage measurement with transport current respectively.

• Journal of Electrical Engineering and Technology
• /
• v.13 no.3
• /
• pp.1326-1336
• /
• 2018

This paper proposes a numerical approach to predict the critical flashover voltages of air gaps under lightning impulses. For an air gap, the impulse voltage waveform features and electric field features are defined to characterize its energy storage status before the initiation of breakdown. These features are taken as the input parameters of the predictive model established by support vector machine (SVM). Given an applied voltage range, the golden section search method is used to compute the prediction results efficiently. This method was applied to predict the critical flashover voltages of rod-rod, rod-plane and sphere-plane gaps over a wide range of gap lengths and impulse voltage waveshapes. The predicted results coincide well with the experimental data, with the same trends and acceptable errors. The mean absolute percentage errors of 6 groups of test samples are within 4.6%, which demonstrates the validity and accuracy of the predictive model. This method provides an effectual way to obtain the critical flashover voltage and might be helpful to estimate the safe clearances of air gaps for insulation design.

• Korean Journal of Materials Research
• /
• v.25 no.3
• /
• pp.119-124
• /
• 2015

This paper investigates the change of the percolation threshold in the carbon powder-filled polystyrene matrix composites based on the experimental results of changes in the resistivity and relative permittivity of the carbon powder filling, the electric field dependence of the current, and the critical exponent of conductivity. In this research, the percolation behavior, the critical exponent of resistivity, and electrical conduction mechanism of the carbon powder-filled polystyrene matrix composites are discussed based on a study of the overall change in the resistivity. It was found that the formation of infinite clusters is interrupted by a tunneling gap in the volume fraction of the carbon powder filling, where the change in the resistivity is extremely large. In addition, it was found that the critical exponent of conductivity for the universal law of conductivity is satisfied if the percolation threshold is estimated at the volume fraction of carbon powder where non-ohmic current behavior becomes ohmic. It was considered that the mechanism for changing the gaps between the carbon powder aggregates into ohmic contacts is identical to that of the connecting conducting phases above the percolation threshold in a random resister network system. The electric field dependence is discussed with a tunneling mechanism. It is concluded that the percolation threshold should be defined at this volume fraction (the second transition of resistivity for the carbon powder-filled polystyrene matrix composites) of carbon powder.

• Proceedings of the KIPE Conference
• /
• 1998.10a
• /
• pp.847-850
• /
• 1998

This paper proposes a new scheme of FLR for improving corner breakdown voltage. The major difference from the conventional FLR is to build extra rings and floating field plates in the corner region. In this structure the additional field plate and ring have reduced th electric field at the junction in the corner region. Thus it improves the breakdown characteristics which are critical for obtaining high breakdown voltage.

• Journal of Environmental Health Sciences
• /
• v.26 no.3
• /
• pp.55-60
• /
• 2000

Wire codes, introduced by Wertheimer and Leeper, are interesting largely because several case-control studies have reported associations between them and certain types of cancers, including childhood leukemia. This paper is concerned with the reliability of wire codes as a surrogate for residential electric and magnetic field, divided into four categories based on the electrical wiring within 40m of homes. To examine the correlation between spot measurements and wire codes, EMF was measured by using HI-3604 and classified by wire codes. The correlation between long-transformed RMS of magnetic field and wire codes was 0.81. But the correlation between log-transformed RMS of electric field and wire codes was 0.27. The results led us to determine a four category from of the Wertheimer and Leeper code that 1) may be useful in domestic epidemiological studies and 2) is not suitable for electric field exposure. Thus, the critical point of exposure assessment in residential magnetic field is to classify a wire code precisely.

• Journal of the Korean Ceramic Society
• /
• v.34 no.6
• /
• pp.620-628
• /
• 1997

The possibility of the existence of a field-induced micro-macrodomain switching was proposed and examined using 9 mol % PbZrO3-doped 0.6Pb(Ni1/3Nb2/3)O3-PbTiO3 (PNN-PT) systems having rhombohedral symmetry at room temperature. the thermally depoled (freshly prepard) specimens prepared from the rhombohedral side of the system exhibited a relaxor behavior for the whole range of temperature examined (for T

• Structural Engineering and Mechanics
• /
• v.60 no.2
• /
• pp.271-299
• /
• 2016

In this article, based on the higher-order shear deformation plate theory, buckling analysis of a rectangular plate made of functionally graded piezoelectric materials and its effective parameters are investigated. Assuming the transverse distribution of electric potential to be a combination of a parabolic and a linear function of thickness coordinate, the equilibrium equations for the buckling analysis of an FGP rectangular plate are established. In addition to the Maxwell equation, all boundary conditions including the conditions on the top and bottom surfaces of the plate for closed and open circuited are satisfied. Considering double sine solution (Navier solution) for displacement field and electric potential, an analytical solution is obtained for full simply supported boundary conditions. The accurate buckling load of FGP plate is presented for both open and closed circuit conditions. It is found that the critical buckling load for open circuit is more than that of closed circuit in all loading conditions. Furthermore, it is observed that the influence of dielectric constants on the critical buckling load is more than those of others.

• Proceedings of the KIEE Conference
• /
• 2003.07a
• /
• pp.555-557
• /
• 2003

As electric power transmission systems grow to supply the increasing electric power demand, transmission capacity is larger. but that's really difficult to secure the location for power transmission and distribution to user. The high temperature superconducting(HTS) cable is a method to solve this problem. But for applying to real systems, it needs to investigate the effect of HTS cable. The most important things is the investigation of fault condition. the fault on HTS cable include the quench state. When a fault occur in a circuit, three critical parameters(temperature, current density, magnetic field) exist. when one of these parameters exceeds the critical value, the superconducting becomes normal-conducting. f the cooling power is insufficient to recover the superconducting state, the normal-conducting zone expands. In order to solve these problem, this paper present simulate the quench state considering the over-current and over-voltage in the informal circuit and analyze the quench state.

• Proceedings of the KIPE Conference
• /
• 2010.11a
• /
• pp.215-217
• /
• 2010

This paper describes the test results of radiated compatibility with Ariane 5 launcher performed on the COMS Satellite test facility. Firstly, the Radiated Emission test results are analyzed in compliance with the Radiated Susceptibility requirement specification of Ariane 5 launcher. The satellite nominal operation is monitored during injection a radiated electric field corresponding to the launcher emissions levels in critical frequency ranges. And also, E-field are measured through a probe located at external units level in order to assess the EMC safety margin in Radiated mode.

• Korean Journal of Food Science and Technology
• /
• v.31 no.2
• /
• pp.410-415
• /
• 1999

Yakju was sterilized with high-voltage pulses of short time of a continuous pulsed electric field (PEF) system. The initial microbial counts of Yakju were $2.2{\times}10^{5}$ CFU/mL for total aerobes. The pH, acidity and electric conductivity of Yakju were 3.82, 0.37% and 1.24 mS/cm, respectively. Yakju was treated with exponential-wave formed electric pulses of 100 Hz for $0{\sim}4000{\mu}s$ under the field strength of $20{\sim}35\;kV/cm$. The lethal effect of electric fields on microorganisms was resulted from the breakdown of the cell membrane induced by the transmembrane electric potential. The critical values of the external field for the sterilization were 16.0 kV/cm for total aerobes. Logarithmic survival rates decreased linearly at low electric field strength, but curvilinearly at high electric field strength with treatment time. The sterilization of Yakju was more largely affected by the electric field strength than by the treatment time. Any changes in pH, acidity, and the growth of microorganisms were not found in the PEF treated Yakju during the storage at both $4^{\circ}C\;and\;30^{\circ}C$.