• Title, Summary, Keyword: Varistors

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Evaluation of Electrical Characteristics of Metal Oxide Varistors for Surge Arresters (초고압용 피뢰기 산화아연소자의 전기적 특성 평가)

  • Cho, Han-Goo;Yoon, Han-Soo;Kim, Suk-Soo;Han, Se-won
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.46-49
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    • 2005
  • This paper presents the electrical characteristics of metal oxide varistors for lightning surge arresters. ZnO varistors were fabricated with typical ceramic production methods and two types of varistors were also prepared to be compared. The nominal discharge current and line discharge class of those varistors are $10kA(8/20{\mu}s)$ and class 3, respectively. The diameter of varistors manufactured and prepared were in the range of 61.6~65.0mm and the thickness of those were in the range of 27~42.52mm. The reference and residual voltage were tested and reference and residual voltage per 1mm and the ratio of reference and residual voltage were calculated. The reference voltage per 1mm of varistors manufactured was about 175V/mm but that of A's and B's varistors was nearly 200V/mm. The residual voltage exhibited the same trends as the reference voltage, so the reference and residual voltage per 1mm of domestic varistors should be increased. According to the results of tests, it is thought that if the reference and residual voltage per 1mm were increased to 200V/mm and 330V/mm, domestic ZnO varistors would be possible to apply to the station class arresters in the near future.

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Fabrication and Electrical Characteristics of ZnO Nano-powder Varistors (ZnO 나노파우더 바리스터의 제작과 전기적 특성)

  • Yoo, In-Sung;Jeong, Jong-Yub;Park, Choon-Bae
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.18 no.12
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    • pp.1117-1123
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    • 2005
  • In this study, our varistors based on M. Matsuoka's composition were fabricated with ZnO nano-powder whose sizes were 50 nm and 100 nm. Before fabrication of ZnO nano-powder varistors, structure and Phase were analyzed by FE-SEM and XRD with size of ZnO nano-powders to obtain manufacturing information to fabricate the first ZnO varistors using by nano-powders. As a results of these analyses, calcination and sintering temperatures were respectively designed at $600^{\circ}C\;and\;1050^{\circ}C$. ZnO nano-powder varistors were analyzed by SEM and XRD to measure the changes of microstructures and phase after sintered by out process conditions. Also, electrical properties of ZnO nano-powder varistors were obtained by capacitance-voltage, frequency-teal impedance, and current-voltage corves. Our ZnO nano-powder varistors had about 2.5 times of electric field at varistor voltage as compared with normal ZnO varistors fabricated with micro-powder. Also, leakage current and non-liner coefficient respectively had $2.0{\times}10^{-6}A/cm^{-2}$ and 41 for ZnO nano-powder varistors with 50 nm.

Nonlinear Properties of ZnO Varistors Doped with Rare earth Oxides (희토류 산화물이 첨가된 ZnO 바리스터의 비직선 특성)

  • Park, Jong-Ah;Lee, Hong-Hee;Kim, Myung-Jun;Ryu, Jung-Sun;Nahm, Choon-Woo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.747-750
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    • 2003
  • The microstructure and nonlinear properties of ZPCMR-based varistors were investigated with various additives. The density of varistors were gradually decreased for the same R in order of NiO, MgO, and $Cr_2O_3$, respectively. The ZPCR-based varistors were not affected by NiO and MgO additives in nonlinear properties, whereas greatly affected by $Cr_2O_3$. Among the ZPCCR-based varistors, ZPCCD varistor exhibited the highest nonlinear properties, in which the nonlinear exponent is in the range of $40.5{\sim}67.4$ and the leakage current is in the range of $1.2{\sim}2.7{\mu}A$.

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Stability of $Pr_{6}O_{11}$-Based ZnO Varistors Doped with $Y_{2}O_{3}$ under d.c. Stresses ($Y_{2}O_{3}$가 첨가된 $Pr_{6}O_{11}$계 ZnO 바리스터의 d.c. 스트레스에 따른 안정성)

  • 윤한수;류정선;남춘우
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.551-554
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    • 2000
  • The stability of $Pr_6$$O_{11}$-based ZnO varistors doped with $Y_2$$O_3$ was investigated under various d.c. stresses. The varistors were sintered at $1350^{\circ}C$ for 1h in the addition range of 0.0 to 4.0 mol% $Y_2$$O_3$. The varistors doped with $Y_2$$O_3$ exhibited much higher nonlinearity than that without $Y_2$$O_3$. In Particular, the varistors containing 0.5 mol% $Y_2$$O_3$ showed very excellent V-I characteristics, which the nonlinear exponent was 51.19 and the leakage current was 1.32 $\mu\textrm{A}$. And these varistors also showed an excellent stability, which the variation rate of the varistor voltage and the nonlinear exponent were -0.80% and -2.17%, respectively, under 4th d.c. stress, such as (0.80 $V_ {1mA}$/$90^{\circ}C$/12h)+(0.85 $V_{1mA}$/$115^{\circ}C$/12h)+(0.90 $V_{1mA}$/$120^{\circ}C$/12h)+(0.95 $V_{1mA}$/$125^{\circ}C$/12h). Consequently, since $Pr_ 6$$O_{11}$-based ZnO varistors doped with 0.5 mol% $Y_2$$O_3$ have an excellent stability as well as good nonlinearity, it is expected to be usefully used to develop the superior varistors in future.

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The Structure and Electrical Characteristics of ZnO Varistors Surface using-Fractal (프랙탈을 이용한 ZnO 바리스터 표면 구조 및 전기적 특성)

  • Oh, Soo-Hong;Hong, Kyung-Jin;Lee, Jin;Lee, Joon-Ung;Kim, Tae-Sung
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.13 no.10
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    • pp.834-839
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    • 2000
  • The structural properties that SEM photograph of ZnO varistors surface studied by fractal mathematics program were investigated to verify the relations of electrical characteristics. The SEM photograph of ZnO varistors surface were changed by binary code and the grain shape of that were analyzed by fractal dimension. The void of ZnO varistors surface was found by fractal program. The relation between grain density and electrical properties depend on fractal dimension. The grain size in ZnO varistors surface was decreased by increasing of Sb$_2$O$_3$ addition. The spinel structure was formed by Sb$_2$O$_3$addition and it was depressed the ZnO grain formation. The grain size of ZnO by Sb$_2$O$_3$addition were from 5 to 10[${\mu}{\textrm}{m}$]. Among of ZnO varistors, fractal dimension of ZnO4 was very high as a 1.764. The density of grain boundary in ZnO2 and ZnO3 varistors surface was 15[%] by formed spinal structure. The breakdown electric field of ZnO2 that fractal dimension has 1.752 was very high to be 8.5[kV/cm]. When the fractal dimensin was high, the grain shape of ZnO varistors was complex and the serial layers of ZnO grain was increased.

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Impulse Degradation Behavior of ZPCCYE Varistors with Y2O3/Er2O3 Ratio

  • Nahm, Choon-Woo;Park, Jong-Hyuk
    • Transactions on Electrical and Electronic Materials
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    • v.12 no.5
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    • pp.213-217
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    • 2011
  • The nonlinear electrical properties and degradation behavior against an impulse-current of 400 A in the ZnO-$Pr_6O_{11}$-CoO-$Cr_2O_3$-$Y_2O_3$-$Er_2O_3$ (ZPCCYE) varistors were investigated with different $Y_2O_3/Er_2O_3$ ratios. The $Y_2O_3/Er_2O_3$ mole ratio has a significant effect on nonlinear electrical properties and impulse degradation behavior of the ZPCCYE varistors. The varistors added with $Y_2O_3/Er_2O_3$ = 0.5/0.5 exhibited the best nonlinear properties with 39 in nonlinear coefficient (${\alpha}$) and the best clamp characteristics, in which the clamping voltage ratio (K) was in the range of K = 1.62-2.18 at an impulse-current of 1-50 A. The varistors added with $Y_2O_3/Er_2O_3$ = 0.25/0.5 exhibited the best electrical stability, with $%{\Delta}E_{1mA/cm^2}$=-5.6%, $%{\Delta}{\alpha}$ = 6.7%, and $%{\Delta}J_L$ = -14.6% against an impulse-current of 400 A. On the contrary, the varistors added with $Y_2O_3/Er_2O_3$ = 0.5/0.5 were destroyed applying an impulse-current of 400 A.

The Study on Surface of Devices Using Fractal. (프랙탈을 이용한 소자 표면의 고찰)

  • Hong, Kyung-Jin;Kim, Chang-Won;Cho, Jae-Cheol
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.47-51
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    • 2001
  • The structural properties of varistors surface studied by fractal phenomenon were investigated to verify the relations of electrical characteristics. The SEM photograph of varistors surface were changed by binary code and the grain shape of that were analyzed by fractal dimension. The void of varistors surface was found by fractal program. The relation between grain density and electrical properties depend on fractal dimension. The grain size in varistors surface was decreased by increasing of oxide antimony addition. The grain size of devices by oxide antimony addition were from 5 to $10[{\mu}m]$. The fractal dimension and electrical properties of varistors surface was related to between grain boundary and grain density. The grain size was decreased by increasing of fractal dimensions.

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Changes of Electrical Characteristic of ZnO Varistors by a Lightning Impulse Current (뇌충격전류에 의한 산화아연형 바리스터의 전기적 특성변화)

  • 이종혁;손원진;김명진;길경석
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • pp.581-584
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    • 2000
  • This paper describes the effect of lightning impulse current on ZnO varistors(390 V, 6.5 kA) used in low-voltage AC mains as a protective device against transient overvoltages. A lightning impulse current standardized in IEC 61000-4-5 is applied to the varistors, and the energy applied to the varistor at each time is about 12 J. In the experiment, various Parameters such as leakage current, reference voltage are measured with the number of applied impulse current. Also, micro-structure changes of the varistors after applying the lightning impulse current of 200 times are compared. The electrical characteristics of the varistors are degraded by overtime impulse current, showing increase in leakage current and decrease in reference voltage.

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