소결 조건 변화에 따른 직류 피뢰기용 ZnO 바리스터의 미세구조 및 전기적 성질에 관한 연구 = A Study on the Microstructure and Electrical Characteristics of ZnO Varistor for d.c. Arrester

다국어 초록 (Multilingual Abstract)

The microstructure and electrical characteristics of A ∼ C's ZnO varistors fabricated according to variable sintering condition, which sintering temperature was 1130 $^{\circ}C$ and speeds of pusher were A: 2 mm/min, B: 4 mm/min, C: 6 mm/min, respectively, were investigated. The experimental results obtained from this study were summarized as follows: The sintering density of A ∼C's ZnO varistors sintered at 1130 $^{\circ}C$ were decreased by sintering keep time to shorten, such as A: 9hour, B: 4.5hour and C: 3hour. A's ZnO varistor exhibited good densification nearly 98 % of theory density. In the microstructure, A∼C's ZnO varistors fabricated variable sintering condition was consisted of ZnO grain(ZnO), spinel phase(Z $n_{2.33}$S $b_{0.67}$ $O_4$), Bi-rich phasc(B $i_2$ $O_3$), wholly. Varistor voltage of A∼C's ZnO varistors sintered at 1130 $^{\circ}C$ increased in order A <B <C's ZnO varistors. C's ZnO varistor exhibited good characteristics that nonlinear exponent was 31.70. Leakage current of A ∼ C's ZnO varistors exhibited below 2 ㎃ at rated voltage. Lightning impulse residual voltage of A's ZnO varistor suited standard characteristics, which was 3.85kV at 2.5kA, 4.4 kV at 5kA and 5.16 kV at 10 kA. After continuous lightning impulse current test of A's ZnO varistor exhibited good discharge characteristics which ZnO varistor reveals no evidence of puncture, flashover, cracking in visual examination. After high current impulse test of A's ZnO varistor exhibited good discharge characteristics, which variation rate of residual voltage was 0.4 % before and after test, and revealed no evidence. evidence.

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