• Proceedings of the KIEE Conference
• /
• 2005.07c
• /
• pp.2175-2178
• /
• 2005

During normal machine operation, partial discharge(PD) measurements were performed with turbine generator analyzer(TGA) in five high voltage motors(rated 6.6kV). These high voltage motors were installed with 80pF capacitive couplers at the terminal box. The PD patterns were displayed two dimensional and three dimensional. TGA summarizes each plot with two quantities such as the normalized quantity number(NQN) and the peak PD magnitude(Qm). Off-line PD measurements were conducted on five motors. These motors were energized to 3.81kV. The PD levels in pC were measured with a conventional digital PD detector. The comparison of positive to negative PD indicates whether the defect elements of PD are within the insulation or on the insulation surface. Internal discharges were generated in phase A, B and C of COP-B and pulv.-B, in phase B of Pulv. C and in phase C of Pulv.-D motor. Discharge at conductor surface was discovered in phase A of Pulv. D motor. Slot discharges occurred in three phases of Pulv. E motor.

• Proceedings of the KIEE Conference
• /
• 2005.07c
• /
• pp.1906-1908
• /
• 2005

In this study, in order to develop the low temperature sintering ceramics, PMW-PNN-PZT ceramics adding CuO, $B_2O_3$ were manufactured, and their piezoelectric properties is investigated. The results of this study were gotten such as follows. The electromechanical coupling coefficient(kp) showed good properites on the whole, showed its maximum value 36.88 in specimens sintered at $900[^{\circ}C]$, 10[mol%] $B_2O_3$. The mechanical quality coefficient(Qm) showed its maximum value 161.601 in specimens sintered at $1100[^{\circ}C]$, 15[mol%] $B_2O_3$.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09a
• /
• pp.163-164
• /
• 2006

A QM-ISP-4 Planetary Mill was employed to activate mechanically the mixtures of anatase and corundum at room temperature for different times. The milled powder mixtures were then sintered at $1300^{\circ}C$ for 1 h. The XRD results showed that the milled powder mixtures were completely transformed into $Al_2TiO_5$ after sintering, except the mixtures milled for 5 and 10 hours. The SEM observations showed the typical morphology of rod-like $Al_2TiO_5$ vary in the range: widths from 0.6 to $1.2\;{\mu}m$, and lengths from 3.0 to $6.0\;{\mu}m$. The rod-like $Al_2TiO_5$ formation was attributed to the positive effects caused by the mechanical activation.

• Microbiology and Biotechnology Letters
• /
• v.6 no.3
• /
• pp.129-133
• /
• 1978

A plating technique was devised to screen for high producing cellulase mutants of Trichoderma viride. The method employs: 1) The use of deoxycholate to limit colony size and 2) saponin to enhance cellulase detection in combiantion with rice straw pulp and pure cellulose on agar plate. The method will be used to isolate constitutive cellulase mutants of Trichoderma viride and should prove useful for isolating high producing mutants from a range of organisms.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.253-254
• /
• 2007

In this study, in order to develop low temperature sintering multilayer piezoelectric actuator, PMN-PNN-PZT system ceramics were fabricated using $Li_2CO_3-Bi_2O_3$-CuO as sintering aids and their piezoelectric and dielectric characteristics were investigated as a function of heating rate. At sintering temperature of $900^{\circ}C$, with increasing heating rate, electromechanical coupling factor(kp), mechanical quality factor(Qm) and dielectric constant $({\varepsilon}_r)$ were increased.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.06a
• /
• pp.274-275
• /
• 2007

In this study, in order to develop low temperature sintering ceramics for multilayer piezoelectric actuator application. At the PMN-PZN-PZT ceramics, the influence of the ball-mill time on piezoelectric characteristics was investigated. All the specimens improved according to the increase of the ball-mill time increase. The specimen showed the optimum value when ball-mill time is 60 hour. Their optimum values were density=$7.93g/m^3$, ${\varepsilon}_r=1371$, kp=0.551, Qm=1609, $d_{33}=321pC/N$, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.288-289
• /
• 2007

In this study, in order to develop low temperature sintering ceramics for multilayer piezoelectric actuator application, PMN-PZN-PZT ceramics were manufactured as a function of the amount of CuO addition and their dielectric and piezoelectric characteristics were investigated. With the amount of CuO addition, the physical characteristics of specimens decreased. The specimens showed the optimum value at 0.5wt%CuO addition. Their optimum values were density=$7.93g/m^3$, ${\varepsilon}_r$=1398, kp=0.560, Qm=1706, $d_{33}$=327pC/N, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.290-291
• /
• 2007

In this study, in order to develop low temperature sintering ceramics for multilayer piezoelectric actuator, sensers, transducers, PMN-PNN-PZT ceramics were manufacrtured with the sintering temperature, and their piezoelectric and dielectric properties were investigated. At the composition ceramics sintered at $900^{\circ}C$, desity, dielectric constant$({\varepsilon}_r)$, electromechanical coupling factor(kp), piezoelectric constant$(d_{33})$ and mechanical quality factor(Qm) showed the optimal value of $7.86g/cm^3$, 1417, 0.634, 410pC/N and 1138, respectively.

• Proceedings of the KIEE Conference
• /
• 2007.07a
• /
• pp.1337-1338
• /
• 2007

In this study, in order to develop low temperature sintering ceramics for multilayer piezoelectric actuator, 0.07Pb$(Mn_{1/3}Nb_{2/3})O_{3}-xPb(Ni_{1/3}Nb_{2/3})O_{3}-(0.93-x)Pb(Zr,Ti)O_{3}$ ceramics system were fabricated using $Li_{2}CO_{3}-Bi_{2}O_{3}$-CuO sintering aids and the specimens were sintered at $930^{\circ}C$. Thereafter their piezoelectric and dielectric characteristics were investigated with the amount of PNN substitution. At 9[mol%] PNN substitution, electromechanical coupling factor (kp), mechanical quality factor (Qm) and piezoelectric constant ($d_{33}$) showed the optimum value of 0.60, 1323 and 387pC/N, respectively.

• Electrical & Electronic Materials
• /
• v.6 no.3
• /
• pp.207-213
• /
• 1993

Pb(Z $r_{0.54}$, $Ti_{0.46}$) $O_{3}$에 B $i_{2}$ $O_{3}$를 0.0wt%까지 첨가하여 미세구조, 유전, 압전, 성질에 미치는 영향을 고찰하였다. B $i_{2}$ $O_{3}$의 고용범위는 약 0.5~0.7wt%정도 이었고 B $i_{2}$ $O_{3}$ 첨가량이 증가함에 따라서 결정립의 크기가 감소하였다. B $i_{2}$ $O_{3}$첨가량이 증가함에 따라 고용한계까지는 $d_{33}$ , tan .delta., .xi.$_{r}$(분극후)값이 증가하였으며 Qm값과 밀도는 감소하였다. $K_{p}$ 값은 B $i^{3+}$ 가 P $b^{2+}$를 치환하므로 형성되는 Pb공공의 형성에 의해 자발분극이 증가됨에 따라 증가하였다.다.