• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.14-17
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• 2008

A poppet type shutoff valve under the pneumatic control has been adapted for the MOV (Main Oxidizer shutoff Valve) for KSLV (Korea Space Launch Vehicle). The MOV controls the supply of liquid oxygen into the combustion chamber just by opening and shutting operations. The poppet part of the poppet valves is usually connected with the piston, but on the other hand that of the MOV is separated and just contacted with the piston in order to secure the flexibility of the valve design. For the prevention of the collision with valve body by an undesirable movement of the piston part, it is necessary to evaluate the force during the valve closing. The analysis of the force balance of the MOV at the moment of the valve closing have been performed and some important design parameters for the force balance control have been introduced.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.8
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• pp.812-818
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• 2009

A MOV(Main Oxidizer shutoff Valve) controls the flow rate of liquid oxygen into the rocket combustor by opening and shutting operations piloted by a pneumatic force. In order to improve the effective design for sealing parts of poppet and piston assemblies, the poppet assembly has been designed to be just contacted with the piston assembly. However, to avoid a gap at the poppet/piston contact surface and to evaluate the MOV operating performance, an analyze on the force balance during the closing motion have been performed. For the accuracy of the analysis, the friction forces and the hydraulic forces have been respectively obtained by experiments and CFD analysis. Through the analysis, some important design parameters such as the spring constant, poppet friction and orifice size in the force balance have been introduced and the required operation performance of the MOV has been proved feasible.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.903-908
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• 2001

A web-based client/server program, MOVIDIK(Motor-Operated-Valve Integrated Database Information of KEPCO) has been developed to perform a design basis safety evaluation for a motor-operated-valve(MOV) in the nuclear power plant. The MOVIDIK consists of seven analysis modules and one administrative module. The analysis module calculates a differential pressure on the valve disk, thrust/torque acting at a valve stem, maximum allowable stress, thermal-overload-relay selection, voltage degradation, actuator output and margin. In addition, the administrative module manages user information, approval system and code information. MOVIDIK controls a huge amount of evaluation data and piles up the safety information of safety-related MOV. The MOVIDIK will improve the efficiency of safety evaluation work and standardize the analysis process for the MOV.

• Proceedings of the KIEE Conference
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• 2002.11c
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• pp.337-341
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• 2002

본 논문은 원자력 발전소의 안전에 있어 매우 큰 비중을 차지하는 모터 구동밸브(Motor-operated valve : MOV)의 성능진단에 직접 센서를 장착하지 않고 전기신호만을 이용하여 성능진단의 가능성을 보이기 위한 것이다. 모터 토크를 계산하기 위한 두 가지 방법으로서 D-Q frame 변환 방법과 Air-Gap 토크 식을 제시하였고, 계산된 두 토크 값은 정확하게 일치하였다. 부하를 변동하면서 토크미터로 측정된 토크 갑과는 1%의 오차범위 내에서 일치함을 확인했다. 따라서 두 토크 식은 모터구동 밸브의 성능진단을 위한 식으로 사용해도 좋다는 결론을 얻어낼 수 있었다. 계산된 토크를 주파수 분석함으로서 부하의 변동에 따라서 슬립 및 모터속도 주파수가 변화됨을 알 수 있었다. 즉 주파수 분석을 통해 MOV의 모터 및 구동기 부분의 성능 저하 감시에 유용한 단서를 제공해 줄 것이다. 결과적으로, MOV에서 전기신호의 분석은 시스템의 전기 및 기계적인 성능 저하 감시에 이용될 수 있을 것으로 기대된다.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.11 no.2
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• pp.6-12
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• 2015

In this study, the performance test was carried out under various operation conditions targeting four representing types of lubricant which are mostly used in nuclear power plants, and mutually compared the characteristic and performance of lubricant. Especially, introducing the concept of the thread friction coefficient (hereinafter, TFC), which makes the friction relation between the stem nut and stem screw dimensionless. The test was performed to compare the lubricant performance for the four kinds of lubricant (Texaco, Alvania, Mobilux, MOVLL). In a test of the room temperature stem, the TFC of MOV Long Life shows the lowest value, next to Alvania EP2, Texaco EP2, and Mobilux EP0 in that order. And in a test of the high temperature stem, the TFC of Texaco EP2 shows the lowest, next to MOV Long Life, Alvania EP2, and Mobilux EP0 in that order. From the test result of the aging condition, three types of lubricant (MOV LL, Texaco EP2, Alvania EP2) show similar patterns up to 36 months, but in 60 months, the TFC of lubricant are increased rapidly.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1361-1363
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• 1997

Zinc oxide-based MOV was fabricated with $SiO_2$ additive ranging from 0.5 to 4.0 mol%, and the microstructure and electrical characteristics were investigated. $Zn_2SiO_4$ phase formed by $SiO_2$ additive was distributed at ZnO grains, grain boundaries, and multiple grain junctions. As the content of $SiO_2$ additive increases, average grain size decreased from 40.6 to $26.9{\mu}m$ due to the Pinning effect by $Zn_2SiO_4$ at grain boundaries Breakdown voltage and nonlinear exponent increased, and leakage current decreased in the range of $11.2{\sim}6.14{\mu}A$ with an increasing $SiO_2$. Donor concentration and interface state density decreased, and barrier height increased in the range of $0.71{\sim}1.04eV$ with an increasing $SiO_2$. While, as the content of $SiO_2$ additive, apparent dielectric constant decreased, peak frequency of dissipation factor decreased in the range of $6.45{\times}10^5{\sim}3.00{\times}10^5Hz$, and dissipation peak was $0.31{\sim}0.22$ at Peak frequency.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.626-637
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• 2004

• 기계와재료
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• v.16 no.1 s.59
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• pp.67-81
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• 2004

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.52-55
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• 2001

This paper is to see the availability of electrical signatures as a means for evaluating the performance and monitoring mechanical anomalies of (MOVs). To estimate motor torque, two methods such as d-q frame conversion and air-gap method are suggested and estimated results are compared with measured values. The error between measured and estimated torques is within acceptable error bound with below $1\%$ under varied load. Frequency domain analysis of calculated torque has been done as well. It is shown that monitoring of peak frequency could give useful clues to detect anomalies of MOV. As results, electrical signatures at MOV motor is expected to be an available tool for estimation of motor capacity and monitoring of electrical and mechanical abnormalities.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.3
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• pp.328-333
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• 2009

In this paper, we have developed high performance SPD(surge protective device) and evaluated the characteristics in comparison with typical SPD used in the inside and outside of the country. The new SPD was composed of MOV(metal oxide varistor), GDT(gas discharge tube) and impedance such as resistors, capacitors or varistors. To estimate operating the characteristic of the SPD which was developed, it was measured surge voltage caused by fault current or surge according to IEC 61000-4-5. As a result it was found that the power supply was cut off by high performance SPD when caused a short-circuit. In addition we could know that it could prevent ELB(earth leakage breaker)'s malfunction caused by surge.