• Journal of the Korean Society of Safety
• /
• v.29 no.1
• /
• pp.7-14
• /
• 2014

Inverter module, which feeds the converted power to the traction motor for EMU. Consists of the power semiconductors with their gate drive unit(GDU)s and the control computer for driving, voltage, current and speed controls. Electrolytic condenser, connected to the gate drive unit and a core component to drive the power semiconductor, has problems such as reduction in lifetime and malfunction caused by electrical and mechanical characteristic changes from heat generation during high speed switching for generation of stable power. In this study, To check the service life of electrolytic condenser, the test was carried out in two ways. First, In the case of accelerated life testing of condenser, the Arrhenius model is a way of life testing. Another way is to analyze the reliability of the failure data by the method of parametric data analysis. Eventually, life time by accelerated life test than a method of failure data analysis(Weibull distribution) was found to be slightly larger output.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.19 no.4
• /
• pp.327-331
• /
• 2014

LED(Light Emitting Diode) is a semiconductor device utilizing electroluminescent effect is a phenomenon in which a type of P-N junction diode, the light of short wavelength which a voltage is applied in the forward direction is released. LED is advantageous in reducing the energy as environmentally materials that can greatly reduce the carbon emissions, recent it has attracted attention IT(Information Technology) and GT(Green Technology) industry. In addition, there are advantages long life, high efficiency, and excellent response speed, LED have come into the spotlight as the illumination means to replace the existing fluorescent light and incandescent light bulb. When connecting to MR16 electronic transformer for existing LED driver circuit, due to malfunction of the dimmer and the electronic transformer, flicker occurs and linear dimming is not possible. Therefore, in this paper, we suggest an LED drive circuit there is no flicker with the corresponding dimming MR16 electronic transformer. Further, we explain the principles of the LED current control technique and the principle of the drive circuit of the LED, in order to validate the proposed circuit through prototyping and simulation.

• Nuclear Engineering and Technology
• /
• v.45 no.3
• /
• pp.347-360
• /
• 2013

This paper presents an experimental investigation of the small-break loss-of-coolant accident (SBLOCA) and the loss-of-feedwater accident (LOFW) in a scaled integral test facility of REX-10. REX-10 is a small integral-type PWR in which the coolant flow is driven by natural circulation, and the RCS is pressurized by the steam-gas pressurizer. The postulated accidents of REX-10 include the system depressurization initiated by the break of a nitrogen injection line connected to the steam-gas pressurizer and the complete loss of normal feedwater flow by the malfunction of control systems. The integral effect tests on SBLOCA and LOFW are conducted at the REX-10 Test Facility (RTF), a full-height full-pressure facility with reduced power by 1/50. The SBLOCA experiment is initiated by opening a flow passage out of the pressurizer vessel, and the LOFW experiment begins with the termination of the feedwater supply into the helical-coil steam generator. The experimental results reveal that the RTF can assure sufficient cooldown capability with the simulated PRHRS flow during these DBAs. In particular, the RTF exhibits faster pressurization during the LOFW test when employing the steam-gas pressurizer than the steam pressurizer. This experimental study can provide unique data to validate the thermal-hydraulic analysis code for REX-10.

• Journal of the Korean Society for Precision Engineering
• /
• v.30 no.10
• /
• pp.1041-1049
• /
• 2013

One of the causes of malfunction of commercial vehicle is corrosion or wear. In order to prevent corrosion and wear, lubricants have to be supplied periodically. However, the period of lubrication usually depends on operator's judgment. If the period is too short, excess lubricant will cause pollution and unnecessary expenses, where as long periodic supply of lubricant might cause wear, damage and eventual breakdown. Therefore, an automatic lubrication system with predetermined interval will reduce the excessive supply of lubricating oil and prevent wear and damage. This thesis presents an automatic lubrication system which consists of a lubricant pump and an embedded controller. An automatic lubrication operating algorithm is used to operate the lubricant pump and feedback the pressure status of the system using pressure sensors. The developed system shows an efficient periodic supply of lubricant.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2009.05a
• /
• pp.139-142
• /
• 2009

Rapid developments in the field of electronic communication have given people's daily life much more convenience and abundance. However, making precise electrical and electronic devices and control systems lighter, smaller, and faster have caused lots of problems such as interference of external electric source, malfunction brought by electric fast transient(EFT), and influence on human body. In this research, the EMC filter in the high powered breaker was designed and fabricated as a countermeasure. The filter attenuated noise more than 30 ~ 75 dB in the range of 10 MHz ~ 1.5 GHz. And, when the EFT of 4 kV in the level 4 of IEC 61000-4-4 was induced, it was soon suppressed to 600 V.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2009.05a
• /
• pp.849-853
• /
• 2009

A generator is in use for a moving vehicle like car, aircraft, ship as well as key industry including a thermal power plant, a water power plant, a nuclear power plant, and so on. Such the AC generator plays an important role in vehicle, ship, aircraft, and so forth, at the point of generating electric power. Especially in the matter of the ship, the emergency generator system is mounted to provide against malfunction of main generator on a voyage. So, it is ordered that the system can monitor the main generator and operate the emergency generator when the emergency happens. This study is about controller for the emergency diesel engine generator and design of a various software.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.32 no.4
• /
• pp.313-319
• /
• 2019

Induction motors connected with a three-phase AC system may malfunction due to reverse phase or open phase faults. Conventional overcurrent relays and overheating relays are used to prevent such accidents; however, their drawbacks include a low response speed and false operation. Therefore, in this study, a digital relay for the reverse-open phase was designed and fabricated. This relay can detect the reverse phase and open phase faults and send a trigger signal to the control circuit. The proposed relay was developed based on a microcontroller. The detection times of the reverse phase and open phase were verified as 320ms and 80ms, respectively. Compared with conventional relays that only protect the motor from one type of fault, the proposed relay can detect both, reverse phase and open phase faults. In addition, the fault detection, identification criterion, and trigger signal patterns can be modified by programming according to the requirements of users.

• Progress in Medical Physics
• /
• v.28 no.4
• /
• pp.156-163
• /
• 2017

To verify the usefulness of a steam sterilizer equipped with an electronic Bowie-Dick test system, this study was carried out using two methods, utilizing both a steam sterilizer and an electronic Bowie-Dick tester. The first method is to confirm the error detection of the chemical Bowie-Dick test pack and the electronic Bowie-Dick tester in a malfunctioning sterilizer environment. For this purpose, the Bowie-Dick test program for the steam sterilizer was used to test three types of test packs commonly used in hospitals and the electronic Bowie-Dick tester by changing the set values of temperature, time, and vacuum frequency. The second is an experiment to check the sterilizer's normal operation with the electronic Bowie-Dick tester and the usefulness of grasping the cause of the malfunction. The results showed that the sterilization temperature was the same as that of the test pack at a temperature $1{\sim}6^{\circ}C$ lower than the reference temperature of $134^{\circ}C$. In the test with the sterilization exposure time as a variable, there was a normal discoloration at a time difference of 30~90 s. In the experiment using the number of vacuum cycles, the test was correct by performing the normal discoloration only at the normal condition of 3 times. The test results of 30 hospitals were 100 failure tests by a total of 291 Bowie-Dick tests. Of these, the failure factors related to an internal temperature that the chemical test packs could not detect were the greatest, and the four factors related to temperature, including the internal temperature, were found to be 71.18% of total malfunctions. In addition, the Bowie-Dick tester was provided within 30 min after the start of the Bowie-Dick test to confirm the performance of the sterilizer and the detailed cause. A steam sterilizer equipped with an electronic Bowie-Dick test system is used to manage individual sterilizers. In the current steam sterilizer with many temperature-related errors, it is possible to check the malfunction of the temperature difference that the test pack cannot detect, and the cause of error for the sterilizer is immediately detected after the test. The steam sterilizer equipped with the electronic Bowie-Dick test system assists with infection control with accurate sterilizer performance assurance.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.34 no.6
• /
• pp.619-627
• /
• 2016

Cells of a PV (photovoltaic) module can suffer defects due to various causes resulting in a loss of power output. As a malfunctioning cell has a higher temperature than adjacent normal cells, it can be easily detected with a thermal infrared sensor. A conventional method of PV cell inspection is to use a hand-held infrared sensor for visual inspection. The main disadvantages of this method, when applied to a large-scale PV power plant, are that it is time-consuming and costly. This paper presents an algorithm for automatically detecting defective PV panels using images captured with a thermal imaging camera from an UAV (unmanned aerial vehicle). The proposed algorithm uses statistical analysis of thermal intensity (surface temperature) characteristics of each PV module to verify the mean intensity and standard deviation of each panel as parameters for fault diagnosis. One of the characteristics of thermal infrared imaging is that the larger the distance between sensor and target, the lower the measured temperature of the object. Consequently, a global detection rule using the mean intensity of all panels in the fault detection algorithm is not applicable. Therefore, a local detection rule was applied to automatically detect defective panels using the mean intensity and standard deviation range of each panel by array. The performance of the proposed algorithm was tested on three sample images; this verified a detection accuracy of defective panels of 97% or higher. In addition, as the proposed algorithm can adjust the range of threshold values for judging malfunction at the array level, the local detection rule is considered better suited for highly sensitive fault detection compared to a global detection rule. In this study, we used a panel area extraction method that we previously developed; fault detection accuracy would be improved if panel area extraction from images was more precise. Furthermore, the proposed algorithm contributes to the development of a maintenance and repair system for large-scale PV power plants, in combination with a geo-referencing algorithm for accurate determination of panel locations using sensor-based orientation parameters and photogrammetry from ground control points.

• The Journal of Korean Obstetrics and Gynecology
• /
• v.23 no.4
• /
• pp.35-46
• /
• 2010

Purpose: This study was designed to investigate the effects of Cyperi Rhizoma (CR) on changes in weights morphological and histopathological observations in Polycystic Ovary(PCO) rats. Methods: PCO was induced by single intramuscular injection with EV(2mg) in female rats. Normal group(n=8) were injected with sesame oil and orally administrated distilled water for five weeks. PCO control group(n=8) were injected with EV and orally administrated distilled water for five weeks. CR treated group(n=8) were injected with EV and orally administrated CR for five weeks. Then we measured weight of body, ovaries. The histopathology changes of ovaries, and the expression of nerve growth factor(NGF) were also evaluated. Results: Single injection of EV induced suppression of weight gain, formation of cysts, increase of NGF expression. Oral administration of CR prevent suppression of weight gain shown in control group. In addition CR group showed upward tendency of ovarian size. Formation of cystic follicles induced by EV injection is suppressed by CR treatment. In additon, CR treatment lowered expression levels of nerve growth factor(NGF), which were elevated by induction of PCOS. Conclusion: These results suggest that CR can be used for patients with PCOS to prevent formation of cystic follicles and malfunction of ovary. And also suggest that the related mechanisms are involved in suppression of NGF expression.