• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.1113-1119
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• 2005

The power electric system is one of the most concerning factor for the reliability of the electric propulsion ship. operation in higher temperature decreases the device's reliability and power efficiency. the management of power loss and temperature of switching devices is indispensable for the reliability fo the power electric system. In this paper, IGBT chip of the switching devices is modeled and MIIR(Motor with Inverter Internal to Rotor)type of the propulsion motors is used. these parts interact with each other to calculate the loss and temperature of device. calculated Results is modeled and designed of the control and monitoring system for the electric propulsion system.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.746-752
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• 2000

A study on discharge characteristics of a rotating discharge hole is very important to enhance the performance of an induction motor which have external forced cooling system. The discharge characteristics of rotating discharge holes are influenced by rotating speed, length-to-diameter ratio, inlet shape of rotor holes, etc. An experimental study on the effect of chamfered inlet edge of rotor inlet part with various depth-to-diameter and inlet chamfered edge angle is conducted. Depth-to-diameter ratios range from 0 to 0.5 and inlet chamfered edge angle range from 0 to 60. As a result, there is an optimal design point of inlet chamfered edge depth. And the inlet edge angle far maximum discharge coefficient is influenced mainly by the rotating speed of discharge holes.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.4
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• pp.422-426
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• 2011

The spindle system is very important unit for the product accuracy in machine tools. A spindle system is designed by using the angular contact ceramic ball bearings, built-in motor, oil-air lubrication method and oil jacket cooling method. The static and dynamic analysis and stiffness evaluation of 45,000rpm spindle for machine tool has been investigated. Using a finite element method, we obtained some analyzed a static and dynamic characteristics of a spindle, such as natural frequency, harmonic analysis and we got the value of compliance through it. We evaluated stiffness by taking the inverse this value. A 45,000rpm spindle is successfully developed using the results.

• The KSFM Journal of Fluid Machinery
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• v.7 no.4 s.25
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• pp.47-52
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• 2004

Cryogenic pump test facility (CPTF) is designed and developed in KARI. Hydraulic and cavitation performance of pump and inducer in cryogenic environment can be measured. Working fluid is liquid nitrogen and operating temperature is $-197^{\circ}C$. Run tank, catch tank of liquid nitrogen and their pressurizing tank has been built and remote tank pressure control system are installed. Maximum power of driving motor is 320 kW and its maximum speed is 32000rpm. Cryogenic fluids and lubricating systems are effectively separated that long test times are acquired. Therefore hydraulic and cavitation performance can be measured accurately and effectively. Pre-cooling test of the facility was successfully accomplished. This facility will contribute greatly to the development of turbopump for KSLV.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.1188-1194
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• 2008

To cope with the demagnetization risk of permanent magnets used in Interior Permanent Magnet Synchronous Motors(IPMSM), an accurate iron analysis and thermal analysis are very important. In this research, to calculate thermal increment of IPMSM for high-speed traction motor, we will extract losses of IPMSM considering the condition of field weakening control. Then we will input the calculated losses such as iron loss and copper loss as the thermal sources. Based on magnetic filed and thermal analysis, we will support the design of IPMSM for high-speed train.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.693-696
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• 2003

Hermetic Compressor circulates refrigerant with constant flow rate regardless of operation condition. so, at the operating condition requiring low cooling capacity, too much refrigerant flow deteriorates seasonal energy efficiency ratio(SEER). In this reason, modulated compressor is needed to improve SEER. Among many types of modulated compressor, non-inverter type modulated compressor is required for its low cost and easy to development. In the modulated scroll compressor by bypass method, EER steeply decreases for many loss like re-compression, changes of volume ratio, decrease of motor efficiency by torque variation. So. the range of modulation ratio for optimized SEER must be selected accompany with air conditioner set development.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.5
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• pp.181-185
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• 2006

A study to get better vehicle fuel economy is described based on an express bus. The approach is based on using a commercial software vehicle simulation to identify the relative efficiency of each of the vehicle systems, such as the engine hardware, engine software calibration, transmission, cooling system and ancillary drives. The simulation-based approach offers a detailed understanding of which vehicle systems are underperforming and by how much the vehicle fuel economy can be improved if those systems are brought up to best-in-class performance. In this way, the optimum vehicle fuel economy can be provided to the vehicle customer. A further benefit is that the simulation requires only a minimum of vehicle testing for initial validation, with all subsequent field test cycles performed in software, thereby reducing development time and cost for the manufacturer.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.674-682
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• 2018

Large industrial motors require a large area because of the high risk of shutdown accidents and large industrial accidents due to the lowering of the dielectric strength of the armature windings and overheating problems. Therefore, there is a demand for a large-capacity motor that has small size, light weight, and excellent dielectric strength compared with conventional motors. Superconducting motors have advantages of high efficiency and output power, low size, low weight, and improved stability. This results from greatly increasing the magnetic field generation by using superconductive field coils in rotating machines such as generators and motors. It is very important to design and analyze the cooling system to lower the critical temperature of the wires to achieve superconducting performance. In this study, a field loss analysis and low-temperature heat transfer analysis of the cooling system were performed through the conceptual design of a 100-HP high-temperature superconducting synchronous motor. The field loss analysis shows that a uniform pore magnetic flux density appears when high-temperature superconducting wire is used. The low-temperature heat transfer analysis for gaseous neon and liquid neon showed that a flow rate of 1 kg/min of liquid neon is suitable for maintaining low-temperature stability of the high-temperature superconducting wire.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.687-692
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• 2016

When turbochargers are applied to engines, the temperature of the engine becomes high, making the cooling of pistons very important. To solve this problem, an oil jet is used. The oil jet provides oil to the underside of piston for cooling. When an oil jet is used, oil pump size-up and oil cooler are needed because of the increased oil flow rate and higher oil temperature. On the other hand, these increase the friction torque of the engine. This study examined how much the friction torque of an engine increases by an oil jet, oil cooler, and oil pump size-up. In addition, the proportions of the friction torque of the engine increased by each part were measured by changing the engine assembly condition. At low speed, the oil pump and oil cooler had a larger effect on the friction torque than the other factors. At high speed, oil cooler had a larger effect than the other factors.

• Journal of the Korean Solar Energy Society
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• v.36 no.5
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• pp.31-50
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• 2016

To develope a greenhouse fog cooling system to control the temperature and relative humidity simultaneously to the target value, a theoretical analysis and experiments were done. The control process includes the measuring of environmental variables, setting and coding of the water and heat balance equations to maintain the target temperature and relative humidity in greenhouse, calculating of the open level of the greenhouse roof window that governs the natural ventilation and spray water quantity, and operating of the motor to open/close the roof window and pump to spray for water. The study results were shown to be very good because the average air temperature in the greenhouse was kept to be about $28.2^{\circ}C$ with the standard deviation of about $0.37^{\circ}C$ compared to the target temperature of $28^{\circ}C$ and the average relative humidity was about 75.2% compared to the target relative humidity was 75% during the experiments. The average outside relative humidity was about 41.0% and the average outside temperature was $27.2^{\circ}C$ with the standard deviation of about $0.54^{\circ}C$. The average solar intensity in the greenhouse was 712.9 W. The wind velocity of outside greenhouse was 0.558 m/s with the standard deviation of 0.46 m/s.