• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.1
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• pp.48-56
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• 2007

In this paper, the rotor losses in high-speed permanent synchronous motor (PMSM) considering the operating condition are discussed. In order to maintain the mechanical integrity of a high-speed permanent magnet machine rotor intended for high-speed operation, the rotor assembly is often retained within a stainless steel or Carbon-Fiber/Epoxy sleeve. The sleeve is exposed to fields produced by the stator from either the slotting or the mmf harmonics that are not synchronous with rotor losses. On the basis of analytical field analysis, the rotor losses are analyzed. In particular, the no-load, rated with air-cooled, and forced water cooled conditions are considered. The results are validated extensively by comparison with non-linear finite element method (FEM).

• Journal of the Korean Society for Precision Engineering
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• v.15 no.4
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• pp.36-43
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• 1998

We experimented turning SCM440, called difficult-to-cut materials in general, using tungsten carbon tool(PIO) in order to elevate machinability by a new cutting method. The cutting tool designed and made to study was cooled to -17$0^{\circ}C$ in about 1 minute by liquid nitrogen. Then, we operated cryogenic cutting by cooling tool with liquid nitrogen and stuided the effect about cutting force, chip thickness, surface roughness, behavior of tool wear and cutting temperature. In addition, we investigated the possibility that sur face roughness of workpiece can be predicted analyzing cutting characteristics.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.04a
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• pp.89-93
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• 1992

We experimented cutting characteristics-cutting force, behavior of chip, surface roughness-under low temperature, which generated by liquid nitrogen(77K). The results obtained are as follows; 1) The workpice is became to-195 .deg. C in 5, minutes, and in cooled cutting, cutting force bycooled workpices is stronger than normal temperature condition. Chip thickness is decreasing comparative toN.C and shear angle in shear plane is in creasing. 2) Chip formation becomes long or short tubular chips in turning SXM440, SNCM21 steel, when cutting speed is low and cutting temperatre is cooled condition, but in the STS304 steel the variation of c formations isn't known to. 3) In C.C, surface roughness of workpices is better than N.C and found to make more the crat wearthan N.C 4) It is possible to detect the behavior of chip by monitoring the maximum amplitude of gai value of cutting force.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.213-215
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• 1993

Silver-sheathed Bi-Pb-Sr-Ca-Cu-O wires by the powder-in-tube method were preparated to study on the superconducting properties with cooling conditions. Superconducting wires were cooled down in the furnace, air and liquid $N_2$ after sintering at $840^{\circ}C$. Critical current density of sample cooled in the furnace is $5.1{\times}10^3\;A/cm^2$ at 77K, zero magnetic field and Jc of sample cooled in the air is very low. 2223 high-Tc superconducting phase of sample cooled in the air was distroyed. Therefore, we knew that superconducting wire need to cool slowly to get the high critical current density.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.5
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• pp.145-150
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• 2013

Recently, many vehicles have applied electric parts for saving fuel consumption and reducing levels of environmental pollution. ISG (integrated starter & generator) is one of main electric parts and can improve fuel efficiency by using idle stop & go function and regenerative braking system. However, if ISG driving inverter works under the continuously high load condition, it will make the performance and durability of the inverter decreased with rising temperature. In this study, we carried out the analysis on the fluid flow and thermal characteristics of the inverter. As a result, we found the MOSFET of the air cooled inverter was increased up to $116^{\circ}C$ over the limit temperature. On the other hand, the liquid cooled type inverter's MOSFET was decreased by about $17^{\circ}C$ compared to that of the air cooled inverter. Therefore, we verified the feasibility of the liquid cooled type using the present cooling structure.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.8
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• pp.404-410
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• 2006

Toward the practical applications, on operation of conduction-cooled HTS SMES at temperatures well below 40[K] should be investigated, in order to take advantage of a greater critical current density of HTS and considerably reduce the size and weight of the system. In order to take advantage of a greater critical current density of high temperature superconducting (HTS) and considerably reduce the size and weight of the system, conduction-cooled HTS superconducting magnetic energy storage (SMES) at temperatures well below 40[K] should be investigated. This work focuses on the breakdown and flashover phenomenology of dielectrics exposed in air and/or vacuum for temperatures ranging from room temperature to cryogenic temperature. Firstly, we summarize the insulation factors of the magnet for the conduction cooled HTS SMES. And Secondly a surface flashover as well as volume breakdown in air and/or vacuum with two kind insulators has been investigated. Finally, we will discuss applications for the HTS SMES including aging studies on model coils exposed in vacuum at cryogenic temperature. The commercial application of many conduction-cooled HTS magnets, however, requires refrigeration at temperatures below 40[K], in order to take advantage of a greater critical current density of HTS and reduce considerably the size and weight of the system. The magnet is driven in vacuum condition. The need to reduce the size and weight of the system has led to the consideration of the vacuum as insulating media. We are studying on the insulation factors of the magnet for HTS SMES. And we experiment the spacer configure effect in the dielectric flashover characteristics. From the results, we confirm that our research established basic information in the insulation design of the magnet.

• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.4
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• pp.1-6
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• 2002

A numerical heat transfer analysis and the structural analysis were performed for the design of sub-scale combustion chamber's coolant passage. The heat flux through the combustion chamber wall was estimated by 2-D heat transfer analysis of compressible hot gas and the result was applied as a thermal boundary condition of 3-D analysis. The heat flux estimated by the present method agreed well with the experimental correlation and proved to be insensitive to cooling condition. So the same thermal boundary condition was applied for various operating conditions. The maximum temperature of combustion chamber wall was predicted by 3-D analysis for single coolant passage and the result will be used for the development of a regeneratively cooled combustion chamber. Also estimated were the stress distribution and structural safety of coolant passage through the static structural analysis.

• Nuclear Engineering and Technology
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• v.54 no.7
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• pp.2720-2727
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• 2022

The Generation IV Lead-cooled fast reactor (LFR) take the liquid lead or lead-bismuth eutectic alloy (LBE) as the coolant of the primary cooling circuit. Combined with the natural characteristics of lead alloy and the design features of LFR, the system is the simplest and the number of equipment is the least, which reflects the inherent safety characteristics of LFR. The nuclear main coolant pump (MCP) is the only power component and the only rotating component in the primary circuit of the reactor, so the various operating characteristics of the MCP are directly related to the safety of the nuclear reactor. In this paper, various working conditions that may occur in the normal rotation (positive rotating) of the MCP and the corresponding internal flow characteristics are analyzed and studied, including the normal pump condition, the positive-flow braking condition and the negative-flow braking condition. Since the corrosiveness of LBE is proportional to the fluid velocity, the distribution of flow velocity in the pump channel will be the focus of this study. It is found that under the normal pump condition and positive-flow braking conditions, the high velocity region of the impeller domain appears at the inlet and outlet of the blade. At the same radius, the pressure surface is lower than the back surface, and with the increase of flow rate, the flow separation phenomenon is obvious, and the turbulent kinetic energy distribution in impeller and diffuser domain shows obvious near-wall property. Under the negative-flow braking condition, there is obvious flow separation in the impeller channel.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.4
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• pp.498-504
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• 2012

The water-cooled Permanent Magnet Linear Synchronous Motor (PMLSM) has a wide range of applications due to high efficiency, high thrust force density and high acceleration. In order to ensure normal operation and maximum output, both the magnetic and thermal performance are vital to be considered. Based on ANSYS software, electromagnetic and thermal finite-element analysis (FEA) models of a 14-pole, 12-slot water-cooled PMLSM are erected adopting suitable assumptions. Firstly, the thrust force and force ripple with different current densities are calculated. Secondly, the influence of different water flow on the motor heat dissipation and force performance under different operationional conditions are investigated and optimized. Furthermore, for continuous operation, the temperature rise and thrust feature are studied under the rated load 8A, the proper temperature $120^{\circ}C$ and the limited temperature $155^{\circ}C$. Likewise, for short-time operation, the maximum duration is calculated when applied with a certain large current. Similarly, for intermittent operation, load time as well as standstill time are determined with the optimal current to achieve better thrust performance.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.12 no.1
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• pp.134-140
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• 2016

The Control Rod Assembly (CRA) controls the reactor power by adjusting its position in the reactor core during normal operation and should be quickly inserted into the reactor core by free drop under scram condition to shut down chain reactions. Therefore, the drop time of the CRA is one of important factors for the safety of the nuclear reactor and must be experimentally verified. This study presents the drop performance test of the CRA which has been conceptually designed for the Proto-type Generation IV Sodium-cooled Fast Reactor. During the test, the CRA was free dropped from a height of 1 m under different flow rate conditions and its drop time was measured. The results showed that the drop time of the CRA increased as the flow rate increased; the average drop times of the CRA were approximately 1.527 seconds, 1.599 seconds and 1.676 seconds at 0%, 100% and 200% of design flow rates, respectively.