• Journal of the Korea Academia-Industrial cooperation Society
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• v.2 no.1
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• pp.53-58
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• 2001

The main noise sources in SMPS are divided into three parts: the switching devices, the rectifiers in secondary part, the output transformer and choke coil. In this paper we performed the noise analysis with respect to bobbin type and winding method, and designed an optimized transformer focusing on the transformer. For the comparison. we measured four parameters for each cases, including EMI conducted emission noise. signal from the switching devices, output ripple/noise voltage and leakage current. As the result, the transformer using a vertically-typed bobbin and a parallel, sandwich winding method showed the best performance. We confirmed that the SMPS developed in this research is satisfied with the IEC 601-1 international standard for the medical instrumentation. by testing its electrical characteristics and safety.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.30-30
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• 2010

The Angle Ring and Cap which is called pressboard are settled at primary and secondary coil winding of 154 kV transformer that can reduce effectively distance of insulation. As it has not manufactured pressboard of Angle Ring and Cap for high voltage grade, insulation components industry especially high voltage transformer has not participate in a competition with worldwide yet. That's why is difficult to make an specialized shape of insulation components of high voltage grade. At first, it is very important to make an utility of deformation manufacturing for high voltage transformer insulation components by itself. Therefore it has finally completed to make an deformation manufacturing utility using an special analysis tools. In this paper, developed insulation components was investigates in tensile strength is introduced.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.5
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• pp.111-117
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• 2020

Centrifugal casting is suitable for producing hollow-products using centrifugal force. Bush type metal bearings are the key parts that facilitate the rotational movement of various machinery. Metal bearings produced by conventional centrifugal casting machines show rotational imbalance. Therefore, after injecting a large amount of material, the product's precision is secured in the secondary processing. Rotational imbalance is caused by the force acting on the rotary disc plate. In order to minimize rotational imbalance, NASTRAN was used for the optimal design and structural analysis. It was concluded that the rotating plate of the conventional centrifugal casting machine should be prevented from tilting. For this purpose, the location & thickness of the stiffeners were obtained through the optimum design. In the conventional centrifugal casting machine, both ends of the product are lower in temperature than the center part, so internal stress occurs. This solves this problem by inserting a heating coil into the rotating plate.

• Journal of Magnetics
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• v.17 no.1
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• pp.36-41
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• 2012

The transcranial magnetic stimulation recharges the energy storing condenser, and sends the stored energy in the condenser to the pulse shaping circuit, which then delivers it to the stimulating coil. The previous types of transcranial magnetic stimulation required a booster transformer, secondary rectifier for high voltages and a condenser for smooth type. The energy storing condenser is recharged by switching the high-voltage direct current power. Loss occurs due to the resistance in the recharging circuit, and the single-pulse output energy in the transcranial magnetic stimulation can be changed because the recharging voltage cannot be adjusted. In this study a booster transformer, which decreases the volume and weight, was not used. Instead, a current resonance inverter was applied to cut down the switching loss. A transcranial magnetic stimulation, which can simultaneously alter the recharging voltage and pulse repeats, was used to examine the output characteristics.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.46-51
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• 2001

To reach high areal density, less track pitch is expected and more servo bandwidth is required. One approach to overcoming the problem is by using dual stage servo system. In this system, a voice coil motor (VCM) is used as the primary stage while a milliactuator is used as the secondary stage. We have suggested new milliactuator based on the shear mode of piezoelectric elements to drive the head suspension assembly. In this paper, we introduce controller design method, PQ method. PQ method reduces the controller design problem for DISO(dual-input/single-output) systems to two standard controller design problems for SISO(single-input/single-output) problems. The first part of PQ method directly address the issue of actuator output contribution, and the second part allows the use of traditional loop shaping to achieve the overall system performance. This paper shows how to employ the PQ method to meet aggressive close-loop performance specifications for a disk drive system with a VCM and piezoelectric milliactuator.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.159-160
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• 2005

The superconducting fault current limiter(SFCLs) provides the effect such as enhancement in the power system reliability due to limiting fault current in a few miliseconds. The Flux-lock type SFCL using the YBCO film among various type SFCLs consists of the primary and the secondary copper coils that are wound in parallel each other through the iron core. The operation can be controlled by adjusting the inductances and the winging directions of each the coil. We compared the current limiting performance on the additive and the subtractive polarity winding directions in case of an open-loop iron core. To analyze quench characteristics, we experimented various phase angle.

• Journal of Magnetics
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• v.19 no.2
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• pp.155-160
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• 2014

The heating produced by the absorption of radiofrequency (RF) has been considered a secondary undesirable effect during MRI procedures. In this work, we have measured the power absorbed by distilled water, glycerol and egg-albumin during NMR and non-NMR experiments. The samples are dielectric and examples of different biological materials. The samples were irradiated using the same RF pulse sequence, whilst the magnetic field strength was the variable to be changed in the experiments. The measurements show a smooth increase of the thermal power as the magnetic field grows due to the magnetoresistive effect in the copper antenna, a coil around the probe, which is directly heating the sample. However, in the cases when the magnetic field was the adequate for the NMR to take place, some anomalies in the expected thermal powers were observed: the thermal power was higher in the cases of water and glycerol, and lower in the case of albumin. An ANOVA test demonstrated that the observed differences between the measured power and the expected power are significant.

• Nuclear Engineering and Technology
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• v.49 no.8
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• pp.1669-1679
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• 2017

Background: Steam generator (SG) is one of the significant components in the nuclear steam supply system. A variety of SGs have been designed and used in nuclear reactor systems. Every SG has advantages and disadvantages. A brief account of some of the existing SG designs is presented in this study. A high surface to volume ratio of a SG is required in small modular reactors to occupy the least space. In this paper, performance improvement for SGs of integral small modular reactor is proposed. Aims/Methods: For this purpose, cross-grooved microfins have been incorporated on the inner surface of the helical tube to enhance heat transfer. The primary objective of this work is to investigate thermal-hydraulic behavior of the proposed improvements through modeling in RELAP5-3D. Results and Conclusions: The results are compared with helical-coiled SGs being used in IRIS (International Reactor Innovative and Secure). The results show that the tube length reduces up to 11.56% keeping thermal and hydraulic conditions fixed. In the case of fixed size, the steam outlet temperature increases from 590.1 K to 597.0 K and the capability of power transfer from primary to secondary also increases. However, these advantages are associated with some extra pressure drop, which has to be compensated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.289-289
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• 2008

We investigated the operational characteristics of the separated three-phase flux-lock type superconducting fault current limiter (SFCL). The single-phase lock type SFCL consist of two coils, which are wound in parallel through an iron core. The high-$T_c$ superconducting(HSTC) thin film connected in series with secondary coil. The separated three-phase flux-lock type SFCL consist of three single-phase flux-lock type SFCL. In a normal condition, the SFCL is not operate. When a fault occurs, the current of a HSTC thin film exceeds its critical current by fault current, the resistance of the HSTC thin film generated. Therefore fault current was limited by SFCL. The separated three-phase flux-lock type SFCL are operated in fault condition such as the the single line-to-ground fault, the double line-to-ground fault and the triple line-to-ground fault. The experimental results, the SFCL operational characteristics was dependent on fault condition.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.8 no.3
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• pp.7-12
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• 2012

Steam generator tubes are critical boundary of the primary and secondary side in nuclear power plants. Eddy current testing is commonly used as the method of non-destructive testing for the safety and integrity of steam generator tubes in the nuclear power plants. Changes in the geometric shape act as a stress concentration factor likely to cause a defect during the steam generator operation. The mixed-signals with the geometric shape are distorted and attributes that are difficult to detect signals. An example is bending stress due to compression process at a U-bend occurring in the intrados region which has a small radius of curvature. The resulting change in the geometric shape may lead to a dent like occurrences. The dent can cause stress concentration and generates stress corrosion cracks. In this study, the steam generator tubes of nuclear power plant were selected to study for analysis of mixed-signal containing dent and stress corrosion cracks.