• Journal of Power Electronics
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• v.4 no.3
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• pp.138-151
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• 2004

In this paper, a constant frequency phase shifting PWM-controlled voltage source full bridge-type series load resonant high-frequency inverter using the $4^{th}$ generation IGBT power modules is presented for innovative consumer electromagnetic induction heating applications, such as a hot water producer, steamer and super heated steamer. The bridge arm side link passive capacitive snubbers in parallel with each power semiconductor device and AC load side linked active edge inductive snubber-assisted series load resonant tank soft switching inverter with a constant frequency phase shifted PWM control scheme is evaluated and discussed on the basis of the simulation and experimental results. It is proved from a practical point of view that the series load resonant and edge resonant hybrid high-frequency inverter topology, what is called, DE class type, including the variable-power variable-frequency regulation function can expand zero voltage soft switching commutation area even under low output power setting ranges, which is more suitable and acceptable for newly developed induction heated dual pack fluid heaters. Furthermore, even the lower output power regulation mode of this high-frequency load resonant tank inverter circuit is verified so that this inverter can achieve ZVS with the aid of the single auxiliary inductor snubber.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.3
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• pp.21-30
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• 2018

Driven by the recent energy saving trend, conventional silicon based power conversion modules are being replaced by modules using silicon carbide. Previous papers have focused mainly on the electrical advantages of silicon carbide semiconductors that can be used to design switching devices with much lower losses than conventional silicon based devices. However, no systematic study of their thermomechanical reliability in power conversion modules using finite element method (FEM) simulation has been presented. In this paper, silicon and silicon carbide based power devices with three-phase switching were designed and compared from the viewpoint of thermomechanical reliability. The switching loss of power conversion module was measured by the switching loss evaluation system and measured switching loss data was used for the thermal FEM simulation. Temperature and stress/strain distributions were analyzed. Finally, a thermal fatigue simulation was conducted to analyze the creep phenomenon of the joining materials. It was shown that at the working frequency of 20 kHz, the maximum temperature and stress of the power conversion module with SiC chips were reduced by 56% and 47%, respectively, compared with Si chips. In addition, the creep equivalent strain of joining material in SiC chip was reduced by 53% after thermal cycle, compared with the joining material in Si chip.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.553-556
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• 2013

Currently green growth and energy saving are major issues and solution using low-power LED lighting devices are gaining popularity. There are a few standards to control these LED lighting equipment and DMX512 protocol is a typical communication control standard used. DMX512 lighting control protocol is one of standard protocols widely used in various fields which include mainly stage lighting and landscape lighting. But in DMX512 protocol, line is to be connected to a wired connection. Advantage of wired connection is stable data transfer operation but it adds complexity and certain constraints as well in wired connection. To solve this problem, wired connection can be replaced efficiently with a wireless connection but for wireless, problem of data loss and two way communications arises. In this paper, these problems of wireless communication for DMX512 have been addressed and solutions for two way communications and data loss problem have been proposed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.5
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• pp.805-815
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• 2001

Glaucoma is an eye disease which is caused by abnormal high IOP (Intra Ocular Pressure). High IOP is caused by the aqueous humor which is produced consistently but not drained due to malfunction of the trabecular system which has a role of draining the aqueous humor into the venous system. Currently, there are three methods to treat glaucoma-using medicines, surgical operation, and using implant device. The first and second methods are not long acting, so the use of implants is increasing in these days in order to drain out the aqueous humor compulsory. However, though conventional implants have a capability of pressure regulation, they cannot maintain IOPs desired for different patients, and too much aqueous humor are usually drained, to cause hypotony. To solve these problems, it is needed to develop a new implant which is capable of controling the IOP actively and copes with personal difference of patients. An active glaucoma implant consists of the valve actuator, pressure sensor, controller, and power supply. In this paper, firstly, we make an analysis of the operation of a conventional implant using a bond graph and show defects and limitations of the conventional valve analytically. Secondly, we design and analyze a valve actuator considering actuation principles, resistance elements, control methods, and energy sources focused on power saving problem. Finally, using simulations the possibility of the proposed valve actuator is investigated.

• Journal of the Korea Safety Management & Science
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• v.12 no.4
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• pp.41-51
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• 2010

This paper describes the development of various lighting equipment adapting Ultra Constant Discharge Lamp that has newly been on commercial supply in the market. Meeting the required conditions of lighting equipment, various types of UCD Lamp equipment with excellent performances could be successfully developed. In order to provide a guideline for the economical lighting product selection, the analyzed data comparison between Hi-pressure Sodium Lamp which has been the most popular lamp for street lighting and UCD Lamp is provided. The conclusions of the study are made as follows; (1) The performance measurement result of UCD Lamp shows excellent Luminous Efficacy as 108Lm/W, daylight-like Color Rendering Index as 90Ra, and the best operating temperature range as $-50^{\circ}C{\sim}+85^{\circ}C$. Comparing to the Hi-pressure Sodium Lamp, UCD could be evaluated as much superior products. (2) In an assembled status with the lighting fixture (Type STB형-60W), UCD Lamp was tested OK for one hour duration at the temperature range form $-50^{\circ}C$ to $+85^{\circ}C$ and the humidity of 98%. The operation at the extremely low temperature can be an excellent feature to enable the export to the cold temperature regions such as Northern Europe and Russia and the specific applications for defense systems and special industry. (3) As UCD Lamp is a genuine Korea made product following Energy-saving and Eco-friendly policy, it should be appreciated as one of the best $CO^2$ reduction Green product.

• KIEAE Journal
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• v.16 no.4
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• pp.63-69
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• 2016

Purpose: This preliminary study investigated a potential of the water wall systems that provide heat storage and natural lighting control simultaneously. Method: In order for transparency of the water wall to be controlled, the study first proposed two measures: to adjust transparency of the water wall; to control transparency of water wall surface. The performance of two measures then was verified and compared by experiments. In addition, a trade-off between heat collect and heat storage resulting from using additive for adjusting transparency was investigated. Result: The experiment showed that the two measures are similar in performance. The investigation of trade-off relation showed the additive should have the same heat storage as the water to prevent decrease in thermal performance of the water wall. As an economical measure to control transparency of the water wall, this study suggested a measure of secondary heat transfer systems using shading device that first absorbs solar radiation and then transfers heat to the water wall. The experiment show that performance of the proposed measure is similar to controlling transparency of water wall surface. In conclusion, it is expected that the performance of the water wall can be economically maximized by using the proposed mean in terms of heating, cooling and lighting energy saving.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.6
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• pp.474-481
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• 2018

This paper is to compare by numerical analysis the flow characteristics and propulsion performance of stern with the shape change of K-duct, a pre-swirl duct developed by Korea Research Institute of Ships & Ocean Engineering (KRISO). First, the characteristics of the propeller and the resistance and self-propulsion before and after the attachment of the K-duct to the ship were verified and the validity of the calculation method was confirmed by comparing this result with the model test results. After that, resistance and self-propulsion calculations were performed by the same numerical method when the K-duct was changed into five different shapes. The efficiency of the other five cases was compared using the delivery horsepower in the model scale and the flow characteristics of the stern were analyzed as the velocity and pressure distributions in the area between the duct end and the propeller plane. For the computation, STAR-CCM +, a general-purpose flow analysis program, was used and the Reynolds Averaged Navier-Stokes (RANS) equations were applied. Rigid Body Motion (RBM) method was used for the propeller rotating motion and SST $k-{\omega}$ turbulence model was applied for the turbulence model. As a result, the tangential velocity of the propeller inflow changed according to the position angle change of the stator, and the pressure of the propeller hub and the cap changes. This regulated the propeller hub vortex. It was confirmed that the vortex of the portion where the fixed blade and the duct meet was reduced by blunt change.

• Journal of the Society of Naval Architects of Korea
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• v.56 no.4
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• pp.373-382
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• 2019

This paper shows numerical results for the estimation of the propulsor efficiency of Pre-Swirl Duct for 176k bulk carrier as well as its design method. Reynolds averaged Navier-Stokes equations have been solved and the k-epsilon model applied for the turbulent closure. The propeller rotating motion is determined using a sliding mesh technique. The design process is divided into each part of Pre-Swirl Duct, duct and Pre-Swirl Stator. The design of duct was performed first because it is located further upstream than Pre-Swirl Stator. The distribution of velocity through the duct was analyzed and applied for the design of Pre-Swirl Stator. The design variables of duct include duct angle, diameter, and chord length. Diameter, chord length, equivalent angle are considered when designing the Pre-Swirl Stator. Furthermore, a variable pitch angle stator is applied for the final model of Pre-Swirl Duct. The largest reduction rate of the delivered power in model scale is 7.6%. Streamlines, axial and tangential velocities under the condition that the Pre-Swirl Duct is installed were reviewed to verify its performance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.138-144
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• 2017

With the increase in power consumption due to the surge in the demand for power, it is necessary to improve the quality or design of the power (supply) for the purpose of reducing the energy consumption and so reduce the power loss. The switchboard is a mechanical device that receives electricity from the electricity generation facilities of KEPCO and divides it into the facilities required for each building. Switchboards generally consist of enclosures, switches, power conductors, and control components. This study deals with energized power conductors, which constitute the main element in the switchboard. Through the measurement of the effective ac resistance, it was confirmed that the vertical array structure of the conventional type plate conductor is inefficient. If the effective AC resistance increases significantly, the sectional area of the conductor becomes relatively large due to the skin effect. In this study, we studied the energy and material savings that could be obtained using the asterisk (*) array structure, which minimizes the effective ac resistance by reducing the skin effect. The core technology principle of this study is the energy saving switchgear based on conductor resistance reduction technology utilizing the asterisk array structure. The present invention involves a plate-shaped conductor arrangement structure capable of canceling out the magnetic field generated on each of the plate conductors (rst or abc) of the AC power supply in the power distribution panel by mutual action. The effect of this structure is to reduce the amount of inductive reactance due to the increase in the cross-sectional area and reduction of the effective AC resistance.

• Membrane Journal
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• v.27 no.5
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• pp.375-388
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• 2017

Wastewater treatment (WWT) technology has been developing from simple pollutant treatment to energy and resource-saving advanced technology, and various technologies combined with IT and BT are developed to minimize the amount of pollutant and toxic substance discharge to the public water areas and to improve operational efficiency. To examine the development trend of domestic wastewater treatment technology, the registered patent technologies were surveyed, classified and analyzed by year and sector. This paper considers the status of patent registration related to WWT from 2010.1 to 2017.5 in terms of the number of specific technical areas, and the trends are analyzed based on the 10 categorization field such as biological and physicochemical treatment process, equipment and device, material, sludge treatment, membrane, process control and 42 specific technical areas. A total of 3,356 patents have been registered since 2010, and the number of patents has been decreasing since the peak at 2013 and maintains 3~400 per year. The total number of patents has not yet been less than other countries, but the number of patents of more advanced technologies, which can lead the global market, such as process monitoring, new concept processing and equipment technologies is still insufficient compared to developed countries.