• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.356-357
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• 2019

본 논문에서는 넓은 충전 전압 범위와 V2G 기능을 갖는 급속 충전기용 DC-DC 컨버터를 제안한다. 제안한 컨버터는 SRC(Series Resonant Converter)와 2상 Buck/Boost 컨버터로 구성된 2-stage 구조로써 넓은 충전 전압 범위에 적합하며, 배터리 충전뿐만 아닌 V2G(Vehicle to Grid) 동작이 가능하다. 또한 2상 인터리빙 방식을 사용함으로써 전류 분담을 통해 소자의 전류 정격 및 출력 필터 사이즈를 낮출 수 있다. 제안하는 컨버터의 시작품 실험을 통해 타당성을 검증하였다.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.221-223
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• 2020

반도체 기반 고전압 펄스 발생장치에 적용 가능한 고전압 스위치는 주로 수 kV 정격의 반도체 스위치를 직렬로 스태킹하여 구성되며, 이때 각 스위치 소자에는 절연과 동기화된 각각의 게이트 신호가 인가되어야 한다. 본 논문에서는 짧은 펄스 폭의 온, 오프 게이트 펄스와, 단일 턴의 고전압 전선을 일차측으로 갖는 게이트 변압기를 통해 직렬로 구성된 반도체 스위치 스택 기반의 펄스 모듈레이터에 적용 가능한 간단한 구조의 게이트 구동회로가 설계되었다. 각 스위치에 게이트 신호를 전달하기 위해 온, 오프 게이트 펄스를 사용함으로써 게이트 변압기의 포화를 방지할 수 있으며, 이때 각 스위치의 게이트 턴-온, 오프 전압은 변압기 이차측의 제너 다이오드와 스토리지 커패시터를 통해 유지된다. Pspice 시뮬레이션을 통해 12개의 IGBT를 직렬로 구성하여 설계된 구조의 게이트 회로를 적용, 최대 10kV 펄스 출력 조건에서 안정적인 동작을 확인하고 설계를 검증하였으며 1200V 급 IGBT를 사용하여 실제 스위치 스택과 게이트 구동회로 모듈을 1리터 이내의 부피로 고밀도화하여 제작하였다.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.7 s.196
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• pp.90-97
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• 2007

This paper describes the development of 6-axis force/moment sensor considered adult weight far an intelligent foot of humanoid robot. In order to walk on uneven terrain safely, the foot should perceive the applied forces Fx, Fy, Fz and moments Mx, My, Mz to itself and control the foot using the forces and moments. The applied forces and moments should be measured from a 6-axis force/moment sensor attached to the foot, which is composed of Fx sensor, Fy sensor, Fz sensor, Mx sensor, My sensor and Mz sensor in a body. Each sensor should get the deferent rated load, because the applied forces and moments to foot in walking are deferent. Therefore, one of the important things in the sensor is to design each sensor with the deferent rated load and the same rated output. In this paper, a 6-axis force/moment sensor (rated load of Fx and Fy are 500Nm and Fz sensor is 1000N, and those of Mx and My are 18Nm, Mz sensor is 8Nm) for perceiving forces and moments in a humanoid robot's foot was developed using many PPBs (parallel plate-beams). The structure of the sensor was newly modeled, and the sensing elements (plate-beams) of the sensor were designed using by ANSYS software (FEM (Finite Element Method) program). Then, a 6-axis force/moment sensor was fabricated by attaching strain-gages on the sensing elements, and the characteristic test of the developed sensor was carried out. The rated outputs from FEM analysis agree well with that from the characteristic test.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.9
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• pp.25-31
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• 2008

The field of induction motor is magnetized and demagnetized for each reversal of the current. This field component of the motor accounts for most of the reactive component of inductive load. Reactive power needs to sustain the electromagnetic field required for the induction motor to operate. Power factor of induction motor is usually low and power factor correction needs. Power factor becomes low by the effect of the reduction operation of load capacity. In most cases, Capacitor capacity for the power factor correction should be complied with the recommendation by the motor capacity. But Capacitor value for power factor correction can't change during the normal operation. In this paper, we analyzed characteristics of power and power factor changing by load fluctuation of low-voltage small size induction motor and show that lower power factor correction's parameter of existing recommendation should be revised by new value.

• Journal of IKEEE
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• v.16 no.1
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• pp.34-44
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• 2012

This paper proposes a practical compensation method by using digital signal processing over the creep error which is representative in strain gauge loadcell. The signal compensation method carry out the simulation by deciding compensation constant (time constant) and coefficient measuring the loadcell output response. Then, compensation constant and coefficient are stored on the microprocessor. By using calculated on microprocessor creep error compensation values, weighting value is showed as a digital signal by reducing error values measured through output signals of loadcell. In addition, we apply error compensation method in order to have a dedicated software for loadcell electronic scale. This technique is useful because it has great influence on error rate reduction that has been produced by conventional electronic scales (0.03%). As a result our technique gives better accuracy (0.01%~0.003%) as what is given by digital electronic scale, while it has less complex operation processing.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.6
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• pp.693-701
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• 2012

In this study, a small wind turbine airfoil specialized for national wind condition was designed in order to develop the furling control type HAWT. And then a flow analysis was carried out based on the blade drawing which was designed to characterize of the developed airfoil. The result of the flow analysis showed that the torque on the 3 blades was 180.23N.m. This is equivalent to an output power of 5.66kw and an output efficiency of 0.44. Then we produced and constructed a 3kW - furling control type HAWT by getting the system unit design technology such as the specialized furling control device. By operating this turbine, we could get 3kW of the rated power at a wind speed of 10.5m/s through the ability test. Cut-in wind speed was 2m/s, generator efficiency was 92% at the rated power output. Sound power level was 87.2dB(A). Also we observed that the output power was limited to 10.5m/s with furling system operation.

• Journal of Energy Engineering
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• v.28 no.2
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• pp.47-54
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• 2019

As absorption type heat pump for waste heat recovery is installed in combined cycle power plant for Energy Service Company, performance test is implemented to confirm the operation data on partial load. The operation data changes according to the heat pump operation on partial load are as follows. Total heat output increases, because waste heat of closed cooling water and a portion of LP steam from HRSG is supplied. But electric power output of steam turbine is reduced, because LP steam to steam turbine is reduced. And heat output from HP district heater and LP district heater is reduced, because HP turbine exhaust steam to HP district heater and LP district heater is reduced. On partial load operation, turbine output reduction is higher than the base load operation. Therefore, on partial load, heat pump should be operated in consideration of the heat output increase and electric power output reduction.

• Journal of IKEEE
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• v.26 no.4
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• pp.537-544
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• 2022

This paper analyzes the occurrence and cause of bond wires fusing used in the manufacture of pulsed high power amplifiers. Recently GaN HEMT has been spotlight in the fields of electronic warfare, radar, base station and satellite communication. In order to produce the maximum output power, which is the main performance of the high-power amplifier, optimal impedance matching is required. And the material, diameter and number of bond wires must be determined in consideration of not only the rated current but also the heat generated by the transient current. In particular, it was confirmed that compound semiconductor with a wide energy band gap such as GaN trigger fusing of the bond wire due to an increase in thermal resistance when the design efficiency is low or the heat dissipation is insufficient. This data has been simulated for exothermic conditions, and it is expected to be used as a reference for applications using GaN devices as verified through IR microscope.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.3
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• pp.243-254
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• 2014

It is essential to predict the coil temperature under over load and over speed conditions for reliability in high speed low torque surface mounted PM synchronous motors(SPM). In the present study, the losses and coil temperature are measured under rated condition and calculated under over speed and over load conditions in the three different motors with 35PN440, 25PN250 and 15HTH1000. The heat transfer modeling has been performed based on acquired losses and temperature. The difference of coil temperature between heat transfer modeling and experiment is less than 6.4% under no load, over speed and over load conditions. Subsequently, the coil temperature of the motor with 15HTH1000 is 84.4% of the coil temperature of the motor with 35PN440 when speed is 0.9 and load is 3.0. The output of motor with 15HTH1000 is 85.2% greater than the output of the motor with 35PN440 when the dimensionless coil temperature is 1.0.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.9
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• pp.2280-2288
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• 2014

The conventional dimming control methods of LED (Light-emitting dioades) include Analog, PWM (Pulse Width Modulation), and FM (Frequency Modulation) Control. Analog dimming is controlled by adjusting forward current of Power LED. Although Analog dimming is possible to control linearly the brightness levels on a whole range (0%~100%), it comes into existence a variation of wavelength by changing the Power LED's forward current. PWM dimming has achieved by varying in duty of full current flowing to the Power LED. Generally, PWM dimming doesn't make variation of wavelength but have difficulty with adjusting the linear brightness level between 0% and 10%. FM dimming method is on the same wavelength as PWM dimming, however, it has problem of flickering at low level of dimming. This paper propose a efficient dimming control method of Power LED in order to overcome the disadvantages of the above mentioned methods. We apply to Analog method in low level of dimming control and use PWM method in dimming range from 10% to 100%. For the experiment, we design and implement a circuit and test the proposed method. Consequently, we can control the linear brightness of Power LED across the whole range and get the constant wave at different dimming level. The experimental results show the benefits of the proposed method.