• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.4
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• pp.280-286
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• 1998

This paper proposes a novel method to reduce the torque ripple due to the non-ideality of the current sensing parts in vector-controlled inverter-fed AC motor drive systems. For PMSM(Permanent Magnet Synchronous Motor), motor output torque equations are derived in terms of their offset voltages and different voltage transducing gains. And the effects of phase current errors on motor torque are analyzed for both salient PMSM and non-salient PMSM. The proposed method can eliminate the torque ripple by nulling the offset voltages and setting the voltage transducing gains to the same value. To verify the proposed method, digital simulations are carried out for non-salient PMSM.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.477-478
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• 2015

2상 유도전동기용 벡터제어 인버터에서는 전류센서를 사용하여 a상 및 b상의 전류를 측정해야 한다. 그러나, 이 전류값을 마이크로컨트롤러의 A/D컨버터로 읽어 들이는 과정에서 전류 센서와 증폭회로로부터 발생하는 오프셋 오차와 변환이득 오차를 포함할 수 있다. 2상 유도전동기의 벡터제어 시스템이 이러한 오차들을 포함한다면 전동기의 출력토크에 리플이 발생한다. 본 논문에서는 이러한 전류측정 오차를 실시간으로 보상하여 전동기의 토크리플을 제거하는 방법을 제안하였으며, 이러한 방식을 360[W]급의 2상 유도전동기용 벡터제어 인버터에 적용하여 컴퓨터 시뮬레이션과 실험으로 유효성을 확인하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.1
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• pp.86-92
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• 2012

The well-used actuators for the attitude control of spacecrafts are thruster, reaction wheel, control moment gyroscope, and magnetic torquer. Among them, the control moment gyroscope(CMG) which generates the torque based on the gyroscopic principle in physics, has an advantage of the high torque output compared to the low power consumption. This paper introduces an outline of CMG hardware technology, its application history in spacecrafts, and their associated hardware characteristics. Moreover, its spin-off cases to the other industrial fields such as ship, robotics, and MEMS including their research trend are provided.

• Korean journal of communication and information
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• v.77
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• pp.9-35
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• 2016

This research focuses on how political talk shows by Channel A and TV Chosun provoke strong, negative emotions, such as anger or loathing, towards certain parties, politicians and groups only, and tries to explain what's the relation to Korean democracy crisis under the circumstances. Those talk shows by Channel A and TV Chosun, predominantly about anger and loathing towards oppositions, opposition politicians and pro-North Korea people, have contributed to practical exclusion of the citizens from the political process by their imaginary political participation rather than a role as a democratic public sphere, so they have functioned very well in order to sustain the system of Korean democracy as a way of 'the politics of exclusion', and have been retained regardless of their commercial success for the reason. In other words, the Korean democracy has systematically excluded every citizen and amplified ideological conflicts, and in that chaos of excessively produced emotions, has dealt with all the crucial matters using political technology, which is a serious problem. However, for the good of the political power who wants to keep such kind of political system, this became a reason why those Channel A and TV Chosun shows-sensational and politically biased-have survived, and since Channel A and TV Chosun are remarkably functional within the continuance of that political system they can keep being influential in politics.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.157-158
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• 2015

본 논문은 직렬 보상 커패시터 사용으로 인해 발생될 수 있는 SSR(Subsynchronous Resonance) 현상을 해석하기 위한 도구로서 EMTDC의 활용에 관해 다루고 있다. EMTDC를 이용한 순시치 기반의 계통 해석은 주파수 스캔이나 Eigenvalue 계산법의 한계를 보완할 수 있다. EMTDC 기반 해석의 효용성을 검증하기 위해 IEEE 2nd Benchmark 모델을 PSCAD/EMTDC로 구현하였고, 시뮬레이션을 통해 유도 발전기 효과와 비틀림 상호작용 및 축 토크 증폭 현상을 검증했다. 또한, SSR의 억제 수단으로 SVC와 보조제어기를 발전기단에 투입하였고, 그 억제 효과를 시뮬레이션으로 검증하였다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.1
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• pp.1-10
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• 2022

In this study, the two horizontal shroud tidal current energy converter, which can generate power even under low flow speed conditions, was developed. In order to determine the shape of the shroud system, a three-dimensional numerical simulation test was conducted, and a 1/6 scale down model was made to perform a hydraulic model experiment. The hydraulic model experiment was performed under four flow conditions, and the flow speed, torque, and RPM were measured for each experimental case. As a result of the numerical simulation test, it was found that the flow speeds passing through the nozzle were increased by about 2~3 times in the cylinder, and when the extension ratio was 2:1, the highest flow speed was shown. In addition, it was found that the flow speeds increased 2.8 times when the diameter ratio between the nozzle and the cylinder was 1.5:1. Meanwhile, as a result of the hydraulic model experiment, it was found that when the tip speed ratio was between 1.75 and 2, the power coefficient was 0.32 to 0.34.