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Yeonho Kwak,Tae Hoon Kang,Seung Hwan Lee,Minjung Kang 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.4
The adoption of aluminum in the mobile industry is driving development of aluminum alloys. Among the additive elements of aluminum alloy, magnesium is a crucial component commonly included in various commercial aluminum alloys. Because of its ability to enhance solid solution strengthening and work hardening, many researchers are investigating methods to increase the magnesium content in aluminum applications. Almag6 contains more than 6 wt% of magnesium and exhibits excellent structural properties; it possesses higher yield and tensile strengths than the commercial 5XXX series of aluminum materials. However, work-hardening alloys are vulnerable to welding heat. In this study, laser and tungsten arc welding processes were performed to study the effect of welding heat on the mechanical and microstructure properties of Almag6. It was found that the mechanical strength and hardness of the welds reduced significantly. Similar to other work-hardening aluminum alloys, the lowest hardness was measured in the fusion zone with a strength of over 200 MPa. Relatively low breaking strengths were measured in the tungsten arc welding specimens owing to grain coarsening in the welds.
Yeonho Ok,Jaeho Choi,Mancheol Shin,Youngkwan Choi 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
In this paper, the phenomenon of voltage rise when the renewable energy power plants are connected to the distribution grid is analyzed. For analysis of voltage rise phenomenon, the actual operation data with some kinds of renewable energy power plants such as small hydro power plant, solar power plant and wind power plant are gathered firstly. And based on these data, the voltage rise phenomenon is analyzed and configured with the equivalent circuit and vector diagram. The implementation results of an effective and economical solution for the voltage regulation using SVC are shown for further discussion in detail.
Yeonho Jeong,Jong-Woo Kim,Cheon-Yong Lim,Dong-Kwan Kim,Jae-Il Baek,Gun-Woo Moon 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
The phase-shifted full bridge (PSFB) converter is widely used in the middle and high power applications such as a server power system. However, due to the newly required trend for high light-load efficiency, the PSFB converter has a limitation for light-load efficiency because of a large circulating current, core losses of the transformer and inductors, and the insufficiency ZVS energy of lagging-leg switches. To achieve high light-load efficiency in PSFB converter, the circulating current in the freewheeling mode and the core loss should be reduced. Therefore, this paper proposes the strategic control scheme employing the control scheme of the two-switch forward (TSF) converter. In addition, by applying the additional one gate signal and the expanded dead-time, the switching loss can be significantly reduced. To verify the proposed method, the prototype converter with 750W (12V/62.5A) is built and tested.