• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.754-755
• /
• 2008

This paper presents a method for reducing the Total Harmonic Distortion(THD) of line-line back_EMF of the IPMSM with distributed winding under the no-load condition. Firstly, the specific harmonic components of line-line back EMF are reduced considering with winding factor. Secondly, THD of line-line back EMF is minimized according to change of pole angle using by Space harmonic Analysis. Finally, the optimal design for minimizing the THD is conducted using response surface methodology with finite element analysis. The validity of the design method dealt with in this paper is demonstrated by comparison between the THD of optimal model and initial model.

• Proceedings of the KIPE Conference
• /
• 2017.07a
• /
• pp.74-75
• /
• 2017

This paper proposes a control scheme of the voltage ripple suppression for the permanent magnet exciter generator. The output voltage of the permanent magnet excitation generator is affected by the field current, load current and the engine speed. The engine speed can be controlled by the governor. But, the actual frequency is changed at the starting and a sudden load variation. As a result, output voltage overshoot and undershoot can decrease the power quality in the grid system. The proposed control scheme uses a frequency factor to control the field current of the generator for the voltage ripple reduction. Because of the linkage flux is proportional to the frequency, the instantaneous frequency can consider the linkage flux. The proposed control method shows the improved control performance for the permanent magnet excitation generator through simulation.

• Journal of the korean Society of Automotive Engineers
• /
• v.9 no.5
• /
• pp.57-65
• /
• 1987

The surface rolling method which is one of the plastic deformation processes increases the surface roughness with reduction of diameter and hardness. In this study, three NACHI 6000 ZZ bearing were used for surface rolling tool on a mild steel The following results have been obtained with the mild steel. 1) The load is major factor in getting fine surface roughness of roller finishing after grinding The optimal surface roughness of SS41 steel can be obtained at the contact pressure of 210 kgf/cm$^{2}$. 2) At the contact pressure range of 200kgf/cm$^{2}$-210kgf/cm$^{2}$ for optimal surface roughness, The surface hardness increased to Hv200-Hv240 from Hv 125 before surface rolling. 3) Within the diameter variation of 13 .mu.m the surface roughness and the surface hardness were increased, but out of variation of 14.mu.m. The surface roughness become worse and the surface hardness was increased.

• Journal of Ocean Engineering and Technology
• /
• v.6 no.2
• /
• pp.71-75
• /
• 1992

기구나 구조물의 피로수명은 노치에서의 피로균열 방생수명에 의하여 지배되기때문에 노치로 인한 피로강도감소계수 $K_f$는 피로설계상 대단히 중요한 인자이다. 노치 선단(Notch root)에서의 피로균열발생명수 N$_c$를 기준으로하면 탄성응력집중계수 $K_t$가 10 정도까지 $K_f$와 $K_t$간에는 거의 직선적인 관계가 있음이 이다- 고에 의하여 명석해졌으나 이는 인장,압축의 축력이 작용하였을 때이며 따라서 기구나 구조부재는 축력외에도 굽힘 피로 하중이 작용하였을때도 많으므로 본 연구에서는 굽힘 피로 하중을 받았을때도 있다. -고의 결론이 적용되는지는 검시코져 본 연구를 실시하였다.

• Wind and Structures
• /
• v.8 no.3
• /
• pp.147-161
• /
• 2005

Two identical tall building models with square cross-sections are experimentally studied in a wind tunnel with high-frequency-force-balance (HFFB) technique to investigate the interference effects on wind loads and dynamic responses of the interfered building. Another wind tunnel test, in which the interfered model is an aeroelastic one, is also carried out to further study the interference effects. The results from the two kinds of tests are compared with each other. Then the influences of turbulence in oncoming wind on dynamic interference factors are analyzed. At last the artificial neural networks method is used to deal with the experimental data and the along-wind and across-wind dynamic interference factor $IF_{dx}$ & $IF_{dy}$ contour maps are obtained, which could be used as references for wind load codes of buildings.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.05a
• /
• pp.266-270
• /
• 2006

Noise reduction the noise of a high precision multi-stage gearbox applied at the industrial robot is investigated by experiment such as the modal test and the signal analysis. The signal analysis performed with the waterfall plot representing the power spectrum as a function of the rotating speed. An eccentric load is installed at the gearbox in order to organize similar condition used in the industrial robot. Exciting sources are found out by the waterfall plot, and then the main factor to make the noise is distinguish. For the low-noise gearbox, the gear design parameter is modified and this gearbox is experimented in the same procedure. The results of the test show the noise level of gearbox reduced.

• Korean Journal of Ecology and Environment
• /
• v.51 no.1
• /
• pp.135-147
• /
• 2018

In order to investigate the runoff characteristics of nonpoint source pollutants in the Lake Doam watershed, water quality and flow rate were monitored for 38-rainfall events from 2009 to 2016. The EMC values of SS, COD, TN and TP were in the range of 33~2,169, 3.5~56.9, 0.09~7.65 and $0.06{\sim}2.21mg\;L^{-1}$, respectively. As a result of analyzing the effect of rainfall factor on the nonpoint source pollutant load, EMCs of SS, COD and TP showed a statistically significant correlation with rainfall (RA) (p<0.01) and SS showed highly significant correlation with maximum rainfall intensity (MRI, R=0.48). The load ranges of SS, COD, TN and TP were 10.4~11,984.6, 1.1~724.4, 0.6~51.6 and $0.03{\sim}22.85ton\;event^{-1}$, respectively, showing large variation depending on the characteristics of rainfall events. The effect of rainfall on the load was analyzed. SS, COD and TP showed a positive correlation, but TN did not show any significant correlation. The annual load of SS was the highest with $88,645tons\;year^{-1}$ in 2011 when rainfall was the highest with 1,669 mm. The result of impact analysis of nonpoint source pollution reduction project and land-use change on runoff load showed that pollutant load significantly reduced from 2009 to 2014 but SS and TP loads were increased from 2014 to 2016 due to increase in construction area. Therefore, we suggested that nonpoint source pollution abatement plan should be continued to reduce the soil loss and pollutants during rainfall, and countermeasures to reduce nonpoint source pollution due to construction need to be established.

• Wind and Structures
• /
• v.31 no.2
• /
• pp.143-152
• /
• 2020

The wind design of buildings is typically based on strength provisions under ultimate loads. This is unlike the ductility-based approach used in seismic design, which allows inelastic actions to take place in the structure under extreme seismic events. This research investigates the application of a similar concept in wind engineering. In seismic design, the elastic forces resulting from an extreme event of high return period are reduced by a load reduction factor chosen by the designer and accordingly a certain ductility capacity needs to be achieved by the structure. Two reasons have triggered the investigation of this ductility-based concept under wind loads. Firstly, there is a trend in the design codes to increase the return period used in wind design approaching the large return period used in seismic design. Secondly, the structure always possesses a certain level of ductility that the wind design does not benefit from. Many technical issues arise when applying a ductility-based approach under wind loads. The use of reduced design loads will lead to the design of a more flexible structure with larger natural periods. While this might be beneficial for seismic response, it is not necessarily the case for the wind response, where increasing the flexibility is expected to increase the fluctuating response. This particular issue is examined by considering a case study of a sixty-five-story high-rise building previously tested at the Boundary Layer Wind Tunnel Laboratory at the University of Western Ontario using a pressure model. A three-dimensional finite element model is developed for the building. The wind pressures from the tested rigid model are applied to the finite element model and a time history dynamic analysis is conducted. The time history variation of the straining actions on various structure elements of the building are evaluated and decomposed into mean, background and fluctuating components. A reduction factor is applied to the fluctuating components and a modified time history response of the straining actions is calculated. The building components are redesigned under this set of reduced straining actions and its fundamental period is then evaluated. A new set of loads is calculated based on the modified period and is compared to the set of loads associated with the original structure. This is followed by non-linear static pushover analysis conducted individually on each shear wall module after redesigning these walls. The ductility demand of shear walls with reduced cross sections is assessed to justify the application of the load reduction factor "R".

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.24 no.9
• /
• pp.142-149
• /
• 2010

Interest in energy efficiency and savings have been rising internationally. For this reason, the domestic housing construction in the area of power equipment is being actively studied. Currently approximately 400,000 per year of domestic housing is being built. Applies to housing construction during the current transformer capacity low utilization and load factor has been applied has been designed. In other words, excessively high reserve capacity has been applied. According to this problem, initial facility costs and power losses will cause because transformer low utilization be appropriated. Thus, the energy efficiency drops. In this paper, analysis of past utilization of the housing transformer, and applying an appropriate demand factor has been analyzing the energy loss reduction. this analysis of current domestic conditions for the proper housing transformer scheme is to calculate the capacity.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.03a
• /
• pp.286-293
• /
• 2005

In soft ground the settlement criterion usually governs. Therefore, it is very important not only reasonable assessment of the allowable bearing capacity of the soil but also reasonable assessment of settlement. In the previous studies by many other researchers, load concentration ratio and settlement reduction factor are usually proposed for estimating the settlement of granular compaction piles. In the previous studies, the reinforced ground with granular compaction piles is simplified as composite ground and the analysis is performed with in the basis of this assumption. However, the lateral deformation of granular compaction pile could not be considered and only the relative vertical strength between pile and soils could be considered in the analysis. In this study, a method adapting the Tresca failure criterion is proposed for calculating settlement of granular compaction pile. Proposed method can be considered the strength of pile material, pile diameter, installing distance of pile and the deformation behavior of vertical and horizontal directions of pile. In the presented study, large-scale field load test is performed and the results are described. Also, predictions of settlements from the proposed method are compared with the results of the load test. In addition, a series of parametric study is performed and the design parameters are analyzed.