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A Technique of Torque Ripple Reduction in Interior Permanent Magnet Synchronous Motor
Un-Jae Seo,Yon-Do Chun,Jae-Hak Choi,Pil-Wan Han,Dae-Hyun Koo,Ju Lee IEEE 2011 IEEE transactions on magnetics Vol.47 No.10
<P>One of the advantages of interior permanent magnet synchronous motors compared to surface permanent magnet synchronous motors is its convenience when modifying the air gap flux density of permanent magnets. This paper introduces a technique of torque ripple reduction by modifying the shape of the rotor to modify the air gap flux density. Three types of rotor surfaces, such as conventional round, slightly cut, and smoothed cut shape, are investigated. The average torque, torque ripple, cogging torque, phase back-EMF, and air gap flux density distribution are analyzed and compared through finite element analysis (FEA). The validity of the proposed model is also verified by comparison between analysis results and measured results.</P>
General Characteristic of Fractional Slot Double Layer Concentrated Winding Synchronous Machine
Seo, Un-Jae,Chun, Yon-Do,Choi, Jae-Hak,Chung, Shi-Uk,Han, Pil-Wan,Koo, Dae-Hyun The Korean Institute of Electrical Engineers 2013 Journal of Electrical Engineering & Technology Vol.8 No.2
The concentrated winding configurations offer significant advantage for reducing end windings. These machines are generally used in low speed high torque application due to relatively low copper loss. However, numbers of fractional slot construction make the designer hard to properly choose pole and slot numbers for the certain application. This paper provides the general information of possible fractional slot concentrated double layer winding machine.
Un-Jae Seo,Dong-Jun Kim,Yon-Do Chun,Jeong-Jong Lee,Pil-Wan Han 한국자기학회 2019 Journal of Magnetics Vol.24 No.3
Regulation of the efficiency of electric motors worldwide has recently been tightened further because the contribution of electric motors to overall energy consumption cannot be denied. For many years, induction motors have fulfilled tasks in various fields of industry; however, alternative motors have also been gaining attention to realize more cost-effective motors over the long term. It is foreseen that induction motors (IMs) may not be replace-able in single-speed applications, excluding a few special applications; however, applications for which the variation of speed is required offers opportunities for the entry of other motor technologies. Synchronous reluctance motors (SynRMs) are one option that could provide such benefits. This paper provides the experimental results of SynRMs which, under the rated condition, aim to satisfy the IE4 efficiency class. Five Syn- RMs ranging in power through 5.5, 15, 37, 75 to 132 kW have been manufactured and tested for experimental comparison with IMs of equivalent output power.
Seo, Dongwook,Lee, Si Un,Oh, Chang Wan,Kwon, O-Ki,Ban, Seung Pil,Kim, Tackeun,Byoun, Hyoung Soo,Kim, Young Deok,Lee, Yongjae,Won, Yu Deok,Bang, Jae Seung The Korean Neurosurgical Society 2019 Journal of Korean neurosurgical society Vol.62 No.6
Objective : To analyze the angiographic features and clinical course, including treatment outcomes and the natural course, of fusiform middle cerebral artery aneurysms (FMCAAs) according to their location, size, and configuration. Methods : We reviewed the literature on adult cases of FMCAAs published from 1980 to 2018; from 25 papers, 112 FMCAA cases, for which the location, size, and configuration could be identified, were included in this study. Additionally, 33 FMCAA cases in our hospital were included, from which 16 were assigned to the observation group. Thus, a total of 145 adult FMCAA cases were included. We classified the FMCAAs according to their location (l-type 1, beginning from prebifurcation; l-type 2, beginning from bifurcation; l-type 3, beginning from postbifurcation), size (small, <10 mm; large, ${\geq}10mm$; giant, ${\geq}25mm$), and configuration (c-type 1, classic dissecting aneurysm; c-type 2, segmental ectasia; c-type 3, dolichoectatic dissecting aneurysm). Results : The c-type 3 was more commonly diagnosed with ischemic symptoms (31.8%) than hemorrhage (13.6%), while 40.9% were found accidentally. In contrast, c-type 2 was more commonly diagnosed with hemorrhagic symptoms (14.9%) than ischemic symptoms (10.6%), and 72.3% were accidentally discovered. According to location, ischemic symptoms and hemorrhage were the most frequent symptoms in l-type 1 (28.6%) and l-type 3 (34.6%), respectively. Most of l-type 2 FMCAAs were found incidentally (68.4%). Based on the size of FMCAAs, only 11.1% of small aneurysms were found to be hemorrhagic, while 18.9% and 26.0% of large and giant aneurysms were hemorrhagic, respectively. Although four aneurysms of the 16 FMCAAs in the observation group increased in size and one aneurysm decreased in size during the observation period, no rupture was seen in any case and there were no significant predictors of aneurysm enlargement. Of 104 FMCAAs treated, 14 cases (13.5%) were aggravated than before surgery and all the aggravated cases were l-type 1. Conclusion : While ischemic symptoms occurred more frequently in l-type 1 and c-type 3, hemorrhagic rather than ischemic symptoms occurred more frequently in l-type 3 and c-type 2. In case of l-type 1 FMCAAs, more caution is required in determining the treatment due to the relatively high complication rate.
General Characteristic of Fractional Slot Double Layer Concentrated Winding Synchronous Machine
Un-Jae Seo,Yon-Do Chun,Jae-Hak Choi,Shi-Uk Chung,Pil-Wan Han,Dae-Hyun Koo 대한전기학회 2013 Journal of Electrical Engineering & Technology Vol.8 No.2
The concentrated winding configurations offer significant advantage for reducing end windings. These machines are generally used in low speed high torque application due to relatively low copper loss. However, numbers of fractional slot construction make the designer hard to properly choose pole and slot numbers for the certain application. This paper provides the general information of possible fractional slot concentrated double layer winding machine.
Seo, Kyo-Un,Jin, Young-Jae,Kim, Hyojin,Sakaguchi, Toshikazu,Kwak, Giseop American Chemical Society 2018 Macromolecules Vol.51 No.1
<P>Achiral poly(diphenylacetylene)s (PDPAs: pMe3, pEt3, piPr3, pMe2OD1, pMe2ODI, and mMe3) with different alkyl side chains at the para or meta position of the side phenyl ring were prepared to examine achiral-to-chiral transformations upon thermal annealing in a chiral solvent. All the para-substituted PDPAs showed significant circular dichroism (CD) enhancement upon annealing, whereas the meta-substituted polymer, mMe3, was inert to the same treatment. To investigate the kinetics, the asymmetric conformational change was monitored by observing the changes in the magnitude of circular polarization (g(CD)) or optical rotation. PDPAs with bulkier, round-shaped side groups (pEt3 and piPr3) had greater g(CD) values at equilibrium than pMe3 with a smaller side group. Moreover, the activation energy for the forward reaction (Ea(f)) was lower in the bulkier polymers than in pMe3 owing to enhanced miscibility with the chiral solvent. Similarly, the long alkyl chains of pMe2O1 and pMe2ODI acted as internal plasticizers to lower their Ea(f) values relative to that of pMe3, whereas their g(CD) values at equilibrium were smaller than that of pMe3. The kinetics of the achiral-to-chiral transformation is discussed in detail based on the spectroscopic changes observed during the annealing process.</P>