• The Transactions of the Korean Institute of Electrical Engineers P
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• v.65 no.2
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• pp.88-93
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• 2016

Soft starters are used with large induction motors in blowers, fans, pumps and the crane hoist drives. AC voltage controllers are used as soft starters in induction motors for starting and to adjust its speed. Soft-starter starting system uses phase control method of input electric source through the setting of the thyristor(SCR) firing angle ${\alpha}$, and it can control input electric source stably and continuously from beginning of starting to ending of starting. In this paper, it is verified that power stack of high-voltage with SCR series system possesses dielectric strength and input electric source is controlled stably by phase control. Especially, from the driving experimental of proposed soft-starter operating, a smoothing acceleration and inrush current decrease can be achieved by the series SCR trigger.

• Journal of Electrical Engineering and Technology
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• v.12 no.3
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• pp.1090-1100
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• 2017

This paper presents the comparison of starting current characteristics of a three-phase induction motor fed by two types of soft starters. The first soft starter under investigation is a conventional AC voltage controller on the basis of a phase-control technique. The other is the proposed asynchronous PWM AC chopper which is developed from the conventional synchronous PWM AC chopper. In this paper, the proposed asynchronous PWM AC chopper control scheme is developed by generating only two asynchronous PWM signals for a three-phase main power circuit (6 switching devices) from a single voltage control signal which is compared with a single sawtooth carrier signal. By this approach, the PWM signals are independent and easy to implement since the PWM signals do not need to be synchronized with a three-phase voltage source. Details of both soft starters are discussed. The experimental and simulation results of the starting currents are shown. It is found that the asynchronous PWM AC chopper efficiently works as a suitable soft starter for the three-phase induction motor due to that the starting currents are reduced and are sinusoidal with less harmonic contents, when being compared with the starting current waveforms using the conventional phase-control starting technique. Also the proposed soft starter offers low starting electromagnetic torque pulsation.

• Food Science of Animal Resources
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• v.27 no.4
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• pp.509-516
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• 2007

Starters of lactic acid bacteria(LAB) were isolated from the commercial yoghurt products and the four isolates have been studied on their identification and some physiological characteristics. For the purpose of identification, microscopic examination, API test, and 16s rRNA gene sequencing were conducted. Isolate A from a yogurt product of local dairy company A was shown to be Gram-positive rod-shaped bacterium. All strains isolated were turned out to be as Lactobacillus paracasei by using a API 50 CHL kit. In contrast, isolate A was identified as a strain of Lactobacillus helveticus based on the 16S rRNA sequencing data, and L. casei ssp. casei for both B and D and L. paracasei for C. All the isolates survived the simulated gastric juice, pH 2.0 within 3 hours and sharply decreased in viability so that no viable cell was observed after 4.5 hours incubation. In addition, the four isolated strains were almost identical in antibiotic susceptibility to six different kinds of antibiotics including erythromycin ($15\;{\mu}g$), ampicillin ($10\;{\mu}g$), gentamycin ($10\;{\mu}g$), neomycin ($30\;{\mu}g$), but rather resistant to colistin ($10\;{\mu}g$) and streptomycin ($10\;{\mu}g$). It was noteworthy that four isolates were confirmed to produce antibacterial substance against foodborne pathogens of Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli 0157:H7 as test organisms based on the inhibitory zones on an MRS soft agar medium. At presence, the inhibitory factor is unknown so that further studies are required to ascertain the active factor responsible for the inhibitory activities.

• Journal of IKEEE
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• v.22 no.2
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• pp.258-265
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• 2018

This paper proposes an algorithm for reducing the starting current when the single-phase induction motor starts and analyzes its operation. Generally, the single-phase induction motors require several starters to generate the starting torque due to their structural characteristics. In this paper, a capacitor-start / capacitor-run method of the single-phase induction motor is basically adopted. This conventional method is efficient and has a large starting torque, but it generates about 5 ~ 6 times of inrush current at startup. As a result, the freezer starting device and peripheral devices are damaged and life time may be reduced. To reduce the inrush current, the current control algorithm based on the virtual dq model is presented to control the starting current. In addition, it validates the proposed algorithm through experiments to smooth transit from start-up operation to the rated operating region.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.817-820
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• 2002

Since a squirrel cage induction motor by NEMA Design types is designed to withstand full-voltage starting, direct starting method can be the most economical one. Starting a squirrel cage motor from standstill by connecting it directly across the line may allow inush currents of approximately 500-600% of rated current at lagging power factor of 35-50%. For many of the large motors, the starting inrush current may be great enough to cause voltage dips, which may adversely affect the building's lighting system. Electric utilities also have restrictions on starting currents, so that voltage fluctuations can be held to prescribed limits. Therefore the need for choosing the most appropriate method of motor starting is quite essential. In this paper, we proposed a plan for the selection of the most appropriate motor starting method, first by way of numeric simulation using manufacturer's data and second by way of actual experience. So far, more often than not, the selection of motor starting method has been accomplished only as regards to the capacity of the motor and the frequency of starting and stopping. But nowadays such high-tech apparatus as soft starters are being developed, and we are on the position to give more attention to clarify the way of selection of the motor starting method.

• Korea Trade Review
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• v.45 no.5
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• pp.1-22
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• 2020

This study explores the role of relationship banking for the exports of SMEs (small and medium sized enterprises) in Korea. Using a sample of SMEs listed on the Korean stock markets between 2004 and 2018, I find that relationship banking has a positive impact on exporting behaviors of SMEs. This result indicates that relationship banking is suitable for SMEs to raise their funds in the export decision-making since the incentive for banks to obtain soft information enhances SMEs' access to external finance. In particular, through further analysis considering financial constraints, I find that the positive impact of relationship banking on exports is amplified for financially constrained SMEs. In addition, the positive impact on exports is also amplified for export starters. Finally, relationship banking provides benefits for SMEs' export decision-making regardless of the financial crisis. To sum up, relationship banking may be useful means of financing for Korean SMEs whose creditworthiness cannot be assessed only by hard information. As the role of finance in international trade has recently been highlighted, this study provides insightful evidence that relationship banking may enhance exports of SMEs as a source of trade finance.

• Journal of Microbiology and Biotechnology
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• v.27 no.10
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• pp.1736-1743
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• 2017

Sourdough is made by fermentation of dough by lactic acid bacteria (LAB) and yeast to improve bread properties like volume, flavor, and texture. A Korean traditional sourdough was made by fermenting rice flour with rice wine (makgeolli) and used to make sponge-like bread (jeung-pyun). The aim of this study was to investigate the microbial diversity of makgeolli products and their influence on the organoleptic quality of jeung-pyun. Three commercial makgeolli were tested for jeung-pyun production, with each product exhibiting varied dough swelling rates and organoleptic qualities, and among them, J-product was ranked highest in texture and taste. Microbial analysis of the three makgeolli also showed a big difference in their population and diversity. J-product had the highest LAB and yeast counts, and the predominant species were Lactobacillus casei, Lactobacillus brevis, Leuconostoc pseudomenteroides, and Saccharomyces cerevisiae. Using J-product, sourdough was fermented at $25^{\circ}C$, $30^{\circ}C$, and $35^{\circ}C$, and the microbial growth in and textural properties of jeung-pyun were examined by instrumental and sensory tests. At high temperature ($35^{\circ}C$), the rates of dough swelling and acidification were fast due to rapid microbial growth mainly caused by LAB, resulting in a short leavening time and soft and sour jeung-pyun. Sensory tests showed consumer preference for the soft and mild-sour jeung-pyun. This study shows that LAB in makgeolli play key roles in production of jeung-pyun, influencing the textural and sensory properties. For the production of high-quality jeung-pyun, development of LAB starters with high gas productivity and low acidity and establishment of an optimal fermentation procedure for rice dough are necessary.