• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.633-634
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• 2006

The current unbalance occurs in an induction motor with the supply of unbalanced voltage. Existence of an current unbalance occurs by various problems at the time of driving by in crease of the noise not to mention output decrease of a motor by increase of a loss. We confirmed how current unbalance occurred by a voltage unbalance because a slip came to change by the driving situation of a subordinate as for the induction motor. We confirmed that case to run to a low slip in a ratio of the same voltage unbalance rate brought a high current unbalance rate.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.3
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• pp.213-218
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• 2020

In this study, we propose a control algorithm to reduce the unbalanced characteristics of a three-phase system power caused by the unbalanced load of the AC electric railway. Then, we verify its performance through the design of a power compensator and experiments applying it. Like electric railway systems, a Scott transformer is applied, and the load and single-phase back-to-back converters are connected to the M-phase and T-phase outputs. The back-to-back converter monitors the difference in active power between the unbalanced loads in real-time and compensates for the power by using bidirectional characteristics. The active power is performed through PI control in the synchronous coordinate system, and DC link overall voltage and voltage balancing control are controlled jointly by M-phase and T-phase converters to improve the responsiveness of the system. To verify the performance of the proposed power compensation device, an experiment was performed under the condition that M-phase 5 kW and T-phase 1 kW unbalanced load. As a result of the experiment, the unbalance rate of the three-phase current after the operation of the power compensator decreases by 58.66% from 65.04% to 6.38%, and the excellent performance of the power compensator proposed in this study is verified.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.11
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• pp.713-719
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• 2000

This paper presents an approach toward improving the performance of Moving Coil Type Linear Oscillatory Actuator (MC-LOA) with the application of Finite Element Method (FEM) to a simple control system. MC-LOA has an unbalanced magnetic circuit due to its asymmetric structure and there is a different flux distribution on the air-gap along the current direction. The interaction driven by two fluxes between the Permanent Magnet (PM) and the current causes the unbalanced thrust and interferes with the proper oscillation of MC-LOA. In order to solve the above problems and improve the driving performance, it is necessary to analyze the rate of the unbalanced thrust according to the current direction by using FEM. Then, the analysis results are used to determine the input currents for both directions. Controlling the input currents can be easily achieved by a simple control system, such as Pulse Width Modulation (PWM), without complex units. The validity of the approach is verified by the experimental results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.1992-1998
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• 2014

This paper aims to understand the meaning of balanced development among regional economies and its importance in the s0-called knowledge-based economy. It is shown that the balanced allocation of human capital is necessary to achieve the efficient allocation of physical capital among regional economies, which makes the equality of marginal product of capital. And a simulation experiment is conducted to calculate the cost of unbalanced growth. It is shown that balanced growth among regional economies may increase the growth rate of whole national economy while unbalanced growth among them reduce it. The policy implication is that for an any economy to grow at a higher rate, the efficient allocation of physical and human capital both are necessary to have the balanced growth of regional economies in knowledge-based economy.

• Korean Journal of Community Nutrition
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• v.9 no.2
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• pp.161-172
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• 2004

The dietary habits of middle-aged obese, overweight and normal subjects were evaluated for the purpose of providing the background information of the degenerative disease control. A survey was conducted with 293 subjects (121 males and 172 females) between the ages 40-64 and they were divided into three groups of normal (BMI 18.5-22.9), overweight (BMI 23-24.9) and obese ($BMI\geq25$) based on the criteria of Korean Obesity Association (2000). The mean age of the subjects was $52.0\pm7.3(male)\;and\;51.9\pm6.9$ (female). Socioeconomic levels of subjects belong to the mid-upper class, since 71.9% of the males and 39.5% of the females received above a college education. More than 40% (44.6%) of males and 22.1% of females were obese, and educational background did not affect the obesity rate in males, whereas in females those who received lower education had a higher rate of obesity (p ＜ 0.001). The subjects had a similar degree of drinking to the national average value. but had a lower degree of smoking. The obese group had the higher rate of drinking (p ＜ 0.01) and smoking (p ＜ 0.01). The annual increase in weight, more than 4 kg, was 8.8% for normal group and 30.9% for obese group. However, there were no differences in the mean annual increase in weight among the three groups. In females there were greater tendencies of weight changes in obese group (p ＜ 0.05). About 44.9% of subjects responded that they were exercising regularly, and the obese group appeared to put into practice less than the other groups and to use more strenuous exercise. There was the greater rate of skipping dinner in the obese female group (p ＜ 0.05). The unbalanced dietary pattern was found more with normal group than the other groups (p ＜ 0.01). The food consumption frequency by food groups was not different among the groups. The obese group consumed less frequently meats, vegetables and fruits and had higher frequency in fish, legumes and their products, instant or fast food. In all subjects the higher rate of obesity was found with males than females and with those of heavier smoking and drinking, and in females the higher rate of obesity was found with lower education levels, skipping meals and having an unbalanced diet. In middle-aged subjects of this study with higher educational and socioeconomic background factors contributing to the effects of obesity may include smoking, drinking, educational background, skipping meals or unbalanced dietary pattern. The predictable characteristics for the development of obesity can be defined as sudden fluctuation of weights, exercise regularity and intakes of vegetables and fruits.

• Journal of the Korean Dietetic Association
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• v.18 no.2
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• pp.126-140
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• 2012

The purpose of this study was to investigate elementary school students' perception of food waste as well as to identify factors affecting the plate waste rate of school foodservice in the Gyeongnam area. Questionnaires were distributed to 280 students from June 20 to July 5, 2011 and a total of 279 were analyzed. The results of this study were as follows. First, the main reason of plate waste was 'big portion size', which suggests that portion size should be adjusted. Second, the attitude for food waste reduction was 3.67 based on a 5-point Likert scale (1: strongly disagree, 5: strongly agree). Third, the average plate waste rate of school foodservice was 18.65%. Fourth, there were four factors affecting plate waste rate; balanced/unbalanced diet, satisfaction of school foodservice, need for nutrition education related to food waste, and attitude towards food waste reduction. The plate waste rates of the students who ate a balanced diet were significantly lower than those of the students who ate an unbalanced diet (P<0.001). The plate waste rates of the students who were satisfied with school foodservice were significantly lower than those of the students who were unsatisfied (P<0.001). The plate waste rates of the students who recognized the need for nutrition education were significantly lower that those of the students who did not recognize this (P<0.01). Finally, the students' attitudes towards food waste reduction were significantly negatively correlated with plate waste rate (P<0.01). In conclusion, in order to successfully reduce plate waste in school foodservice, nutrition education should be provided on proper portion size, balanced diet, and food waste. Further, introduction of partial self-service by school foodservice should be reviewed, and strategies for the improvement of school foodservice satisfaction should be applied.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.4
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• pp.695-703
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• 2016

The maintenance method for the electrical facility of high speed railway has been evolved from inspection by personnel to the automated way by the detection devices. In particular, the signalling equipment in order to increase the safe and efficient operation of the trains is required to maintain normal operation by periodic maintenance. Because the return current gives the most important effects to the wayside equipment in case of the failures, a method is needed to measure the unbalanced rate of return current on the train at high speed driving. The Hot Box Detector(HBD) device that is installed at track-side has a function to recognize the abnormal axle box by detecting the temperature that occurs in the axle of train passing over its device. In order to implement the measurement equipment for unbalanced rate of return current and axle temperature, the design method is proposed and the experimental test results by test bed are included in the paper.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.641-643
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• 2005

It is usual to operate the long transmission line with transposition of each phase in order to avoid voltage unbalance due to unbalanced capacitances at each phase of the line end. This paper described the Ferranti voltage rise of line end, charging current and secondary arc current according to the transposition of line or not. The positive and negative sequence current was derived by the phase current, and then the unbalanced rate was calculated. Then, we obtained the reclosing dead time of the single phase reclosing scheme for 500 kV single circuit horizontal arrangement transmission line system.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.6
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• pp.316-324
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• 2003

This paper applied Elite-based Simplex-GA hybrid approach combined with Muptipop-GA (ESGA) to determining the location, size and number of capacitors to improve voltage profile and minimize power losses in unbalanced distribution systems. One of the main obstacles in applying GA to complex problems has been the high computational cost due to their slow convergence rate. To alleviate this difficulty, ESGA approach was developed that combines Elite-based Simplex-GA hybrid approach with Muptipop-GA. The objective function formulated consists of two terms: cost for energy losses and cost related to capacitor purchase and capacitor installation. The cost function associated with capacitor placement is considered as a step function due to banks of standard discrete capacities. Its efficiency was proved through the application in IEEE 13 bus and 34 bus test systems and was compared with several methods using GA.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.5
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• pp.882-889
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• 2010

This paper presents a method of finding the optimal operating point minimizing a given objective function with 3 phase power flow equations and operational constraints, called 3 phase optimal power flow (3POPF). 3 phase optimal power flow can provide operation and control strategies for the distribution systems with distributed generation assets, which might be frequently in unbalanced conditions assuming that high penetration rate of renewable energy sources in the systems. As the solution technique for 3POPF, this paper adopts a simulation-based method of particle swarm optimization (PSO). In the PSO based 3POPF, a utility function needs to be defined for evaluation of the degree in operational improvement of each particle's current position. To evaluate the utility function, in this paper, NR-based 3 phase power flow algorithm was developed which can deal with looped distributed generation systems. In this paper, illustrative examples with a 5-bus and a modified IEEE 37-bus test systems are given.