• Journal of the Korean Society of Industry Convergence
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• v.20 no.3
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• pp.213-220
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• 2017

This paper proposes an optimal current control method for improving efficiency of Brushless Direct Current (BLDC) motor. The proposed optimal current control method is based on the maximum torque point analysis of Finite Element Analysis (FEA). The proposed method can increase the effective voltage at the maximum torque point of BLDC motor and increase the output torque per unit current to increase the efficiency. In order to verify the proposed optimal current control method, have developed the prototype of a 50 [W] class motor drive and experimented by 20 [W] motor using the dynamometer set. This was verified.

• Progress in Superconductivity and Cryogenics
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• v.5 no.2
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• pp.1-7
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• 2003

Nowadays, one of the serious problems in KEPCO(Korea Electric Power Co-Operation) system is the more higher fault current than the SCC(Short Circuit Capacity) of circuit breaker. There are many alternatives to reduce the increased fault current such as isolations of bus ties, enhancement of SCC of circuit breaker, applications of HVDC-BTB(High Voltage Direct Current-Back to Back) and FCL(fault current limiter). But, these alternatives have some drawbacks in viewpoints of system stability and cost. As the superconductivity technology has been developed, the HTS-FCL(High Temperature Superconductor -Fault Current Limiter) can be one of the attractive alternatives to solve the fault current problem. Under this background, this paper presents the EMTDC(Electro-Magnetic Transient Direct Current) model for resistance type HTS-FCL considering the nonlinear characteristic of final resistance value when quenching phenomena occur.

• 전기의세계
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• v.16 no.1
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• pp.7-13
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• 1967

There are many kinds of motors operating by rated voltage which is constant. In this paper, the characteristics of separately excited direct current motor is analyzed when its terminal voltage is varied as its load current. As for this source, direct current generator of a series field is used, and it is driven at constant speed by a primemover. The induced voltage of the generator is propotional to its load current but it saturates as its load current is large. The charateristics of motor is studied by analog computer because of the nonlinearity of generator. The results are as follows: (1) The load current and the rotor speed of motor increase as the load of motor increases. But the speed of rotor decreases for the influence of the saturation of the iron of generator field when its load current is large. (2) Decreasing the inertia of motor and increasing the inductance of the armature circuit improve the stability of motor and the region of stable state. (3) By changing the field current of the motor, the speed and the direction of rotor can be controlled in wide range.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.736-741
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• 2005

This paper presents electric characteristics analysis and safe configuration for extension power supply between existent 6.6kV ungrounded distribution system and establishment and improvement 22.9kV direct grounding distribution system. For this, we model 6.6kV ungrounded and 22.9kV direct grounding distribution system of urban underground, ground region. and rural electrical, unelectrical region using PSCAD/EMTDC and analyze voltage drop, charging current, ground and short fault through simulation. To analyze electric characteristics of extension power supply, we simulate extension power supply of overhead line of 6.6kV ungrounded system and underground line of 22.9kV direct grounding system of rural electrical region and propose operation condition for safe extension power supply through result of analysis. Characteristics of voltage drop, charging current, ground and short fault appear almost similarly with electrical characteristic of direct power supply. However, because unbalance of phases may cause relay's malfunction of ungrounded system and ground fault current of direct grounding system may demage facilities of ungrounded system, we propose safe system configuration such as impedance grounding system of neutral point.

• Korean Journal of Agricultural Science
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• v.35 no.2
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• pp.247-262
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• 2008

The purpose of this study is to evaluate farmer's general contents on the current direct payment schemes and to derive some improvement measures, based on the survey data for the three types of direct payment schemes currently executed in Korea; Rice Farmer's Income Support, Early Retirement Aged Farmer's Support and Less Favored Area Direct Payment. In recent years we have introduced diverse direct payment schemes that are expected to have immediate effects in a short term period without enough preparation of the policy, which raises some contradiction between the agricultural policy and the original purpose of the direct payments. The result shows some important revisions should be made related the direct payment schemes, such as farmer's income stability through the improvement of unit payment and the payment length jointed with criteria of the payment, in addition to keeping up multifunctionality of agriculture and enhancing the effect of structural adjustment in agriculture.

• Proceedings of the KIPE Conference
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• 1996.06a
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• pp.109-112
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• 1996

In this paper, we composed utility interactive photovoltaic generation system of current source inverter, and controlled that low harmonic and high power factor are hold by supposing control and compensation method which is concerned with synchronous signal distortion and modulation delay. And we put parallel resonant circuit into dc link, so, magnitude of direct reactance was reduce by restraining direct current pulsation which had accumulation of pulsating power in alternating electrolytic condenser. Also we controlled that modulation factor is operated around maximum output of solar cell.

• The Journal of the Korea Contents Association
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• v.20 no.9
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• pp.520-530
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• 2020

The purpose of this study was to investigate the effects of occupation-based bilateral upper extremity training and transcranial direct current stimulation on upper limb function in stroke patients. The study group was divided into 13 experimental groups with occupation-based bilateral upper extremity training and transcranial direct current stimulation, and 13 controls with only occupation-based bilateral upper extremity training. A total of 4 weeks, 50 minutes, 5 times a week conducted, the patients were tested with Canadian Occupational Performance Measure(COPM), Accelerometer, Fugle-Meyer Assessment(FMA), and Motor Activity Log(MAL). As a result of the study, the experimental group and the control group showed significant improvement in both occupation satisfaction and performance, usage of the affected side and the tendon side, recovery of upper limb function, and quality of movement, In particular, the experimental group showed a significant difference in the amount of the affected side than the control group. Therefore, it was found that the combination of occupation-based bilateral upper extremity training and transcranial direct current stimulation had a positive effect on the recovery of upper limb function in stroke patients.

• Journal of The Korean Society of Integrative Medicine
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• v.7 no.3
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• pp.159-169
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• 2019

Purpose: The purpose of this study was to provide an effective method of exercise therapy for patients with cervicogenic headache. Methods: The subjects were divided into the following three groups according to the intervention received: cervix-stabilizing exercise (n=12, group 1), transcranial direct current stimulation (n=12, group 2), and cervix-stabilizing exercise combined with transcranial direct current stimulation (n=12, group 3). The intragroup and intergroup differences in muscle characteristics and neck disability index were compared and analyzed. Results: The comparison and analysis of the changes in muscle tone and post hoc analysis revealed statistically significant intragroup decreases in the upper trapezius and suboccipitals in groups I and III, and statistically significant intergroup differences in the upper trapezius, with greater changes in group III than in group II, and in the suboccipitals, with greater changes in groupIII than in groups Iand II. The comparison and analysis of the change in muscle stiffness and post hoc analysis revealed a statistically significanti ntra group decrease in the upper trapezius in group Iand suboccipitals in group III, and a statistically significant intergroup difference in both muscles, with greater change in group III than in group II. The comparison and analysis of change in neck disability index and post hoc analysis revealed a statistically significant intragroup decrease in all the three groups and a statistically significant intergroup difference, with greater change in group III than in groups I and II. Conclusion: The neck-stabilizing exercise and transcranial direct current stimulation were shown to be effective in decreasing the tone of the cervical muscles by stabilizing the cervical bone and improving muscle durability, and in improving the movement and limitation of joint range of motion by decreasing muscle tone and stiffness.

• Journal of the Korean Applied Science and Technology
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• v.38 no.6
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• pp.1476-1484
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• 2021

The purpose of this study was to compare the golf performance on transcranial direct current stimulation(tDCS). Ten collegiate golfers were participated. SAMPutt basic unit was used to analyze the kinematic data of putter head. A putting platform and a tDCS were used for putting tasks. It was performed paired t-test to compare between before tDCS and after tDCS. A significant level of .05 using SPSS 24.0. Face at aim and backswing variables of putter head were significantly different during flat putting. Impact spot of putter head was significantly different during 2° of hook slope. However, there were not significantly different others slope angle. It was found that transcranial direct current stimulation had a positive effect on kinematic variables. Based on these results, further research is needed to confirm the effect of transcranial direct current stimulation on body stability during putting task.

• Korean Journal of Optics and Photonics
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• v.14 no.4
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• pp.423-428
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• 2003

In a direct modulated semiconductor laser diode. the structural dependence of current blocking layers was studied in view of the leakage current reduction and the bandwidth expansion. To analyze the leakage current and the parasitic effects, the current-voltage derivation characteristics and the subtraction method were used, respectively. It was shown that the‘inin’type current blocking structure might be the best choice for the purpose of the static and dynamic characteristics.