• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.1
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• pp.29-37
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• 2007

In the automatic operation of an urban rail vehicle, a conventional PID control algorithm is applied to run the vehicle between stations within time limit and jerk limit. But the energy consumption in the automatic operation is much higher than in the manual operation. In this study, the optimal control algorithm for automatic operation is proposed to minimize energy consumption, which satisfies automatic operation for the urban rail vehicle, compared with the conventional PID control algorithm.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.508-513
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• 2014

Heavy load start but light load operation is a common case in practical drive applications. When an induction motor is employed for such applications, its rated power is usually chosen according to the heavy load start. Then, during light load operation, its efficiency and power factor are low. To solve this problem, it is proposed to adjust the motor windings from the startup to the normal operation conditions. In this paper, arrangement of the adjustable windings is introduced, air gap field with different windings is investigated, and steady state operation performance under various loads is examined. It can be seen that by using proper winding arrangement both startup and operation performances are satisfactory.

• Nuclear Engineering and Technology
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• v.35 no.4
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• pp.261-273
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• 2003

The characteristics of the recirculation operation of LMR which are different from the conventional plants such as PWR and fossil fuel plants were investigated using a computer code TSGS developed in this study. For simulating the transient behavior of the steam generation system, a water level control algorithm utilizing digital control hardware features was introduced. By investigation, the function of the recirculation operation was defined, the major features of the operation were found. Also good performance of the level control algorithm was confirmed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.1
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• pp.223-231
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• 1994

When manufacturing mold dies, an operation sheet is required for each part of the mold dies. The consistent estimation of standard operation time in the operation sheet is difficult, because the estimation is mainly based on subjective judgement. In order to resolve it, concept of feature is introduced in this study. For CAD/CAPP integration, feature technology is being implemented to represent geometrical and technological information of part drawings. A feature database has already been designed, and then used to generate data for process and operation planning modules. Related to this former research, standard operation time is calculated using the feature information and tables used in a real factory.

• Journal of Power Electronics
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• v.19 no.5
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• pp.1099-1107
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• 2019

A soft switching converter with wide voltage range operation is investigated in this paper. A series resonant converter is implemented to achieve a high circuit efficiency with soft switching characteristics on power switches and rectifier diodes. To improve the weakness of the narrow voltage range in LLC converters, an alternating current (ac) power switch is used on the primary side to select a half-bridge or full-bridge resonant circuit to implement 4:1 voltage range operation. On the secondary-side, another ac power switch is adopted to select a full-wave rectifier or voltage-doubler rectifier to achiever an additional 2:1 output voltage range. Therefore, the proposed resonant converter has the capacity for 8:1 (320V~40V) wide output voltage operation. A single-stage hybrid resonant converter is employed in the study circuit instead of a two-stage dc converter to achiever wide voltage range operation. As a result, the study converter has better converter efficiency. The theoretical analysis and circuit characteristics are verified by experiments with a prototype circuit.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.4
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• pp.263-270
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• 2021

Active AC/DC converters with PWM operation are utilized to regulate rectified DC bus voltage of a permanent magnet synchronous generator in the maritime DC power system. A DC bus voltage regulation strategy that exploits the six-step operation is proposed in this study. Compared with that of the PWM operation, switching loss of the converter can be significantly reduced under the six-step operation. Moreover, conduction loss can also be reduced due to the high modulation index and reduced flux-weakening current of the six-step operation. A controller is used for the proposed DC bus voltage regulation strategy to verify its validity with the simulation and experimental setup. The simulation and the experimental test results showed that the converter loss reduces to a maximum of 70% and 19%, respectively.

• International Journal of Advanced Culture Technology
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• v.10 no.4
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• pp.487-498
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• 2022

This study aims to determine the importance of each factor considered when operating a rotorcraft in a city. After identifying factors that could affect urban air mobility, we reviewed the influencing factors by applying an analytic hierarchy process (AHP). Level 1 classifies the essential factors of the urban operation of rotorcraft in nominal and off-nominal situations. The factors corresponding to the characteristics of each were composed of lower levels, such as Levels 2 and 3. Using this, the importance of influencing factors was analyzed and the most important factors were determined. The most influential factors of the urban operation of rotorcraft included engine failure, fire situations, and vehicle safety. Accordingly, an environment that can guarantee safe operation by considering the most influential factors in advance in an actual operation stage must be constructed.

• International conference on construction engineering and project management
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• 2015.10a
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• pp.537-539
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• 2015

considerate operation is a major issue in the equipment-intensive operation. Identifying an optimal equipment combination is important to achieve low-energy operations. An Earthwork operation planning system, which measures the energy consumption of construction operations by taking into account construction equipments' engineering attributes (e.g., weight, capacity, energy consumption rate, etc.) and operation conditions (e.g., road condition, attributes of materials to be moved, geometric information, etc.), is essential to achieve the low-energy consumption. This study develops an automated computerized system which identifies an optimal earthmoving equipment fleet minimizing the energy consumption. The system imports a standard template of earthmoving operation model and compares numerous scenarios using alternative equipment allocation plans. It finds the fleet that minimizes the energy consumption by enumerating all cases using sensitivity analysis. A case study is presented to verify the validity of the system.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.06a
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• pp.187-189
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• 2022

As the structure and operation method of MASS(Maritime Autonomous Surface Ship) are discussed accroding to the IMO degree, the interest and necessity for remote operators who manage and supervise the operation of MASS are increasing gradually. The form of MASS operation is clearly accompanied by various changes including new technologies and equipment in comparison with the current operation of ship. In IMO Degree 2 and 3, the capabilities that remote operators who will operate them must differ from those of existing seafarers(navigation officers, engineers and ratings). Regarding this remote operation, the NI(Nautical Institute) is the first in the world to present a syllabus and a curriculum of qualification for remote operator. Based on this, the paper introduces and compares the education model of MASS remote control operation and NI model, and further uses it as basic data for the creation of curriculum for future MASS remote operator.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.480-483
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• 2001

Recent power quality measurement projects report that voltage sags are the most frequent disturbances in the sites [1]-[4]. DVRs were emerged as the best effective and economic solution for this problem [11]. This paper analyzed the power flow of a DVR in distribution grids. This paper showed various operation modes and boundaries such as inductive operation, capacitive operation, and minimal power operation beside the in-phase compensation.