• Wind and Structures
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• 제28권6호
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• pp.369-380
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• 2019

Statistical distributions are very useful in describing wind speed characteristics and in predicting wind power potential of a specified region. Although the Weibull distribution is the most popular one in wind energy literature, it does not seem to be able to perfectly fit all the investigated wind speed data in nature. Thus, many studies are still being conducted to find flexible distribution for modelling wind speed data. In this study, we propose a new Odd-Burr Rayleigh distribution for wind speed characterization. The Odd-Burr Rayleigh distribution with two shape parameters is flexible enough to model different shapes of wind speed data and thus it can be an alternative wind speed distribution for the assessment of wind energy potential. Therefore, suitability of the Odd-Burr Rayleigh distribution is investigated on real wind speed data taken from different regions in the South Africa. Numerical results of the conducted analysis confirm that the new Odd-Burr Rayleigh distribution is suitable for modelling most of the considered real wind speed cases and it also can be used for predicting wind power.

• 대한조선학회논문집
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• 제58권6호
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• pp.366-374
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• 2021

This paper presents the analysis of the speed-power performance in the real sea using a large container vessel data provided as a test bed from a shipping company. To perform a speed trial of the vessel during a commercial voyage, the on-board measuring device and various operation data acquisition systems were mounted on the vessel for long-term performance monitoring and the voyage operated under the container loading condition close to the design draft was adopted. The content of this paper consists of Part I and Part II. Part I, such as this paper, contains the speed trial method and analysis results of the operating vessel. Part II contains the analysis of the speed-power characteristics change over time and before and after hull cleaning using operation data measured from the voyage operated under a condition similar to the speed trial.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.3052-3058
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• 2011

A high-speed train is the system that the electric power is supplied through the overhead contact line and drives motors. In this case that the de-wiring beteen the overhead contact line and the pantograph of a high-speed train, the occasion that smooth power supply is not accomplished occurs sometimes. If the de-wiring occurs, the arc discharge may damage the overhead contact line or the pantograph, and the falling-off in power quality may cause the damage and malfunctioning of motor block. This paper presents the methodology that the arc discharge by de-wring between overhead line and pantograph is discriminated through measuring the PT and CT in the vehicle, and measures the current collection characteristics for a high speed train.

• 대한기계학회논문집
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• 제14권2호
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• pp.349-357
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• 1990

Power transmission characteristics and speed ratio-torque load-axial force relationship for a metal V-belt CVT were investigated theoretically and experimentally. In the metal V-belt CVT drive, it was found that the power was transmitted by thrust force and that band tension should be greater than compression force between the metal blocks. The experimental results for the speed ratio-torque load-axial force relationship showed good agreement with those predicted using equations developed from theoretical considerations.

• 동력기계공학회지
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• 제21권4호
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• pp.5-17
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• 2017

This study focuses on the application of the PEM Fuel Cell(PEMFC) hybrid system, which includes a regenerative braking system with supercapacitor(SC) and battery. The purpose of this study is to evaluate the characteristics of regenerative energy and to propose solutions to increase regenerative energy via vehicle simulation. To achieve this target, we set the rated motor speed to 3,000/2,500/2,000 rpm. Because the flywheel is directly connected to the motor, the generator activates regenerative braking by using the rotational momentum of the flywheel when the flywheel reaches the set speed after the motor stops. We could then measure the characteristics of regenerative braking of voltage, current, power, energy change, etc. Meanwhile, we calculate the storage efficiency of the SC or the battery. Our results show that the SC stores 18% of the regenerative energy, while battery stores 15% of the energy. Since the regenerative energy decreases with the decrease of the motor rotating speed that 5,027 J and 2,915 J are restored at 3,000 and 2,500 rpm, respectively. The experimental results also prove that regenerative braking energy is able to be obtained if and only if the speed of flywheel is over 2,500 PRM, and the efficiency of the system can be further improved.

• 전기학회논문지
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• 제62권12호
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• pp.1668-1677
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• 2013

This paper deals with the power loss and thermal characteristics of induction motor for machine tools according to the rated power and speed. To reduce the fabrication error by thermal strain in rotational machine tools, we calculated the power loss and thermal behavior of induction motors. Firstly, the inverse design of general induction motors for machine tool spindle has been performed. The inverse design results are compared with the torque-speed characteristic curve in motor's catalog. The power loss are calculated by finite element method(FEM) at rated condition. Secondary, the transient thermal characteristics of induction motors are calculated by equivalent thermal resistance model from Motor-CAD S/W. The inverse design, power loss and thermal behavior calculation for induction motors with various rated power and speed has been performed. Finally, to verify the design and calculation process of induction motor, we implemented the experimental set with 0.4kW 1710rpm class industrial induction motor model. The obtained thermal characteristics of experimental model confirmed that the design and power loss calculation processes are appropriate to the prediction of thermal strain in rotational machine tools.

• 동력기계공학회지
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• 제20권3호
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• pp.51-56
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• 2016

In this study, the tensile tests and hardness tests were carried out for the joints characteristics in friction stir welds of Al 5052 alloy. Three way factorial design was applied to optimal welding conditions, whose control factors were shoulder diameter, rotation speed and welding speed of tool. From the results of this study, the optimum condition for maximum yield strength was predicted as the shoulder diameter of 15 mm, welding speed of 500mm/min and rotating speed of 1000 rpm. And the presumed optimal yield strength was estimated to be $167.36{\pm}7.82MPa$ with 99% reliability. In addition the increaser rotation speed of tool and the decreaser welding speed, the decreaser the hardness at welding part.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.565-568
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• 2005

This paper presents dynamic characteristics of super high speed SRM and it's drive. The nonlinear model of super high speed SRM is implement by Matlab/simulink and the simulation results show that the prototypeSRM can operate up 20,000[rpm]with stable performance.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2017년도 전력전자학술대회
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• pp.577-595
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• 2017

${\bullet}$ Silicon Carbide (SiC) had excellent material properties as the base material for next generation of power semiconductor. In developing SiC MOSFET, gate oxide reliability issues had to be first overcome before commercial application. Besides, a high and stable gate-source voltage threshold $V_{GS(th)}$ is also an important parameter for operation robustness. SiC MOSFET with such characteristics can directly use existing high-speed IGBT gate driver IC's. ${\bullet}$ The linear voltage drop characteristics of SiC MOSFET will bring lower conduction loss averaged over full AC cycle compared to similarly rate IGBT. Lower switching loss enable higher switching frequency. Using package with auxiliary source terminal for gate driving will further reduce switching losses. Dynamic characteristics can fully controlled by simple gate resistors. ${\bullet}$ The low switching losses characteristics of SiC MOSFET can substantially reduce power losses in high switching frequency operation. Significant power loss reduction is also possible even at low switching frequency and low switching speed. in T-type 3-level topology, SiC MOSFET solution enable three times higher switching freqeuncy at same efficiency.

• 동력기계공학회지
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• 제5권3호
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• pp.11-16
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• 2001

In the DI diesel engine of passenger cars, common rail injection system have been used to improve the engine performance and reduce the exhaust emission by controlling injection timing, injection pattern, and injection duration. In case that common rail injection system is applied to high speed DI diesel engine, it is necessary to have high response and good repetition characteristics. These characteristics of injector depend on the characteristics of solenoid. Thus, to apply the common rail injection system in the high speed diesel engine, we had designed and made a multi-pole solenoid, and carried out repetition, response test to compare the multi-pole solenoid with the gasoline Injector solenoid. The result shows that repetition and response characteristics of multi-pole solenoid have better characteristics than the gasoline injector solenoid.