• Proceedings of the KIPE Conference
• /
• 2005.07a
• /
• pp.687-689
• /
• 2005

Francis turbine of commercial small hydro -power plants under 10kw which is investigate a flow characterist and an efficiency in the research which it sees, the problem and an improvement is investigate. In the research which it is simply model with casing, guide-vane, runner, draft tube for simulation numerical analysis of small-sized Francis turbine. model uses the Gambit and it composes with approximately 800,000 nonuniform lattices. Solutions are investigate the hydraulic characteristics against an outward angle of guide vane, the number of guide vane, head(inlet velocity) by using FLUENT which is a commercial business code.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.28 no.6
• /
• pp.45-51
• /
• 2014

Synchronous generators and induction generators are mainly used in hydroelectric power generation. Synchronous generator is mainly applied to large hydroelectric plants but induction generator is applied to the small hydro power plants. Stability of induction generator is slightly less than the synchronous generator. However, induction generator has many advantages rather than a synchronous generator in terms of price and maintenance. So Induction generator is used primarily in small hydroelectric power station less than 1,000kW recently. Squirrel cage induction generator generates a high inrush current at the grid-connection. This high inrush current causes a voltage drop on the grid. In order to reduce the voltage drop and to analyze the power flow, the analysis for operating characteristics of the induction generator should be reviewed in advance. In this study, we analyzed the voltage drop and power flow analysis when a 1500kW induction generator is connected to the grid. The voltage drop is slightly higher than the acceptable range of distributed power supply voltage and the power flow of the generator is performed well.

• Journal of Korean Society of Forest Science
• /
• v.108 no.4
• /
• pp.562-573
• /
• 2019

In a cable yarding system, a small-scale tower yarder attached to a farm tractor wasdeveloped and used for small-diameter tree harvesting operations. Based on this design, improvement of traction performance was required for medium- and large-diameter tree harvesting operations. In this study, the mechanical transmission employed for the tower yarder was modified into ahydro-mechanical transmission system. Maximum traction forces, including tractor engine speed and hydraulic power pressure, were investigated, and comparisons were made between the mechanical and hydro-mechanical transmission systems. Six tractor engine speeds (1,200, 1,400, 1,600, 1,800, 2,000, and 2,200) and three levels of power transmission mechanism pressure (4.9, 6.9, and 8.8 MPa) were investigated in the two different transmission systems. Results showed a maximum traction force of 15,146.6 N at an engine rotation speed of 757 rpm in the current mechanical transmission system, and 36,140.0 N at anengine rotation speed of 1,575 rpm in the modified hydro-mechanical transmission system. The maximum traction forces for the hydro-mechanical transmission were 2.4 times greater than those of the mechanical transmission, and may therefore be applicable to medium and large-diameter tree harvesting operations. Thus,as a modified version of the conventional transmission system, the new hydro-mechanical transmission system may be cost-effective for use in large-scale cable yarding operations. In the future, however, it will be necessary to investigate problems that may arise from field application tests.

• Proceedings of the KIEE Conference
• /
• 2015.07a
• /
• pp.1469-1470
• /
• 2015

Recently induction generator has been applied to many small hydro power plants. Induction generator needs a reactive power for magnetization. The reactive power of induction generator is being supplied from the supply side mostly. The use of induction generators in the power distribution grid can affect the power factor. The power factor of induction generator is fixed already during production. The power factor in the distribution system is due to the increase or decrease of the load rather than due to the induction generator. In this study, we analyzed how the power factor is changed according to the load increase or decrease in the distribution lines.

• 한국태양에너지학회:학술대회논문집
• /
• 2011.04a
• /
• pp.229-234
• /
• 2011

Feasibility assessment for small hydropower plants using diversion weirs located in stream for agricultural purpose has been studied. The model, which can predict flow duration characteristic of stream, was developed to analyze the inflow caused from rainfall. And another model to predict hydrologic performance for small hydropower plants is established. Preliminary survey was performed identifying several candidate sites, and two sites were selected finally for actual site reconnaissance. During the course of site survey, generating capacity, construction and equipment cost, and payback through life time of each sites were calculated for economical feasibility analysis. The results of this study have estimated that the small hydropower plants using diversion weirs for agricultural purpose may offer better opportunities in future with increasing fuel cost and nation's energy policy.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.25 no.3
• /
• pp.373-380
• /
• 2019

In this paper, a pico hydro turbine employing low head circulation water at fish farms is designed and evaluated. Due to the advantages of simple structures, small head requirements, and low-cost investment, the constant thickness propeller turbine is considered as a feasible solution. The design process based on the free vortex method is presented in full detail, and a 4-blade runner is built using BladeGen. The turbine performance is analyzed both numerically and via experimental methods. Despite slight differences, the results show similar trends between CFD simulations and experiments carried out on factory test-rigs in a wide range of working conditions. At the design flow rate, the turbine achieves the best efficiency of 70 %, generating 3.5 kW power when rotating at 420 rpm. The internal flow field, as well as the turbine's behavior, are investigated through the distribution of blade streamlines, pressure, and velocity around the runner. Moreover, the pressure coefficient on the blade surface at 3 span positions is plotted while the head loss for each simulation domain is calculated and displayed by charts.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.60 no.12
• /
• pp.2225-2229
• /
• 2011

Squirrel cage induction motor is the main driving system of industrial field and familiar with its use in a large variety of applications. However, many engineer are unfamiliar with the induction generator, even though no difference exists between both machines except for the mode of operation. But an induction generator is commonly used for micro & small hydro power applications due to its simplicity, reliability, low cost and robustness. Input and output of induction motor has turned against at the induction generator operation. Rotation speed of induction generator is small faster than induction motor. As output of induction machines increases with the increasement of speed, so loss is same. Actually, generator efficiency is lower than motor at this condition. If induction generator is connected with mechanical load, total efficiency is decreased. In this paper, we analyzed that input, output, torque and efficiency is different from each other above and below synchronous speed.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.26 no.5
• /
• pp.561-568
• /
• 2020

A performance analysis was conducted according to changes in inflow velocity and the tip speed ratio of a portable horizontal-axis hydro turbine that can be used for marine leisure sports and outdoor activities by using the commercial computational fluid dynamics software ANSYS CFX. By using the analysis result and flow field analysis, the design was reviewed and the performance of the device was confirmed. In addition, data necessary to improve the performance of the hydro turbine were acquired by performing an additional performance analysis according to the variable blade pitch angle. The results among the numerical analysis cases show that the highest performance at all inflow velocities and blade pitch angles if achieved at a tip speed ratio of 4. The output power was found to be 30 W even under some conditions below the design flow rate. Among the numerical analysis cases, the highest output power (~ 85 W) and power coefficient (~ 0.30) were observed at an inlet flow rate of 1.5 m/s, a blade pitch angle of 3°, and a tip speed ratio of 4.

• Proceedings of the KIEE Conference
• /
• 2006.07a
• /
• pp.93-94
• /
• 2006

The sheath of a single-conductor cable for ac service acts as a secondary of a transformer, the current in the conductor induces a voltage in the sheath. When the sheaths of single-conductor cables are bonded to each other, as is common practice for multi-conductor cables, the induced voltage causes current to flow in the completed circuit. This current causes losses in the sheath. Various methods of bonding may be used for the purpose of minimizing sheath losses. In korea, sheath cross bonding system was employed for the prevention of sheath losses, the sheaths wire subjected to at voltages, and the bonding was designed to keep the magnitude of the induced voltages within small limits so as to prevent the possibility of sheath corrosion. But, sheath cross bonding system without transposition of cable can not achieve an exact balance of induced sheath voltages unless the cables are lain in trefoil. This paper describes a transposition system with sheath cross bonding using EMTP(Electromagnetic Transient Program). The transposition system with cross bonding can be extended to longer cable circuits for laid in flat as wall as trefoil by the methods described in this paper.

• International Journal of Fluid Machinery and Systems
• /
• v.5 no.4
• /
• pp.152-160
• /
• 2012

Model tests and CFD were carried out to find out the cause of cavitation surge in hydraulic power plants. In experiments the cavitation surge was observed at flow rate, both with and without a surge tank placed just upstream of the inlet volute. The surge frequency at smaller flow rate was much smaller than the swirl mode frequency caused by the whirl of vortex rope. An unsteady CFD was carried out with two boundary conditions: (1) the flow rate is fixed to be constant at the volute inlet, (2) the total pressure is kept constant at the volute inlet, corresponding to the experiments without/with the surge tank. The surge was observed with both boundary conditions at both higher and lower flow rates. Discussions as to the cause of the surge are made based on additional tests with an orifice at the diffuser exit, and with the diffuser replaced with a straight pipe.