• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.45-50
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• 2005

Agricultural water is the main portion of water resources in Korea. And water loss of agricultural water is estimated 6% of all water resources. But studies and data for water loss aren't sufficient. We classified the agricultural water losses and measured the water losses in 6 experimental site. Measurements says that water losses ratio in main canal is 13.8%, water losses for distributing irrigation water is 31.1%. So, the total water losses is about 45%. But the water losses for distributing irrigation water is imperative factor for irrigation, So, it is not right that the water losses for distributing irrigation water is classified water losses and it is necessary to reclassify the agricultural water losses.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.2
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• pp.117-125
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• 2016

In this paper, the inverter switch losses of BLDC motor for three types of PWM methods and power devices were analyzed. When the BLDC motor is driven at low currents, the inverter switch losses for MOSFET are low because MOSFET operates like resistance. However, the inverter switch losses for IGBT are higher than MOSFET due to its large turn-off losses. Moreover, synchronous rectification switching method is adaptable because MOSFET has 2-channel. So, MOSFET can be driven with more low impedance and losses. For low power inverter with MOSFET, the power losses of unified PWM are lower than that of unipolar and bipolar PWM. Proposed method and losses analysis results are verified by examination and simulation using Matlab/Simulink.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.2
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• pp.111-120
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• 2001

This paper aims at estimating instantaneous prestress losses by measuring the actual prestress forces in prestressed concrete (PSC) box girder bridges. Measurement were taken to study initial prestress losses such as friction losses and slip losses. A new strain gauge system was developed to measure strains in internal tendons. The system was installed on a total of 20 tendons in a PSC box girder bridges. The variation of prestress forces were monitored during prestressing tendon and after prestress transfer. The prestress losses are also calculated including friction losses and slip losses. The measured data were compared with the theoretical values. The result shows that the measured prestress forces agree well with the theoretical values. It is shown that prestress force of each strand in the same tendon is a bit different. This study also shows that prestress losses of continuity tendons during prestress transfer are significantly different each other, which results from the variety of buttress location and tendon profile. The present study provides realistic information on the estimation of actual prestress forces and losses in PSC box girder bridges.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.882-883
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• 2011

This paper deals with comparison on Electromagnetic losses of slotted and slotless high-speed PM Machine for Micro Turbine. Losses are consist of core losses, copper losses and eddy current losses. We are using both analytical method and 2D Finite Element Method for more detailed losses analysis. And then We compare Electromagnetic losses of slotted and slotless PM synchronous machine. This machine has designed of a generator of 800W, 400000rpm and a starter of 400W, 200000rpm.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.3
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• pp.143-151
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• 2004

High-speed permanent magnet machines are likely to be a key technology for electric drives and motion control systems for many applications, since they are conductive to high efficiency, high power density, small size and low weight. In high-speed machines, the permanent magnets are often contained within a retaining sleeve. However, the sleeve and the magnets are exposed to high order flux harmonics, which cause parasitic eddy current losses. Rotor losses of high-speed machines are of great importance especially in high-speed applications, because losses heat the rotor, which is often very compact construction and thereby difficult to cool. This causes a danger of demagnetization of the NdFeB permanent magnets. Therefore, special attention should be paid to the prediction of the rotor losses. This paper is concerned with the rotor losses in permanent magnet high-speed machines that are caused by permeance variation due to stator slotting. First, the flux harmonics are determined by double Fourier analysis of the normal flux density data over the rotor surface. And then, the rectilinear model was used to calculate rotor losses in permanent magnet machines. Finally, Poynting vector have been used to investigate the rotor eddy current losses of high-speed Permanent magnet machine.

• International Journal of Air-Conditioning and Refrigeration
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• v.6
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• pp.80-92
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• 1998

A third-order simulation model of a Vuilleumier{VM) heat pump has been developed. This model takes into account the major losses such as the heat conduction losses through regenerators and displacers, the pumping losses and the wall-to-gas heat transfer losses in active volumes, in addition to the heat exchanger and regenerator losses. The working volume was divided into 12 control volumes and the conservation equations of mass and energy were applied to each control volume. Pressure drops were considered in regenerators only. Thermodynamic behavior of the working gas in a VM heat pump was investigated and effects of the major losses and operating conditions on the performance of a VM heat pump were shown.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.3
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• pp.283-287
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• 2013

This paper presents a method for calculating iron losses in three-phase induction motors under the inverter supply through the field-circuit coupled time-stepping finite element method (FEM). Iron losses are calculated by using the three-term iron losses separated model and modifying the loss coefficients obtained by the iron losses curves which are provided by the manufacturer under the sinusoidal supply. Simulation results by the presented method are verified by the measured results with an error lower than 5%, confirming the validity of the proposed method. Finally, iron losses distribution of the inverter-fed three-phase induction prototype motor is shown.

• KEPCO Journal on Electric Power and Energy
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• v.4 no.2
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• pp.47-53
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• 2018

VSC technology is now well established in HVDC and is, in many respects, complementary to the older Line Commutated Converter (LCC) technology. Despite the various advantages of VSC technology, VSC HVDC stations have higher power losses than LCC stations. Although the relative advantages and disadvantages are well known within the industry, there have been very few attempts to quantify these factors on an objective basis. This paper describes methods to determine the operating losses of every component in the valve of VSC-HVDC system. The losses of the valve, including both conduction losses and switching losses, are treated in detail.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1998.10a
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• pp.484-489
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• 1998

The GLEAMS nutrient submodel was evaluated to predict nutrient losses in surface runoff following application of two rates (9 and 18 t/ha) of poultry litter and a recommended rate of commercial fertilizer on corn plots. Nutrient submodel was evaluated with calibrated runoff and sediment losses to the observed field data. Simulation of nitrogen transformation effects on nitrogen losses in surface runoff did not agree with field data. The model simulated higher NH$_4$-N than NO$_3$-N losses in surface runoff, while field data showed the opposite.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2000.02a
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• pp.58-59
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• 2000

The influence of voltage lead and tape arrangements on self-field losses was investigated by using a 1.5m long Bi-2223 tape. Experimental results show that the measured losses are strongly dependent on voltage lead configurations but not contact positions. The losses are independent on frequencies below critical current of the tape. It menas that the self-field losses are purely hysteretic.