• Journal of Magnetics
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• v.16 no.1
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• pp.64-70
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• 2011

Surface-mounted permanent magnet (PM) machines were examined experimentally and theoretically, through power loss measurements and calculations. Windage, friction and copper losses were calculated using simple analytical equations and finite element (FE) analyses. Stator core losses were calculated by determining core loss coefficients through curve-fitting and magnetic behavior analysis through non-linear FE calculations. Rotor eddy current losses were calculated using FE analyses that considered the time harmonics of phase current according to load. Core, windage and friction open-circuit losses and copper loss were determined experimentally to test the validity of the analyses.

• Proceedings of the KIEE Conference
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• 1995.07b
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• pp.528-530
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• 1995

In the conventional power flow calculations, the slack bus is assumed to undertake the total transmission loss for the convenience of numerical computation. This is an unrealistic assumption because, in real power system, the transmission loss is supplied by all the generators and makes the power flow calculation results somewhat distorted. This paper proposes a new loss redistribution algorithm that can reduce the distortion of power flow results. In the proposed method, the system power loss redistribution algorithm is added to the conventional power flow equations and jacobian elements that are related the real power are newly constructed. In each iteration step, the power output of each generator is updated to consider the effect of calculated total power losses. Finally the usefulness of proposed method are tested through the some appropriate case studies.

• Journal of Power Electronics
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• v.16 no.4
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• pp.1598-1611
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• 2016

In some special occasions with strict size requirements, such as mine hoists, improving the design accuracy of the forced-air cooling systems of NPC three-level inverters is a key technology for improving the power density and decreasing the volume. First, a fast power-loss calculation method was brought. Its calculation principle introduced in detail, and the computation formulas were deduced. Secondly, the average and dynamic power losses of a 1MW mine hoist acting as the research target were analyzed, and a forced-air cooling system model based on a series of theoretical analyses was designed with the average power loss as a heat source. The simulation analyses proves the accuracy and effectiveness of this cooling system during the unit lifting period. Finally, according to an analysis of the periodic working condition, the maximum power-loss range of a NPC three-level inverter under multi cycle operation was obtained and its dynamic power loss was taken into the optimized cooling system model as a heat source to solve the power device damage caused by instantaneous heat accumulation. The effectiveness and feasibility of the optimization design based on the dynamic power loss calculation of the maximum power-loss range was proved by simulation and experimental results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.11
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• pp.1651-1657
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• 2015

In MHz operating wireless power transfer systems, skin- and proximity-effect losses in the transmitter and the receiver coils dominate the coil-to-coil efficiency of the system. A Litz-wire was regarded as a common solution for minimizing such Ohmic losses in high frequencies. In this paper, equivalent series resistances of 12 different cables including Litz-wire and copper tubing have been calculated and measured for a 6.78 MHz, 100W, 30 cm wireless power transfer system. It has been shown that the copper tubing has lower resistances compared to the Litz-wire in that frequency and a wireless power transfer system with the copper tubing was able to achieve much higher efficiency than a system using the Litz-wire. Calculations of the resistances and efficiencies were accomplished with analytical equations and those calculations were evaluated by experimental results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.3
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• pp.117-124
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• 2007

This paper is about the Extra-High voltage distribution system in the customer's area. The power loss in the distribution system in the customer's area is disregarded and rarely managed so far. But, economically, this loss is not small quality to ignore. So, in this paper, we calculate the power loss of the Extra-High voltage distribution system in the customer's area by changing the locations of power transformer and other power facilities to decrease power loss in decreased secondary line length. And we also show the payback time of the proposed Extra-High voltage distribution system in the customer's area by simplified calculations.

• Nuclear Engineering and Technology
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• v.41 no.3
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• pp.307-318
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• 2009

KAERI (Korea Atomic Energy Research Institute) has developed the GAMMA+ code for a thermo-fluid and safety analysis of a VHTR (Very High Temperature Gas-Cooled Reactor). A key safety issue of the VHTR design is to demonstrate its inherent safety features for an automatic reactor power trip and power stabilization during an anticipated transient without scram (ATWS) accident such as a loss of forced cooling by a trip of the helium circulator (LOFC) or a reactivity insertion by a control rod withdrawal (CRW). This paper intends to show the ATWS assessment capability of the GAMMA+ code which can simulate the reactor power response by solving the point-kinetic equations with six-group delayed neutrons, by considering the reactivity changes due to the effects of a core temperature variation, xenon transients, and reactivity insertions. The present benchmark calculations are performed by using the safety demonstration experiments of the 10 MW high temperature gas cooled-test module (HTR-10) in China. The calculation results of the power response transients and the solid core temperature behavior are compared with the experimental data of a LOFC ATWS test and two CRW ATWS tests by using a 1mk-control rod and a 5mk-control rod, respectively. The GAMMA+ code predicts the power response transients very well for the LOFC and CRW ATWS tests in HTR-10.

• Journal of Mechanical Science and Technology
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• v.18 no.3
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• pp.481-490
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• 2004

Steady state flow calculations are executed for turbo-pump inducers of modern design to validate the performance of Tascflow code. Hydrodynamic performance of inducers is evaluated and structure of the passage flow and leading edge recirculation are also investigated. Calculated results show good coincidence with experimental data of static pressure performance and velocity profiles over the leading edge. Upstream recirculation, tip leakage and vortex flow at the blade tip and near leading edge are main sources of pressure loss. Amount of pressure loss from the upstream to the leading edge corresponds to that of whole pressure loss through the blade passage. The viscous loss is considerably large due to the strong secondary flow. There appears more stronger leading edge recirculation for the backswept inducer, and this increases the pressure loss. However, blade loading near the leading edge is considerably reduced and cavitation inception delayed.

• KIEE International Transactions on Power Engineering
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• v.3A no.1
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• pp.35-41
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• 2003

To ensure resource adequacy in restructured electricity markets, policymakers have adopted installed capacity (ICAP) markets in some regions of the United States. These markets ensure that adequate generation exists to satisfy regional Loss of Load Probability(LOLP) criterion. Since the incentives created through ICAP mechanisms directly impact new generation and transmission investment decisions we examine one important factor that links ICAP markets with LOLP calculations;, determining the amount of ICAP credit assigned to particular generation units. First, we review and critique the literature on electric power systems' market failure resulting from demand exceeding supply. We then summarize the method of computing (the LOLP) as a means of assessing reliability and relate this method to ICAP markets. We find that only the expected value of available generation is used In current ICAP markets while ignoring the second and higher order moments, which tends to mis-state the ICAP value of a specific resource. We then consider a proposal whose purpose is to avoid this ICAP assignment issue by switching from ICAP obligations to options. We find that such a proposal may fail to not provide the benefits claimed and suffers from several practical difficulties. Finally, we conclude with some policy recommendations and areas for future research.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.5A
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• pp.517-525
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• 2008

In this paper, we cary out system level simulations to investigate the effect of cell shape(i.e., different base station displacements in the two directions defined by the street grid) on minimizing transmitter power, interference power, and blocking probability for CDMA system in urban microcellular environments. In urban microcell, path loss to the base station depends on the orientation of the street where the mobile is located. Interference from mobile stations to the base station in the reference cell is considered up to second tier. The wrap around method is used to include the second tier interference with realistic computational complexity without reducing the accuracy of interference calculations. The investigation shows that the transmitter power, interference power, and blocking probability in a cell can be reduced by proper selection of the efficient cell shape.

• Nuclear Engineering and Technology
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• v.20 no.3
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• pp.145-154
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• 1988

This paper is a study on an accurate and computationally efficient method for reconstructing pointwise power distributions from coarse-mesh nodal calculations. The modern nodal codes can calculate global reactor power shapes and criticality very efficiently and accurately. But inherent in the nodal procedures, there is inevitable loss of information on local heterogeneous quantities. In this study, an improved form function method which reflects the exponential transition of the thermal flux near the assembly surface is developed for the reconstruction of the heterogeneous fluxes. Use of the new form function method in several pressurized water reactor (PWR) benchmark problems reduces the maximum errors in the reconstructed thermal flux to those in the reconstructed fast flux. Even for assemblies adjacent to the steel baffle in realistic PWR cores, use of this method also results in improved pointwise power reconstruction.