• Journal of Electrical Engineering and Technology
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• v.13 no.6
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• pp.2364-2375
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• 2018

Two-phase simultaneous excitation mode of the switched reluctance motor (SRM) has been shown to effectively improve the average torque output compared with traditional single-phase excitation mode. But the torque ripple of the two-phase excitation SRM with traditional winding distribution increases because of the inconsistent electromagnetic field. To reduce the torque ripple, a two-phase excitation 8/6 SRM with novel winding distribution is proposed in this paper. The static torques generated by various magnetic circuits are analyzed and obtained to verify the torque increase. Then the electromagnetic characteristics of the proposed SRM are investigated by the numerical calculation method in detail, including flux linkage, inductance, and torque. Finally, an experiment for measuring the SRM static electromagnetic characteristics and dynamic performance is designed and performed based on the novel mode, and the comparing results show that the proposed two-phase SRM is effective.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.150-152
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• 2000

This paper introduces an advanced three-phase load flow analysis algorithm in the radial distribution network. This method is an extension of the Novel method for solving radial distribution networks with the emphasis on expanding from single phase to three-phase. The proposed method involves only simple algebraic computation without any form of Jacobian matrix but has a desirable convergence characteristic. Computationally, The suggested technique is very efficient and requires less computer memory storage and maintains high execution speed. Also, the submitted process can be easily programmed and be simply extended to different types of load characteristics. A simulation results applied to the IEEE 34 bus radial distribution feeder are examined by using the MATLAB.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.8 s.251
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• pp.780-787
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• 2006

Several types of different header designs are numerically studied to have uniform distribution of two phase flow in the evaporator header having multi-channels. The different geometries include the inlet tube position into the header and the width of header. In the numerical calculation, two types of two-phase model such as homogeneous model and VOF(Volume Of Fluid) model are employed. In this study, the mal-distribution number, $M_d$, is newly defined to evaluate the averaged level of the flow distribution in the whole passes of the evaporator. As results, two phase flow in the header can be visualized using post-processing of numerical results. Furthermore, the optimum position of the inlet tube into the header and the width of header can be proposed for the better distribution of refrigerant(R-134a) flow.

• Journal of Electrical Engineering and Technology
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• v.8 no.2
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• pp.215-222
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• 2013

Electrical power distribution systems are critical links between the utility and customer. In general, power distribution systems have unbalanced feeders due to the unbalanced loading. The devices that dependent on balanced three phase supply are affected by the unbalanced feeders. This necessitates the balancing of feeders. The main objective of reconfiguration is to balance the loads among the phases subject to constraints such as load flow equations, capacity and voltage constraints and to reduce the real power loss, while subject to a radial network structure in which all loads must be energized. Therefore, the distribution system reconfiguration problem has been viewed as multi-objective problem. In this paper, the hybrid heuristic algorithm has been used for reconfiguration, which is the combination of fuzzy and greedy algorithms. The purpose of the introduction of greedy is to refrain the searching for the period of phase balancing. The incorporation of fuzzy helps to take up more objectives amid phase balancing in the searching. The effectiveness of the proposed method is demonstrated through modified IEEE 33 bus and modified IEEE 125 bus radial distribution system.

• Polymer(Korea)
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• v.25 no.5
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• pp.744-753
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• 2001

One of the most important factors which affect the impact strength of high impact polystyrene (HIPS) is the rubber-phase particle size and size distribution. In this study, HIPS was prepared from a batch reactor to observe the influence of reaction conditions such as rubber content, agitation speed and prepolymerization time on the particle size and size distribution. Measurements concerning the particle size distribution were conducted using a particle size analyzer. Due to swelling, the particle suspended in toluene increases in size with lower heat-treatment temperature and shorter heat-treatment time, while the particle in methyl ethyl ketone shows quite reasonable size without any effort of heat-treatment. As rubber content increases, the average particle size increases substantially, but the increase in agitation speed at lower rubber contents does not have much influence on the size. However, the polystyrene-phase particles occluded in rubber-phase become more uniform as agitation speed increases. Longer prepolymerization time produces rubber-phase particles with narrower particle size distribution.

• Progress in Superconductivity
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• v.5 no.2
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• pp.144-148
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• 2004

Uniform current distribution among conductor layers in HTS cables using IPTs (inter-phase transformers) was investigated. Conventional methods for current distribution, in which resistors are inserted to conductor layers, causes additional loss. In contrast, IPTs, which use magnetic coupling, make it possible that the current in parallel circuits is distributed uniformly with any load, and minimize the loss. In this study, IPTs were designed and fabricated for examination of uniform current distribution in the conductor layers of HTS cables. The ITP was designed through calculation of its impedance that can cancel the inductance of the conduction layers. The experimental setup consisted of four IPTs and four inductors that simulate the conductor layer inductance. Each layer was designed to feed 10 A. We examined the behavior of current distribution with IPTs for various layer inductances.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.19 no.4
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• pp.443-457
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• 2015

We consider the M/M/c/c queues in which the customers blocked to enter the service facility retry after a random amount of time and some of idle servers can leave the vacation. The vacation time and retrial time are assumed to be of phase type distribution. Approximation formulae for the distribution of the number of customers in service facility and the mean number of customers in orbit are presented. We provide an approximation for M/M/c/c queue with general retrial time and general vacation time by approximating the general distribution with phase type distribution. Some numerical results are presented.

• KIEE International Transactions on Power Engineering
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• v.3A no.2
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• pp.79-84
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• 2003

Unbalanced systems, such as distribution systems, have difficulties in fault locations due to single-phase laterals and loads. This paper proposes new fault locations developed by the direct three-phase circuit analysis algorithms using matrix inverse lemma for the line-to-ground fault case and the line-to-line fault case in unbalanced systems. The fault location for balanced systems has been studied using the current distribution factor, by a conventional symmetrical transformation, but that for unbalanced systems has not been investigated due to their high complexity. The proposed algorithms overcome the limit of the conventional algorithm using the conventional symmetrical transformation, which requires the balanced system and are applicable to any power system but are particularly useful for unbalanced distribution systems. Their effectiveness has been proven through many EMTP simulations.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.10
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• pp.509-516
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• 2001

Isolated phase bus(IPS) has a special structure for carrying large current generated by a generator to a main transformer. In the analysis of IPB, the understanding of the magnetic field distribution generated by large current is important. Especially, while the bus conductor current is flowing, almost same amount of current as bus conductor current is induced in the enclosures under the influence of time varying magnetic field, and therefore the large electric loss and the deterioration of insulating capability might occur due to Joule heating effect. Hence for the optimal design of IPB satisfying the condition to minimize the loss, the accurate analysis of magnetic field distribution and the eddy current characteristics of three phase isolated phase bus have been investigated. In the analysis of time varying magnetic field, instead of finite difference method(FDM) which is generally used, finite element method with phasor concept is investigated under the assumption that the bus current is purely sinusoidal. The characteristics is studied along the phase angle by comparing the effect of eddy current on the magnetic field distribution with the case that eddy current is not considered, and also the effect of material, thickness and radius of enclosure on the eddy current distribution is discussed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.9
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• pp.741-748
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• 2002

The present study investigated the two-phase flow characteristics of refrigerant R-22 in T-branch with horizontal and vertical inlet tube The key experimental parameters were the orientation of inlet and branch tubes (horizontal and vertical), diameter ratio of branch tube to inlet tube (1 and 0.61), inlet mass flux (200~500 kg/$m^2$s) and inlet quality (0.1~0.4). Predicted pressure profile agreed with the measured data within 25.4%. The flow distribution ratio decreased as the mass flux increased. The flow distribution ratio decreased by 12~25% as the tube diameter ratio decreased from 1 to 0.61, and decreased by 38~47% as the orientation of branch changed from horizontal to vertical upward for horizontal inlet tubes. As the orientation of inlet tube changed from horizontal to vertical upward for horizontal branch, the flow distribution ratio increased by 15~68%, but the quality in the branch tube decreased by 28~92% due to phase separation.