• Journal of Power Electronics
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• v.14 no.5
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• pp.866-873
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• 2014

In this paper, a novel 12/8 segmental rotor type switched reluctance motor (SRM) is proposed for cooling fan applications. Unlike conventional structures, the rotor of the proposed structure is constructed from a series of discrete segments, and the stator is constructed from two types of stator poles: exciting and auxiliary poles. Moreover, in this structure, short flux paths are taken and no flux reversion exists in the stator. While the auxiliary poles are not wound by the windings, which only provide the flux return path. When compared with the conventional SRM, the proposed structure increases the electrical utilization of the machine and decreases the core losses, which may lead to a higher efficiency. To verify the proposed structure, the finite element method (FEM) and Matlab-Simulink are employed to get the static and dynamic characteristics of the proposed SRM. Finally, a prototype of the proposed motor was tested for characteristic comparisons.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.3
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• pp.244-251
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• 2010

High speed motors have been widely used in industries to reduce system size and improve power conversion efficiency. However, the high speed motors sometimes suffer from core losses caused by PWM current ripple; noting that the phase inductance, $L_s$, of high speed motor is smaller than that of ordinary motors. In the proposed topology, three PWM inverters are connected in parallel through nine coupled inductors. Compared to the PWM current ripple of the conventional single inverter system, that of the proposed scheme can be conspicuously reduced without the voltage drop at the inductors. In this paper a theoretical analysis of the output voltage of the proposed topology is presented, and then the validity of the proposed method is verified by experimental results.

• Progress in Superconductivity and Cryogenics
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• v.13 no.2
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• pp.9-12
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• 2011

Superconducting motor has a lot of benefits from high power density for ship propulsions, so a number of research project are in progress worldwide. Despite of all the benefits, there is always a difficulty of cryo-moving part for conventional air-core superconducting synchronous motors. In order to get rid of this moving cryogenic part, we propose a homopolar superconducting synchronous motor, which has high temperature superconducting armature and field coils. The rotor is supposed to be made of iron only and excited by the stationary HTS field coils. The stationary field coils make the cooling system simple and easy to realize because there is no cryo-moving part. A design result of a 10 hp homopolar synchronous motor is presented in this paper. The self and mutual inductance of the motor having the size of air gap as variable parameter are calculated by a 3-dimemsional finite element method. The value of design variables such as the dimension of a motor and the number of turns, etc. is decided by performing the coordinate transformation of the calculated inductance. The operating frequency is supposed to be below 5 Hz for low rotating speed which is needed for a purpose of ship propulsion. Low frequency also has the benefit of low AC losses.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.5
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• pp.359-366
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• 2008

A two-dimensional thermal model of proton exchange membrane fuel cell with large active area is developed to investigate the performance of fuel cell with large active area over various thermal management conditions. The core sub-models of the two-dimensional thermal model are one-dimensional agglomerate structure electrochemical reaction model, one-dimensional water transport model, and a two-dimensional heat transfer model. Prior to carrying out the simulation, this study is contributed to set up the operating temperature of the fuel cell with large active area which is a maximum temperature inside the fuel cell considering durability of membrane electrolyte. The simulation results show that the operating temperature of the fuel cell and temperature distribution inside the fuel cell can affect significantly the total net power at extreme conditions. Results also show that the parasitic losses of balance of plant component should be precisely controlled to produce the maximum system power with minimum parasitic loss of thermal management system.

• Advances in Energy Research
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• v.1 no.2
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• pp.117-126
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• 2013

In this paper, core-shell semiconductor quantum dots (QDs) CdSeS/ZnS with emission at 490 nm and 450 nm were investigated for their use in luminescent down-shifting (LDS) layers. Luminescent quantum yield (LQY) of the QDs measurements in solution proposed that they were suitable candidates for inclusion in LDS layers. QDs were encapsulated in poly(methyl,methacrylate) (PMMA) polymer matrix and films were fabricated of $134{\pm}0.05$ microns. Selections of organic dyes from BASF Lumogen F range were also investigated for their use as LDS layers; Violet 570 and Yellow 083. The addition of LDS layers containing Violet 570 dye demonstrated a unity LQY when encapsulated within a PMMA matrix. A PV device of an LDS layer of Lumogen Violet 570 deposited on top of a crystalline silicon cell was fabricated where it was demonstrated to increase the efficiency of the cell by 34.5% relative.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.2
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• pp.130-137
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• 2005

LCD needs a backlight that is a light source as a photodetector that has a light modulation function and CCFL is used usually. Inverter that composes using existent winding transformer operates multi lamps, however, this efficiency falls by losses of core or winding and volume or weight increases or there is danger of fire by overheating. In order to solve these problems, a multi lamp driving Inverter using PT is composed according to the design guideline in this paper. We conformed whether the multi lamp drive method using EEFL that a current burden is less in applicable to piezoelectric inverter, and used the method that connect two piezoelectric transformers by parallel to an inverter.

• Journal of Power Electronics
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• v.15 no.4
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• pp.899-909
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• 2015

A dual-input boost-buck converter with coupled inductors (DIBBC-CI) is proposed as a thermoelectric generator (TEG) power conditioner with a wide input voltage range. The DIBBC-CI is built by cascading two boost cells and a buck cell with shared inverse coupled filter inductors. Low current ripple on both sides of the TEG and the battery are achieved. Reduced size and power losses of the filter inductors are benefited from the DC magnetic flux cancellation in the inductor core, leading to high efficiency and high power density. The operational principle, impact of coupled inductors, and design considerations for the proposed converter are analyzed in detail. Distributed maximum power point tracking, battery charging, and output control are implemented using a competitive logic to ensure seamless switching among operational modes. Both the simulation and experimental results verify the feasibility of the proposed topology and control.

• Transactions on Electrical and Electronic Materials
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• v.18 no.4
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• pp.190-194
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• 2017

Present-day solar panels incorporate inverters as their core components. Switching devices driven by specialized power controllers are operated in a transformerless inverter topology. However, some challenges associated with this configuration include the absence of isolation, causing leakage currents to flow through various components toward ground. This inevitably causes power losses, often being also the primary reason for the power inverters' analog equipment failure. In this paper, various aspects of the leakage currents are studied using different circuit analysis methods. The primary objective is to convert the leakage current energy into a usable DC voltage source. The research is focused on harvesting the leakage currents for producing circa 1.1 V, derived from recently developed rectifier circuits, and driving a $200{\Omega}$ load with a power in the milliwatt range. Even though the output voltage level is low, the harvested power could be used for charging small batteries or capacitors, even driving light loads.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.1
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• pp.57-63
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• 2012

A surfaced permanent magnet spherical motor is capable of operating as three degree of freedom that used for the joints of the robot's arm, leg, and eyes. Ongoing research like new concept is essential part of motor field, it will make a great contribution in the future the overall portion of the motor, is becoming expected. The author analysis torque characteristics in spherical motor with state of rotating and positioning. And future design direction is smaller motors with equivalent or higher output. Solutions as torque and efficiency improvements are selecting the core with special processing type like powder metallurgy materials. Their special characteristic is high permeability and low eddy current losses at high speed, so improved the torque and efficiency.

• Journal of Electrical Engineering and Technology
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• v.11 no.4
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• pp.878-888
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• 2016

Cogging torque has a negative impact on the operation of permanent magnet machines by increasing torque ripple, speed ripple, acoustic noise and vibration. In this paper Magnet Shifting Method has been used as a tool to reduce the cogging torque in inset Line Start Permanent Magnet Synchronous Motor (LSPMSM). It has been shown that Magnet Shifting Method can effectively eliminate several lower-order harmonics of cogging torque. In order to implement the method, first the expression of cogging torque is studied based on the Fourier analysis. An analytical expression is then introduced based on Permanent Magnet Shifting to reduce cogging torque of LSPMS motors. The method is applied to some existing machine designs and their performances are obtained using Finite Element Analysis (FEA). The effect of magnet shifting on pole mmf (magneto motive force) distribution in air gap is discussed. The side effects of magnet shifting on back-EMF, core losses and torque profile distortion are taken into account in this investigation. Finally the experimental results on two prototypes 24 slot 4 pole inset LSPMS motors have been used to validate the theoretical analysis.