• 한국유체기계학회 논문집
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• 제14권5호
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• pp.24-30
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• 2011

500W class MTG(Micro turbine generator) operating at 400,000 rpm is under development. From the cycle analysis, it is decided that the self-sustaining speed of MTG is 200,000rpm and the generating speed is 400,000 rpm. Therefore, motor should be designed so that it is able to rotate the rotor up to 200,000rpm and generator should designed so that it is able to generate 500W output at 400,000rpm. First step to design motor/generator is to determine the power and efficiency requirement. Not only the power into the compressor and from the turbine at the operating speed but also the mechanical and electrical losses should be considered in determining the power and efficiency requirement. This study presents the procedure and the results of determining the power and efficiency requirement considering the mechanical and electrical losses depending on the rotating speed which is measured from the experiment.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.533-536
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• 2003

YIG(Yttrium Iron Garnet) is one of the most widely used ferrites for microwave telecommunication. It used as a passive devices such as isolators and circulators. In order to reduce the insertion losses of these passive devices, it is very important to reduce magnetic loss of the ferrites. In general, the magnetic losses of ferrites is closely related to the microstructure of the ceramics. In the sintering of YIG, pores are easily trapped in grains and grain boundaries. These pores cause to increase magnetic losses of the sinterted bodies. In this paper, the effect of the $SiO_2$ addition on the microstructure was discussed. Increasing the $SiO_2$ addition, the grain size was reduced, which means that added acts as a grain-growth inhibitor. During the sintering, $SiO_2$ settled down on the grain boundaries, and drag the grain growth. Therefore, there is enough time for pores to move out. The relative density of YIG sintered at $1350^{\circ}C$ with 1 mol% $SiO_2$ addition was 99.6%. $\Delta$H of these samples was under 50 Oe.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2006년도 춘계학술대회 논문집
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• pp.321-326
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• 2006

This paper is proposed an efficiency optimization control algorithm for a synchronous reluctance motor which minimizes the copper and iron losses. The design of the speed controller based on adaptive fuzzy-neural networks(AFNN) controller that is implemented using fuzzy control and neural networks. There exists a variety of combinations of d and q-axis current which provide a specific motor torque. The objective of the efficiency optimization controller is to seek a combination of d and q-axis current components, which provides minimum losses at a certain operating point in steady state. It is shown that the current components which directly govern the torque production have been very well regulated by the efficiency optimization control scheme. The proposed algorithm allows the electromagnetic losses in variable speed and torque drives to be reduced while keeping good torque control dynamics. The control performance of the hybrid artificial intelligent controller is evaluated by analysis for various operating conditions. Analysis results are presented to show the validity of the proposed algorithm.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 F
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• pp.2217-2220
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• 1997

To achieve the high performance speed control of synchronous permanent magnet motor, the influence of iron loss can not be negleced as the increase of driving frequency with high speed operation. This paper proposes a maximum efficiency control algorithm for permanent magnet synchonous motors by controlling the d-axis component of the armature current at any speed and torque. The objective of the optimum efficiency controller is to seek a combination of d-q axis current components which provide minimum input power (minimum losses) at a certain operating point by adding a small amout of perturbation to the d-axis current reference.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.266-271
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• 2003

The numerical study was carried out to effectively cool Induction motor applied to a washing machine. The outer rotor made of steel periodically spins up and down. The stator consists of the thin layered iron plates and copper coil. The effective cooling system is necessary to solve the reliability problem caused by the electric losses at the coil and the iron plate. Because the heat transfer rate of the natural convection in partially open space is generally low, thus it is necessary to enhance the heat transfer using rotating perforated plate. The flow phenomena around the motor are very complex due to the motor geometry and the outer rotor motion. The mixed convection takes place due to the slow rotation speed. The three dimensional flow simulation was performed using rotating reference frame technique and Boussinesq approximation but the radiation effect was neglected. It was found that the angle and direction of the cooling blades play an important role in the stator temperature.

• Journal of Power Electronics
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• 제2권1호
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• pp.67-75
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• 2002

This paper presents the control algorithm for maximum efficiency drives of an induction motor system with the high dynamic performance. This system uses a simple model of the induction motor that includes equations of the iron losses. The model, which only requires the parameters of the induction motor, is referred to a field-oriented frame. The minimum point of the input power can be obtained at the steady state condition. The proposed optimal efficiency control algorithm calculates the reference torque and flux currents for the vector control of the induction motors. A 32 bit floating point TMS320C32 DSP chip implements the drive system with the efficiency optimization controller. The results show the effectiveness of the control strategy Proposed for the induction motor drive.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 추계학술대회 논문집 학회본부
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• pp.86-88
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• 1994

In this paper, we present the design procedure and analysis the fundamental characteristics for Linear DC motor using permeance method and finite element method. Designed LDM is made of two permanent magnets, three iron core and amateur windings. For the design the LDM, first of all it is nessary to calculate the air gap flux density and thrust force, after that to determine core size, the numbers of winding turns, winding width, motor cross section area and losses in the coil. Also, we analysis the fundamental characteristics for implemented LDM according to proposed design procedure, and we find that the implemented LDM generated constant thrust force for costant current as long as iron of core is not saturated. Finally, we find that the proposed design procedure in this paper is effective to design and implementation of LDM.

• 전기학회논문지
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• 제56권5호
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• pp.869-875
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• 2007

Magnetic properties of electrical steel are, in general. measured by using Epstein frame or single sheet tester (SST). These methods, however, require very strict regulation of a specimen in its size and shape. thus, can not be easily applied to various types of specimen. On the other hand, a ring-test method, which measures only the isotropic properties, can be easily applied to most cases because it requires a toroidal-type specimen of arbitrary size. This method, especially, is considered as an unique available method for a bulk-type specimen. In this paper, a ring-test method is developed, and applied to the measurement of magnetic properties of a bulk-type electrical steel with a toroidal-type specimen. In the measurement, the magnetic properties and iron losses are measured and compared with each other at the both sinusoidal magnetic flux density and sinusoidal magnetic field intensity conditions under 0.2Hz and 60Hz alternating magnetic fields excitation. Through experimental measurements, a sinusoidal magnetic flux density condition is proven appropriate for the measurement of magnetic properties, including iron loss characteristics, of electrical steels.

• 조명전기설비학회논문지
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• 제20권1호
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• pp.100-110
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• 2006

자속 역전식 전동기(Flux Reversal Motor: FRM)는 고정자 치 표면에 영구자석을 갖는 구조이며 회전자가 돌극 형태이므로 관성이 적고 기계적으로 강인한 특성을 지녀서 고속기로의 적용이 가능하다. 그러나 단상 FRM은 구조적 특징으로 인하여 영구자석의 감자가 쉽게 일어나며, 고속 구동시 스위칭 주파수가 커짐에 따라 철손이 크게 상승하게 된다는 한계점을 지닌다. 본 논문에서는 유한요소법을 이용하여 단상 FRM의 설계 파라미터가 전동기의 감자특성에 주는 영향을 고찰해보았고 그 해결 방안을 제시하였으며 철손 특성을 분석하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.625-626
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• 2008

The magnetic domain-refining techniques such as ball scratching, laser irradiation and plasma have been developed to reduce the domain wall spacing and thus iron losses in Fe-3%Si grain-oriented silicon steels. In view point of magnetic properties, it was supposed that the locally residual stresses change the magnetoelastic energy of the material and thus the spacing between $180^{\circ}$ domain walls decreases in order to reduce the magnetostatic energy. The effect of laser irradiation on iron loss and magnetostriction reduction for Fe-3%Si grain-oriented steel were investigated. Since the local tensile stresses were induced at the surface of Fe-3%Si steel by the laser irradiation, the minimum iron loss caused by reducing eddy current loss was obtained in spiete of the decrease of permeability by hindering eddy current loss was obtained in spite of the decrease of permeability by hindering the domain wall movement around the induced stress field. Furthermore, the laser treated 3%Si steel has lower magnetostriction as compared to non laser-treated steel and is less sensitive to applying pre-stresses due to the volume reduction of $90^{\circ}$ domain in materials.