• Proceedings of the KIEE Conference
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• 2000.11b
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• pp.315-317
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• 2000

Linear induction motor(LIM) have static and dynamic end effects due to its finite core length, so that per-phase impedances are asymmetric and the air gap flux distribution is distorted. So, this paper propose the d-q axis equivalent circuit and vector control method considering both static and dynamic end effects of the LIM. This vector control method consists of the slip frequency control, the time-invariant control and decoupling control. As a result, it is shown that the results of equivalent circuit method have a goof agreement with the results of finite element method.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.410-411
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• 2019

본 논문에서는 홀 센서를 사용하지 않고 단상 영구자석 동기 전동기의 초기 회전자 자극을 검출하여 안정적인 오픈루프 기동 및 센서리스 운전 기법을 제안한다. 제안한 회전자 초기 자극 검출 방법은 비대칭 공극을 갖는 단상 영구자석 동기 전동기에 고주파 전압을 인가한 후 회전자 초기 극성에 따른 자기회로의 비 포화 및 포화여부를 저역통과필터를 이용하여 빠르게 검출하는 방법을 제안하였다. 제안된 초기 자극 검출 방법은 다수의 실험 결과를 통해 안정적 기동 및 센서리스 운전이 가능함을 입증하였다.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.184-188
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• 1999

Switched Reluctance Motor has doubly salient poles in stator and rotor, windings are wound in just stator and no magnet or windings on the rotor. This configuration is robust mechanically and thermally. The inverter of SRM is more robust than that of induction or brushless DC(BLDC) motor, but still its drive is comparatively expensive for home appliance. To drive the conventional three or four-phase SRM, 6 to 8 power switches are required when asymmetric bridge inverter is employed. Generally, more than 50% of the cost for the SRM drive is allocated to power devices and gate drives. This paper proposed single phase SRM that have both radial and axial air gaps. The stator and rotor were stacked with two types of stampings that have different diameters. This configuration is very effective to increase align inductance(Lmax). The high value of Lmax increases the motor efficiency and power density. The proposed single phase SRM(Claw SRM) can be driven by only two power switches. To show the validity of the proposed idea, the analysis using finite element method(FEM) and experimental works are carried out. The proposed SPSRM can be driven with high efficiency and can be made compactly and inexpensively because of high value of align inductance and less number of switches. For the comparison, we used same stator for three-phase and single phase, and slightly different stator and rotor for proposed single phase SRM(Claw SRM)

• Korean Chemical Engineering Research
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• v.49 no.4
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• pp.498-504
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• 2011

In this research, hollow fiber membranes were used in order to investigate to permeation and selectivity of the $CH_4$ and $N_2$. Polyimide and polyethersulfone hollow fiber membrane were prepared by the dry-wet phase inversion method and the module was manufactured by fabricating fibers after surface coating with silicone elastomer. The scanning electron microscopy (SEM) studies showed that the produced fibers typically had an asymmetric structure. The permeance of $CH_4$ and $N_2$ were increased with pressure and temperature. However, the selectivity was decreased with increasing temperature. The permeances of $CH_4$ and $N_2$ were decreased with increasing the air gap and the effect of post-treatment on membrane showed the increase in permeance up to 3.2~7.0 times.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.8
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• pp.413-424
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• 2002

Recently, in the linear motion system, high performances are required In dynamic characteristics. Vector control method is capable of instantaneous thrust control can meet these high performance requirements. Linear induction motor(LIM) have static and dynamic end effects due to its finite core length, so that per-phase impedances are asymmetric and an air gap flux distribution is distorted. These points of the d-q axis equivalent circuit model considering both end effects is more complicated. This paper proposes the d-q axis equivalent circuit and the vector control method considering both static and dynamic end effects of the LIM. As a result, it is shown that the results of the equivalent circuit method(ECM) have a good agreement with those of the finite element method(FEM).

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.905-911
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• 2009

The viscosity drive method by the wheel which is widely used in the conventional railway systems needs a large friction force between the wheel and the guide-rail, which brings on a thrust force for a quick acceleration and a high-speed travelling. In addition, the viscosity drive method needs an increase of the vehicle weight for a large friction force. However, a maglev train is possible to be driven by the electro-magnet instead of the wheel, which produces a levitation and thrust force without any contact. In general, low-speed maglev train uses a linear induction motor(LIM) for propulsion that is operated under 300[km/h] due to the power-collecting and end-effect problems of LIM. In case of high-speed maglev train, a linear synchronous motor(LSM) is more suitable than LIM because of a high-efficiency and high-output properties. LSM has a driving principle as same as a conventional rotary synchronous motor(RSM), and the torque of RSM becomes the thrust force of LSM. A conventional LSM has relatively large air-gap compared with a conventional RSM. So, it must be achieved a design that is considered normal force by finite-asymmetric structure, end-effect on the entry and exit part, and support structure of a moving part. Therefore, in this research, authors accomplish a conceptualizing and basic design of a small-scaled LSM, and characteristics analysis using FEM.

• Membrane Journal
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• v.15 no.2
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• pp.147-156
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• 2005

It is well-known that polyethersulfone (PES) has high $CO_2$ selectivity over $N_2\;(or\;CH_4)$ and excellent pressure resistance of $CO_2$ plasticization among muy commercialized engineering plastics[1-4]. Asymmetric PES hollow fiber membranes for flue gas separation were developed by dry-wet spinning technique. The dope solution consists of PES, NMP and acetone. Water and water/NMP mixtures are used in outer and inner coagulants, respectively. Gas permeation rate (i.e., permeance) and $CO_2/N_2$ selectivity were measured with pure gas, respectively and the micro-structure of hollow fiber membranes was characterized by scanning electron microscopy. The effects of polymer concentration, ratio of NMP to acetone, length of air gap, evaporation condition and silicone coating were investigated on the $CO_2/N_2$ separation properties of the hollow fibers. Optimized PES hollow fiber membranes exhibited high permeance of $25\~50$ GPU and $CO_2/N_2$ selectivity of $30\~40$ at room temperature and have the apparent skin layer thickness of about $0.1\;{\mu}m$. The developed PES hollow fiber membranes, would be a good candidate suitable for the flue gas separation process.

• Journal of IKEEE
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• v.24 no.4
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• pp.1004-1010
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• 2020

This paper proposes an initial rotor magnetic pole detection method for single-phase permanent magnet synchronous motors. The target motor cannot obtain position information based on the back emf in the low speed and stop state. Therefore, an open loop starting process is required, and in this process, initial rotor position information for low current and soft start is need. The proposed initial rotor magnetic pole detection algorithm considers the effect of asymmetric air- gap and magnetic flux. In addition, the high-frequency voltage signal injection and the offset voltage for accurate detection is used. As a result, the permanent magnet poles are is determined by acquiring the maximum value of the induced current using the virtual dq-axis.

• Membrane Journal
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• v.21 no.4
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• pp.367-376
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• 2011

Huge amount of $CH_4$ mixtures has been emitted from landfills and organic wastes via anaerobic digestion. The recovery of high purity $CH_4$ from these gases has two merits: reduction of green house gases and production of renewable fuels. Membrane technology based on polymeric materials can be used in this application. In this study, asymmetric gas separation hollow fiber membranes were fabricated to develop the membrane-based bio-gas purification process. Polyethersulfone (PES) was chosen as a polymer materials because of high $CO_2$ permeability of 3.4 barrer and $CO_2/CH_4$ selectivity of 50[1]. Acetone was used as a non-solvent additive because of its unique swelling power for PES and highly volatile character. The prepared PES hollow fiber showed excellent separation properties: 36 GPU of $CO_2$ permeance and 46 of $CO_2/CH_4$ selectivity at optimized preparation conditions: 9wt% acetone content, 10cm air-gap and 4wt% PDMS coating processes. With the PES hollow fiber membranes developed, mixed $CO_2/CH_4$ test was done by changing various operating conditions such as pressures and feed compositions to meet the highest recovery of CH4 with 95% purity. High $CH_4$ recovery of 58 wt% was observed at 10 atm feed pressure for the 50 vol% of $CO_2$ in $CO_2/CH_4$ mixture.