• 한국자동차공학회논문집
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• 제6권2호
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• pp.235-243
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• 1998

For motor operation at low speeds and loads, torque pulsation by the cogging torque is often a source of vibration and control difficulty. In this paper, the magnetic field of a motor is calculated by finite element method. The periodic cogging torque is determined using Maxwell stress method and time stepping method, and then decomposed using fourier series expansion, The purpose of this paper is to characterize design parameters on the cogging torque and to design a permanent magnet motor with a cogging torque less vulnerable to vibration, without sacrificing the motor performance. The design parameters include stator slot width, permanent magnet slot width, airgap length and magnetization direction. A new design with a less populated frequency spectrum of the cogging torque is proposed after characterizing individual effect of design parameters. Magnet pole edge shaping, by gradually increasing the cogging torque with reduced higher harmonics.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.92-94
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• 2004

This paper presents modeling of dynamic system for slot less air-cored PM linear synchronous motor using space vector PWM. The vector control requires Information about rotor position. And we can need to the Hall sensor for sampling current. In order to agree with this purpose, Digital Signal Processor(TMS320F2406A) developed for implementation of a speed Field Oriented Control.

• 전기전자학회논문지
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• 제22권2호
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• pp.413-419
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• 2018

이중 대역저지 특성을 가지는 UWB(Ultra Wide Band) 안테나를 설계 및 구현하였다. 슬롯을 포함한 평면 방사패치, 스트립선로 양쪽의 기생소자와 아랫면의 접지면으로 제안된 안테나가 구성되어있다. 평면 방사 패치 내에 있는 슬롯과 기생소자가 각각 해당 대역을 저지한다. 슬롯은 WiMAX(World interoperability for Microwave Access, 3.30~3.70 GHz) 대역을, 기생소자는 X-Band(7.25~8.395 GHz) 대역을 저지하는데 각각 기여한다. 제안된 안테나의 설계하고 성능을 평가하는데 Ansoft의 HFSS(High Frequency Structure Simulator)가 사용되었다. 전산모의실험결과는 저지 대역인 3.30~3.86 GHz, 7.21~8.39 GHz를 제외한 구간에서 VSWR(Voltage Standing Wave Ratio)는 2.0 이하를 보였다. 구현된 안테나의 VSWR 측정 결과는 저지 대역인 3.25~3.71 GHz, 7.25~8.46 GHz를 제외한 3.10~10.60 GHz 구간에서 VSWR 값이 2.0 이하로 나타났다.

• 전기학회논문지
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• 제60권9호
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• pp.1783-1787
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• 2011

The slip frequency is included in feature frequency for fault diagnosis of rotor bar, so rotating rotor speed is needed. In this study, rotor slot harmonic(RSH) method is suggested for speed estimation of induction motor. When the rotor is rotating, motor current signal include the harmonic signal of back-emf voltage related with number of rotor slot. So from the power spectrum of current signal, the rotor speed can be founded. This method of rotor speed estimation gives the slip frequency, and the feature frequency of rotor bar fault can be calculated. Comparing with stroboscope speed meter, the error rate of suggested method is less than 0.1[%].

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.131-134
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• 2002

The optimum design technology using combind F.E.M and eauivalent circuit is so fast and accurate that it can be applied to the optimum rotor design of an inverter-fed induction motor in high efficiency motor making industry. The optimum characteristics fer a rotor slot model of a 3 phase inverter-134 nduction motor was previously verified by a time-step F.E.M. In this paper, four verification models with the design variables near the optimum point are designed to chech whether the characteristics of a slot model presented is not less than those of the near models. The outputs of whole models are analyzed in a time-step Finite Element Method and compared in the experimental test. The economical and efficient selecting method of design variables fur the computer simulation and experimental test is presented in order to assure the optimum point.

• Journal of the Optical Society of Korea
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• 제11권4호
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• pp.162-172
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• 2007

Scanning Laser Optical Tweezers(SLOT) is an optical instrument frequently employed on a microscope with laser being delivered through its various ports. In most SLOT systems, a mechanical tilt stage with a mirror on top is used to dynamically move the laser focal point in two-dimensions. The focal point acts as a tweezing spot, trapping nearby microscopic objects. By adding a mechanical translational stage with a lens, SLOT can be expanded to work in three-dimensions. When two mechanical stages operate together, the focal point can address a closed three-dimensional volume that we call a workspace. It would be advantageous to have a large workspace since it means one can trap and work on multiple objects without interruptions, such as translating the microscope stage. However, previous studies have paid less consideration of the volumetric size of the workspace. In this paper, we propose a new method for designing a SLOT such that its workspace is maximized through optimization. The proposed method utilizes a matrix based ray tracing method and genetic algorithm(GA). To demonstrate the performance of the proposed method, experimental results are shown.

• 한국군사과학기술학회지
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• 제25권2호
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• pp.135-143
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• 2022

In this paper, the compact waveguide slot array antenna for interferometric radar altimeter is proposed. The proposed antenna structure consist of corrugation structure which is applied between each channel to improve isolation, three-channel waveguide slot array antenna and feeder. In addition, to reduce the occurrence of phase ambiguity, the baseline spacing of the three-channel antenna is analyzed and the results are applied to the design. For compact design, reduced height and SMP connector structure are used and the dip brazing method which is the conjugation method after dipping to flux is used for the fabrication of the lightweight antenna. The measurement result of the proposed antenna shows less than 1.41 : 1 (VSWR) and 48.3 dBc (isolation). The antenna gain is higher than 20.2 dBi and the side lobe levels are lower than 18.8 dB (vertical plane) and 10.0 dB (horizontal plane).

• 한국전자파학회논문지
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• 제23권10호
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• pp.1145-1150
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• 2012

본 논문에서는 슬롯-결합 선로를 이용한 개선된 쉬프만 위상천이기를 제안하고자 한다. 제안된 쉬프만 위상천이기는 일반적인 결합 선로와 결합 선로 바로 밑에 단순한 직사각형 모양의 슬롯으로 이루어졌다. 슬롯과 결합된 결합 선로의 두 독립적인 전송 모드인 우 모드와 기 모드의 임피던스와 위상 특성을 계산하여 제안된 쉬프만 위상천이기의 위상 특성을 해석하였다. 본 논문에서는 일반 결합 선로로는 구현이 어려운 높은 임피던스 비를 갖는 $90^{\circ}$ 쉬프만 위상천이기를 제작하였다. 동작 중심 주파수는 2.4 GHz로 하였다. 실험 결과, 대역폭은 위상 오차 ${\pm}5^{\circ}$의 위상천이기에서 약 74.2 %의 밴드폭을 얻었다. 또한, 측정 반사 특성은 동작 대역에서 15.0 dB 이하이며, 삽입 손실은 1.5 dB 이하로 측정되었다.

• 한국정보통신학회논문지
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• 제22권1호
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• pp.169-174
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• 2018

본 논문에서는 고조파 억제 응용을 위한 광대역 저역 통과 필터(low pass filter; LPF)에 대한 설계 방법에 대하여 연구하였다. 제안된 광대역 LPF는 동일면 도파관(coplanar waveguide; CPW)의 접지면에 대칭적으로 추가한 4개의 크기가 다른 원형 슬롯 쌍으로 구성된다. 4개의 원형 슬롯 쌍은 결함접지구조 역할을 하며 광대역 저역 통과 특성을 가진다. 직경이 가장 작은 원형 슬롯이 포트 1 측에 위치하고 포트 2측으로 가면서 직경이 커지는 형태로 배치하였다. 각각의 원형 슬롯의 저역 통과 특성을 제안된 광대역 LPF와 비교하였다. 최종 설계된 LPF를 FR4 기판 상에 제작하고 특성을 실험한 결과, 측정된 S11 특성은 1.89-20.00 GHz 대역에서 -3.3 dB 이상을 유지하였고, S21 특성은 2.66-20.00 GHz 대역에서 -21.4 dB 이하를 유지하였다.

• 한국산업보건학회지
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• 제29권2호
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• pp.208-216
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• 2019

Objective: The aim of this study is to control residual chemicals or by-products generated in chambers during preventive maintenance (PM) in the semiconductor manufacturing industry. We designed local exhaust ventilation using computational fluid dynamics (CFD). Methods: The air flow characteristics and capture efficiency between rectangular and slot hoods were compared numerically. The software Fluent 18.1 was used to estimate uniform velocity distribution and capture efficiency for contaminants. A metal from group 15 in the periodic table was released at the bottom of the chamber to simulate emissions. Results: The slot hood had a higher capture efficiency than a rectangular hood under the same conditions because the slot hood provided uniform air flow and higher face velocity. Also, there was no rotating swirl in the plenum for slot, that is why slot had better efficiency than rectangular even though they had similar face velocity. With less than 10 slots, the capture efficiencies for contaminants were nearly 95%. The optimum conditions for a hood to achieve high efficiency was 8 to 10 slots and a face velocity over 1 m/s. Conclusions: Well-designed ventilation systems must consider both efficiency and convenience. For this study, a slot hood that had high capture efficiency and no work disturbance was designed. This will contribute to protection of the worker's health in a PM area and other areas as well. Also, this study confirms the possibility of the application CFD in the semiconductor fabrication industry.