• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1338-1343
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• 2000

This paper deals with an application of Magneto-Rheological (MR) fluid to a small size mount for precision equipment of automobiles. MR fluid is known as a class of functional fluids with controllable apparent viscosity of fluid by the applied magnetic field strength. A typical MR fluid is a suspension where pure iron particles of $1{\sim}20mm$ in diameter are dispersed in a liquid such as mineral oil or silicone oil, at the concentration of $20{\sim}40$ vol%. Electro magnetic coil is installed at the bottom of a variable-damping mount filled with MR fluid, and its performance was investigated experimentally. Furthermore, the properties of the MR Mount on experimental Study were explained analytically by mechanical model of the MR mount.

• 소음진동
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• 제5권1호
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• pp.59-65
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• 1995

In this study, we investigated the operational limit of magnetic bearing-rotor system due to the maximum force limit and slew rjate limit of the electromagnetic actuator as a function of the time dependent control characteristics. The feedback gain of the controller varies the current of the electromagnet coil with the motion of the rotor. The distorsion of magnetic force due to the slew rate limit is not occurred jup to 30, 000 rpm in the magnetic bearing that we have a close relation with the rotational speed and vibration level of the rotor and the proportional gain of the controller. Therefore the maximum force limit determines the maximum allowable orbit radius of the magnetic bearing-rotor system. The maximum allowable vibration levels are exponentially decreased according to the increment of rotational speed and proportional gain of the controller.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.510-513
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• 2003

The paper represents the stability of a rotor system with the squeeze film damper (SFD) using an electromagnet. The electromagnet is installed in the inner damper of the SFD. The proposed SFD has basically property of a conventional SFD and variable damping property according to variation of the applied electric current. Therefore, when the applied current controlled, the whirling vibration of the rotor system can be effectively reduced in a wide operational speed range. In the present work, the performance of the SFD was experimentally investigated according to changing the magnetic field strength. When the applied current increased, the whirling amplitude greatly reduced and the damping ratio also increased.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권11호
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• pp.604-610
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• 1999

Vibration of a rotor-bearing system driven by an electric motor is a coupled phenomenon between mechanical characteristics and magnetic origins through the air-gap. With the advent of new high-energy magnets together with high precision motor applications, magnetic sources of vibration are becoming more serious. This paper investigates the transient whirl responses of a rotor system with purely mechanical origins and compares it with that of magnetically coupled origins. A perturbation method is applied to model the magnetic field associated with rotor eccentricity. Electromagnetic forces are obtained by the Maxwell stress method, which utilizes the analytical expression of radial flux density distribution. The FEM was applied to a rotor-motor system to illustrate magnetically coupled effects in rotor dynamics. Results show that magnetically coupled sources significantly affect the vibration of the rotor-motor system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 B
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• pp.1152-1154
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• 1996

In power transformers, vibration occurs at winding, core and case due to current, voltage, temperature changing and winding reformation. Winding deformation and change of vibration signals are occurred due to electromagnetic force induced by fault current. In this paper, in normal and fault states, the trends of fundamental waves and higher harmonics are considered. To inspect the factors that affect the fundamental waves and higher harmonics, the trends are considered with varying voltage and load. Determination functions are generated and applied to signals so that normal and fault state are determined by determination functions.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 D
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• pp.2251-2253
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• 2003

This paper is concerned with the active vibration control of flexible cantilever beam system using electromagnetic force actuator. The main objective of this paper is to propose the control algorithms and implement the experimental setups for active vibration control. Several control algorithms are proposed and implemented on the experimental setups to show their efficacy. These include a PID control design, an optimal $H_2$ control design, and a fuzzy PID control design. Effectiveness and performance of the designed controller were verified by both simulation and experiment results.

• 한국소음진동공학회논문집
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• 제13권6호
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• pp.484-489
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• 2003

The paper represents stability of a rotor system with the squeeze film damper (SFD) using an electromagnet. The electromagnet is installed in the inner damper of the SFD. The proposed SFD has basically the property of a conventional SFD and variable damping property according to variation of the applied electric current. Therefore, when the applied current Is controlled, the whirling vibration of the rotor system can be effectively reduced in a wide operational speed range. In the present work, the performance of the SFD was experimentally investigated according to changing the magnetic field strength. As the applied current increased, damping ratios increased, while whirling amplitudes greatly reduced.

• 한국압력기기공학회 논문집
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• 제19권1호
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• pp.6-10
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• 2023

Only about 10% of selected equipment in nuclear power plants are monitored by wiring to address failures or problems caused by vibration. The purpose is primarily for preventive maintenance, not for predictive maintenance. This paper shows that vibration monitoring and diagnosis using Industrial 4.0 enables the complete predictive maintenance for all vibrating equipments in nuclear power plants with the convergence of internet of things; wireless technology, big data through periodic collection and artificial intelligence. Predictive maintenance using wireless technology is possible in all areas of nuclear power plants and in all systems, but it should satisfy regulatory guides on electromagnetic interference and cyber security.

• 한국산학기술학회논문지
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• 제17권5호
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• pp.269-274
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• 2016

본 연구는 호퍼와 같은 공정에서 필연적으로 발생하는 스케일 또는 막힘 현상을 방지하기 위해 적용할 수 있는 저주파 전자해머 구동 시스템의 개발에 관한 것이다. 전자기계식 hammering 구동 방식은 진동과 충격량을 동시에 발생시키는 방식으로, 본 논문에서는 전자해머의 특성을 고찰하기 위하여 전자해머에 장착된 직/병렬 스프링 상수 해석을 하였고 발생에너지는 E코어에 부착된 스프링 상수가 모두 같을 경우에 계산된 등가 스프링 상수와 E코어와 I코어 사이의 동작 변위의 곱으로 계산할 수 있음을 보였다. 또한 전자해머의 충격량을 최대화하기 위하여 맥동파 구동 알고리즘을 적용하였으며, 이 알고리즘은 논리 AND 연산과 마이크로 콘트롤러(atmega128)의 타이머 인터럽트와 PWM 기능을 사용하여 구현하였다. 전자해머의 구동회로는 IGBT로 구성된 H-브리지 방식으로 설계하였고, 가속도계 측정법으로 개발한 전자 해머 시스템의 성능을 검증하였다. 실험 결과 제안한 시스템이 기계적 에너지를 양호하게 발생시킬 수 있으며, 호퍼와 같은 공정에 적용할 수 있음을 보였다.

• 한국추진공학회지
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• 제3권4호
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• pp.12-22
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• 1999

Class-B 증폭기를 사용하는 가진기 시스템의 운용으로 인하여 다른 전자 시스템에 전자파 장해가 나타날 수 있으며, 이런 경우에 사용자가 이 장해를 해결하기 위하여 필요한 대책을 마련하기를 요구하고 있다. 한 가진기 시스템에서는 공통모드 잡음전압의 효과를 줄이기 위하여 Class-D 증폭기에서 차동증폭기가 사용되었고, 다른 가진기 시스템에서는 접지루프를 막기 위하여 변압기가 삽입되었다. 이 방법들은 이전에 발생하였던 불필요한 진동의 감소를 보여주고 있다. 전하증폭기의 변압기가 접지루프를 방지하기 위하여 Class-AB 증폭기를 사용한 가진기 시스템에서 수 년간 사용되었으나, Class-D 증폭기를 사용하는 가진기 시스템에서 이것은 잡음에 민감하였다. 따라서 전하증폭기와 진동 제어분석 시스템 사이의 접지루프를 변압기를 사용하지 않고 해결하였다. 이 방법의 유용성이 실험결과를 통하여 확인되었다.