• Proceedings of the KIPE Conference
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• 2018.11a
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• pp.62-64
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• 2018

In two-stage single-phase inverters, inherent double line frequency component is present at both input and output of the front-end converter. Generally large electrolytic capacitors are required to eliminate the ripple. It is well known that the low frequency ripple shortens the lifespan of the capacitor hence the system reliability. However, the ripple can hardly be eliminated without the hardware combined with an energy storage device or a certain control algorithm. In this paper, a novel power-decoupling control method is proposed to eliminate the double line frequency ripple at the front-end converter of the DC/AC power conversion system. The proposed control algorithm is composed of two loop, ripple rejection loop and average voltage control loop and no extra hardware is required. In addition, it does not require any information from the phase-locked-loop (PLL) of the inverter and hence it is independent of the inverter control. In order to prove the validity and feasibility of the proposed algorithm a 5kW Dual Active Bridge DC/DC converter and a single-phase inverter are implemented, and experimental results are presented.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.580-582
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• 2002

A major problems of Switched Reluctance Motor(SRM) is torque ripple which causes undesirable acoustic noise and vibration. To reduce the torque ripple two different approaches are used. One is to modify a motor geometry, the other is to manipulate motor current to improve performance. This paper presents modifications of the rotor pole shape which reduces the torque ripple.

• Journal of electromagnetic engineering and science
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• v.8 no.3
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• pp.119-128
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• 2008

In this paper, we propose a developing approach of 600 W super high frequency(SHF) traveling wave tube amplifier (TWTA) for communications. Also, we make a TWTA called the experimental-TWTA(ETWTA), which uses a cathode ripple reduction technique to improve RF performance. After implementation, we discuss, and compare it with some other TWTAs. Its RF performance is better than that of other TWTAs. Therefore, this methodology can be used to develop the high power SHF TWTA for communications.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.11
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• pp.1976-1980
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• 2008

This paper deals the characteristic analysis of Switched Reluctance Motor(SRM) driven by single-pulse mode considering dc link voltage ripple. Two dimensional time-stepped Finite Element Method(FEM) is used to analyze the characteristic of SRM driven by single-pulse mode with dc link voltage ripple. The analysis results is verified by experimental test.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.12
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• pp.2391-2395
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• 2009

Active control schemes which modify the excitation to correct for any of the nonideal characteristics of the SPMSM is described. Especially, because of design limitations(size and cost) in automobile, the back-EMF of SPMSM can't be perfectly designed with sinusoidal wave and iron core of stator is saturated so that torque ripple is unavoidable. An active cancellation method of the pulsating torque components which would otherwise be generated using the classic sinusoidal current excitation is illustrated.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.337-341
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• 1998

Brushless DC motors have trapezoidal back emf waveform. Generally, because it is drived by a voltage source inverter, the ideal rectangular phase current is not available and therefore produce torque ripple. In this paper, the torque ripple due to commutation is analysed and the practical method that can reduce the torque ripple is proposed. Simulation and experimental results show the effectiveness of the proposed method.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.342-346
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• 1998

The brushless DC motor with trapezoidal back emfs has torque ripple due to phase commutation. The torque ripple generates noise and vibration and cause errors in position control so this makes the brushless DC motor less suitable for high performance servo applications. In this paper, we propose a new current control method to reduce the torque ripple due to commutation, when the unipolar PWM method is applied for the phase current control of brushless DC motor.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.12 s.177
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• pp.51-60
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• 2005

This paper describes a robust control scheme for high-speed and long stroke scanning motion of high precision linear motor system consisting of linear motor, air bearing guide and position measurement system using heterodyne interferometer. Nowadays, semiconductor process and inspection of wafer or LCD need high speed and long travel length for their high throughput and extremely small velocity fluctuations or tracking errors. In order to satisfy these conditions, linear motor system are widely used because they have large thrust force and do not need motion conversion mechanisms such as ball screw, rack & pinion or capstan with which the system are burdened. However linear motors have a problem called force ripple. Force ripple deteriorates the tracking performances and makes periodic position errors. So, force ripple must be compensated. To maximize the tracking performance of linear motor system, we propose the control scheme which is composed of a robust control method, Time Delay Controller (TDC) and a feedforward control method, Zero Phase Error Tracking Control (ZPETC) for accurate tracking a given trajectory and an adaptive force ripple compensation (AFC) algorithm fur estimating and compensating force ripple. The adaptive ripple compensation is continuously refined on the basis of tracking error. Computer simulation results based on modeled parameters verify the effectiveness of the proposed control scheme for high-speed, long stroke and high precision scanning motion and show that the proposed control scheme can achieve a sup error tracking performance in comparison to conventional TDC control.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.2
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• pp.113-122
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• 2010

The ripple within the quiet zone in the CATR(Compact Antenna Test Range) would be increased due to the diffraction at the edge of the reflector. Therefore, the reflector equipped with the serrations is generally used to reduce the ripple within the quiet zone. In this paper, the modified asymmetric triangular serrations are proposed, and the diffraction of the proposed serrations is analyzed using the Fresnel diffraction formula. The ripple of amplitude and phase between the conventional triangular and the proposed serrations are compared to confirm the ripple of the proposed serrations. As the result of the modulated the reflector size, height of the serrations and numbers of serrations, it is confirmed that the ripple of the proposed serrations is less than the conventional triangular serrations. Accordingly, proposed serrations are expected to reduce the ripple within quiet zone.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.470-473
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• 2018

Using High-order Modulation in wideband system is sensitive to change of wireless channel environment as well as changes in ripple characteristics that can occur when baseband signals pass through RF equipment. Therefore, it is necessary to design and RF tuning that minimizes ripple characteristics change, which is difficult to implement systematically and takes a long time. In this paper, we analyze the fixed ripple characteristics of the baseband signal distored through the RF transmitting and receiving equipment. And the function of compensating the compensation filter by the modem receiver is implemented in 256 TCM. Also, it is confirmed that SNR and received sensitivity are improved by applying a digital compensation filter in a channel with poor RF equipment ripple characteristics.