• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.2
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• pp.135-141
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• 2012

PMSM(Permanent Magnet Synchronous Motor) has periodic torque ripple from the cogging torque and load conditions. This paper proposes the modified PID speed controller to reduce the speed ripple of the PMSM. The proposed modified PID controller uses a selective D(Differential) control term according to the speed error and the differential of the speed error. The proposed speed controller produces an additional torque reference such as torque compensator based on PI controller according to the speed error and the differential of the speed error, and it can reduce the vibration of the conventional D-control term with reduced speed ripple. Since the additional torque reference of the proposed speed controller is changed by the sign of the speed error and the differential of the speed error, a simple function to determine the sign of the error is used to produce the compensated torque. The proposed control scheme is verified by the computer simulation and the experiments.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.4
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• pp.143-148
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• 2023

Among the characteristics of SRM, due to nonlinearity, it is difficult to properly operate to form maximum torque and minimum torque pulsation. In addition, in the case of fixed switching angle control, torque formation according to speed variation is unstable, thereby reducing efficiency. Therefore, active switching angle control according to speed variation is required. Therefore, active switching angle control according to speed variation is required. In this paper, a method for improving driving performance by reducing torque ripple by automatic control of the advance angle and increasing output torque was sought from the problem caused by the nonlinearity of the SRM. In addition, the optimal operation of SRM due to the switching variable according to the performance of the hysteretic current controller was examined.

• Journal of the Microelectronics and Packaging Society
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• v.6 no.3
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• pp.9-18
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• 1999

In this study, Metallugical properties between Sn-3.5Ag, Sn-37Pb eutectic solders and Au/Ni/cu substrate according to time span above the melting point were investigated. A conventional reflow soldering machine wert used for this study and time span above the melting point was determined by changing peak soldering temperature and conveyor speed. As results, scallop type intermetallic compounds of $Ni_3Sn_4$ were formed at joint interface and no Cu-Sn compounds were found at all; Ni layer performed as a barrier for Cu diffusion. As the peak soldering temperature increased, thickness of the intermetallic compound layer increased; maximum thickness of the scallop-layer was 2.2$\mu\textrm{m}$. The shape of scallops were transformed from hemi-sphere type to elliptical shape with smaller size. Micro-hardness of the solder joint decreased as the eutectic structure of Sn-3.5Ag and Sn-37Pb increased.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.2
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• pp.61-67
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• 2003

The interfacial reaction between ultra-small 58Bi-42Sn solder and Au/Ni/Ti under bump metallurgy (UBM) for ultra-fine flip chip application was investigated. The ultra-small 58Bi-42Sn solder bump, about $46{\mu}m$ in diameter, was fabricated by using the lift-off method and reflowed using the rapid thermal annealing (RTA) system. The intermetallic compounds were characterized using a secondary electron microscopy (SEM), an energy dispersive spectroscopy (EDS), and an x-ray diffractometer (XRD). The faceted and polygonal intermetallic compounds were found in the Bi-Sn solder bumps on $Au(0.1{\mu}m)/Ni/Ti$ UBM and they were indentified as $(Au_xBi_yNi_{1-x-y})Sn_2$ Phase. The intermetallic compounds grown from the $Au(0.1{\mu}m)/Ni/Ti$ UBMinterface were dispersed in the solder bump.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.1
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• pp.66-70
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• 2013

The input current of three phase rectifier which is mainly used in the propulsion system of the electric propulsion ship includes a variety of low order harmonics. To reduce these harmonics, the power conversion system, used in the large vessels which high power is required, is currently used the rectifiers of 12-pulse output, but it still has a problem that occurs $12{\pm}1$ harmonics. Also, in the case of the direct torque control technique which is widely used for the speed and torque control, the torque ripple is severe and the input current of motor has greatly included harmonics by the switching of the inverter. In order to reduce harmonics and improve the performance of torque control, this paper presents that the auxiliary supply assisted into the 12-pulse rectifier of the electric propulsion system using direct torque control technique. We confirm the validity of the proposed method through the simulation under the environment of a real vessel system.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.4
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• pp.328-339
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• 2006

In this paper the characteristic analysis of a single-phase switched reluctance motor (SRM) drive system with power factor correction (PFC) circuit is presented. The SRM is a low cost, simple and has a good high speed performance. The SRM drive with diode rectifier and filter capacitor has a low power factor because of short switch on time of capacitor. A novel switching topologic is presented to improve power factor and reduce torque ripple based on analysis of PFC circuit. Accordingly the SRM drive system with PFC circuit is also presented. Through the numerical analysis of the system, the toque ripple, power factor and efficiency with the change of rotary speed, load torque and capacity of the capacitor are achieved and compared with actual measured value.

• Proceedings of the KIEE Conference
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• 2008.04a
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• pp.242-243
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• 2008

사다리꼴 역기전력을 갖는 BLDC 전동기 제어는 구형파 전류를 인가함으로서 DC 모터와 같은 제어를 할 수 있어 많은 응용 분야에 사용되고 있다. 구형파 전류를 인가하기 위하여 연구된 PWM방식을 분석해 보면 몇 가지 문제점을 가지고 있다. 기존의 연구내용으로는 유니폴라 PWM방법, 바이폴라 PWM 방법, 하이브리드 PWM 방법이 있으나 PWM을 정확히 분석해보면 원하는 전압을 인가할 수 없는 부분이 있음을 알 수 있다. 특히 방향을 바꾸는 시점이나 속도를 급격히 줄이는 부분에서는 원하는 전압이 인가되지 않음을 알 수 있다. 본 논문에서는 이러한 문제점을 분석하고 정확한 전압이 인가될 수 있는 방법을 제안한다.

• Proceedings of the KIEE Conference
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• 2003.10b
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• pp.24-26
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• 2003

본 연구에서는 고효율, 반영구적인 수명 및 환경친화성으로 인해 효과적인 전력저장장치로 대두되고 있는 플라이휠 에너지 저장시스템 (FESS : Flywheel Energy Storage System)의 구동원으로 적용되는 전동발전기와 전력변환기에 대한 설계 및 제작을 수행하였다. 연구 대상 FESS의 저장용량은 5[kWh]이며 운전 속도는 30,000rpm이다. 전동발전기는 슬롯리플에 의한 와전류 손실이나 열손실을 고려하여 슬롯리스 Ring-wound형으로 선정하였으며, 전력변환기는 PWM Boost 컨버터를 통해 역률 및 DC 전압제어 그리고 Full Bridge 인버터를 통해 전동발전기 고속운전 제어를 실현할 수 있는 Topology를 채택하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04c
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• pp.130-132
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• 2003

1990년대 초반에 등장한 자바 언어는 빠른 속도로 프로그래머들 사이에 보급되었으며 인터넷의 등장과 더불어 이는 더욱 가속화되었다. 또한 무선 플랫폼 등과 같은 새로운 컴퓨팅 환경에 빠르게 대처함으로써 자바 언어의 끝을 예측하기는 쉽지 않은 상태이다. 초기 자바 어플리케이션들은 단일 티어(single-tier)로 개발되었으며 환경의 변화로 인해 이런 어플리케이션들을 네트워크로 연결할 필요성이 대두되고 있다. 자바 언어는 분산 컴퓨팅 환경의 솔루션으로 Enterprise JavaBean(EJB)［1］을 제시하고 있다. 본 논문에서는 기존에 개발된 자바 어플리케이션을 EJB로 래핑하기 위한 기법들을 제공한다. 핵심 비즈니스 로직을 가진 클래스들을 수작업을 통해 EJB로 변환할 수도 있지만 본 논문에서는 반자동화된 방법을 통해 변환 상의 효율을 증대시키고 변환 과정에서 발생할 수 있는 오류를 최소화하고자 한다. EJB 래핑 기법은 세션 빈(session bean)［1］래핑과 엔터티 빈(entity bean)［1］래핑으로 구성된다. 세션 빈 래핑은 자바 어플리케이션을 구성하는 클래스 가운데 질의문(query)을 가지지 않는 자바 클래스들을 래핑한다. 엔터티 빈은 질의문을 포함하는 자바 클래스를 래핑한다. EJB 래핑을 위해 리플렉션(reflection)［2］과 위임 (delegation) 장치를 사용한다.

• The Transactions of the Korean Institute of Power Electronics
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• v.2 no.2
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• pp.49-56
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• 1997

Switched Reluctance Motors(SRMs) have a considerable inherent torque ripple due to the driving characteristics of pulse current waveform and the nonlinear variation inductance profile. This paper describes a current shape characteristics to effect a torque ripple reduction, and one pulse mode switching control method is proposed to minimize torque ripple of a switched reluctance motor regardless of speed and load condition by regulating tow parameters, such as, advance angle and exciting voltage. The experiments are performed to verify the capability of proposed switching method on 6/4 salient type SRM.