• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 제37회 하계학술대회 논문집 C
• /
• pp.1689-1690
• /
• 2006

This study is for implementation of PC based Motor fault diagnosis system. By using harmonics and current signals of the motor, this system diagnoses the motor condition by accumulated harmonic contribution rate. In this proposed system that was composed of 5 parts. A sensor, connection box, evaluation board, device server, and main computer are those. There were two types of sensor, one was harmonic sensor the other was current sensors. The signal was acquired by sensor, and transferred to evaluation board. Second one is connection box. Because the output type of sensor and input type of evaluation board is different, connection box was necessary. Third one was evaluation board. The signal from the sensor was converted to digital signal in evaluation board. And this signal was transferred to device server. Fourth one was device server Device server transferred the data from evaluation board to main computer. And the last one was other parts controlled by main computer. In main computer, there were communication and diagnosis algorithms. The result was derived by main computer. In the result, there were 12 categories and 5 levels of motor conditions. The proposed system had some advantages comparing with stand alone type commercial motor fault diagnosis system. The first, by using remote access it was easier to get the conditions of motor. The second, there was no need to handle the sensors when users measured the motor signals. By this property, no one was necessary at motor location site. The third, this system was less restricted by times and places than commercial stand alone type diagnosis system. Therefore users can operate this system only using the main computer. Once the sensors are installed at the motor, users doesn't need to move to check up the condition of motors. Moreover, if there is ethernet hub, many motors can be not only diagnosed at once but also decreased its cost.

• 전력전자학회논문지
• /
• 제4권5호
• /
• pp.413-422
• /
• 1999

Auto-connected multipulse(12/24pulse) rectifier schemes are cost effective methods for reducing line current hamonics in PWM drive systems. Employing these schemes to enhance utility power quality requires careful attention to several design considerations In particular, excursion of dc-link voltage at no load, effect of pre-existing voltage distortion, impedance mismatches, unequal diode drops on rectifier current sharing and performance, are fully analyzed, Several corrective measures to improve the performance of 12/24­pulse rectifier systems are also discussed. Finally, experimental results on a 460V, 60Hz 400kVA commercial ASD, retrofitted with 12/24pulse rectifier systems are discussed in detail.

• 조명전기설비학회논문지
• /
• 제13권3호
• /
• pp.25-33
• /
• 1999

본 논문에서는 다이오드 정류기와 부스트 컨버터가 결합되 단상 PWM컨버터의 역률보상 및 고조파 저감 기법에 관하여 연구하였다. 일반적인 다이오드 정류기의 경우에서는 전원 입력측에 불연속 펄스 전류가 흘러서 역률의 저하 및 고조파 왜곡이 포함되어 다른 전원계통에 악영향을 주는 문제점이 있다. 이를 해결하기 위하여 본 논문에서는 3차 고조파가 주입된 PWM 기법을 사용하여 입력전류에서의 고조파왜곡이 감소되는 AC-DC 부스트 컨버트를 제안하였다. 이때의 부스트 컨버터는 스위칭 손실 및 회로구성이 용이한 불연속적전류모드 제어방식을 채용하였다. 스위칭 주파수가 5[kHz]인 컨버터를 구성하여 컴퓨터 시뮬레이션 및 실험을 행하였으며 그 결과 역률 보상 및 전 고조파 왜곡이 감소되었음을 확인하였다.

• KIEE International Transactions on Electrophysics and Applications
• /
• 제5C권3호
• /
• pp.131-137
• /
• 2005

This paper describes a new approach to the algorithm and fundamental characteristics of the device for monitoring the leakage currents flowing through zinc oxide (ZnO) surge arresters. In order to obtain a technique for a new on-line monitoring device that can be used in the deterioration diagnosis of ZnO surge arresters, the new algorithm and on-line leakage current detection device for extracting the resistive and capacitive currents using the phase shift addition method were proposed. The computer-based on-line monitoring device can sense accurately the power frequency leakage currents flowing through ZnO surge arresters. The on-line leakage current monitoring device of ZnO surge arresters proposed in this work has the high sensitivity compared to the third harmonic leakage current detection devices. As a consequence, it was found that the proposed leakage current monitoring device would be useful for forecasting the defects and degradation of ZnO surge arresters.

• 한국전기전자재료학회논문지
• /
• 제19권2호
• /
• pp.169-175
• /
• 2006

This study investigated variation leakage current maximum value and waveform considering applied voltage phase angel by simulating three environmental conditions, such as fog, salt fog, and kaolin contamination .As the result of applied voltage phase angel characteristics, leakage currents presented almost in phases in the early stage regardless of environmental conditions just after applying the voltage, and the phase of leakage currents certain phase lags for the discharge of the applied voltage when surface discharges occurred due to the continuous environmental contamination. In addition, the difference in phase significantly increased according to the intensity of discharges. The change in distortion rates according to the environmental contamination presented a nearly same level just after applying the voltage. The distortion rate of third harmonic for the fundamental wave presented by the order of fog>salt fog>kaolin when surface discharges occurred due to the applied voltage for certain continued periods. In the case of the fog and salt fog, the scale of spectrums decreased according to the increase in frequencies from the results of the analysis of high frequencies. In addition, the even number frequency presented a relatively large level compared to the odd number frequency under the kaolin contamination.

• Journal of Electrical Engineering and Technology
• /
• 제11권2호
• /
• pp.416-424
• /
• 2016

In this study, automatic detection of stator winding inter-turn short circuit fault (SWISCFs) in surface-mounted permanent magnet synchronous motors (SPMSMs) and automatic classification of fault severity via a pattern recognition system (PRS) are presented. In the case of a stator short circuit fault, performance losses become an important issue for SPMSMs. To detect stator winding short circuit faults automatically and to estimate the severity of the fault, an artificial neural network (ANN)-based PRS was used. It was found that the amplitude of the third harmonic of the current was the most distinctive characteristic for detecting the short circuit fault ratio of the SPMSM. To validate the proposed method, both simulation results and experimental results are presented.

• Journal of Power Electronics
• /
• 제14권5호
• /
• pp.874-881
• /
• 2014

This study presents a single-phase power factor correction AC-DC converter that operates in discontinuous conduction mode. This converter uses the pulse-width modulation technique to achieve almost unity power factor and low total harmonic distortion of input current for universal input voltage $90V_{rms}$ to $264V_{rms}$) applications. The converter has a simple structure and electrical isolation. The magnetizing-inductor energy of the transformer can be recycled to the output without an additional third winding. The steady-state analysis of voltage gain and boundary operating conditions are discussed in detail. Finally, experimental results are shown to verify the performance of the proposed converter.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2000년도 하계학술대회 논문집
• /
• pp.144-147
• /
• 2000

The effect of accelerated aging test on ethylene-propylene-diene monomer(EPDM) rubber used for outdoor insulation was studied by X-ray photoelectron spectroscopy(XPS), scanning electron microscope(SEM), FFT spectrum alalysis, and electrical pulse counts using PC by oscilloscope(300 MHz). In electrical alalysis, FFT spectrum analysis indicated arcing caused a significant increase in the third harmonic content of the leakage current of polluted insulator. Also, pulse counts increased as aging time. The surface oxygen and aluminum content were found to increase and that of carbon and nitrogen were found to decrease with time. The detailed XPS analysis indicated that the concentration of carbon in C-C decreased and concentration of highly oxidized carbons increased with time, which was due to the oxidation of EPDM rubber polymer SEM analysis indicated that crack and erosion of EPDM rubber occurred with time.

• 한국전자파학회논문지
• /
• 제23권12호
• /
• pp.1343-1350
• /
• 2012

본 논문에서는 모노폴 안테나의 각 모드별 전계 분포를 분석하여 전류가 상대적으로 약한 부분(전계가 강한 부분)에 스터브를 이용해 기본 공진 모드에는 영향을 주지 않으면서 안테나의 하모닉 성분인 3차 모드 공진 주파수를 효율적으로 제어하고, 스터브의 두께를 조절하여 임피던스 특성을 조절할 수 있는 방법을 제안한다. 이 방법을 이용하여 일반적인 USB Dongle 크기($20{\times}45mm$)에 안테나를 설계하였으며, -10 dB 기준 2 GHz 대역에서 대역폭이 600 MHz(2.3~3 GHz), 5 GHz 대역의 대역폭은 1 GHz(4.9~5.9 GHz)로 WLAN 주파수 대역을 만족하는 성능과 50 % 효율이 달성되었다.

• 전력전자학회논문지
• /
• 제4권5호
• /
• pp.423-432
• /
• 1999

This paper proposes a 12­pulse diode rectifier system with low kVA components suitable for powering switch mode power supplies or ac/dc converter applications. The proposed 12-pulse system employs a polyphase transformer, a zero sequence blocking transformer (ZSBT) in the dc link, and an interphase transformer. Results produce near equal leakage inductance in series with each diode rectifier bridge ensuring equal current sharing and performance improvements, The utility input currents and the voltage across the ZSBT are analyzed the kVA rating of each component in the proposed system is computed. The 5th , 7th , 17th and 19th harmonics are eliminated in the input line currents resulting in clean input power. The dc link voltage magnitude generated by the proposed rectifier system is nearly identical to a conventional to a conventional 6-pulse system. The proposed system is suitable to retrofit applications as well as in new PWM drive systems. Simulation and experimental results from a 208V , 10kVA system are shown.