• Journal of Power Electronics
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• v.2 no.1
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• pp.1-10
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• 2002

An advanced active power filter for the compensation of instantaneous harmonic current components in nonlinear current load is presented in this paper. A novel signal processing technique using an adaptive neural network algorithm is applied for the detection of harmonic components generated by three-phase nonlinear current loads and this method can efficiently determine the instantaneous harmonic components in real time. The control strategy of the switching signals to compensate current harmonics of the three-phase inverter is also discussed and its switching signals are generated with the space voltage vector modulation scheme. The validity of this active filtering processing system to compensate current harmonics is substantiated on the basis of simulation results.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.7 no.2
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• pp.102-108
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• 2007

The issues of preventive and condition-based maintenance, online monitoring, system fault detection, diagnosis, and prognosis are of increasing importance. This study introduces a technique to detect and identify faults in induction motors. Stator currents were measured and stored by time domain. The time domain is not suitable for representing current signals, so wavelet transform is used to convert the signal; onto frequency domain. The raw signals can not show the significant feature, therefore difference values are applied. The difference values were transformed by wavelet transform and the features are extracted from the transformed signals. The dynamic time warping method was used to identify the four fault types. This study describes the results of detecting fault using wavelet analysis.

• Proceedings of the KIEE Conference
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• 2005.10c
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• pp.53-55
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• 2005

The signals of the eddy current testing(ECT) for the examination of the steam generator(SG) tubes in the nuclear power plant(NPP) determine the existence, size, and kind of defects using the variation of impedance signals when a testing coil, driven by alternating current, passes through the SG tube contains defects. The aim of this paper is building a database of the RPC probe signals on the basis of the sizes variation of defects and frequency variation of probe. In this paper 3-D numerical analysis of the ECT signals using the finite element method is performed. Through this study, it is shown variation of magnitude and phase of impedance according to variation of defect size and frequency. From the result of this paper, we can obtain the information which is useful in defect discrimination of SG tube in nuclear power plant.

• Journal of Korea Spatial Information System Society
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• v.4 no.1 s.7
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• pp.27-37
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• 2002

Ideas providing an optimal car route using current traffic condition, maintaining the current location and the history of driven route of a car in the main central office, in where GPS signals transmitted from the driving cars are received, have been proposed. Since GPS signals occurred in certain time interval instead of all GPS signals are transmitted from the car due to the cost of transmission, an algorithm that is able to recover the missing GPS signals is required. In this paper, an efficient algorithm, which finds the driven route and the current location of a car fast, is proposed. To verify the efficiency of the proposed algorithm, it is applied to the various real GIS map and it turns out to be very effective.

• Journal of Power Electronics
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• v.18 no.2
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• pp.604-614
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• 2018

This paper proposes a synchronous switching technique for a Vienna rectifier that uses carrier-based pulse width modulation (CB-PWM). A three-phase Vienna rectifier, similar to a three-level T-type converter with three back-to-back switches, is used as a PWM rectifier. Conventional CB-PWM requires six independent gate signals to operate back-to-back switches. When internal switches are operated synchronously, only three independent gate signals are required, which simplifies the construction of gate driver circuits. However, with this method, total harmonic distortion of the input current is higher than that with conventional CB-PWM switching. A reactive current injection technique is proposed to improve current distortion. The performance of the proposed synchronous switching method and the effectiveness of the reactive current injection technique are verified using simulations and experiments performed with a set of Vienna rectifiers rated at 5 kW.

• Current Optics and Photonics
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• v.1 no.4
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• pp.308-314
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• 2017

A particular optical receiver has its own optical receiver modes (ORMs) determined by its optical and electrical filters. Superposing the ORM waveforms at the transmitter, we can generate a new type of optical signals, called ORM signals. After optical detection, they produce pre-specified voltage waveforms accurately, which is advantageous for digital signal processing. Assuming a Gaussian optical receiver, where the optical and electrical filters are Gaussian, we illustrate various phase-shift keying ORM signals using two ORMs by changing their relative phase. We also illustrate multi-level ORM signal patterns using two or more ORMs.

• Bulletin of the Korean Chemical Society
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• v.10 no.3
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• pp.302-308
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• 1989

Species selective spectroelectrochemistry (SSSE) is described by relating the derivative absorbance (dA/dt) signals with electrochemical currents for conventional transient electrochemical experiments. Expressions relating the currents with the dA/dt signals were obtained. From these expressions, physical constants such as coefficients and molar absorptivities of electrogenerated species can be determined. By obtaining both derivative absorbance and current signals concurrently and comparing them, one can perform the SSSE experiments. The utility of the SSSE in sorting out electrochemical information is demonstrated.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.922-924
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• 1998

In this paper, an optical fiber sensor(OF sensor) utilizing the principal of Mach-Zehnder interferometer were proposed to detect the partial discharge signals in insulating oil. At first the AC breakdown signals were detected to check the response of the OF sensor. The detected signals from OF sensor was consistent with that from current probe. After the response checking, simultaneous measurements and continuous recording were made of electrical and the OF sensor signals from partial discharge(PD) produced by IEC(b) electrode system immersed in insulating oil. The continuous recording made it possible to extract basic quantities of PD from the OF sensor signals, such as pulse phase and pulse amplitude distribution. Through the signal analysis, the absolute peaks of the OF sensor PD signal was found to be increased with the amplitude of electrical signals, and these results mean that there is a strong correlation between OF sensor and electrical PD signals. It was demonstrated that the OF sensor in this research had a possibility to detect the PD signals in power apparatus.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.942-944
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• 2005

In this study, eddy current signals from various anomalous defects in the heat exchanger tube are predicted af their signal slope characteristics no analyzed. The signal changes due to frequency increase are also observed. Based in the accumulated knowledge, the analysis of superimposed signal is attempted which includes the effects of support plate. Both differential and absolute bobbin probe signals are analyzed. For the prediction of signals, axisymmetric finite element modeling is used and this leads us to the utilization of slope angle analysis of the signal. Results show that differential signals are useful to locate the position of defect under the support plate and absolute signals no easy to predict and analyze even though they no superimposed signals. Combined use of these two types of signals will accomplish a reliable inspection.

• Transactions on Electrical and Electronic Materials
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• v.18 no.4
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• pp.221-224
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• 2017

This paper dealt with the extraction of series arc signals based on wavelet transform in order to improve the accuracy of arc detection in indoor wiring systems. Three types of arc sources including a cord-cord, a terminal-cord, and an outlet-plug were fabricated to simulate typical arc defects. An arc generator fabricated according to UL 1699 was used to generate arcs. The optimal mother wavelet was selected as bior1.5 by calculating the correlation coefficients between the detected single current pulse and the wavelet. The detected arc current signals were then decomposed into eight levels using the discrete wavelet transform that implements the multi-resolution analysis method. By analyzing the decomposed components, the detail components D6, D7, and D8 were associated with arc signals, which were used for signal reconstruction. From the result, it was verified that the proposed method can be used for the extraction of the series arc signal from the AC mains, which is expected to be applied to further analysis of arc signals in indoor wiring systems.