• Journal of Power Electronics
• /
• 제15권4호
• /
• pp.1139-1147
• /
• 2015

In this paper, an algorithm based on a model analysis of the online calculation of the root-mean-square (RMS) value of welding current for single-phase AC resistance spot welding (RSW) was developed. The current is highly nonlinear and typically non-sinusoidal, which makes the measuring and controlling actions difficult. Though some previous methods focused on this issue, they were so complex that they could not be effectively used in general cases. The electrical model of a single-phase AC RSW was analyzed, and then an algorithm for online calculation of the RMS value of the welding current was presented. The description includes two parts, a model-dependent part and a model-independent part. Using a previous work about online measurement of the power factor angle, the first part can be solved. For the second part, although the solution of the governing equation can be directly obtained, a lot of CPU time must be consumed due to the fact that it involves a lot of complex calculations. Therefore, a neural network was employed to simplify the calculations. Finally, experimental results and a corresponding analysis showed that the proposed algorithm can obtain the RMS values with a high precision while consuming less time when compared to directly solving the equations.

• ETRI Journal
• /
• 제35권3호
• /
• pp.431-438
• /
• 2013

This paper presents a new realization of the implicit root-mean-square (RMS) detector, employing three second-generation current conveyors and MOS transistors. The proposed circuit can be applied in measuring the RMS value of complex, periodic signals, represented in the form of the Fourier series. To verify the theoretical analysis, circuit Simulation Program with Integrated Circuit Emphasis simulations and experiment results are included, showing agreement with the theory.

• 대한임베디드공학회논문지
• /
• 제12권2호
• /
• pp.79-88
• /
• 2017

One of the important applications of activity sensing in the home is energy monitoring. Many previous methodologies for detecting and recognizing household appliances have been proposed. This paper presents an approach that uses an energy metering circuit (EMC) to classify and identify the various electrical devices in home based on root-mean-square (RMS) consumed current value. EMC gathers the RMS current values created by appliance state transition (e.g., on to off) and apparatus operating process. In this paper, an identification algorithm is proposed to detect a change in current levels using the standard deviation of current signals and their average values. In addition, characteristic of the appliance is extracted concerning four feature parameters concerning the number of current levels, the minimum level, the maximum level, and signal-to-noise ratio (SNR) of them. Experiment results validate the reliable performance of the proposed identification method for 11 representative appliances.

• 한국전자통신학회논문지
• /
• 제18권5호
• /
• pp.817-826
• /
• 2023

본 논문에서는 스마트 그리드 배전 계통에서 선로상의 고장으로부터 계통을 보호하기 위한 인공 신경 회로망을 기반으로 하는 고장 판단 방법론을 제안하였다. 제안된 방법론에서는 먼저 전류 실효값 크기를 기반으로 일반 고장 여부를 판단하고 다음, 정상 전류로 판단되는 경우 인공 신경 회로망을 기반으로 하는 normal/HIF classifier를 이용하여 고 임피던스 지락 고장 여부를 판단하도록 설계하였다. 반복적인 DSP 모듈 기반 알고리즘 검증 시험들 중에서, 실효 값 크기가 최소 동작전류보다 작은 정상 전류 파형 시험인 경우에 normal/HIF classifier가 전류 파형을 정상상태로 인식하여 부 동작하였으며, 반면에, 저 임피던스 고장의 경우는 고장 상태로 인식하여 정해진 절차에 따라 재폐로 동작을 보임으로써 제안된 방법론의 유효성을 확인할 수 있었다.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 1998년도 연구회 합동 학술발표회 논문집
• /
• pp.18-22
• /
• 1998

A PWM inverter with an induction motor often has a problem with a high frequency leakage current that flows through stray capacitor between stator windings and a motor frame to ground. This paper presents an equivalent circuit for high frequency leakage currents in PWM inverter feeding an induction motor, which forms an LCR series resonant circuit. A conventional common mode ckoke or reactor in series between the ac terminals of a PWM inverter and those of an ac motor is not effective to reduce the rms and average values of the leakage current, but effective to reduce the peak value. Furthermore, this paper proposes a leakage current damper which is different in damping principle from the conventional common mode choke. It is shown theoretically and experimentally that the leakage current damper is able to reduce the rms value of the leakage current to 25%, where the core used in the leakage current damper is smaller than that of the conventional common-mode choke

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2005년도 춘계학술대회 논문집
• /
• pp.819-824
• /
• 2005

This paper describes the measurement result of leakage current flowing arresters connected in feeder lines to propose an optimal management method. Twenty seven arresters set in seven areas were analyzed on a regular basis for 4 months. The results showed that the RMS and the peak value of the total leakage currents for soundness arresters were a range of $200uA{\sim}00uA$. respectively. During the period of measurement, the magnitude of the leakage current didn't show conspicious changes and there were impossible places to analyze arrester's status due to including high THD rate in a feeder line, From the study, leakage current measurement has to be performed at a condition without running an electric train in the line, and the allowable RMS value of soundness arrester is bellow 600uA.

• 한국해양학회지:바다
• /
• 제13권1호
• /
• pp.42-55
• /
• 2008

금강하구 연안역에서 HF radar로 측정한 유속의 정확도를 평가하기 위해 HF radar의 마주보는 radial 유속들을 비교하고, HF radar로 측정한 유속을 현장측정 유속과 비교하였다. 비교 자료들에 대한 회귀선과 편차는 주성분 분석(Principal Component Analysis)으로 구하였다. HF radar site를 연결하는 선의 중간지점에서 마주보는 radial vector를 비교하였을 때 RMS 편차는 동계에 4.4 cm/s, 하계에 5.4 cm/s이었다. HF radar와 유속계로 측정한 유속성분을 비교하여 분석된 RMS 편차에서 GDOP(Geometric Dilution of Precision) 효과를 제거하였을 때 HF radar의 합성 속도 측정오차는 GDOP 값이 적절한 정점들에서 5.1 cm/s 이내였다. 서로 다른 두 방법에 의해 구해진 이 결과는 연구해역에서 HF radar로 측정된 유속의 정확도 하한이 5.4 cm/s임을 제시한다. 기존의 연구에서와 같이 RMS 편차는 섬 주변에 있는 관측점에서 크게 되고, 두 radar에서 평균거리가 멀어질수록 신호 대 잡음수준과 radial vector 교차각의 감소로 인해 증가하였다. GDOP 값을 이용한 오차분리 과정에서 속도성분별 GDOP 값이 유사하고 비교 유속의 성분별 RMS 편차도 비슷한 값을 보이는 경우 HF radar 유속의 오차가 불확실한 값으로 도출될 수도 있음이 밝혀졌다. GDOP가 정상적인 radar 관측 범위 내에 있는 정점에서 측정된 유속을 조류와 해류로 분리하였을 때 HF radar 유속에서 구해진 조류타원의 특성은 유속계로 측정된 타원특성과 잘 부합하였고, 해류의 시간적 변화는 바람과 밀도장의 외력에 의한 물리적 과정을 반영하는 반응을 보였다.

• 한국전기전자재료학회논문지
• /
• 제17권6호
• /
• pp.673-677
• /
• 2004

We present the basic properties of a superconductive fuse (SF) based on YBCO/Au films. The SF consists of YBCO stripes covered with Au layers for current shunt. The fault current was limited to a designed value in less than 0.4 msec by resistance development in YBCO/Au upon quenching. This enabled the SF to transfer small fault power and the suppressed current was sustained for more than 0.5 msec while Au layer melting and arcing. The arcing time was less than 2.5 msec, that is short enough to do self-interruption. Under the source voltage of 100 $V_{rms}$, the longer the duration time of fault current was, the shorter its discharge time was. The duration time of fault current and its discharge time were reduced by increased voltages in the range of 200 - 300 $V_{rms}$. We thought that this was because the quench propagation was limited by local melting generated with higher voltage.age.

• KIEE International Transactions on Power Engineering
• /
• 제4A권3호
• /
• pp.146-151
• /
• 2004

The most widely used primary protection for the internal fault detection of the power transformer is current ratio differential relaying (CRDR) with harmonic restraint. However, the second harmonic component could be decreased by magnetizing inrush when there have been changes to the material of the iron core or its design methodology. The higher the capacitance of the high voltage status and underground distribution, the more the differential current includes the second harmonic during the occurrence of an internal fault. Therefore, the conventional second harmonic restraint CRDR must be modified. This paper proposes a numerical algorithm for enhanced power transformer protection. This algorithm enables a clear distinction regarding internal faults as well as magnetizing inrush and steady state. It does this by analyzing the RMS fluctuation of terminal voltage, instantaneous value of the differential current, RMS changes, harmonic component analysis of differential current, and analysis of flux-differential slope characteristics. Based on the results of testing with WatATP99 simulation data, the proposed algorithm demonstrated more rapid and reliable performance.

• 대한전기학회논문지
• /
• 제41권9호
• /
• pp.953-959
• /
• 1992

As the TC(time-current) curve corresponding to symmetrical time invariant RMS value has been traditionally chosen and used for setting the relay, it has caused the misoperation errors on relay coordination because of CT secondary current being actually an asymmetrical time varying RMS value. In this paper, an algorithm for calculating the relay operating time is developed to study the asymmetrical effect using the step-by-step method. We represent the relay operating time errors between with and without DC offset versus PSM(plug setting multiplier), TMS(time multiplier setting) and X/R ratio. And also we present the correction factor. Finally we confirm the validity of this technique through the case study.