Current Signals In Time Domain Research Articles

Weld Defect Categorization from Welding Current using Principle Component Analysis

Real time welding quality control still remains a challenging task due to the dynamic characteristic of welding. Welding current of gas metal arc welding possess valuable information that can be analyzed for weld quality assessment purposes. On-line monitoring of motor current can be provided information about the welding. In this study, current signals obtained during welding in the short- circuit metal transfer mode were used for real-time categorization of deliberately induced weld defects and good welds. A hall-effect current sensor was employed on the ground wiring of the welding machine to acquire the welding current signals during the welding process. Vector reduction of the current signals in time domain was achieved by principle component analysis. The reduced vector was then classified by various classification techniques such as support vector machines, decision trees and nearest neighbor to categorize the arc weld defects or pass it as a good weld. The proposed technique has proved to be successful with accurate classification of the welding categories using all three classifiers. The classification technique is fast enough so it can be used for real time weld quality control as all the signal processing is carried out in the time domain.

Differential evolution applied to line-connected induction motors stator fault identification

The three-phase induction motor is the main machine used for electromechanical energy conversion, due to its consolidated construction characteristics. As a consequence of its great importance and industrial application, researches in the fault identification area are constantly conducted to reduce the maintenance rate and the losses, during the productive process, caused by undesirable downtime. In this sense, this work proposes an alternative methodology, based on the differential evolution algorithm, to identify stator short-circuit fault in induction motors connected directly to the electrical grid, using voltage and current signals in time domain. The differential evolution algorithm is used to estimate the electrical parameters of the induction motor, based on the model of the equivalent electrical circuit. Stator fault is identified by calculating the variation of the estimated magnetizing inductance of the motor under no fault condition. The proposed method is validated through experimental tests on 1 HP and 2 HP motors under conditions of load torque variation and unbalanced voltages.

Architecture Design and FPGA Implementation of an FFT based Reactive Power Meter

Reactive power measurement is increasingly paid attention by power industry. A novel architecture to measure the reactive power is proposed in this paper. Architecture is described in verilog and implemented using Xilinx ISE 13.1i. In this method voltage and current signals in time domain are converted to the frequency domain and power on each component is calculated to obtain the total reactive power.

Methods for multi-functional converter control in three-phase four-wire systems

An active rectifier-based shunt compensator plays a vital role in present-day static power compensation. This includes the conventional compensation features such as power factor improvements, harmonic compensation and neutral current elimination in a three-phase four-wire system. Recently, in addition to conventional compensation, the compensator has also been considered for bi-directional active power exchange, simultaneously, with grid-connected systems, when used with adjustable static drives or wind generators. The authors aim to investigate the appropriate control methods for this kind of multi-functional compensation to accurately generate the reference current signals in time domain. In this context, two prominent instantaneous power theories, namely p-q theory and p-q-r theory are compared from a multi-functional perspective. The compensation based on instantaneous p-q-r theory is analysed comprehensively for the proposed compensator. A new approach to eliminate the neutral current completely from four-wire systems with p-q-r theory is suggested. A control system for multi-functional compensation is designed based on instantaneous p-q-r theory. The control algorithm is verified through simulation and experimentation for both positive and negative active power exchange across the DC bus. The experimental results are shown to verify the effectiveness of the proposed controller.