Monthly Archives: January 2024

An Example of Performance Achievement Based on Errors Analysis for Low-Cost Circuits Design

Abstract

To create high-performance equipment, low-performance components, such as those from the old generations, can also be used. For example, if a conditioning stage (amplification/attenuation or filtering) is made with high-end components having increased performance, the costs are appropriate – using “classical” functional ones, the price of the equipment will become competitive. Low-cost devices may have features that do not make them attractive for inclusion in high-performance equipment but certain errors’ analysis may lead to practical and useful results. A converter circuit from PWM pulses to DC voltage was used. Experimental determinations were made using several types of operational amplifiers and errors analysis and correction was carrying out.

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Estimation of the Heating of Crimped Connections Based on Experimental Tests

Abstract

In this work, some analytical formulas based on experimental tests are presented that can be used to estimate the heating of the crimped connections used in construction of electrical machines, saving the experimenter from additional, long and expensive tests. The formulas are based on the energy balance equation and combine practical results obtained from previous steady-state heating cycles for a set of 6 crimped connections of the same type, at currents close to the nominal value. There are standards that allow the estimation of the heating of the elements in the circuit at small variations of the test current. Thus, based on the heating obtained at one value of the current, the heating at another, slightly different value can be estimated, without the need for the actual experiment. For a more accurate estimation, the variation with temperature of the electrical resistances of the 6 connectors must be taken into account, which allows the extension of the estimation range. In this case, if there are two heating cycles performed at two different values of the current, estimations can also be made at other values, much different from the two. A global temperature coefficient of resistance can be deduced that can simplify the formulas while keeping the precision, serving to estimate the average heating of the connectors. The formulas have been validated for several types of crimped connections used in the construction of electrical machines.

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Installation for Carrying out Thermal Tests on the Current Paths of Electrical Power Equipment

Abstract

Today’s electrical networks, as part of the national power system, must meet a number of requirements imposed on power transmission and distribution equipment. The main requirements are: continuity of electricity supply to consumers, operational safety, quality of electricity supplied, development of networks, economic viability of investments, environmental impact requirements. In this context, the testing of the technical performance of the various elements that make up the electrical networks, both at the design stage and, in particular, at the certification stage, is of great importance and is regulated by internationally recognised technical standards and norms. The performance of tests under laboratory conditions requires the existence of specialised installations and equipment capable of generating the electrical parameters to which the various elements of electrical networks are subjected, for the purpose of performance testing and certification. The paper presents an installation for carrying out thermal tests on the current paths of electrical power equipment with a fully digital control system based on virtual instrumentation, which replaces the physical control panel made up of electronic modules and analogue devices. This enables the transition from primarily manual local control by the operator to remote control and eventually full automation of the thermal test process for medium and low voltage switchgear. By taking advantage of virtual instrumentation, the solution can be easily implemented and enhanced by integrating process control and computerisation applications. images

Influence of Electrical Circuit Parameter Changes on the Local Stability of a Three-Phase Cage Induction Motor Fed with Variable Frequency

Abstract

The paper presents the mathematical support and the results of some simulations related to a new method of analyzing the stability of induction motors powered at variable frequency. After a brief introduction to the proposed issue, the mathematical model of the motor, written with relative values, is detailed. Taking this model as a starting point, a Matlab stability analysis program was created. By running this program, a series of graphs were obtained, detailed in the paper (two graphs are represented each, obtained for different conditions, which facilitate their comparison and obtaining conclusions). They refer to four specific cases regarding the modification of static inductance, rotor inductance, stator resistance and rotor resistance. Analyzing these graphs, the necessary conclusions were drawn. The conclusions are important, mainly in the design phase of the machine, to finalize the structure corresponding to the most stable operation of the drive system with asynchronous motor and static voltage and frequency converter. They highlight the influences of the most important parameters of the motor on the stability of the functioning of systems with such a structure. The paper ends with a representative bibliography for the proposed study.

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Annals of the University of Craiova, Series : Electrical Engineering, No. 47, Vol. 47, 2023

ANNALS OF THE UNIVERSITY OF CRAIOVA – Electrical Engieneering Series, no. 47, vol. 47, Issue 1, 2023 (click to download)

On the Induction Motor Rotor Flux Estimation in the Electric Traction Systems with Rotor Flux-Oriented Control –  Mihaela Popescu, Alexandru Bitoleanu, Constantin Vlad Suru, Tudor Mătușa

System for Monitoring Asynchronous Motors Powered at Variable Voltage – Monica-Adela Enache, Ion Vlad, Sorin Enache

Influence of Electrical Circuit Parameter Changes on the Local Stability of a Three-Phase Cage Induction Motor Fed with Variable Frequency – Sorin Enache, Ion Vlad, Monica-Adela Enache

Installation for Carrying out Thermal Tests on the Current Paths of Electrical Power Equipment  – Gheorghe-Eugen Sbtirelu, Petre Pistol, Adrian Vintilă, Mihăiță Constantinescu

Estimation of the Heating of Crimped Connections Based on Experimental Tests  – Alin-Iulian Dolan

An Example of Performance Achievement Based on Errors Analysis for Low-Cost Circuits Design – Constantin Daniel Oancea, Daniel Bostan, Viorel Constantin Petre

Integrated System for Remote Health Status Monitoring and Analysis  – Marian-Ștefan Nicolae , Florentina-Fulgina Bîzîc, Nicolae-Leonide Sîrbu, Iurie Nucă, Raluca-Cristina Presură (Nicolae)

Equipment for the Detection of People Falling  – Constantin-Daniel Oancea

Experimental Study of the Pressure Exerted in the Body of a High-Voltage Fuse and Metal Enclosed Switchgear  – Cristian-Eugeniu Sălceanu, Cătălin Dobrea, Daniel Constantin Ocoleanu, Daniela Iovan

Comparative Performance Analysis of Photovoltaic Power Plants – a Case Study  – Mihaita Linca, Ion Popa, Constantin Vlad Suru, Florin Ravigan

Modelling, Simulation and Implementation on dSpace 1103 of the Direct Power Control in a Three-Phase Shunt Active Power Filter System  – Mihaiţă-Daniel Constantinescu, Mihaela Popescu, Gheorghe-Eugen Subţirelu, Ionuţ-Cosmin Toma

Data-Driven Control of the Second Order Inertial Systems with Astatism – Irina Cojuhari

The Design of a Location Monitoring System for a Fleet of Electric Scooters  – Florin Ravigan, Mihăiță Lincă, Laurențiu Alboteanu

Configuration of SCADA System Graphical User Interface for Electrical Station  – Cosmin-Ionuț Toma, Mihaela Popescu, Mihăiță Daniel Constatinescu, Gabriel Cosmin Buzatu

Small Scale Models of Solar Tracking Systems  – Ionel Laurentiu Alboteanu, Cristian Bratu, Florin Ravigan

System for Monitoring Asynchronous Motors Powered at Variable Voltage

Abstract

This paper presents some experimental aspects related to the operation of asynchronous motors powered at variable voltage. A modern system for actuation of low-power asynchronous motors is presented, equipped with a voltage and frequency converter. Also, a data acquisition system is presented, with a sampling frequency of up to 100 kHz, supervised by an acquisition program that allows the visualization of the variations of the main characteristic sizes of the motor. The program contains both graphic interfaces developed by the manufacturer and by the authors of the paper. This program solves, among other things, an electromagnetic compatibility problem. The experimental tests carried out with the help of this system (in permanent non-sinusoidal regime at various power supply frequencies) are detailed. Technical details of the main system components are provided. The tests are accompanied by photos taken during the experiments and many original explanatory graphics. The authors’ contributions are mainly in the software area. Thus, in the original program, a series of windows for harmonic analysis and visualization of the characteristic phasors of the analyzed electrical quantities were implemented. The paper ends with the main conclusions resulting from the completion of the study and with a representative bibliography.

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On the Induction Motor Rotor Flux Estimation in the Electric Traction Systems with Rotor Flux-Oriented Control

Abstract

Characterized by very good performance in both steady-state and dynamic regimes and also by a relatively simple control structure, the induction motor control with rotor flux orientation is frequently adopted in electric drive systems, especially in electric traction applications. This paper analyses the possibilities of rotor flux estimation in a real Romanian electric traction system of locomotives.  Thus, to estimate the magnitude of rotor flux and the angular position of the rotor flux vector, two possibilities are identified and discussed. First, the use of the sensed speed and stator currents is taken into consideration, and then the use of the measured supply voltages and the stator currents is the second alternative. Dedicated algorithms were designed for their related control. Both variants are analyzed through the results of the simulations obtained based on the specific models created in the Matlab/Simulink software. Four values of the imposed speed are taken into account in the performed analysis. It is highlighted that, in real conditions where the drive system is provided with speed sensor and there is no sine filter for the distorted motor supply voltage, the best option to estimate the rotor flux is to use the measured speed and the stator currents. images