Monthly Archives: January 2023

Annals of the University of Craiova, Series : Electrical Engineering, No. 46, Vol. 46, 2022

ANNALS OF THE UNIVERSITY OF CRAIOVA – Electrical Engieneering Series, no. 46, vol. 46, Issue 1, 2022 (click to download)

Dynamic Procceses of Electric Motors for Operating some Aircraft Equipment – Sorin Enache, Ion Vlad, Monica-Adela Enache

Harmonic Analysis of Electromagnetic Torque in Brushless Direct Current Motors – Monica Adela Enache, Ion Vlad, Sorin Enache

Fuzzy Model for Estimating the Power Consumed in a Transformer Station – Cristian Bratu, Daniela Popescu, Cătalin-Constantin Luţu

Current Issues Regarding the Analysis of the Physico-Chemical and Electrical Properties of Transformer Oil – Mircea Emilian Ardeleanu, Aurelia Scornea, Dan Gabriel Stănescu, Ionuţ Marius Burciu, Ioana Gabriela Sîrbu

Modeling of Thermal Transfer Parameters by Transparent Construction Elements – Felicia Elena Stan Ivan, Radu Cristian Dinu, Adelaida Mihaela Duinea

Exhaustive Optimization Method Applied on Electromagnetic Device – Alin-Iulian Dolan

Automatic Sorting System for Educational Training – Laurentiu Alboteanu, Florin Ravigan

Reactive Energy Compensation Equipment Used in High Power Laboratories – Daniel Constantin Ocoleanu, Cristian-Eugeniu Sălceanu, Mihai Ionescu, Marcel Nicola, Daniela Iovan, Sorin Enache

Comparative Analysis in the Case of Indirect Current Control in a Shunt Active Filtering System – Mihăiță Daniel Constantinescu, Mihaela Popescu, Cosmin-Ionuț Toma, Constantin Vlad Suru

Application of Electrical Substation, Ring Topology versus Star Topology – Cosmin-Ionuț Toma, Mihaela Popescu, Mihăiță Daniel Constatinescu, Ion Cristian Popa

Analyzing the Influence of Harmonic Parameters on Accuracy Indices When Applying Wavelet Transform – Dusan Kostic, Ileana Diana Nicolae, Iurie Nuca, Petre Marian Nicolae

Dynamic Procceses of Electric Motors for Operating some Aircraft Equipment


In this paper are detailed some results obtained within a European program in the field of avionics. The objectives of the program and the implementation team are briefly presented. A number of technical details are provided regarding the electric motor used to steer an airplane’s running gear: advantages, comparative densities between the motor used (HDD) and the competitive motors, cross-section of the used motor, winding scheme of the motor, motor scheme with partial short-circuit. The mathematical model of the motor is presented, Simulink scheme of a simulation program in case of using a voltage inverter and a series of simulations obtained with its help (MSMP supplied by a voltage inverter, transmission ratio 1000, inertia10000 Nm2 and MSMP supplied by an inverter with prescribed currents, transmission ratio 1000, inertia 10000 Nm2). The paper concludes with the conclusions obtained by conducting the research. It is mentioned that
the following notable results were obtained: decrease with 30% of the production and maintenance costs, decrease with 10% of the airship weight, carrying out a drive with a
probability to lose the functionality.

Harmonic Analysis of Electromagnetic Torque in Brushless Direct Current Motors


This study has aimed at establishing and analyzing the causes that produce oscillations of electromagnetic torque developed by brushless direct current motor. The study opportunity is given by the progresses obtained in command and power electronics, which made this motor performant from technical and economic viewpoint. The
specialty literature reveals that important torque oscillations occur in this motor in a complete rotation. That is why, this study and the simulations presented here emphasize
that there are five classes of slots relatively to the torque magnitude developed and the fact that all the slots are active, that meaning that the average torque developed occurs
in the rotation direction. The harmonic analysis reveals that the torque distortion, within the five classes of slots, is variable between 51.03% and 97.63%. The torques computed
for the slots classes are between the minimum limit of 0.029 Nm and the maximum one of 0.077 Nm. The low speed torque oscillations can be reduced with a high inertia moment,
a speed reaction loop and a performant control system. The importance of the research theme is justified by what we have presented before and is a subject of major interest for engineering.

Fuzzy Model for Estimating the Power Consumed in a Transformer Station


The paper studies the implementation of a new transformer station in a network designed to take over some of the existing consumers, to provide the necessary energy
for a number of new consumers and a reserve for future new connections to the electricity grid. By creating a fuzzy model, a number of rules have been created to highlight the power consumtion regimes, manifested at the level of the transformer station. Also, the possibility of optimizing and taking over from existing clients was created so that a balance and an optimization can be created regarding the disposition of the consumers on each station.

Current Issues Regarding the Analysis of the Physico-Chemical and Electrical Properties of Transformer Oil


Researchers and practitioners interested in the operation, monitoring and diagnosis of electrical equipment (such as: transformers, motors and generators, circuit
breakers, etc.) know that in order to ensure a safe operation of such equipment it is necessary to know, among other things, the condition of the insulation system. This is one of the essential information to know because about 40% of failures which occur in the operation of the electrical equipment are due to insulation breakdown; in some cases
they can reach even close to 100%. In this context this paper proposes the presentation of several modern methods and equipment for the study and analysis of physical and chemical properties (namely: analysis of water content, density and interfacial tension, dissolved gas analysis and furan components determination) and electrical parameters
(namely: determination of loss factor and relative permittivity) of transformer oil. Samples of transformer oil type MOL TO 30.01 (uninhibited electrical insulator, nonadditive), new StaSo Transformer Oil I (high quality inhibited insulating oil) and TR 30 oil were studied. Two samples were collected directly from the original barrel, two samples were collected from the transformer tank after dielectric tests at the transformer’s manufacturer and also two samples of used TR 30 oil were collected from two transformers. The tests were carried out in an accredited laboratory with calibrated equipment. The results highlighted the properties of each analyzed sampled. The interpretation of the results emphasized the qualities and defects of each analyzed oil
sample and whether or not they fit the standards in the field.

Modeling of Thermal Transfer Parameters by Transparent Construction Elements


The article presents a case study on the modeling of heat transfer parameters through transparent construction elements. Conducting experimental studies on the scale of an entire building is very complex, on the one hand due to the size and geometric  complexity of the studied objectives and, on the other hand, due to numerous random
factors (climatic conditions or how the buildings are operated). In order to be able to carry out a study on the real behavior of the buildings, models are made for them, taking
into account the real mode of operation of the installations related to these  constructions. The present article consists in making a modeling for a simple exterior window, with a single sheet of glass that separates the interior space of an enclosure (rooms) from the exterior environment. The modeling will be performed both for the case of a building located inside a locality and for the case of the location of the building outside the locality.

Exhaustive Optimization Method Applied on Electromagnetic Device


This paper presents the application of an exhaustive optimization method based on the design of experiments (DOE) and the finite element method (FEM), with the aim of improving the actuation force developed by a DC electromagnet. The optimization of this device has been the subject of several previous works, allowing comparisons between the optimization methods applied in terms of the obtained precision and the workload.
According to previous studies, two geometric parameters (the angle ratio of the support tip and the coil shape ratio) are very influential on the force developed at the maximum
air gap. Thus, the exhaustive optimization method took into account these two  parameters for its maximization, having as constraints the maintenance of the global dimensions of the device (external radius, the height of carcass, height of the plunger with support) and of the cross-section of the winding. The optimization algorithm used the results of 2-D FEM numerical experiments carried out with the FEMM program in combination with the LUA language and is based on the response surface methodology (RSM) and analysis of variance (ANOVA). Second-order polynomial models of the objective function were calculated using full factorial designs with three levels per factor. After three iterations, a very good result was obtained, comparable to those obtained by other methods, but with a significant cost in terms of workload, the optimum obtained being a global one.

Automatic Sorting System for Educational Training


At the same time as the introduction of automated equipment in industry, production operators and maintenance workers servicing automated stations require professional training courses depending on the category and job. Depending on the particularity of the production process, these training courses can be done internally at the production unit, at external industrial partners or at universities. The paper presents an automatic tire sorting system made on a small scale. The sorting system is composed of an input stock and two output stocks of sorted tires. Tire storage in the two output stocks is done with an electro-pneumatic manipulator robot. The sorting is done according to the tire bead width, for which the system is equipped with the appropriate sensors. The structure is
controlled by an Arduino Mega2560 microcontroller development system. The sorting station can also be controlled manually by the operator via a joystick and some buttons. In comparison to other sorting systems, the robot structure is simpler. It performs the transfer of the tires by only two movements, thus reducing the handling time. Also,
the automatic sorting system realized corresponds to the requirements imposed on flexible production systems. The automatic system can be used both for training students
from technical faculties and industrial operators in the field.

Reactive Energy Compensation Equipment Used in High Power Laboratories


The power quality covers the means to conserve energy resources, such means consist in improving the power factor and judiciously managing the reactive energy in the power system. Electric grids do not have an unlimited energy transmission capacity, therefore any load on the grid with reactive energy is measured by the energy distributor/supplier and billed to the consumer. On the premise that for industrial consumers, the main consumers of reactive energy are the low-load induction motors and transformers, this paper presents a synchronization equipment for a wound-rotor induction motor with a power of 2000 kW, nominal voltage 6kV, nominal current 210A, which allows the increase of the power factor, significantly reducing the reactive energy consumption. The equipment presented was designed, built, tested and validated by tests carried out in
the high-power laboratory.

Comparative Analysis in the Case of Indirect Current Control in a Shunt Active Filtering System


In this paper, the performance of a three-phase four wire shunt active power filter (APF) using indirect current control with active load current calculation was compared with that corresponding to using indirect current control with prescribed current calculation from the voltage controller. It is clear that, under balanced and sinusoidal voltage conditions, these two methods give similar results. The variant of the indirect current control with prescribed current calculation from the voltage controller has the  advantage of simplicity, but exhibits increased sensitivity to voltage ripples on the compensation capacitor, as they are reflected in the output of the voltage controller. The whole system was modeled using MATLAB-SIMULINK software. The simulation results demonstrate the applicability of both methods for APF control. images