Category Archives: Fără categorie

The Influence of the Treatment Mode of the Neutral in the 6-35 kV Networks on the Displacement Voltage in the Quasi-Stationary Regime

8 January 2020Fără categoriecburada

Abstract

Contactless energy transfer 1 has indubitable advantages in modern technique given by the lack of electro-mechanical contacts predisposed to pitting and failure: use in aggressive or explosive (no sparks) environments, application to mechanisms with translation or rotation move-ments (robotics), high efficiency on relatively short distances a.s.o. Recent researches carried out in Romania demonstrate the feasibility of these systems for a wide power range, from a few watts up to tens of kW, suitable for the expansion of the electro-mobility and proliferation of multimedia and mobile communication devices. Such systems impose storing the energy in batteries requiring frequent charging. The concept of high frequency transformer with separable windings, as well as a capacitor with separable electrodes working in near field regime, the use of resonance and magnetic flux concentrators for increasing the transfer efficiency, some practical achievements and also maintaining of electromagnetic compatibility within well-defined limits are presented. The paper aims to draw the attention of users and also of prospective investors on the applications and advantages of these systems and to encourage national partnerships for developing theoretical and applied research in this field.

Graphical User Interface to Plot the Torque Speed Curves of Multiples Cage Induction Motor

8 January 2020Fără categoriecburada

Abstract

The aim of this paper is to propose an interdisci-plinary approach in study of asynchronous machine with multiple cages rotor. There were two reasons to choose as subject of studying the asynchronous motor with multi-ple/double cages rotor: firstly, because of its large applica-tion in fans and water pumps for various industrial and irrigation systems, as well as in lathe and drilling machines, and secondly, because the theoretical background of this subject is a very complex one. Because the torque-speed curve has a crucial importance in improving the perform-ances of a system, the final results of this study is to propose a Graphical User Interface in Matlab which could be used to calculate the characteristics of an asynchronous motor with multiple /double cages rotor. After a brief introduction about the constraints of systems with multiple cage asyn-chronous motors, paper propose a short review on theoreti-cal background of these machines. The next step will be to underline the designing aspects of the machine and finally to models in Matlab its characteristics. The importance of this work is bringing in attention usual aspects which could be improved by revising in learning process and in new indus-trial technologies. The results of this work could be used to design a virtual laboratory in area of electrical machine.

Parameter Identification of Transformers and Transmission Lines Based on Synchronized Measurements

8 January 2020Fără categoriecburada

Abstract

The parameters of power transformers and transmission lines, as a rule, are determined by reference data, but during the operation, it might vary essentially from the actual data. There are noted the reasons for the parameters’ modification. This paper explains the opportu-nity of parameter identification based on the synchronized measurements during the operation of the studied object. The methods of parameter identification can be based on one, two or more measurements. Two-winding power trans-formers and transmission lines can be represented in the form of quadripole, so, applying only the current and volt-age synchronized measurement on both terminals it is pos-sible to obtain parameters of the Г-, Т- and П-forms equiva-lent schemes. There are presented a final and intermediate formula for transformer parameters. Also, there are ob-tained a similar formula for transmission lines. Besides, for transmission lines, there are obtained expressions for the method of the current balance, then for power balance. The last-mentioned methods are based on two samples of meas-urements and haven’t been previously described in any other source. All proposed methods were verified with the models of real transformers and transmission lines. The obtained results show the high accuracy of parameter iden-tification for the proposed methods. For power transform-ers, the influence of load factor upon the values of parame-ters was analyzed. It is worth noting that the most reliable results are obtained from measurements at the load factor β=0.55..0.85. For the model of the transmission line, there were compared the results of all proposed methods: the relative errors of calculation for all mentioned methods are less than 1%. The main contribution of this paper lies in the explanation of the novel method of quadripole (based on one measurement) for parameter identification of transformers and electric lines. That represents a good advantage over other methods with multiple measurements.

Comparison between Fuzzy Controller and Classical Methods for Determining the Degree of Polymerization

8 January 2020Fără categoriecburada

Abstract

This paper shows a fuzzy logic-based method for determining the degree of polymerization of the solid insulation of a transformer, taking into account the 2-FAL (2-furfuraldehyde) content. The proposed method generates information on the “health” condition of the transformer, with a high precision degree. The proposed system is based on two fuzzy-type controllers, and for each input/output of them it is defined a type of membership functions, triangle and trapezoid for a better response of analysis. The obtained results were compared to the results got by classical methods applied for the same 2-FAL content. For verifying the precision and accuracy, the proposed method was applied on more than a hundred of samples subjected to verification.

Determination of the Dielectric Stresses that Appear in the Windings of a Lightning Impulse Autotransformer

8 January 2020Fără categoriecburada

Abstract

This paper presents two methods for determining the dielectric stresses occurring in the tap winding of a lightning pulse autotransformer. The first method is to im-plement the equivalent circuit using the ATP / EMTP pro-gram, and the second method consists in testing the auto-transformer at a low voltage impulse before being put into the tank. The design of the autotransformer was done tak-ing into account the results obtained with ATP/EMTP. This fact allowed the design of the winding structure as well as their location in space to obtain uniformly distributed over-voltages along the axial and radial direction of the coil as-sembly. The results of the laboratory tests performed on the autotransformer, validated the results obtained with ATP / EMTP.

A Cost-Effective Smart Irrigation System For Water Reduction

8 January 2020Fără categoriecburada

Abstract

A cost-effective solution for water reduction based on a smart irrigation system is presented in this pa-per. The system consists of a microcontroller, moisture sen-sors, relays, solenoid valve and water pump. Depending on the conditions of a specific location (soil condition – wet, dry, etc.) the system can control the amount of used water by modifying some parameters. In this application were considered 2 zones which mean that 2 humidity sensors were used. When the humidity drops below a threshold val-ue on one of the two zones, the corresponding humidity sen-sor transmits the information to the controller, opens the solenoid valve and starts the water pump until the humidity reaches at the preset value. If humidity decreases in the meantime on the other zone the information received from the humidity sensor leads the solenoid valve to open and the pump starts until the desired humidity is attained. When the humidity is over the threshold value, the system is in “stand-by” until the sensors send new information to the microcon-troller and thus the system resumes its operating cycle. In this way various crops can be watered without using a high quantity of water. In addition, a smartphone application was used in order to provide to the user information about the soil condition. In order to implement this solution, a laboratory model was constructed and experimental results were performed to test the performance of the irrigation system.

Contributions Regarding the Modernization of the Anti-Hail Rocket Launcher Monitoring System

8 January 2020Fără categoriecburada

Abstract

The University of Craiova – Center for Innovation and Technology Transfer carried out systematic research on the complementary equipment for the anti-hail system. One of the research topics covered the anti-hail rocket launcher monitoring system. At present, the monitoring system for the launching ramps is composed of slave modules mounted on ramps and a central master module provided with a small display for viewing the parameters of the launching ramps. To view all the parameters, operators must perform several maneuvers at the master module buttons. The paper presents one of the adaptations made this year to take into account the experience gained by those who manage the Romanian national anti-hail system. The optimization of the rocket launcher monitoring system structure is based on the practice of using it and consists of the use of a single piece of equipment for simultaneous display of information in a sug-gestive form, easily used by human operators under stress in real condition of shooting with rockets. The proposed solu-tion allows displaying all the parameters on the monitor screen and helps the operators in the activity of combating the hail by reducing the number of operations they have to perform. This reduces the intervention time and the stress to which the operators are exposed. The software part of the monitoring system ensures its flexibility and competitive-ness.

Tuning the PID Controller to the Model of Object with Inertia Second Order According to the Maximum Stability Degree Method with Iteration

8 January 2020Fără categoriecburada

Abstract

In this paper there was elaborate the procedure for tuning the PID controller to the object with inertia of the second order according to the maximum degree of stability method with iterations. The characteristic equation of the closed system is determined. By derivative operations on the unknown variable of the maximum degree, analytical expressions of the parameters of the PID controller are obtained as functions of the parameters of the object and the degree of stability. By graph-analytical procedures these functions are constructed by varying the argument. By procedures with iterations on these curves for the same value of the argument, sets of values of the parameters controller are chosen. The synthesized system is simulated and the system performances are evaluated. Two examples of objects with inertia less and greater than one according to the proposed method and the pole-zero allocation method by simulating on the computer system were examined. The parameters of the objects were varied and the robustness of the system at the unit step reference action was verified. The advantages of the proposed method are highlighted by reduced calculations and minimal time, which lead to the simplification of the procedure for tuning the controller for these objects.

Achievement of Current Pulses of High Amplitude Using a Voltage Pulse Generator

8 January 2020Fără categoriecburada

Abstract

This paper presents a comprehensive project aim-ing to achieve high amplitude current impulses using a high voltage generator (GIT) as a power supply. To obtain im-pulse currents with GIT, a wide range of simulations has been carried out to obtain the optimal parameters of the current impulse. LC delay cells were introduced in the test system circuit in order to increase the duration of the cur-rent impulse. A current impulse generator (GIC) circuit has been developed to meet the standards in force. This system has enabled new test methods to be developed and improved equipment developed. The development of this project al-lowed current impulses to be obtained with minimum costs. The methods and procedures used can be used to expand research fields by using current impulses to determine the dynamic and thermal stability of electrotechnical and elec-tro-energetic equipment as well as the functional stability of electronic devices in electromagnetic disturbed environ-ments.

Modified Petri Nets for Hybrid Systems Modeling - a Case Study

8 January 2020Fără categoriecburada

Abstract

In this paper we deal with the problem of modeling and simulation a DC electric drive system using a Hybrid Petri Net formalism, considering that the electric drive is a hybrid system which switches between its states under the occurrence of generic and non-generic external events. The synthesized topology is called a Modified Hybrid Petri Net and is a hybrid model that combines both differentials and discrete Petri Nets dynamic and enables us to simulate and to analyzing the behavior of DC electrical drives in different operating regimes due to the particularities imposed by the load of electrical motor. A real application case was finally considered; different scenarios were analyzed, depending on the nature of the engine load and the specific working conditions. The correctness of the initial model was verified by simulation and, also, by comparison of the results with those obtained experimentally, on a physical model. The modified Petri Nets model is carried out with an available software Visual Object Net ++, which allowed at the same time the synthesis of a hierarchical Object Petri Net structure. All models obtained through this method had been synthesized through an ascendant technique, around a central core, by adding new elements according to the studied processes.