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The paper presents a laboratory micro hydroelectric power plant destined to applicative activities. The hydraulic turbine is a Pelton turbine, rebuilt by fast prototyping in Geomagic Design X and printed on a 3 D printer. The turbine casing and the afferent elements are made in-house. The hydrogenator is synchronous being an alternator from a Dacia vehicle. The hydrogenerator load is constituted by 3 groups of light bulbs. We analysed the working of the micro-hydroelectric power plant in idle run and for different loads. As a result of the analysis we found out that it stably works for different loads and by its open construction it is useful for developing students’ ability to understand the phenomena. The installation designed and executed is useful for the engineering students as the pandemic forbids the thematical visits in hydro-energetic facilities.

In the context of the electricity crisis, measures are needed to reduce energy consumption. The case study was conducted on the lighting system at a university sports hall. To determine the efficiency and quality, the lighting systems and technical characteristics of the sources used were identified, lighting level measurements were made, the luminotechnical coefficients and the power of the whole lighting system were calculated and the results were compared to the values set out in the standards. Following analysis, the lighting system was found not to meet the quality requirements and was energy inefficient. For financial efficiency, only the replacement of lighting was sought, keeping the same equipment and granting the same facilities to the building users. Some lighting source options were analyzed and the option to have the highest luminous efficacy and the highest energy class was chosen. The analysis shows that the investment is amortized within a maximum of 17 months. The innovative aspect is based on linking the measurements with the determination of power and the proposal of modernization solutions, which shows the need for investments to ensure the quality of the system and the increase in energy efficiency.

In the design and construction of Direct Current (DC) windings, depending on the number of slots, number of pole pairs, and on the type of winding we find same potential points. To correct for the execution imperfections between same potential points, equipotential connections are provided, depending on the type of winding. There are situations where same potential points are not physically accessible, being placed in slots or on different frontal parts. Connection equipotential points is done by means of connections placed in holes made in the magnetic rotor core, such that no electromotive voltages are induced. This makes the design of the magnetic rotor core more complex and can lead to asymmetries in the machine. The work presented in this paper proposes the use of equalizer links between different potential points. In these links, which are placed in suitable slots, electromotive voltages are induced. These voltages must compensate for the difference between the winding points they are applied to. The use of the equations presented here must result into an as small as possible drop in the relative voltage between the connected points, while the number of elementary coils should be an integer multiple of the equalizing links.

Air conditioning (AC) installed on vehicles must insure passenger comfort no matter the year season. To this end we make a series of measurements and readings of the interior temperature of vehicles with such AC installations. This work presents a study on the AC efficiency on public transportation vehicles, namely articulated busses. Our study shows that the AC appliances installed on the examined busses were not able to ensure the temperature assumed by the AC contractors. We propose that, for public transportation, AC installations should be sized accordingly to the vehicle’s interior volume and to the transportation’s body thermic insulation.

Low power photovoltaic installations must ensure the necessary energy level requirements of the installation’s beneficiary. At the same time, it must be conform to the legal regulations and norms. When a photovoltaic installation is to be delivered into the power supply network, its operating parameters must be closely monitored. In this work we present the results of our monitoring of a low power photovoltaic installation. Upon examination of the voltage variations, of the currents, of the voltage and current harmonics, we conclude that the installation we studied does indeed fulfill the necessary requirements for connecting to the national power grid. Examining the energy levels consumed by the beneficiary, we find that the photovoltaic installation cannot continuously ensure the required energy levels, which recommends the acquisition of an additional photovoltaic installation.

The operation at maximum power in condition of rapid wind velocity modifications poses a challenge for wind power plants. Based on measured data, the authors determine for generator and turbine, the mathematical models. Also, with current measured values for mechanical angular speed, ω, and wind speed, v, the authors determine the mathematical model in a timely manner and, on its basis, compute the optimal mechanical angular speed ωOPTIM, at which the value of the wind turbine power is maximum. We determine the dependence of the optimal / ideal mechanical angular speed, ωOPTIM, to the wind speed, v, and bring the wind turbine into optimal operating area by modification of the generators load. By measuring the wind velocity and monitoring the electric energy flowing from the permanent magnets synchronous generator (PMSG), we compute the wind turbine power. Based on those remarks, to get maximum power out from a wind turbine, it is necessary that between wind velocity and mechanical angular speed should always exist a correlation, according to the wind velocity changes and the inertia moment, J.

This paper presents a case study resulting from the implementation of the project “Informed student-guaranteed success”, a project that aimed to familiarize young people with various aspects of the labour market. Within the project, the students involved carried out several documentation visits to various companies in the area and the region, and finally completed a questionnaire. Following the processing of the results, we identified the desire of young people for professional and personal development, as well as the interest and usefulness of study visits. The study allows the identification of intervention directions by educational institutions, employers, organizations and even the government. Thus, the use of modern teaching methods, combined with new technologies and visits to enterprises will contribute to the enhancement of the educational act and, implicitly, to the reduction of school dropout. In order to train the next generation, it is imperative to establish a close connection between economic agents and educational institutions, so that future graduates will be able to choose the right job, and adapt to the new status more quickly and easily. These documentation visits should be included in the activities of pre-academic students so that they can choose the right career.

In this work we underline the importance of the optimal design for outdoor light systems such that light posts and sources are placed correctly. We present a case study where we considered a city road section equipped with LED sources. On this section, we measured technical luminous coefficients, which were then compared with values listed in standard and normative documentation. Based on this we did a new design that had to follow certain requirements on street and lighting post configuration. Comparing the two designs we conclude that, to have an optimal street light system, the engineer must aim for the best possible design and consider this when deciding on the position of the light sources.

Today's World is getting more efficient in mail deliveries or other applications using autonomous vehicles as drones because of their improved performances. The quadcopter appertains to the drone family having the advantage of flying stability light weight and accurate maneuverability. This paper describes the design and the adaptive tuning for dynamic control of a quadcopter using PID control technique. The experimental tests show improved response related to the previous results under the same input conditions

It has been found that inside some of the buildings with protection from lightning systems, electronic appliances are damaged after storm caused electrical discharges. Induced electric-motor voltages in the appliances’ circuits during the atmospheric discharges are damaging the appliances. In this paper we establish the minimum distance from the wall on which the lightning conductor between the lightning rod and the grounding rods should be fitted, such that the voltages induced in electrical or electronic appliances, connected or not, are at safe levels.

The present paper determines the optimum energy operation area of an electric wind power system, under time varying wind speed conditions. The determinations of the optimal area, from the energy point of view, is done based on experimental values from the Romanian black sea cost, Dobrogea area. The optimum operation area is defined by the optimal mechanical velocity, ω OPTIM . For this, the dependence between the wind speed, v, and ω OPTIM are computed based on the current wind speed and the current mechanical velocity ω. Due to the high inertia of the wind turbine (WT), the generators speed is not able to follow the changes of the wind speed. Knowing the optimum value ω OPTIM , the solution is to determine the load at the permanent magnet synchronous generator (PMSG) in order that the mechanical speed should timely reach his optimum.

This paper presents an application of digital cascade control implemented in Scilab / Xcos environment, using a P type regulator for the position adjustment circuit, a PI controller for the speed circuit adjustment; the current respectively moments control circuits are rendered by elements of PT1 type. On this basis the program is done in Scilab and the related signal block diagram implemented in Xcos; through simulation, the step response of the system is analyzed for different sampling times.

We analyse in this work three outdoor lighting systems using three types of light sources, in order to determine their performance with respect to outdoor lighting restrictions. The study in this work contributes to gaining insights on how to increase the outdoor lighting systems’ energy efficiency. We analyse two LED source types and one sodium fumes light source type, which illuminates various sections on a street in Reşiţa, Romania. Upon analysing and processing the data, we establish the performances of each of the three lighting sources, whether they respect the imposed standards, and which one is the best lighting source to choose. This work shows the necessity of field measurements regarding the lighting system efficiency before the acquirement of a specific system type.

The paper presents the results of the scientific investigations performed on an Otto engine. One conducted surveys on the analytic and experimental modelling of the internal combustion engine, considered as automated system element. The results of the analytical study are concretised in the mathematical model of the engine, expressed in the operational. The experimental results are concretised in the indicial response in rotating speed, as well as in the determination of the constants of interest. The investigation methods used in conducting the survey were: experimental identification based on the indicial response of the engine and the analytical identification based on the mathematical models of diverse engine subsystems.

To have a more comprehensive overview of failures to railroad traffic installations, the installations must be monitored permanently. In this work we propose a record software that allows a rapid identification of the train stations with the most failures, their causes, of the installations with the most number of failures, and so on. Based on the data shown by the software, coercive measures can be taken to improve the quality of the maintenance work, or to detect the weak components. The software we present in this work can be used at the (Romanian) national level and graphically shows the monitoring results.

In this work we present a specialized software that should be used in the bidding or design phases for the optimal choice of the equipment that make up the automatic switching system from the base source to the backup source. The use of the software does neither require wide electric engineering knowledge, design knowledge nor electric circuit sizing know-how, and can be used by the bidding and supply staff. The advantage of using this software is the possibility to quickly select the necessary technical equipment in order to obtain a technically competitive automation system at a convenient price. The software we propose in this work is based on sizing calculations and predefined lists of standardized equipment provided by various producers and suppliers. Upon inputting variable values, the software outputs a price estimate and a list of electric gear, including the life-size equipment dimensions. The software application allows the sales engineer to draw up the necessary documentation, without the assistance of the design engineer, in order to establish a correct price estimate.

To optimise the diagnosis process for Romanian railroad traffic safety installations a series of diagnosis charts were devised on which a diagnosis software package was created. In the first part of the paper we explain the installation’s operation mode. At this point, the installation diagnosis is classically done at its sequence of operation steps, without detailing the actual failure cause. That is, only the schema where the failure appears is identified. In our work, through the diagnosis charts and the afferent software we can determine the actual failure cause. The software is written in Visual Basic. The maintenance staff using this software are quick and correct in reaching a decision about failure causes. Thus, train traffic delays caused by lengthy and problematic failure diagnosis is kept to a minimum. At the same time wrong maintenance decisions are eliminated and serious traffic events avoided

The diagnosis of failures in train traffic installations can be done in several ways: direct observations and measurements, software assisted diagnosis using specific software packages, process variable monitoring for electronically centralized installations. This work presents basic concepts for Model Based Diagnosis (MBD) that uses fuzzy logic to analyse the integrity of Centralized Traffic Control Installations (CTC) in train traffic. We define the diagnosis relations to be used and show how to apply them to train traffic security installations. Implementing these concepts into an expert system assists maintenance operators in quick failure diagnosis of the train traffic security installations.

Modern applications for PCs, mobile phones or tablets are increasingly stirring the interest of users and contribute to the labour productiveness in diverse fields. The paper presents the method of computer diagnostic of output signals in railway stations, based on the diagrams and diagnosis software, elaborated by the authors. The diagnostic diagrams were drawn up by using the diagrams from the stations with electrodynamics centralisation (CED) of the CR4 type. The software may run on diverse modern devices and can be also adapted for other types of CED installations. Grace to the answers to different questions asked by the application, the possible causes of the failure or fault may be displayed fast and accurately. The purpose of the computer diagnostic is to reduce the normal diagnosis time.

Electric power supply installations must ensure a permanent power feed to the train traffic security installations. Any damage to the power feed components lead to delays in train traffic. This work proposed a modern computer-based diagnosis method based on diagnosis charts, both created by the authors. Running the hereby proposed software package and following its indications, the failure cause can be quickly identified, implicitly reducing traffic time delays. The software is user friendly, does not affect the traffic security in any way, and does not necessitate a specific, additional training of the maintenance staff. The software has a simple interface, is intuitive, and runs both on PCs and on mobile devices.

This paper shows a review of the present methods of testing the high-duty and high voltage electric machines and transformers, to which the authors brought their own contributions concerning their elaboration and exploitation. We have especially presented the methods which make possible the concluding heating tests in factories and the elimination of the eventual errors which can occur at the installation place.

The paper presents the computing of control circuits in the frequency domain, starting from the mathematical model of the frequency response H(j) obtained from the transfer function H(s) where the operational variable keeps just the image part. For PT1 and PT2 elements, using Scilab, the geometrical place is illustrated and the frequency diagrams are determinate for different duping constants (PT2). The logarithmic frequency diagrams (Bode), determine the amplitude and phase reserve for a control circuits with three PT1 elements.

The paper presents a study made on choosing LED street lighting installations, such that the quality requirements for exterior artificial lighting are fulfilled. We analyze two types of LED street lighting installations from a technical point of view, together with lighting level and brightness values obtained during the measurements. Following on the field measurements, the lighting quality parameters are calculated, and, for the lighting installation with the best performance, optimal mounting suggestions are made. The optimal quality parameters are calculated by simulations using the Dialux software. The same software and the same light sources we also compute an optimal street lighting by determining the size of the installation that provides the best lighting parameter values.

The paper presents the results obtained from the study conducted on an execution element in view of its modelling and identification. The mathematical model obtained from the studied execution element con-stitutes the basic information serving to the design of the adjustment algorithm of the automatic system where the actuator will be introduced, as well as the establishment of the technical parameters of the static converter for the supply of the electric motor.

This work presents solutions to improve the quality parameters for outdoor illumination. The work starts from a case study which measured the outdoor lighting quality indicators on a street of the town Reşiţa. We measured levels of lighting and brightness, and we computed various lighting indicators. The obtained values were then compared to the values recommended by actual technical norms observing that they do not fit into the normed limits. Using the Dialux software we calculated the optimal mounting variant of the lighting installation for the street under lighting analysis. In the optimizing software we kept the pole’s height and place in space constant to the values in the real situation. This work presents new variants of lighting installations that can ensure the best lighting indicators possible.

This paper shows a review of the present methods of testing the high- duty and high voltage electric machines and transformers, to which the authors brought their own contributions concerning their elaboration and exploitation. We have especially presented the methods which make possible the concluding heating tests in factories and the elimination of the eventual errors which can occur at the installation place.

During the design of synchronous generators is very important to establish the values of their electromagnetic stresses. The specific literature recommends that these stress values are to be chosen from the curves obtained during experimental design, where the independent values are the polar pitch and the number of pole pairs. The authors of this work propose a method of finding the dependency between the electromagnetic stress and the synchronous generator rated speed to rapidly estimate the stresses in a given interval of rated speed values.

This work presents the limits of mathematical models of wind turbines. At a wind turbine, WT, in the region of negative powers, Pwt, usual mathematical models are no longer valid, the errors being unacceptably high, the obtained values are much different from real values. In the area of positive power, the mathematical models are valid and approach to the real power characteristics. These considerations are especially useful in making accurate simulations of different operating regimes. In the maximum power point area — MPP, the models can be used with good results, but only at constant wind speed. For large angular mechanical velocity (AMV), over AMV at without load, Ouai, these models can no longer be applied. The mathematical models are very useful in various simulations and are therefore used, both, in the design — construction phases as well as in operation.

This article presents a method for the computerized diagnosis of entry lighting signals in a CFR1 railway station. The railway station is controlled by a Electrodynamic Centralized type 4 block-and-interlocking installation. The work presented here deals with interrupted glowing wire signals of the red light and with the inability to command the call signal. The proposed method substantially shortens the diagnosis time and, therefore, shortens the delays in railroad traffic. The method is based on diagnosis charts which, in turn, are used to devise a specialized software, which allows fast and accurate detection of signal defects. The diagnosis software does not interfere with the traffic security, can be used in maintenance staff training sessions. The software runs on personal computers as well as on mobile devices.

Continuous development of urban areas and extending industrial zones have lately generated an accentuated trend in the transition from aerial electrical lines to cable lines. At the same time with this transition, a number of problems occurred connected to the normal operation of the power cables and their use in powering domestic and industrial electric consumers. This work discusses actual issues on the design of techniques and methods to detect failures of power cables, design based on the data collected by specialized operators. Selecting the correct diagnosis technique can identify quickly, with low errors, the location of the cable defect. This work presents the use of two cable lines diagnosis methods in concrete situations: the impulse method and the returned flame arc method. The current impulse method is characterised by high measure precision and non-destructiveness, being recommended for defect location where long use and aged power cables are involved. The comparison between the two diagnosis methods underlines the detection errors that imply high time and financial costs. The current pulse method is recommended also for power cables mounted within PVC tubes, with no direct contact with earth.

In practice, vector control methods are widely used offering the possibility to reach high performance. Certain application areas need optimum control in at limit operating conditions, as, operation at maximum torque. The paper presents how through the proposed control scheme at the output of the flux and the voltage controllers, provide direct the frequency and voltage values for an asynchronous machine (ASM) operating at variable speed. The simulation analyses for the considered control structure are based on the use of two controllers: flux regulator for determining the stator flux and the speed regulator for determining the stator frequency. The dynamic analysis of the system is done highlighting the tuning process for the two controllers, which enables conclusions on the proposed method with different applications, as the ASM in wind turbines.

The entry signal of a Romanian railway station is an installation that allows or forbids the entry of a train in the station. Together with other, interconnected installation, the entry signal insures the railroad traffic safety. Any defect to the signal cause train delays, signal malfunctions may cause railroad traffic events. The diagnosis method proposed in this work comes to the aid of railroad maintenance staff by reducing the diagnosis times. This method is based on specially designed diagnosis diagrams, which are in turn based on electrical schemas of Centralising Electrodynamic block-and-interlocking installations. The diagrams are used by a software package that allows maintenance staff to perform failure diagnosis on modern hand-hold devices. The software package substantially reduces the failure diagnosis time for a malfunctioning entry signal.

Practical installations of illuminance systems use Light Emitting Diodes (LED) more and more. In most of the cases, tests in the field have shown that the details listed on the lights' technical specifications differ from the field values. The present study has been done on 7 W light sources with a 700 lm nominal light flux. We use statistical methods on multiple measurements sets on LEDs to determine the simple and synthetic indicators by which we estimate the homogeneity of the LED sample set and verify the truth of the technical descriptions listed on the packages sold on the market. In various studies on the behavior of LED sources we found significant differences between the values determined luminous fluxes and those listed in the box trading. These findings have led us to conduct tests on larger groups of the same type of LED sources, to see if it complies with the Certificate of Conformity, referring to standard deviation. For the analyzed group it was found that the manufacturer does not comply with this regulation.

Optimal structural dimensions and reduced costs are current requirements in electrical machines. Such requirements can be fulfilled already in the design phase by establishing optimal parameter and quantities values, such that the objective function is satisfied. The main optimization variable of this work is the current layer, the resulting optimal values and the charts analyzed here are obtained using a specific program for optimal design. This program is based on the classical design of the synchronous generator. Depending on the aimed objectives the program returns the values of the dimensions of interest. Using an optimal design, for the generator in question, costs have decreased with 4.7% compared to the classical design costs.

In line with the nowadays requirements, the synchronous generators must fulfill the technical specifications and their costs should be as low as possible. For this, the electromagnetic stresses, which significantly influence the synchronous generator costs, must have optimal values. The use of optimal designs helps achieve this objective. In this work we show how the current layer A and the air gap magnetic displacement Bδ influence the generator’s costs.

Structural dimensions as well as the ability to safely operate in often transient processes or short emergency situations are usual customer requirements. These requirements can be fulfilled already in the design phase by careful selection of electromagnetic stress values (current layer, air gap magnetic displacement).This work contributes to finding optimal values for the above mentioned stresses such that customer requirements are fulfilled

This paper presents a program of rapid determination of certain sizes required in the design of synchronous machines using Mathcad software. During the design of electrical machines are phases in which certain sizes are extracted from different tables depending on certain variables. This operation is difficult and sometimes hard to do. To eliminate this problem and greatly shorten the time of determination of sizes and to ensure accurate values we have designed a program allowing even interpolation between two known values. The program developed applied, in this paper, to quickly determine the value of the voltage form factor kB and the value of the ideal polar coverage coefficient αi of polar step τ.