Study for a photovoltaic system to supply electricity to an isolated apiary

The paper presents, based on the study and the experience of the authors in the field, some considerations, especially from an application aspect, useful in building a photovoltaic system for supplying electricity to an isolated apiary, as well as simulations for such a system, made with the PVGIS program . The main high-performing electric machines of today with relatively high energy consumption from an isolated beehive are identified, as well as their specific mode of use, during a calendar year, an essential factor for establishing the installed power of such a photovoltaic system and a its effective technical-economic design

The strain energy in loosening the clamped end of a beam (part II)

In the second part of the paper, the dynamic behavior of a doubly clamped beam is presented, where the right clamped end of the beam is weakened by introducing a weakening coefficient. The analytical calculation is based on the determination of the bending moment from the weakened clamped end expressed as a function of slope, after which the modal function, strain energy, and the characteristic equation are determined to obtain the eigenvalues of the first six vibration modes depending on the weakened coefficient of the clamped end. The obtained mode shapes and strain energies are determined for seven values of the weakened coefficient

Simulating an improved algorithm for propagation of transverse oscillations through a string

In present paper we bring under discussion a mathematical algorithm for determining oscillations through an elastic string. We have noticed that the algorithm has a flaw which can be solved by introducing an approximation into the system. For improved algorithm we have developed a program in order to obtain a simulator for propagation of transverse oscillations through a string, which allow us to obtain graphical representations for n-order harmonics

Virtual instrument designed for data acquisition

Current software development directions open up a world of possibilities, especially in the engineering field. Present paper is meant to highlight the advantages and in particular the ease of using virtual instrumentation facilities, with a proper and adequate design and implementation of desired instrument. In this idea we bring into discussion a design for virtual instrument which can be used for data acquisition that can be stored for further simulations according to the needs required by the process in discussion

Effects of Structural Damage on Dynamic Behavior at Sandwich Composite Beams - Part I-Theoretical Approach

This paper series presents an analysis regarding the dynamics of sandwich composite beams, embedded at one end, in order to highlight the effect of geometrical and material discontinuities upon the natural frequencies. In first part (Part I), analysis was performed with EulerBernoulli analytical method for determining the vibration modes and in second part (Part II), analysis was performed with numerical simulation in SolidWorks software for a five-layer composite. In the last section of the paper, an example is shown regarding how to interpret the obtained results

Optimizing the Cost of Manufacturing Welded Thermo-resistant Steel Pipes

The presence of stresses in the pipes of unalloyed and low alloyed steels with characteristics specified elevated temperature (hightemperature) can be put in the pipe-Dent the deformations occurring in the welded parts and the knowledge of their size allows to appreciate the ability of the test structures welded. To remove or reduce residual stresses and consequently to dimensional stabilization of the parts, use the thermal process. Comparisons have been made regarding the dimensional stabilization of the welded assembly by heat treatment of stress relief and dimensional stabilization by means of low frequency mechanical vibrations. Starting from the technological flow, two simulations were performed and the results obtained determined that the processing times were reduced in the case of vibration stabilization. The vibration stabilization system decreases thus reducing the manufacturing costs and consumes only a fraction of the heat demanded by the heat process, being one of the processes used predominantly for large welded assemblies, the intent being capable of being chipped at the place where the process of production

Study of the Accelerated Degradation of the Insulation of Power Cables under the Action of the Acid Environment

Over operation time, there are a number of internal and external factors that change the characteristics of dielectric materials that are part of the electrical equipment. In areas with high pollution, an important requirement is the acidic chemical compounds in the soil in which the power cables are laid, which penetrate the insulation by infiltration, resulting in changes in the parameters of electrical insulation and causing a decrease in operating time. The paper is focused on the analysis, through a series of experimental determinations, of the effects of stresses to which the power cables laid in acidic environments are subjected, by simulating the operating conditions in the laboratory, obtaining concrete results. It also describes the direct current test installation used in the laboratory and presents the two stages of testing the cable sample inserted in the electrolyte, the first being a stage of accelerating the degradation of the insulation by supplying higher voltages to require insulation, and the second stage being the testing in the absence of the electric field, under the direct action of the chemical compounds from the installation tank. Given that in alternating current, the electric field causes an additional heating of the dielectric due to energy losses by electric polarization, the test is performed in direct current, precisely to be able to monitor the variation of insulation resistance in relation to temperature and losses through conduction currents, as a result of the Joule–Lenz effect and not as a result of the dielectric polarization process. At the same time, the power of the direct current source used is lower compared to that of an alternative current test source and does not contribute to the generation of electrical discharges during testing

Study of the Accelerated Degradation of the Insulation of Power Cables under the Action of the Acid Environment

Over operation time, there are a number of internal and external factors that change the characteristics of dielectric materials that are part of the electrical equipment. In areas with high pollution, an important requirement is the acidic chemical compounds in the soil in which the power cables are laid, which penetrate the insulation by infiltration, resulting in changes in the parameters of electrical insulation and causing a decrease in operating time. The paper is focused on the analysis, through a series of experimental determinations, of the effects of stresses to which the power cables laid in acidic environments are subjected, by simulating the operating conditions in the laboratory, obtaining concrete results. It also describes the direct current test installation used in the laboratory and presents the two stages of testing the cable sample inserted in the electrolyte, the first being a stage of accelerating the degradation of the insulation by supplying higher voltages to require insulation, and the second stage being the testing in the absence of the electric field, under the direct action of the chemical compounds from the installation tank. Given that in alternating current, the electric field causes an additional heating of the dielectric due to energy losses by electric polarization, the test is performed in direct current, precisely to be able to monitor the variation of insulation resistance in relation to temperature and losses through conduction currents, as a result of the Joule–Lenz effect and not as a result of the dielectric polarization process. At the same time, the power of the direct current source used is lower compared to that of an alternative current test source and does not contribute to the generation of electrical discharges during testing

Effects of Structural Damage on Dynamic Behavior at Sandwich Composite Beams – Part II- FEM Analysis

This paper presents results obtained by modal analysis on composite beam like structures in healthy and damaged state. The aim is to obtain damage “signatures” for all possible damage scenarios and to use these data to assess transversal cracks based on vibration techniques, by involving natural frequency shifts. The analysis was performed in SolidWorks software for a five-layer composite, 20 vibration modes being obtained by numerical simulation

Implementation of an Automatic System for the Monitoring of Start-up and Operating Regimes of the Cooling Water Installations of a Hydro Generator

The safe operation of a hydro generator depends on its thermal regime, the basic conditions being that the temperature in the stator winding fall within the limits of the insulation class. As the losses in copper depend on the square current in the stator winding, it is necessary that the cooling water debit should be adapted to the values of these losses, so that the winding temperature falls within the range of the values prescribed in the specifications. This paper presents an efficient solution of commanding and monitoring the water cooling installations of two high-power hydro generators