Volume 2 Issue 3

Authors: Ayele Nigussie Legesse; Mengesha Mamo

Abstract: This paper describes the application of a stepper motor in controlling the frequency of a standalone mini hydropower plant. In Ethiopia, the frequencies of the existing mini hydropower plants are controlled by mechanical governors. Unfortunately, these governors are expensive, complex and slow in response. Furthermore, the governors do not act fast enough during big load changes; consequently, frequency spikes are created. In this research, a stepper motor which is cheap, fast, easy to control and less complexis used to control the frequency of a mini hydropower plant.Thestepper motor is used to rotate aspear valve which in turn controls the flow of water into the turbine of a mini hydropower plant. The position of the stepper motor is controlled by a controller. Thus,a frequency control system usinga stepper motor is modeled, designed and simulated. Simulation results for mini hydropower plants with different capacities demonstrate that transient and steady state performances are enhanced by replacing mechanical governors with stepper motors. Moreover, frequency spikes are reduced.

Keywords: Stepper Motor; Mini Hydropower Plant; Frequency Control System; Spear Valve


Authors: Alexander A. Bolonkin

Abstract: A new method of harvesting electric energy from wind is offered. A special injector sprays electrons into the atmosphere which then picks up the electrons and moves them in the natural direction of the wind, which is also against the direction of electric field. At some distance from injector a unique capturing grid acquires the electrons, thus charging and producing electricity. This method does not require, as does other wind energy devices, strong support columns, wind turbines, or electric generators. This proposed wind installation is cheap to build. The area of wind braking may be large and produces a great deal of energy. Although this type of electron wind installations may be located within a city, the population will not see them—they will not be considered industrial urban blight!

Keywords: Wind Energy; Utilization of Wind Energy; Electronic Wind Electric Generator; EABG


Authors: Alejandro García Rodríguez

Abstract: The present work is directed to the evaluation of the electric behaviour of covered electrodes and its main objective is to communicate to the international scientific community a novel methodology developed with this purpose. Methods of digital processing of the welding voltage and current signals and statistical methods based on non-parametric technical were used for the evaluation of the electric conduct of the process, using a feed by gravity dispositive for the elimination of the operator influence, in comparison with the process using standard electrodes. The proposed methodology allows the detection of destabilization events in anyone of the well-known transfer modes, in periods of arc and short circuit as well as during the re-ignition picks; and to evaluate the grade of the general electric stability of feed by gravity covered electrodes, proposing a novel index combining 5 parameters not referred before as stability criterion. A new index for the stability of the metallic transfer and another new index for evaluating the stability in the load transfer during the arc re-ignition were proposed. For validation of the developed methodology results obtained by means of metallographic technical, of visual inspection and of determination of the consumption indexes were analyzed, overcoming the well-known previous methods and allowing the evaluation of the electric behaviour in all types of covered electrodes and other welding processes, such as SAW, GMAW and GTAW.

Keywords: Specific Electric Behaviour; Coated Electrodes; Feed by Gravity