Wyniki 1-2 spośród 2 dla zapytania: authorDesc:"Stepan KOVALYSHYN"

Reducing the dissymmetry of load currents in electrical networks 0,4/0,23 kV using artificial neural networks DOI:10.15199/48.2019.11.56

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The problem of the quality of electric energy plays a prominent role in development strategies of virtually every state. In European countries, it is believed that if the electricity losses exceed 7 - 9%, then such a transfer of electric energy is inefficient. Therefore, a need has emerged to develop new methods and measures of reducing the losses and improving the indicators of electric energy quality. Numerous studies on the analysis of voltage up to 0,4/0,23 kV in rural networks operating modes [1 - 3] showed that current dissymmetry is due to of municipal and household workload, most of which consists of casual switching, single-phase power-consuming equipment that is non-uniformly distributed over the phases. Knowledge of current values of asymmetry in a network allows specifying its additional power losses comparing to the symmetrical mode and the possibility of applying measures to reduce the losses [2]. The changing load of single-phase residential consumers of electricity is erratic and it is very difficult to predetermine its value at any given time. Boundaries of load change can only be established with a certain probability [4, 5, 6]. Technical and economic characteristics of the network performance deteriorate sharply in single-ended mode: energy losses increase and the voltage deviation from the nominal [7, 8]. Lifetime of asynchronous motors attached to a network also declines sharply. Furthermore, there are a number of adverse electromagnetic effects, both in the network and in the load. Therefore, losses of active energy, resulting in non-uniformity of phase load lines 0,4/0,23 kV and consumer transformers 6-10/0.4 kV, may increase by more than a third compared with the losses that would have occurred with a uniform load [3]. Analyzing two types of asymmetry, systematic, which is caused by a constant uneven phase load over time, and probable, which is determined by randomly varying loads in time, one fir[...]

The Study of Electrical Properties of Components of a Winter Rape Seed Mixture DOI:10.15199/48.2020.01.15

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The seed industry of plant growing has strategic importance in providing agricultural manufacturing with seeds of high quality. In many countries worldwide, it has great importance, since a sufficient quantity of high-quality sowing material with high yields, which does not contain any kind of damaged or biologically defective non-viable seed, directly impact production of one or another crop and the growth of yield produced by manufacturers. The above arguments are confirmed by research results done by numerous scientists [1-10]. In the structure of sowing cultures an important place is allocated to oilseeds, especially winter rape. In Ukraine, its cultivating area occupies about 10% [11]. Obtaining of sufficient quantity of high-quality seed material of this culture for the needs of commodity producers is quite a difficult task. One of the reasons for this is that a significant percentage of seeds are damaged during harvesting and after-harvesting [12]. Another reason is that in the process of producing this culture there are weeds, especially cleavers, which seeds, by most physical and mechanical properties, practically do not differ from the seeds of the main culture. This is confirmed by the data [13], according to which the approximate length of the winter rape seed is between 1.89-2.3 mm and cleavers’ length - 1.95-2.4 mm, the height - 1.95-2.5 mm and 1.58-2.42 mm respectively, the width - 2.1-2.5 mm and 1.9-2.7 mm. The coefficient of friction of winter rape seeds on the steel is 0.81, and cleavers is 0.85. It is practically impossible to separate all sorts of damaged seeds and seeds of difficult-to-separate impurities from winter seed rape with the use of existing seed cleaning machines that perform separation according to shape, surface condition or geometric dimensions of the separating mixture components [14]. It is possible to create more perfect separating machines or fundamentally new ones by using th[...]

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