Electric drives adjustment for improvement of energy efficiency of technological processes
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Authors:
O.S. Beshta, Dr. Sci. (Tech.), Professor, Corresponding Member of the National Academy of Science of Ukraine, State Higher Educational Institution “National Mining University”, Vice-Rector for Research, Head of the Electric Drive Department, Dnipropetrovsk, Ukraine
Abstract:
Purpose. To explain the scientific rationale for the possibility of improvement of energy efficiency of technological processes by means of electrical drive adjustment.
Methodology. Methods of the research include theoretical studies of power and specific energy-dependent performance of certain technological systems. We have set the task of determining the dependence of these parameters on the average productivity of the equipment and its standard deviation at a given bar chart performance for a duty cycle of technological complex. The general principles have been tested on the two power-intensive classes of mechanisms namely pumping stations and conveyers which are the most common in the industry. For the purpose the correlations between the energy parameters of these mechanisms and their performance with different ways of the performance regulation, including regulation by change of machine tools work speed have been theoretically determined. Based on these correlations the parameters of the most energy-efficient mode of the machine tools have been established. The results coincide with the results arising from the established general laws.
Findings. We have established that the control of the machine tools speed in technological systems allows reducing the specific energy per unit of productivity by providing rational proportional dependence of the load torque and the technological process productivity on the speed. We have proved that the greatest effect of this regulation type can be achieved in the range of control 2:1. If the range of the adjustments is wider, the two machine tools should be chosen, one of which should operate with a nominal capacity and the other one should be controlled in the speed range 2:1.
We have determined that the efficiency strongly depends on the machine tool productivity oscillations relative to the average level in the duty cycle. Therefore, if the standard deviation exceeds 5–10%, the machine tool with large productivity should be replaced by several machine tools of lower productivity and the productivity of one of them should be regulated.
We have established that the theoretical maximum of the efficiency, in terms of saving power required to control the flow rate by adjusting the pump speed, compared to the control of the flow rate by valve is within 4% with the support of sustainability in hydraulic pressure and about 40% without the support of sustainable pressure. Feed control of a pump should be in the range
(5–10)...(40–50)% of its nominal performance.
Use of the adjustable electric drive on trunk pipelines and drainage systems with the constant pressure or low range of supply regulation is inappropriate in terms of energy saving. But, if we need to maintain the sustainability of flow rate, the use of adjustable speed drives on pumping units is the most appropriate decision in terms of effective energy saving.
We have determined the extreme dependence of the energy consumption on the speed mode of the conveyor with the constant productivity of intermediate bunker. So we have theoretically determined the conveyor speed for minimal energy consumption during transportation.
Reducing the average speed of the conveyor while maintaining constant specific load level reduces the losses of energy, but increases the energy consumption per unit weight of products transported (unit costs). Minimization of the specific energy consumption in this case is possible only by increasing the speed level.
Originality. General regularities which make the most energy efficient modes of parameters of technological systems have been established.
Practical value. The most energy efficient modes of parameters of technological systems have been determined.
References:
1. Бешта А.С. Выбор рационального способа регулирования подачи воды насосным агрегатом / БештаА.С., Азюковский А.А. // Технічна електродинаміка. – 2009. – №3.
Beshta, A.S. and Azyukovskiy, A.A. (2009), “Selection of the efficient way of control over water supply fulfilled by a pump”, Tekhnichna elektrodynamika, no.3
2. Pivnyak, G., Beshta, A. and Balakhontsev, A. (2010), “Efficiency of water supply regulation principles”, New Techniques and Technologies in Mining, Proceedings of the school of underground mining, © CRC Press / Balkema, Taylor & Francis Group, London.
Beshta, A., Beshta, D., Balakhontsev, A. and Khudoliy, S.S. (2011), “Energy saving approaches for mine drainage systems”, Technical and geoinformatical systems in mining, © CRC Press / Balkema, Taylor & Francis Group, London.
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