Virtual Three-phase Laboratory Exercise During Pandemic Situation

The Corona pandemic has changed our way to teach, even our laboratory experiments. The exercises for the three-phase systems had to be transferred to the web. The virtual exercises are described and the results are shown. The pros and contras of this way to teach are discussed.

Extraction of Eu(III), Gd(III), and Tb(III) in aqueous two-phase systems based on polyethylene glycol 1500-NaNO3-H2O with the addition of extractants (D2EHPA, TBP, TOMAN)

Luminophores that used, for example, in fluorescent lamps, contain a large number of rare earth elements. Therefore, the processing of waste equipment containing luminophores is a rational approach to the obtaining of rare-earth metals, firstly, from the economics point of view, since they have a high cost, and secondly, from the ecological point of view, since environmental pollution will not occur. The cheapest way to extract rare earth elements from waste products is to dissolve them in strong acids and the following reprocessing by liquid extraction methods. In this case, neutral or ion exchange extractants (tributyl phosphate, di(2-ethylhexyl)phosphoric acid and quaternary ammonium salts) are used, which show high extraction ability and, in some cases, selectivity. Their applying is associated with the use of non-polar organic solvents, which contradicts the principles of «green» chemistry. A good and promising alternative to organic solvents can be aqueous two-phase systems, which have already proved themselves as low-toxic, but highly effective systems for the separation of a number of metals. Thus, in this work, we performed an experimental study of the interphase distribution of Eu(III), Gd(III), and Tb(III) in two-phase systems based on water-soluble polymers with or without the introduction of traditional organic extractants as an additive. The possibility of using such ATPS as a «green» solvent for traditional extragents for Eu(III), Gd(III), and Tb(III) extraction has been shown.

Power Conversion Techniques Using Multi-Phase Transformer: Configurations, Applications, Issues and Recommendations

Recently, the superiority of multi-phase systems in comparison to three-phase energy systems has been demonstrated with regards to power generation, transmission, distribution, and utilization in particular. Generally, two techniques, specifically semiconductor converter and special transformers (static and passive transformation) have been commonly employed for power generation by utilizing multi-phase systems from the available three-phase power system. The generation of multi-phase power at a fixed frequency by utilizing the static transformation method presents certain advantages compared to semiconductor converters such as reliability, cost-effectiveness, efficiency, and lower total harmonics distortion (THD). Multi-phase transformers are essential to evaluate the parameters of a multi-phase motor, as they require a multi-phase signal that is pure sine wave in nature. However, multi-phase transformers are not suitable for variable frequency applications. Moreover, they have shortcomings with regard to impedance mismatching, the unequal number of turns which lead to inaccurate results in per phase equivalent circuits, which results in an imbalance output in phase voltages and currents. Therefore, this paper aims to investigate multi-phase power transformation from a three-phase system and examine the different static multi-phase transformation techniques. In line with this matter, this study outlines various theories and configurations of transformers, including three-phase to five-, seven-, eleven-, and thirteen-phase transformers. Moreover, the review discusses impedance mismatching, voltage unbalance, and per phase equivalent circuit modeling and fault analysis in multi-phase systems. Moreover, various artificial intelligence-based optimization techniques such as particle swarm optimization (PSO) and the genetic algorithm (GA) are explored to address various existing issues. Finally, the review delivers effective future suggestions that would serve as valuable opportunities, guidelines, and directions for power engineers, industries, and decision-makers to further research on multi-phase transformer improvements towards sustainable operation and management.

New proposed fractional-polynomial functions: new recommendation for overcome the imbalance in three-phase systems

Non-linear loads or load imbalances, etc., are the typical causes of asymmetric operation of three-phase systems. The appearance of inverse (positive) and homopolar (zero) symmetric components cause damage to the systems and electrical equipment and increase the power losses on the transmission lines. Reactive power compensation is one of the solutions that can overcome this asymmetry. The difficulty that exists in many different methods is the optimal calculation of the value of the compensator. In this paper, a new method to overcome these problems is proposed and investigagted. The proposed method is based on the fundamental electrical quantities (voltages and currents) on the controllable values of the static compensation devices and overcoming of the asymmetric operation regime in the three-phase systems.