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This paper aims to present an optimal variable speed drive of a doubly fed induction motor (DFIM) with minimum losses and reduced inverter capacity. The operation with minimum losses ensures that the DFIM develops the required load torque at desired speed with maximum energy saving. Moreover, the control of rotor voltage ensures the reduced inverter capacity. The water cycle algorithm (WCA) as one of meta-heuristic optimization techniques is used to estimate the optimal rotor voltages to drive the DFIM with minimum losses. The results of WCA are confirmed with other well-known and reliable optimization method such as particle swarm optimization along with classical method.

The DFIM is an efficient alternative solution of synchronous motor (SM) because of its speed is synchronized with both stator and rotor frequencies regardless the load torque. As a result, the speed of variable speed drive associated with DFIM can be controlled through a rotor inverter with reduced capacity rather than SM. The output voltage of rotor inverter is controlled to develop the demanded output power with minimum motor losses.

A complete DFIM drive model is developed under MATLAB/SIMULINK environment using d-q dynamic model to verify the strength and significance of the proposed controller. An experimental setup using a 300 W three-phase wound rotor induction motor is established to validate the mathematical models and theoretical results. The motor performances with proposed rotor voltage control (minimum losses) are compared with conventional method of constant voltage to frequency ratio (V/f constant). It is found that the proposed WCA based on controller achieves significant reductions in motor losses, input power and rotor inverter power.

The paper presents an efficient method to maximize the energy saving of DFIM with a reduced inverter capacity using WCA.

This paper aims to develop a simple and efficient plasma technology for the production of copper (I) oxide with the ability to control the morphology and size of Cu₂O particles. To achieve this goal, the phase composition of the precipitate formed was estimated, the composition and size of the obtained particles were determined and Pourbaix diagrams were constructed.

An integrated approach combining thermodynamic calculations and experimental research methods is used. The constructed Pourbaix diagram makes it possible to suggest the phase composition of the sediment. The use of cyclic voltammetry made it possible to establish the mechanism of deposit formation on the cathode during the treatment of the solution with contact nonequilibrium low-temperature plasma. The resulting product was examined using X-ray phase analysis and scanning electron microscopy.

The article presents the results of theoretical and experimental studies on the synthesis of copper (II) oxide. The influence of the parameters of plasma-chemical synthesis on the shape and phase composition of the deposits formed has been studied.

A plasma-chemical technology for obtaining copper oxide in the form of single crystals of a regular faceted shape is proposed. The mechanism of formation of copper oxide has been established by cyclic voltammetry. The constructed Pourbaix diagrams show the area of existence of the product.