Analysis of start-retardation modes in high-power synchronous electric drives

The article analyzes the start-retardation modes of synchronous electric drives of high-power exhausters, which are accompanied by high starting currents, not only under a direct start, but also under control of electric energy flows from a semiconductor converter. A mathematical model of electric drive is proposed and substantiated for the analysis of transition processes of ac electric drives. This model has an electromechanical converter that constitutes the links with distributed parameters. A distinctive feature of the model is refinement of the magnetization characteristic of the magnetic-circuit steel, which was carried out during full-scale measurements of the variables of the synchronous electric drive with direct start of the exhauster. To check the adequacy of the mathematical model, the results of a full-scale test were compared with the simulation results by statistical methods using Student’s criterion. The computational results using the proposed model were compared with the calculations by the classical models with lumped parameters. It has been noted that, in the overload zone (for M > 1.5 MN) the calculated values differ considerably, with this being especially evident at low speeds. The obtained results can be recommended for selection of the parameters of semiconductor converters.     

Parametric optimization of a synchronous electric drive with improved mass and size parameters

This article describes a possible new synchronous drive with an active concentrated winding and a stator with a number of phases other than three, control laws, and nonsinusoidal phase currents. This drive is characterized by improvements in weight and size achieved by taking into account the interaction of the electric motor and the inverter. Using the criterion of maximum effort to volume ratio of the electric machine, we have carried out parametric geometry optimization of the stator and rotor backs and windings slots. We have listed recommendations on selection of the number of phases and main circuit connections of the electric power converter that feeds the electric machine. We have proven that, by means of intelligent selection of geometrical parameters for an electrical–mechanical converter slot, it becomes possible to improve the mass and size parameters by approximately 30% relative to conventional solutions.     

Synthesis of electric drives realizing limit operating regimes in terms of operation speed and overload capacity

A special class of machine electric drives, which have an increased range of variation of the load torque and speeds with harsh and extreme operating conditions, are considered. It is shown that expansion of these parameters without increasing the rated power of the electric drive provides a significantly improved quality of technological regimes without increasing the cost of the electric drive. The strategy of the synthesis (design) of electrotechnical complexes is formulated providing the limit characteristics and consisting of the following stages: synthesis of a generic mathematical model, determination of the limit capacity of the object of control, parameter optimization of the electrotechnical complex in order to provide the limit characteristics, selection of simplified mathematical models of an electric drive, synthesis of the structures and the control system, and the search for the phase path of motion of the electric drive–working body system realizing the extreme operating regime. A determination of the possibilities of each stage is given.     

Characterization of the Organic Matter of Humic Acids by Pyrolytic Gas Chromatography–Mass Spectrometry

The results of the pyrolytic analysis of products of the organic matter of Sphagnum fuscum, fuscum peat, and humic acids separated from peat with the use of pyrolysis–chromatography–mass spectrometry in the Rock-Eval version are presented. It was shown that Sphagnum fuscum and peat differed only slightly in the degrees of chemical transformation. Benzene, phenol, and their alkyl-substituted homologues predominated in the thermal desorption products of humic acids upon pyrolysis to 400°C. Acetic acid, monohydric phenols, syringol, and guaiacol, which are the basic compounds in the high-temperature fraction, were formed on the pyrolysis humic acids to 700°C from the carbohydrate, phenylpropionic, and guaiacylpropane structural fragments.     

Extraction of Pt(IV) and Pd(II) from Hydrochloric Acid Solutions Using Polypropylene Glycol 425

Theoretical Foundations of Chemical Engineering - An environmentally friendly extraction system based on polypropylene glycol 425 and sodium chloride for the extraction of Pt(IV) and Pd(II) from...     

Dichotomous indexing of array in recursive construction of voxel-graphic images

Rapid development of the cluster multiprocessor computer systems allows one to pose to the designers of the computer-graphical systems the problem of organization of graphical information enabling efficient use of the parallel algorithms. Consideration was given to the use of the dichotomous principle of binary construction of a numerical sequence for successive indexing of the elements of a multidimensional array in the problems of recursive decomposition of the multidimensional space. This principle was used to advantage in recursive construction of the voxel graphical information used in the program accelerators of graphical processing based on parallelization of the algorithm and partial sorting of the graphical output flow in terms of the recursion depth.     

Unloading angular momentum for inertial actuators of a spacecraft in the pitch channel

The problem of gravitational unloading of the angular momentum of inertial actuators of a spacecraft in the pitch channel for circular and elliptic orbits is considered using the band theory of modal control. Control laws for gravitational unloading and stabilization of a given spacecraft position unambiguously determined by the object parameters and given coefficients of characteristic equation are obtained.     

Limit theorems for queueing systems with doubly stochastic poisson arrivals (Heavy traffic conditions)

We consider a single-server queueing system with a doubly stochastic Poisson arrival flow under heavy traffic conditions. We prove the convergence of the limiting stationary or periodic distribution to the exponential distribution. In a scheme of series, we consider the C-convergence of the waiting time process to a diffusion process with constant coefficients and reflection at the zero boundary. Examples of computation of the diffusion coefficient in terms of characteristics of the arrival flow and service time are given.     

Synthesis of stabilizing spacecraft control based on generalized Ackermann’s formula

Problem of modal synthesis of controllers and observers using the generalized Ackermann’s formula is solved for a spacecraft as a complex dynamic system with high interconnections. All possible controller matrices (the whole set of controllers) are obtained for solution of the problem of stabilization of orbital orientation of the spacecraft in inseparable channels of bank and yaw angles.     

Quasi-distributed measuring system based on Bragg sensors of mechanical stress with increased sample rate

Functionality and technical features of modern industrial fiber-optic sensors on Bragg gratings are considered. Feasibility to design information-measuring systems for such sensors involving the improved concept of calibration based on acetylene cavity is studied. The results of investigation regarding the design and analysis of the prototypical information-measuring system are discussed.