Vol 89, No 11 (2018)

The power transfer capacity of cable lines is substantially affected by the conditions of cable laying. The laying of power cables at a rated ac voltage of 10 kV and frequency of 50 Hz with an aluminum multiwire compacted current-carrying conductor with a cross section of 240 mm² and XLPE insulation in a cable channel, which is placed into the ground and filled with air, has been considered. The suggested technique to determine rated current loads of cables in the cable channel with the distributive parameters is based on the solving the problem of steady-state heat conduction and allows one to eliminate the problem of convective heat exchange. The numerical implementation of this problem is divided into two stages. At the first stage, when determining the current loads of cables, the dependence of mean air temperature in the cable channel on the power of an internal heat source is determined. At the second stage, the rated current loads of cables are calculated taking into account the obtained air temperature distribution in the cable channel. In this case the problems of steady-state conduction are solved at both stages using the ANSYS software. The rated current loads of cable lines are selected by the iteration procedure taking into account the admissible insulation and shell temperatures. The performance characteristics of single conductor cables laid in the same plane and three-conductor cables with sector-shaped conductors in the cable channel have been studied.

An algorithmic implementation of a method of calculation of the modes of electric power systems with arbitrary structure is considered based on nodal-voltage equations, which is distinguished by the absence of reduction of the elements of electric power systems to each ratio transformation step. The interaction of electrically connected elements is arranged by the electrical parameters of the mode (of currents and voltages). The calculations of the modes of electric power systems are based on the solution of equations formulated based on the method of nodal-voltage equations. Based on analysis, the model was selected in the form of complex nodal-voltage equations as the balance of currents when setting a load by constant conductivity using topological matrices. As a result of proposed approach, the currents and the voltages of the branches are expressed through the components along the longitudinal d and the transverse q axes, the transition to instantaneous values of currents and voltages is carried out using a coordinate transformer by Gorev’s formulas. The representation in the d and q axes makes it possible to use directly the catalogued data of equipment when simulating synchronous machines. The method can also be used when tuning the excitation control systems of generators to check the correspondence of the excitation voltages of the system to the nodal voltages. It is proposed to develop the model of electric power system to the level of simulation of transient processes in structural elements at which the equations in the Park–Gorev coordinates are predominantly used.

The task of useful sheet remnant nesting is as important as that of nesting of standard sheets; however, in practice, it is usually solved manually because of the complexity of the work with the irregular shape of the remnant and analysis of the defective areas. A method is proposed for searching for nonstandard sheets for nesting without remainder for a given order. The method is based on analysis of the nesting order composition—a grouping of the drawings of all parts and determination of the prevailing type of the parts. The process of determination of the necessary groups is considered. Each group of parts is described by a combination of the dimensionless geometric features, for which reason, if necessary, the list of groups can be supplemented or reduced for the use at a particular enterprise. Knowing of the prevailing group of the parts allows the nesting system to exclude inefficient nesting from consideration. The model of the proposed method is based on calculation and analysis of the nesting coefficient and has optimal conditions for controlling the amount of the used useful remnants. The implementation and testing of the developed method were carried out based on the nesting software package ITAS Nesting at several known test assemblies. The testing revealed the more high-quality results of nesting as compared to the existing algorithms of the ITAS Nesting nesting system.

Automated systems for controlling technological processes on the basis of a position-tracking electromechanical control system (PTECS) are characterized by a program known in advance for changing the working tools. However, to control a position-tracking electromechanical system that operates under unpredictable changes in a wide range of driving forces, traditional controlling methods are not sufficient for securing not only optimal, but even stable, operation of the system. A position-tracking electromechanical system is developed for controlling the working tools of technological process on the basis of neural-fuzzy technology, which removes the restrictions and expands the field of its application.

Over the past 20 years, polymer composite materials have become widespread in the aviation industry. The use of these materials can significantly reduce weight and improve the environmental parameters and efficiency of the aircraft. This, in turn, requires a high level of automation and robotization of the main technological processes in production; moreover, the nondestructive testing and flaw detection of the component parts and assemblies occupy about 30% of the labor intensity of the technological production process. The article presents a brief description of a nondestructive testing system developed to solve this problem consisting of the five-link manipulator with the X-ray emitter and portal with a radiation receiver. The kinematic diagrams of the system components are described, and a mathematical model of the solution of the problem of direct and inverse kinematics using the geometric method is presented for the manipulator and receiver. The testing of the constructed model is made, which shows its adequacy.

A method of identification of induction motor parameters based on a phase-locked loop frequency control algorithm was considered. The existing identification methods of the equivalent circuit parameters were analyzed and classified. The methods operating in real time and in the adaptation mode of electric drive during the first operative startup of electric drive were distinguished. In addition, using the methods of active identification, in which an additional test information signal is injected into the power circuit of an electric drive, is unacceptable during electric drive operation and they are used at the time of prior adjustment of electric drive until its operative startup or for a short time to adaptation of changing parameters. An evaluation algorithm of motor parameters was proposed, and functional and structural diagrams of parametric identification system were developed. The developed identification method based on a phase-locked loop frequency control algorithm is constructed upon leveling of the phase difference between the real (measured) stator current vector and the stator current vector calculated by the model. The simulation results of the implemented parametric identification system are presented. According to the results of model experiments, the error of estimation of motor parameters did not exceed 1%. The proposed parametric identification system can be used as part of a vector control system to determine the coefficients of internal regulators of electric drives.