Vol 89, No 1 (2018)

This paper presents the results of an investigation of an intelligent starter–generator (SG) with a capacity of 16 kV A and rotation frequency of 12000 rpm. In designing the SG, a multidisciplinary approach was used in which all the calculations of an electrical machine were interdependent and had the form of a symbiosis of electromagnetic, thermal, and mechanical calculations concerning the rotor dynamics. Interrelated optimization problems were simultaneously solved during such calculations using genetic algorithms. Such an approach provides maximum accuracy, especially when designing highly loaded electrical machines, where even an insignificant change of any parameter can lead to a considerable change in the structural diagram of the SG and its dimensions. The experimental model of the SG was tested in the full-power regime and at rated speed. The measurement results of the output voltage and heating temperature of the active elements correspond to the design ones. The deviation from the design voltage data was 1.7%. This small error confirms the efficiency of the multidisciplinary design methods used. Based on the test results, a comparison with the characteristics of aircraft generators of similar power is carried out and the developed SG is shown to be efficient.

The problem of determining the effective ratio of conventional and renewable energy sources is considered, as well as the problem of predictive assessment of development trends in the Russian electricpower industry. A conceptual model of the use of renewable and conventional energy sources developed on the basis of the Lotka–Volterra differential equations is proposed to check the benchmarks. Coefficients of the differential equations system are identified on the basis of official statistical reports. The correctness of benchmarks for the share of electricity produced on the basis of renewable energy sources is estimated. Recommendations are given for increasing the share of renewable energy sources in the structure of the Russian energy sector.

Many variants are known of expulsion-type semiconductor plugs for capacitive ignition systems for gas-turbine engines, which differ in the design of discharge chambers. A distinctive feature of serial-produced expulsion-type plugs, which are manufactured by domestic industry, is the relative arrangement of semiconductor element and side electrode, at which the working surface of semiconductor is located not along the plug axis, but at an angle. The working surface of the side electrode is near the discharge-chamber base. There is no systematized information on research on discharge processes in the expulsion-type plugs in the technical literature. This work is dedicated to the study of interrelation between the energy parameters of spark discharges, space–time characteristics of plasma ejection from the discharge chambers of plugs, and plug-ignition effectiveness. The oscillography, together with plasma-ejection high-speed photographing methods, are used as research techniques. A serial-produced semiconductor plug and a specially developed model of expulsion-type plug with a window made of organic glass were chosen as the objects of research. The organic-glass window made it possible to photograph the process of plasma-discharge development within the discharge chamber. The oscillograms of discharge current and voltage drops in the plugs were recorded with a two-beam oscilloscope using a noninductive coaxial shunt and a resistive voltage divider. The parameters of plasma ejection were correlated with the plug-ignition effectiveness. The obtained results complement the general understandings of the regularities of development of plasma ejection from the discharge chambers of semiconductor plugs and confirm that the discharge parameters have an effect on the initial ignition speed from the standpoint of thermal and chain igniting mechanisms.

The results of a study of the development of small-sized electric precipitators obtained by the Department of Electrical Engineering of Ufa State Aviation Technical University are presented.

The properties of a magnetic field that the current of a three-phase winding of the starter of an induction motor generates greatly depend on winding type. The smaller the quantity of higher (parasitic) harmonics with respect to the fundamental (working) harmonic in the curve of magnetomotive force, the greater the winding efficiency. Three-phase six-band windings have become widespread. Increasing the number of phases promotes a decrease in the quantity of higher harmonics, but a special six-phase supply source is needed for this. A three-phase combined 12-band winding is considered, the electromagnetic properties of which are close to the properties of a six-phase winding. Such a winding is compared to a standard six-band winding with respect to the differential scattering coefficient that characterizes the magnetic field on the basis of the content in it of higher harmonics. Two variants of windings were compared: with continuous and noncontinuous phase bands. The calculation results of differential scattering coefficients of windings for 24, 36, and 48 slots falling per pair of poles are presented. Calculation of the least theoretically possible differential scattering coefficient was performed for a combined winding with continuous phase bands. A high efficiency of combined winding with continuous phase bands as compared with standard winding and combined winding with noncontinuous phase bands was demonstrated.

A power supply for electronic high-voltage measuring-current transformers with extraction of energy from the measured current that flows through a high-voltage line has been considered. A magnetic core of the supply transformer from the windings of which the necessary power is extracted is mounted on the line for this purpose. When the line current changes over a wide range, the supply transformer should have a quickly saturated magnetic core. It has been shown that, to reduce the losses and decrease the loading of the elements of a power-supply circuit in a wide current range, a ballast load should be introduced in the circuit of a secondary winding. Three variants of the ballast load have been compared: resistive, capacitive, and in the form of a transistor-current limiter. The results of simulations in the VisSim software have been considered for all three variants, as well as for the case of absence of a ballast load in the power-supply circuit. The simulations were carried out for the lowest and highest measured currents, as well as for the line short-circuit mode. The results of simulations have shown the advantages of a power supply based on a saturated transformer with a transistor-current limiter. A variant of a circuit of a transistor-current limiter has been suggested.

Devices based on the method of absolute measurement of the level of higher harmonics in zerosequence currents of connections of a protected object are the most commonly used for protection from earth faults in compensated 6- to 10-kV cable networks of industrial and urban power-supply systems. However, many years of operating experience have shown that the technical refinement (the selectivity and the sensitivity) of overcurrent protection from earth faults based on the method of absolute measurement of higher harmonics is not always sufficient. One of the reasons for the low technical refinement of these protection devices is the inaccuracy in estimating the maximum and minimum possible higher harmonics levels in the earth-fault current of compensated 6- to 10-kV cable networks, which are required for the selection of the operating current settings and the sensitivity determination. The main factors influencing the maximum and minimum higher harmonics levels in the earth-fault current and their ratio were revealed on the basis of the computational experiments using the imitation models for 6- to 10-kV cable networks, the limiting values of these levels were determined, an determination of the harmonics-level instability in the fault current for cable networks with different total load compositions was given, and its interrelation with the fluctuations of the total coefficient of harmonic voltage components on 6- to 10-kV buses of network power centers was established. The conditions of applicability and the area of application of overcurrent protection from this type of failure based on the use of higher harmonics of the zero-sequence current for different objects of 6- to 10-kV compensated cable networks were determined taking into account the above estimates. Specifications for a method for selecting the operating current settings were proposed.

In the following articles, South Ural State University was omitted from the list of authors’ affiliations. The affiliations should be added to the below-mentioned articles.