Том 89, № 3 (2018)

The results of an investigation of an asynchronous motor in the modes of direct starting and load changing obtained with mathematical modeling using a block of nonlinear systems of Lookup Table type and functional block F_cn of the MATLAB/Simulink software package. Introducing the above-mentioned elements into the model makes it possible to simply take into account changes in the parameters of an electrical machine caused by saturation of the magnetic circuit and the effect of current displacement in the rotor bars in transient modes. The saturation of the magnetic system when passing the main magnetic flux and leakage fluxes is taken into account using functional dependences, which are specified in the blocks by tabular methods, which provides model simplicity and clarity of the modeling process. Unlike a model created based on a standard block of an electric motor of Asynchronous Machine type, the proposed variant makes it possible to observe the changes of any variables of asynchronous machine during the transition process and creates good preconditions for various investigations of electric drives. Using the developed model. the comparative analysis was done of dynamic characteristics, which revealed that the transient processes in the asynchronous motor under direct starting, taking into account the saturation of the magnetic circuit and the effect of current displacement in the rotor flow that is 1.5 times faster than in the ideal machine. In addition, the first maximum of torque is 1.6 times greater than in a simplified motor model. Under a load surge, the differences in the curves of changes of torques and angular velocities are insignificant. If to neglect the effect of current displacement in the rotor bars, the transient processes do not coincide only when starting. The most essential differences are observed between the transient characteristics of the developed model and the model composed of the standard MATLAB Simulink blocks. The obtained results make it possible to draw a conclusion as to the effectiveness of applying the developed motor model when investigation of dynamical modes, selecting a starting and protective equipment of asynchronous electric drives.

Like-pole reluctance machines with one or more permanent magnets on a rotor, which create net excitation that is closed in the axial–radial direction, are analyzed. Design practices are developed for them that have to be checked via basic methods. One such method is the finite-element technique, or grid method. However, it cannot be applied in the form of a two-dimensional model for the structure under analysis. Hence, a method is presented for constructing three-dimensional models of unipolar inductor machines. The construction is performed by extruding (pressing out) areas of the sector, which outline tooth or pole partition in a plane that is perpendicular to the axis of rotation, coated with projections of boundaries of all axially placed cylindrical sections of the same cutset within each section, forming a 3D model of a stator or a rotor. The method is designed for subsequent mesh generation and for calculation by means of the finite-element method related to magnetic scalar potentials, followed by determination of energy gain and rotating electromagnetic torque, defined by change of a magnetic field energy before and after the rotor is rotated by some basic angle. The described method of creating 3D models is also studied in application to like-pole machines with electromagnetic excitation on the part of a stator. In addition, it is applicable to creating models intended for examining leakage fields in the sphere of the front parts of machines by ordinary geometry reduced to a two-dimensional one.

The discharge processes in a capacitive ignition system with a unipolar pulse, which offers advantages as compared with ignition systems of oscillatory discharge, are investigated. It is noted that the received wisdom concerning the dynamics of development of a unipolar discharge pulse is rather conditional. It is shown that, for small values of inductance of discharge circuit, the discharge in the plug becomes oscillatory, with a pronounced oscillating component being superimposed onto the aperiodic component of the current. An experimental setup and a technique for investigating the oscillatory discharges when changing the parameters of the discharge circuit including the storage-capacitor capacitance and the inductances in the circuit of a shooting semiconductor plug and in the circuit of a high-voltage diode are described. The results of oscilloscope experimental studies and an analysis of results of measuring of the energy of spark discharges in the shooting semiconductor plug are presented depending on the parameters of the discharge circuit. The regularities of development of oscillatory discharges are laid out. It is shown that oscillatory discharges are generated not only under small inductances of the discharge circuit, but also when increasing the inductance in the case of connecting an additional inductance, the value of which is lower than the value of the main inductance, to the high-voltage diode circuit. It is proved that the energy efficiency of the capacitive ignition system of oscillatory discharge can exceed the efficiency of modern ignition systems with a unipolar pulse.

A prototype of an electrodynamic separator based on a two-side linear-induction machine (LIM) for induction sorting of nonferrous metals is considered. A mathematical model is developed for studying the LIM-based electrodynamic separator. The modeling of the interaction between the magnetic field and the conductive particles is complicated by various electromagnetic (in particular, lengthwise and crosswise) and mechanical (gravity and friction) forces. Separation results from the combined impact of various forces on conductive particles. An important part of the model is made up of equations for the combined electromagnetic mechanical effect. The results of testing the pilot sample are presented. The computed paths and deviations of the particles are compared with the experimental data.

The results of experiments on the initiation of an arc-discharge-like Z-pinch in a coaxial magnetoplasma accelerator in different ways have been considered. It has been found that, with increasing resistance between the electrodes, the switching voltage increases and the time of arc-discharge ignition decreases. The electrophysical parameters of an arc, such as voltage, discharge current, pulse duration, transferred charge, and input energy, are unaffected by the method of initiation of an arc discharge.

This article describes an algorithm that has been developed for optimization of the compound and capacity of diesel generators (DGs) and wind turbines (WTs) functioning in wind–diesel systems (WDSs) taking into account data of grid loads and wind- and air-density variability as dependent on the elevation and time period for each area. The cost of electric energy generated by a WDS, degree of substitution of diesel-fuel consumption (by using wind turbines), payback period, net present value, and internal rate of return of WDS projects were chosen as optimization criteria. We developed software, EAST, based on the described algorithm, and determined the optimal configuration of a WDS for the town of Tiksi (Yakutia). Our findings are given in this paper. Optimization was performed for different ratios of the nominal capacity of diesel generators and wind turbines. We also calculated the energy and economic effect of using WDSs, which reaches a maximum if the ratio is around 1 (according to wind-energy-potential and grid-load data for the town of Tiksi). The degree of substitution of diesel-fuel consumption in this case reaches 35%, and the generated-energy cost drops up to 25%. According to calculations, the most energy- and cost-effective models of wind turbines for the WDS in Tiksi are VestasV-850 (Denmark) and GamesaG-58 (Spain), both with a rated power of 850 kW and a tower height of 55 m.

An interrelation is shown to be valid and grounded between the density of specific magnetic-hysteresis loss W_h and of steels measured over minor magnetic-hysteresis loops under magnetization reversal, as well as technical saturation magnetization M_s, coercive force H_cs, remanent magnetization M_rs measured over the saturation-hysteresis loop, and maximum strength of the magnetizing field H_m measured over a minor hysteresis loop. A formula is found that allows one to calculate W_h for steels based on their M_s, H_cs, M_rs, and H_m. The features of the effect of the magnetic properties of steels exerted on W_h depending on H_m are analyzed. It is established that, with increasing H_m, the changes in M_rs affect the value of W_h to a lesser extent. At the same time, the increase in M_rs always causes an increase in W_h. On the contrary, the increase in H_cs leads to increasing W_h only in the case of steel magnetization reversal in strong fields. In the case of H_m<H_cs, the dependence of W_h(H_cs) becomes inverse. This phenomenon is a physical property of ferromagnetic materials under magnetization reversal in weak magnetic fields. Another consequence of this property consists in a change in the dependence of W_h for carbonized heat-treated steels on tempering temperature T_t from inverse to direct at small H_m. So, for example, at small H_m, the dependence of W_h(T_t) for steel 30 becomes monotonous for the entire feasible range of T_t. This is a prerequisite for using the W_h parameter measured in a small magnetizing field and for quality control of mid- and high-temperature tempering of medium-carbon steels.

The design principle, structure, and synthesis of parameters of a positional electric-drive system with a nonlinear correction providing a high level of performance when working out a given motion are considered. The structure of the positional system is created on the basis of the standard electric drive with a thyratron (brushless) motor and microprocessor module, in which the program of nonlinear correction switches the feedbacks in the function of error of a given motion. The algorithm of nonlinear correction operates in real time and provides the working out of a given motion in two stages. At the first stage, a positive feedback by the motor-rotation speed is introduced to the speed-regulator input, which provides the system movement with an acceleration limit. As soon as the mismatch error reaches a predetermined value, the algorithm of the second stage begins to operate. Instead of positive feedback to the speed-regulator input, a negative feedback by the motor speed with programmable coefficient is introduced that makes it possible to provide effective braking of the electric drive and generate a transition process with given quality indicators. A comparative analysis is carried out of the operation of the system with the standard electric drive, in which the control is constructed on the basis of the principle of subordinate regulation of coordinates. In addition, it was revealed that introducing into the regulating system of nonlinear corrector makes it possible to reduce the working out time of given motion by 2.4 times. This is because the motion speed in the system with nonlinear correction varies by a triangular law that makes it possible in to fully use the overload capacity of the thyratron motor, while, in the electric-drive system without nonlinear correction, the motion speed varies by a trapezoidal law. The obtained results make it possible to draw a conclusion about the effectiveness of application of a nonlinear correction in positional electrical drives with subordinate regulation of coordinates.

The surname of the last co-author should read Trinh