Том 88, № 10 (2017)

The problems of asynchronous self-excitation of a synchronous machine with two windings on the rotor and a series capacitance in the circuit have been considered. A formula for calculating free oscillations has been given. It has been shown that, for a system consisting of a symmetric synchronous machine and a series capacitance, there are two natural frequencies, each corresponding to a certain zone of self-excitation. The equation of the curve that describes the region of self-excitation has been obtained. The effects of different parameters of machine on the lower part of the self-excitation zone have been investigated. It has been shown that this part of the zone is determined by the ratio between the active resistances of the machine circuits, but not their absolute values. A method to determine parameters providing the required compensation of the machine reactance has been given.

Equipment for carrying out onboard diagnostics is an important component in systems for controlling the state and reliability of rolling stock, in particular, that of diesel locomotives. It makes it possible to monitor a locomotive’s service quality, to detect and predict changes in its technical state without interrupting the carriage process, and to efficiently use the high-cost stationary and local diagnostic means, as well as to correct service time and volume by taking into account the real technical state. Therefore, it is important to develop methods for determining the technical state of locomotive units by using an MCS-T(N,E) (micro-processor control system) locomotive’s diagnostic subsystem of a locomotive and software for processing the measurement data. The main aim of such a method is to monitor the technical state of a locomotive’s equipment and predict changes in it. At the present time, simplified diagnostic models are used to solve such problems. However, to increase the efficiency and reliability of the process of checking complicated objects such as a locomotive, it is necessary to use more complex diagnostic models based on artificial neural networks. A way to use a neural-network method and neural fuzzy diagnostic models for diagnosing the excitation system of traction generators of modern diesel locomotives is presented in this paper. Information collected by the MCS-TP subsystem is used as diagnostic information. It is transferred online to a remote diagnostic server. The method for diagnosing the excitation system of a traction generator is checked by processing the measurement information.

Dependences between the currents and voltages at terminals of a homogeneous long line were analyzed. They make it possible to more correctly explain the changes in current and voltage in an electric-traction network when switching the thyristor arms of a rectifier–inverter converter than do conclusions obtained during replacement of a long line with a circuit with lumped parameters. An imitation model of the homogeneous low-loss long line in the MATLAB/Simulink software environment is proposed that adequately represents the propagation of incident and reflected electromagnetic waves along the line. Transfer functions are presented that approximate the frequency dependences of the specific parameters of the equivalent rail–ground loop and the overhead catenary–ground loop calculated taking into account the increase in the resistance of the wires due to the eddy currents and the surface effect. The influence of frequency dependences of the specific electric parameters of an electric-traction network calculated by various methods on the free voltage oscillation decay on the electric locomotive pantograph obtained by modeling the electromagnetic processes in the traction substation–electric traction network–electric locomotive system is revealed.

The transient electric resistance of a contact system has been considered. The dependence of the transient electric resistance of contacts on the roughness of surfaces that are in contact with each other has been determined, which is especially important at low contact pressures. The transient resistance is substantially affected by, in addition to the parameters of roughness, the physical and mechanical characteristics of surfaces that are in contact with each other. A technique for determining the transient electric resistance of contacts taking into account the material, roughness, and shape of surfaces that are in contact with each other, as well as forces of contact pressure, has been suggested. The value of a transient resistance obtained using the suggested technique is in good agreement with the experiment in the range of actual contact pressures in electric contacts.

Special circuit designs making it possible to limit the current-surge amplitude are used to increase the reliability of traction motors with the voltage fluctuations under the conditions of a sharp increase of currents of the armatures. The simplest engineering solution, which entails the parallel connection of a larger capacitor to the excitation windings of the energy storage units, is imperfect, as it does not allow adjusting the excitation current. An alternative approach is proposed to provide the reliability of operation of the traction motors. The circuit designs are presented, and modelling is performed as a result of which the main characteristics and regularities of the studied designs are revealed. It is shown that the direct connection of the excitation winding to the network does not exclude current surges of the armatures, and the use of the resistors in the excitation windings is ineffective. The modelling of the processes and calculation show the feasibility of including a bypass diode and, if necessary, a reactor, as well as implementing pulse regulation of the excitation current.

Railway transport is characterized by high energy consumption and effect on the environment. This applies, first of all, to the rolling stock with series excitation traction motors and a resistor–contactor control system. The low coefficient of adhesion between the wheel and the rail severely limits the ability to effectively use the power of the traction motor in the traction- and electric-braking modes. The use of sand to increase the coefficient of adhesion leads to contamination of the upper structure of the road, damages the environment, and causes wear of wheel bars and wheel rails. A new algorithm for detection of yoke and wheel pairs and a device for its implementation have been developed, and a mathematical model of the proposed algorithm is given.

A new control method for a rectifier based on a transformer with a rotating magnetic field (TRMF) containing an even number of sections of circular winding (CW), which makes it possible to double the number of ripples of rectified voltage in the supply-voltage period, is considered. It leads to a reduction in the ripple amplitude and improves the quality of rectified voltage. The geometrical similarity of the CW of a TRMF making it possible to implement the new control method is analyzed. Switching algorithms of power switches for the classical and new control methods for any quantity of an even number of CW sections are presented. As an example, a switching queue of power switches for a CW with ten sections is considered. The output-voltage shapes for different depths of control are shown. The calculating procedure of the control characteristic for the classical and new control methods, as well as corresponding diagrams, are presented. For the presented example with ten sections of CW, the efficiency of the new control method was evaluated and the dependences of the voltage-ripple ratio on the RMS of rectified voltage are presented. A comparative analysis of the number of ripples for different quantity of CW sections was conducted, and the harmonic composition of output voltage spectrum for the example under consideration is determined. It has been concluded that, in the case of using the new control method for achieving the desired quality of rectified voltage, the number of CW sections may be halved compared with the classical control method, which will simplify the manufacture of a transformer magnetic conductor, halve the number of pairs of power switches switching the CW taps, and decrease the mass, dimension, and cost factors of a semiconductor switch and the TRFM itself as a whole. Using the new control method makes it possible to make a controlled rectifier with an even number of sections of a CW transformer almost as efficient as using a transformer with an uneven number of CW sections and the classical control method. The new control method ensures the fulfillment of the requirements for the available value of the ripple ratio of the output voltage of a controlled rectifier based on a transformer with a rotating magnetic field set out by State Standard YuST 13109-97 at a lower RMS of rectified voltage.

The influence of the technical condition of bearings on the efficiency of induction motors (IMs) with a squirrel-cage rotor was considered. The experiments were carried out using induction-motor tests in the rated nominal regime with one operable bearing and two faulty ones, which had defects of the outer and inner parts. The bearing defects increase the energy loss, which leads to increased heat dissipation in the contact zone of its components, overheating, and reduction of motor efficiency. More accurate data on changing the efficiency of IMs with faulty bearings taking into account the heated state of the machine that is close to actual operating conditions were obtained. Thermal-imaging inspection of motor was performed, the graphic data characterizing the changes of temperatures of units and the machine efficiency when operating with a faulty bearing are presented. A diagnostic technique of the bearing condition by means of integral parameters of vibration acceleration that makes it possible to analyze the potential defects taking into account the weak level of their activation and the shift over the frequency response is considered.