ELECTRICAL ENGINEERING, ENERGETICS

Proceedings

ELECTRICAL ENGINEERING, ENERGETICS

N:2

2019

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Dear readers,

Here is the 16th issue of the journal “Proceedings of National Polytechnic University of Armenia - Electrical Engineering, Energetics”.

Over eight years, the results of scientific research are presented, the analysis and discussion of the issues related to the following areas have been carried out in our journal: electrical engineering, electromechanics and electrical materials; electrical technologies and power electronics; measurements, control, diagnostics; non-traditional sources of energy; power stations; power plants and electric networks.

This issue contains articles devoted to the study of numerous and diverse theories and concepts on electrical and energy issues, as well as measuring equipment. The authors of the papers are the university professors, research staff and post-graduate students.

Dear readers,

We inform you that the last four issues of the Proceedings, including the series “ Electrical Engineering, Energetics” are already included in the Russian Science Citation Index (RSCI), which has made it possible to place the full versions of the journal articles in the eLIBRARY.RU library. This permits to present the journal on an international platform, increase the efficiency of the information transfer to the scientific community and increase the citation numbers for the scientists published in our journal. In the near future, we will present numerical data regarding the citations to the our journal publication.

Dear readers, we are expecting your suggestions for improving the journal.

Headings

  • магнитореологическая жидкость

  • математическая модель

  • метод обобщенного приведенного градиента

  • нелинейные магнитные сопротивления

  • схема замещения магнитной цепи

  • форма магнитных частиц

  • шар

  • электромагнитная система

A electromagnetic system with magnetorheological fluid is investigated. Unlike the previous works of the authors, where the shape of the particles of magnetic material in the oil of the magnetorheological fluid was taken in the form of a cube, in this work, it is assumed that these particles (hereinafter referred to as balls) have the shape of a ball - closer to the real shape of the particles. It is assumed that the balls magnetized under the influence of an external magnetic field create elementary columns, which are combined in columns.

The mathematical model of the magnetic circuit of the electromagnetic system is compiled (the electromagnetic system of the magnetorheological brake is adopted as the object under study)․ Expressions of magnetic conductivities (resistances) of characteristic sections of the passage of magnetic flux are obtained. In this case, the area occupied by the balls was represented by the nth number of magnetic flux tubes in the form of a cylinder (one tube) and a hollow cylinder ((n-1) tubes), and the area occupied only by non-magnetic materials - oil and non-magnetic coating - one tube. As a result, an equivalent circuit of the magnetic circuit is constructed in which there is an nth number of parallel branches with linear and nonlinear magnetic resistances and one branch with linear magnetic resistance. To solve a nonlinear system with (n + 1) equations compiled according to the first and second Kirchoff laws, and describing the equivalent circuit, the generalized reduced gradient method is used.

For an electromagnetic system with the given sizes and particle material, numerical solutions of the system of equations are obtained and analyzed. In this case, the number of parallel branches of the equivalent circuit was taken to be six (n = 5), respectively, a non-linear system of equations of the 6th order was obtained and solved.

  • компенсирующая способность

  • модель

  • регулятор

  • система.

  • ток возбуждения

 The possibility of using the compensating abilities of synchronous motors in order to save energy consumption in the ore grinding technological process has been substantiated.

It is revealed that to use the compensating abilities of synchronous motors in the process of grinding mineral raw materials, additional difficulties arise associated with the regulation of the excitation modes of the synchronous motor. It is shown that, based on the variety of engines used in the technological process of grinding mineral raw materials, modelling a regulator of the excitation modes of the synchronous motor for circuits with an m number of synchronous and an n number of induction motors is of practical interest. The law of regulation of excitation for the system of automatic regulation is selected.

The excitation mode controller was simulated using the MATLAB software package in the Simulink environment. The study was conducted on the model of the controller built in accordance with the selected law of regulation of excitation without using and by using the PID controller. Simulink models of components of an automatic excitation control system are presented. A comparative analysis of the time dependences of the excitation voltage in the model using the PID controller shows that the specified excitation voltage can be provided regardless of the motor power, load and supply voltage. The results of the study on a model with an integral regulator showed that the given excitation voltage undergoes a slight change.

The obtained results suggest that when using the compensating abilities of synchronous motors in the process of grinding mineral raw materials, it is possible to provide the required regulation of the excitation current independent of internal and external influences.

  • коэффициент полезного действия.

  • магнитопровод

  • оптимизация

  • потери

  • трансформатор

The issues on improving the energy efficiency of power transducers at operating in regulated modes are considered.

The work is aimed at the implementation of energy-saving technologies. For the first time, experimental confirmation of the new method of topological optimization of the transformer magnetic circuit is carried out based on the use of the level of losses in the magnetic core as a criterion used in practice to determine the rational parameters of the magnetic circuit design taking into account the restrictions on the choice of the electrical steel grade.

It is shown that when determining the basic dimensions and topology of a transformer magnetic circuit, it is important to achieve a given level of the no-load loss ratio, taking into account the non-uniform distribution of magnetic flux over the magnetic flux cross-section, which allows finding a rational solution, taking into account the numerous functional limitations. In the approximation that no-load losses are directly dependent on the mass of the magnetic circuit, the formulation of the problem of finding the minimum mass of the magnetic circuit when the transformer operates in regulated modes is considered. The paper substantiates the use of the level of losses in the magnetic circuit as a criterion for determining the rational design parameters in optimizing the magnetic circuit in order to increase the energy efficiency of the transformer.

The results of experimental studies of the dependence of the no-load losses of a transformer on the mass of the magnetic circuit are presented. The features are considered and it is shown that when determining the basic dimensions and topology of a transformer magnetic circuit, the achievement of a given level of the no-load loss ratio when the transformer operates in regulated modes plays an important role. It is also shown that reducing the mass of the magnetic circuit by 15% of the total mass reduces the idling loss by 5%. It is also seen that the reduction of no-load losses allows in the range β = 0.1 ... 0.3 to increase the efficiency of the transformer by 7.8% from 0.77 to 0.83.

  • асинхронный двигатель

  • двигатель электромобиля.

  • дополнительный статор

  • массивный ротор

  • механическая характеристика двигателя

 

The technical solution of traction electric motor for an electric vehicle is proposed, To Traction motors for modern electric vehicles high requirements of reliability, absence of sliding contacts, flexible handling in the field, features “torque-speed”, small weight and dimensions – with the aim of placing the engine in confined motor-wheel. Are set as electric motors of electric vehicles the most suitable according to design and reliability are induction motors with a massive rotor, according to the controllability and simplicity of the power supply (U, f = const) - induction motors with a phase-wound rotor. In the known devices, these requirements are incompatible in a single design. A scheme and design of the induction motor, where these requirements are combined in a single design of the electric motor are proposed: a scheme and design of an induction motor with a massive rotor, which allows, without the use of winding on the rotor, and without sliding contacts, to control the position of the mechanical characteristics of the motor, are proposed. In the coordinate field of the characteristics " torque - the speed of rotation” from zero to their nominal values at any load moment, almost any speed of rotation can be achieved. These characteristics are achieved due to the fact that the massive rotor of the motor is elongated, the elongated part of the rotor is taken out of the zone of magnetic coupling with the stator winding and is covered by an additional stator, the AC windings of which are closed to external adjustable active resistances. Thus, an external adjustable active resistance is introduced into the circuit of the currents induced in the rotor by contactless means. As an adjustable active resistance, an adjustable variable resistor is used, which is carried outside the machine. By adjusting the value of the external active resistance, the controllability of the position of the mechanical characteristic of the engine is achieved. The external variable resistor is the accelerometer of an electric vehicle. High reliability of the engine is provided due to the absence of winding on the rotor and the sliding contacts on the rotor, high controllability and acceleration of the rotor-when using the engine as a traction motor of an electric vehicle.

  • влажная среда.

  • восстанавливающееся напряжение

  • обмотка

  • повреждение изоляции

  • электродвигатель

Over time, the insulation of the motor windings can become dirty, wet, and also exposed to high temperatures and voltage surges. This leads to aging of the insulation and, as a result, its breakdown, and as a result, the engine failure. There are various methods for assessing the state of insulation of electric motors, however, the choice of a particular method depends on the specific task. Despite the results achieved in determining the insulation state of the motor winding, of particular interest is the problem of assessing the insulation of motors, operating in a humid environment. This is due to the fact that in many industries electric motors are used to drive technological mechanisms, which are operated when exposed to moisture. In this article, the dynamics of changes in the technical state of the insulation of the motor winding at different degrees and the duration of its presence in a humid environment is studied by the method of the recovering voltage and absorption current coefficient.

The application of the method of recovery voltage to assess the quality of insulation is justified. In particular, it is shown that by this method it is possible to determine the coefficient of dielectric absorption, the insulation time constant, the insulation resistance and, thereby, evaluate the quality of insulation at an earlier stage of diagnostics of the motor winding. The stator winding insulation capacitance relative to the housing, the dielectric loss angle tgδ, and also the dynamics of the recovering voltage were determined experimentally. Experimental studies were carried out on a three-phase squirrel-cage motor. Engine conditioning was carried out in a chamber where relative humidity and temperature could be changed.

Studies have shown that with increasing humidity of the insulation, on the one hand, the dielectric loss angle tgδ increases, on the other hand, the insulation resistance begins to drop sharply at a humidity of 70...80%.

  • гармонический состав

  • генератор

  • несинусоидальное напряжение

  • переменная частота вращения вала

  • полупроводниковый ключ переменного тока

  • преобразователь частоты

  • система возбуждения

  • скольжение

  • фильтр.

In autonomous power supply systems, an important place is occupied by electromechanical devices for stabilizing the frequency of the output voltage at a variable frequency of rotation of the shaft of the primary engine, where the latter can be either a running engine of vehicles or diesel in diesel generator sets. At that, in most cases, very strict requirements are imposed on autonomous power supply systems for weight and size indicators and the quality of the shape of the output voltage curve. Such devices are built on the basis of both a synchronous generator with an output static frequency converter designed for load power and on the basis of asynchronized synchronous generator with an excitation system designed for power proportional to the product of the slip at the load power.

It is shown that for a certain frequency range, the primary engine shaft rotation and the load power factor, from the point of view of overall dimensions, it is more expedient to build an electrical part power supply system based on an asynchronized synchronous generator. Two structural schemes of an asynchronized synchronous generator excitation system are considered. The first block diagram consists of an input three-phase transformer at the output of which a three-phase-three-phase static direct frequency converter is connected which is a direct freguency transformer with quasi-band modulation on completely controlled AC semiconductor switches and operating in subtraction mode frequencies. The second block diagram consists of a single-phase transformer at the input which is connected to a three-phase-single-phase direct converter frequencies with quasi-band modulation, operating in the mode of summing frequencies, a single-phase-three-phase direct converter is connected at the output frequencies with quasi-band modulation, operating in the mode of subtraction of frequencies. Mathematical descriptions of output non-sinusoidal voltages are given to the selected frequency converters, as well as a numerical estimate of the coefficients, characterizing the quality of the shape of the curve of their output voltages and weight indicators of the filters connected to them.

  • входное сопротивление.

  • метод структурных чисел

  • обобщенные параметры четырехполюсника

  • передаточные функции

  • разветвленная цепная схема

The work is devoted to the investigation of the modes of branched-chain circuits. To solve the problem, the analytical expressions of input impedances, the transfer functions by current and voltage of n two-port homogeneous chain circuits under load obtained by the method of structural numbers are used.

By the method of structural numbers, analytical expressions, connecting the mode parameters (currents, voltages) of the units of the chain circuits, depending on the initial parameters are obtained. This approach allows calculating not only the mode of the chain circuits but also to explore the properties of the resulting expressions.

The numerical calculation of the chain circuit modes is carried out by the classical methods of the theoretical foundation of electrical engineering.

A branched-chain circuit is presented as a connection of different chain circuits. Each chain circuit is a cascade interconnection of the same asymmetrical two - ports. By equivalently replacing a homogeneous chain with input impedance, the initial circuit in the form of a cascade interconnection of the same asymmetrical two – ports in the load condition is presented. The regime at the output of each unit of the chain circuit is obtained using the transfer functions of current and voltage. Then, returning to the original branched-chain circuit, having a regime at the input of the branched sections, the currents and voltages of each unit of the branched-chain circuit are obtained.

In the article, the definition of a branched-chain scheme is given. The calculation method is based on the method of the algebra of structural numbers.

  • аналого–цифровой преобразователь

  • магазин сопро¬тивле¬ний.

  • термо¬преобразователь сопротивления

  • термоэлектрический преобразователь

  • цифровой термометр

 

Digital thermometers (DT) are currently widely used for temperature measurement. Analog to digital converters (ADC) are also used for resistive temperature transducer (RST) and thermoelectric converter (TC) signals which have better metrological and operational characteristics than the analog thermometers and normalizing measuring converters of the RST and TC signals. The calibration and verification of DT have some peculiarities, which are caused by TC’s low level signals, nonlinearity of static characteristics of the RST and TC, the presence of the device for auto compensation of thermo-EMF of free ends of TC in DT that works with TC, high accuracy of DTs. The thresholds of confidence interval values for the 3-rd level standard temperature devices under test, and the requirements for verification errors of temperature measurement devices are presented. The expediency for the choice of the price of the unit for the least significant digit of the reading device of DT, working with RST, being no less than 0,01°C, and 0,1°C when working with TC, is justified.  The questions of how to choose the sources of calibrating signals are investigated. The main metrological characteristics of the sensors are presented, the requirements for the choice of calibrating signals are justified. The metrological characteristics are analyzed for decade resistance boxes, digital multimeters that are being currently produced and used for process calibration; recommendations are given regarding their usage. It is shown that the method of linearization of static characteristic of the sensor must be considered during the checked point selection. For instance, if linearization is performed using piecewise linear approximation of the static characteristic, then the linearization error will be the maximum in the middle points of the approximation area.

Recommendations are given for the choice of the source of calibrating signals for DT that work with RST; the source of calibrating signals for DT working with TC is designed.

  • математическая модель

  • система слежения

  • функциональная схема.

  • электродвигатель малой мощности

The mathematical models of several types of efficient electric models used in the monitoring system designed for the measurement of harmful gas components found in the layers of the Earth`s atmosphere are considered. At that, the direct current motors with successive excitement are preferred.

The main prerequisites of the requirements and principles of creating a tracking system for automatic guidance and tracking of the Sun with spectrometric equipment intended to be based on various types of vehicles, in particular on research vessels, taking into account the conditions of sea pitching, are described. When designing a servo system, the issue of frequent power switching of low-power electric motors due to non-stationary operating conditions was also considered. For this purpose, two types of block diagrams were developed: a control unit-relay circuit with a significant margin for switching, as well as a contactless circuit on optocouplers. The use of low-power electric motors of both direct and alternating currents was also considered, and for the case of three-phase voltage, a special circuit was developed to protect the electric motor from unbalanced power.

In order to calculate the parameters of the tracking system and ensure the stability and quality of tracking, a linearized model of the tracking system was compiled and studied using an electronic computer. As a result of several repeated decisions by selecting the required parameters, the system parameters are established to ensure the stability of the tracking process and the required quality of regulation.

A mathematical model of a tracking system is presented, the implementation of which on a computer made it possible to establish the necessary engine parameters, which made it possible to ensure the stable operation of the system.

At that, the direct current motors with successive excitement are preferred.

Council

Editorial Council of Proceedings:  Yu.L. Sargsyan (Editor-in-chief, doctor of tech. sciences), A.Kh. Grigoryan (vice Editor-in-chief, doctor of tech. sciences),  A.G. Avetisyan (responsible secretary, doctor of tech. sciences), S.G. Aghbalyan (doctor of tech. sciences), M.K. Baghdasaryan (doctor of tech. sciences), B.S. Balasanyan (doctor of tech. sciences), V.Z. Marukhyan (cand. of tech. sciences), S.H. Simonyan (doctor of tech. sciences),
A.V. Tadevosyan (cand. of tech. sciences)

 

Editorial Council of the journal: M.K. Baghdasaryan (Editor-in-chief of the Journal, doctor of tech. sciences), V.S. Safaryan (vice Editor-in-chief of the Journal, doctor of tech. sciences), A.L. Mayilyan (responsible secretary of  the Journal, cand. of tech. sciences), M.A. Aramyan (doctor of tech. sciences), N.P. Badalyan (doctor of tech. sciences), G.V. Bareghamyan (doctor of tech. sciences), Zh.D. Davidyan (doctor of tech. sciences),
 B.M. Mamikonyan (doctor of tech. sciences), V.Z. Marukhyan (cand. of tech. sciences), Z.A. Melikyan (doctor of tech. sciences), V.G. Petrosyan (doctor of tech. sciences)